2016 Severe Storm Thread

[nrgjeff]

Looks like a decent shot a local severe today. BNA sounding had reasonably good lapse rate for this time of year. A little more heating ahead of existing thunderstorms should yield close to the CAPE that SPC advertises. I still think a little less if heating gets cut off too early. Upper winds are pretty light but not zero like they could be mid-July. Kentucky upper wind is a little better but Tennessee south has greater instability. Some leading edge isolated straight line winds would not surprise me. Like to see a little better consolidation for shelfies. New stuff may go on the Plateau as well. 

Full MD http://www.spc.noaa.gov/products/md/md1273.html

[nrgjeff]

Sent a little thunderstorm treat to Knoxville. Any shelfies?

[rbowman]

A lot of clouds in mid Tenn this morning. May cut back on heating and uplift from below as Jeff stated above.

Sent from my LG-H901 using Tapatalk

[jaxjagman]

Though it would be into next years severe thread from the IMME.It's the most interesting thing i've seen yet.We still have the 2nd half of severe season coming up thouugh.It'll  be interesting when we get into FMA and watching the TNI

[nrgjeff]

La Nina would help in the severe department. Chart above matches Nina precip. Just shifted slightly west which follows the long trend of central US trough tendency.

[jaxjagman]

 DAY 3 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0226 AM CDT TUE OCT 18 2016

   VALID 201200Z - 211200Z

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM THE MID AND UPPER OH
   VALLEY ACROSS THE MID-SOUTH REGION...

   ...SUMMARY...
   A FEW STRONG/LOCALLY SEVERE STORMS WILL BE POSSIBLE THURSDAY
   AFTERNOON AND EVENING FROM THE MID AND UPPER OHIO VALLEY
   SOUTH-SOUTHWESTWARD ACROSS THE MID-SOUTH.

   ...SYNOPSIS...
   A MID-LEVEL TROUGH INITIALLY ALIGNED OVER THE CENTRAL U.S. IS
   PROGGED TO CONTINUE ADVANCING EWD WITH TIME...AMPLIFYING AND
   ACQUIRING NEGATIVE TILT BY THE END OF THE PERIOD.  AS THIS
   OCCURS...A WEAK FRONTAL WAVE INITIALLY INVOF THE KY/TN AREA IS
   EXPECTED TO GRADUALLY STRENGTHEN AND SHIFT NEWD ACROSS ERN KY AND
   WV...WHILE A TRAILING COLD FRONT SWEEPS SEWD ACROSS THE SRN PLAINS
   AND SERN STATES.  THIS LOW/FRONT WILL FOCUS A BAND OF SHOWERS AND
   EMBEDDED THUNDERSTORMS -- PARTICULARLY DURING THE AFTERNOON AND
   EVENING HOURS.

   ...MID AND UPPER OH VALLEY REGION SSWWD ACROSS THE MID-SOUTH...
   AS THE FRONTAL WAVE STRENGTHENS AND MOVES INTO THE CENTRAL
   APPALACHIANS REGION THROUGH LATE AFTERNOON...A TRAILING COLD FRONT
   IS FORECAST TO SHIFT ACROSS THE KY/TN AND AL/MS VICINITIES THROUGH
   THE AFTERNOON.  MODEST DESTABILIZATION OF THE PRE-FRONTAL WARM
   SECTOR AND INCREASING LARGE-SCALE ASCENT SHOULD YIELD AN INCREASE IN
   CONVECTIVE COVERAGE AND INTENSITY THROUGH THE AFTERNOON AND INTO THE
   EVENING HOURS.  WEAKLY VEERING/INCREASING FLOW WITH HEIGHT IN THE
   WARM SECTOR IMMEDIATELY AHEAD OF THE FRONT WILL PROVIDE SHEAR
   SUFFICIENT FOR ORGANIZED UPDRAFTS...WHICH MAY LOCALLY ENHANCE STORM
   INTENSITY/LONGEVITY...POSSIBLY RESULTING IN ISOLATED/LOW-END SEVERE
   RISK.  AS SUCH...A 5%/MRGL RISK AREA IS BEING INTRODUCED
   ATTM...ALONG AND W OF THE APPALACHIAN CREST.

[jaxjagman]

 DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1230 AM CDT THU OCT 20 2016

   VALID 201200Z - 211200Z

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM SWRN NY SWWD ACROSS THE OH
   AND TN VALLEYS INTO THE LOWER MS VALLEY...

   ...SUMMARY...
   A FEW SEVERE STORMS WILL BE POSSIBLE THURSDAY AFTERNOON AND EVENING
   FROM SOUTHWEST NEW YORK ACROSS WESTERN PENNSYLVANIA AND EASTERN OHIO
   AND SOUTHWESTWARD ACROSS THE MID-SOUTH.

   ...SYNOPSIS...
   A STRONG UPPER TROUGH WILL SHIFT EWD ACROSS THE MS VALLEY DURING THE
   DAY AND TOWARD THE OH/TN VALLEYS INTO THE GREAT LAKES THU NIGHT. AT
   THE SFC...LOW PRESSURE WILL MOVE FROM KY INTO WRN PA BY 00Z WITH
   COLD FRONT TRAILING SWWD INTO THE LOWER MS VALLEY.  E OF THE SFC
   LOW...A WARM FRONT WILL LIFT NWD ACROSS PA AND SWRN NY. SWLY WINDS
   WILL MAINTAIN LOWER TO MID 60S F DEWPOINTS ACROSS THE WARM SECTOR
   WHICH WILL RESULT IN INSTABILITY SUPPORTIVE OF SCATTERED
   THUNDERSTORMS. INCREASING SWLY FLOW ALOFT WILL ENHANCE SHEAR
   PROFILES AND WILL LIKELY SUPPORT ISOLATED SEVERE THUNDERSTORMS
   MAINLY DURING THE AFTERNOON.

   ELSEWHERE...A LARGE AREA OF HIGH PRESSURE WILL RESULT IN STABLE
   CONDITIONS W OF THE MS RIVER EXCEPT FOR THE PACIFIC NW WHERE
   LOW-TOPPED SHOWERS AND A FEW THUNDERSTORMS WILL BE POSSIBLE IN
   ASSOCIATION WITH A LOW-AMPLITUDE SHORTWAVE TROUGH.

   ...SWRN NY SWWD ACROSS THE OH VALLEY AND MID-SOUTH...
   AN EXTENSIVE AREA OF RAIN AND THUNDERSTORMS IS EXPECTED TO BE
   ONGOING ALONG THE LENGTH OF THE COLD FRONT THU MORNING FROM THE
   ARKLATEX NEWD ACROSS THE OH VALLEY...AND IN ASSOCIATION WITH WARM
   ADVECTION OVER PA/NY WITH STRONG SWLY 850 MB FLOW.  WINDS ALOFT WILL
   INCREASE WITH THE APPROACHING UPPER TROUGH THROUGHOUT THE DAY...WITH
   FLOW ROUGHLY PARALLEL TO THE COLD FRONT. THIS...ALONG WITH AREAS OF
   HEATING...SHOULD ALLOW FOR AN UPTICK IN CONVECTIVE INTENSITY AND
   COVERAGE BY AFTERNOON...MAINLY FROM ERN TN/KY NEWD INTO PA.
   HERE...THE COMBINATION OF DEEP-LAYER SHEAR AND INSTABILITY SHOULD
   SUPPORT AT LEAST ISOLATED FAST-MOVING CELLS OR LINE SEGMENTS CAPABLE
   OF MARGINALLY SEVERE WIND OR HAIL.

   FOR NRN AREAS INCLUDING ERN OH...WRN PA AND SWRN NY...LOW-LEVEL
   SHEAR WILL BE ENHANCED BY THE PRESENCE OF THE WARM FRONT. IF ENOUGH
   DESTABILIZATION OCCURS...A FEW SUPERCELLS COULD NOT BE RULED OUT
   WITH PERHAPS A WEAK/BRIEF TORNADO THREAT.

   ..JEWELL/GLEASON.. 10/20/2016

[jaxjagman]

ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 200923
   SPC AC 200923

   DAY 4-8 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0323 AM CST SUN NOV 20 2016

   VALID 231200Z - 281200Z

   ...DISCUSSION...
   MODEL CONSENSUS MAINTAINS A PROGRESSIVE UPPER PATTERN THROUGH DAYS
   4-8...BUT SIGNIFICANT DIFFERENCES IN TIMING AND AMPLITUDE OF
   INDIVIDUAL SHORTWAVES BEGIN TO EMERGE AFTER DAY 6.

   DAY 4 (WEDNESDAY) UPPER TROUGH IS FORECAST TO DEAMPLIFY AS IT MOVES
   THROUGH THE EASTERN STATES...AND THE ASSOCIATED SURFACE LOW WILL
   OCCLUDE OVER THE GREAT LAKES. TRAILING COLD FRONT WILL MOVE THROUGH
   THE TENNESSEE VALLEY AND A PORTION OF THE SOUTHEASTERN STATES.
   INLAND MOISTURE ADVECTION SHOULD WEAKEN AS THE PRIMARY LOW-LEVEL JET
   SHIFTS FARTHER AWAY FROM THE COAST AND TOWARD THE TENNESSEE AND OHIO
   VALLEYS. THUS CONVECTION DEVELOPING ALONG AND AHEAD OF THE FRONT
   WILL ENCOUNTER DIMINISHING INSTABILITY...LIMITING THE SEVERE THREAT.

   DAY 5-6 (THURSDAY THROUGH FRIDAY) THE FRONT WILL STALL NEAR THE GULF
   COAST WITH STABLE CONDITIONS INLAND.

   ..DIAL.. 11/20/2016

 

 

Fixing to head off to Florida in a couple hours for T-Giving :).Better chance for severe looks possible the week after next.

[jaxjagman]

Euro shows some good gust tomorrow night into the early morning hours.Seems like there could be some good damage from the recent fires,the trees that have been burned should be rather weak,plus add the drought in as well

[jaxjagman]

 DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1155 PM CST SUN NOV 27 2016

   VALID 291200Z - 301200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS TUESDAY NIGHT ACROSS PARTS OF
   THE LOWER MISSISSIPPI VALLEY...AND ADJACENT GULF COAST...INTO
   PORTIONS OF THE TENNESSEE VALLEY...

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS AREAS SURROUNDING THE
   SLIGHT RISK...AS FAR NORTHEAST AS THE SOUTHERN APPALACHIANS...

   ...SUMMARY...
   SEVERE STORMS ARE POSSIBLE ACROSS PARTS OF THE LOWER MISSISSIPPI
   VALLEY AND ADJACENT GULF COASTAL AREAS...NORTHEASTWARD TOWARD THE
   SOUTHERN APPALACHIANS...TUESDAY NIGHT.  ACTIVITY MAY BE ACCOMPANIED
   BY POTENTIALLY DAMAGING WIND GUSTS...SEVERE HAIL...AND THE RISK FOR A
   FEW TORNADOES...ONE OR TWO OF WHICH COULD BE STRONG.

   ...SYNOPSIS...
   THE CENTER OF A BROAD DEEP LOWER/MID TROPOSPHERIC CYCLONE MAY LINGER
   OVER THE UPPER MIDWEST THROUGH THE BALANCE OF THIS PERIOD...BUT IT
   APPEARS LIKELY TO BEGIN TO GRADUALLY FILL/WIND DOWN.  AS IT DOES...
   AND THE REMNANTS OF ONE SIGNIFICANT SHORT WAVE IMPULSE TURN EAST
   NORTHEAST OF THE LOWER GREAT LAKES REGION DURING THE DAY...SOUTHERLY
   LOW-LEVEL WIND FIELDS ACROSS AND EAST OF THE MISSISSIPPI VALLEY
   STILL APPEAR LIKELY TO BE IN THE PROCESS OF WEAKENING EARLY IN THE
   DAY.

   HOWEVER...MODELS CONTINUE TO INDICATE THAT THE LAST ONE OR TWO...IN A
   SERIES OF SHORT WAVE PERTURBATIONS DIGGING INTO LARGE-SCALE UPPER
   TROUGHING OVER THE INTERIOR U.S....WILL EMERGE FROM THE FOUR CORNERS
   REGION DURING THE DAY.  AS DOWNSTREAM SUBTROPICAL RIDGING CENTERED
   OVER THE CARIBBEAN/BAHAMAS REMAINS STRONG...AS FAR NORTHWEST AND
   NORTH AS PORTIONS OF THE EASTERN GULF AND SOUTH ATLANTIC COAST
   STATES...IT APPEARS THAT THE AXIS OF THE REMNANT TROUGHING WILL PIVOT
   IN POSITIVELY TILTED FASHION ACROSS THE SOUTH CENTRAL PLAINS...MIDDLE
   MISSISSIPPI VALLEY AND OZARK PLATEAU BY 12Z WEDNESDAY.

   IN THIS MANNER...GUIDANCE INDICATES THAT IT WILL CONTRIBUTE TO
   INCREASING DIFLUENT AND DIVERGENT UPPER FLOW ALONG A STALLED FRONTAL
   ZONE...WHICH IS EXPECTED TO EXTEND FROM THE SOUTHERN APPALACHIANS
   THROUGH PORTIONS OF THE LOWER MISSISSIPPI VALLEY AND WESTERN GULF
   COAST REGION AT THE OUTSET OF THE PERIOD.  THE FRONT MAY BE PRECEDED
   BY A CONVECTIVELY GENERATED OUTFLOW BOUNDARY NEAR COASTAL LOUISIANA...
   MISSISSIPPI AND ALABAMA.  HOWEVER...MODELS APPEAR INCREASINGLY
   BULLISH WITH SOUTHERLY 850 MB JET STRENGTHENING (50-70 KT)...NEAR AND
   EAST OF THE LOWER MISSISSIPPI VALLEY TUESDAY EVENING.  THIS IS
   EXPECTED TO ACCOMPANY A DEVELOPING FRONTAL WAVE...AND APPEARS LIKELY
   TO SUPPORT AN INFLUX OF BOUNDARY LAYER MOISTURE (CHARACTERIZED BY
   MID/UPPER 60S F SURFACE DEW POINTS) OFF THE WESTERN GULF OF MEXICO...
   AT LEAST AS FAR NORTHEAST AS PORTIONS OF THE TENNESSEE VALLEY.

   ...LOWER MISSISSIPPI VALLEY INTO SOUTHERN APPALACHIANS...
   IT APPEARS THAT THE ENVIRONMENT WILL BECOME INCREASINGLY CONDUCIVE
   TO ORGANIZED SEVERE STORM DEVELOPMENT ACROSS THE LOWER MISSISSIPPI
   VALLEY BY TUESDAY EVENING.  BENEATH CONTINUING STRONG CYCLONIC
   MID-LEVEL FLOW...DEEP LAYER VERTICAL SHEAR WILL BE MORE THAN
   FAVORABLE...AND ENLARGING LOW-LEVEL HODOGRAPHS COULD PROMOTE A THREAT
   FOR TORNADOES...IN ADDITION TO A RISK FOR SEVERE HAIL AND POTENTIALLY
   DAMAGING WIND GUSTS.  HOWEVER...TORNADIC POTENTIAL REMAINS A BIT
   UNCERTAIN...AND MAY LARGELY HINGE ON THE DEGREE TO WHICH A RESIDUAL
   NEAR-SURFACE STABLE LAYER LINGERS ACROSS SOUTHERN LOUISIANA...
   MISSISSIPPI AND ALABAMA.

   AT THE PRESENT TIME...IT IS APPEARING INCREASINGLY PROBABLE THAT
   LARGE-SCALE FORCING FOR ASCENT COULD SUPPORT AN ORGANIZING LINE OF
   THUNDERSTORMS ALONG OR AHEAD OF THE EASTWARD ADVANCING COLD FRONT. 
   DAMAGING WIND GUSTS MAY BECOME THE PRIMARY THREAT WITH THIS
   ACTIVITY...WHICH COULD DEVELOP NORTHEASTWARD THROUGH PORTIONS OF THE
   TENNESSEE VALLEY AND SOUTHERN APPALACHIANS BY LATE TUESDAY NIGHT. 
   OTHERWISE...SUSTAINED DISCRETE SUPERCELL DEVELOPMENT ALSO APPEARS
   POSSIBLE WITHIN A NARROW CORRIDOR OF RICHER BOUNDARY LAYER
   MOISTENING PRECEDING THE EVOLVING SQUALL LINE...PARTICULARLY ACROSS
   PARTS OF SOUTHEAST/EAST CENTRAL MISSISSIPPI INTO WEST CENTRAL
   ALABAMA BY THE 30/03-06Z TIME FRAME.  ONE OR TWO STRONG TORNADOES
   MAY NOT BE OUT OF THE QUESTION.

   ..KERR.. 11/28/2016

[jaxjagman]

 DAY 4-8 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0349 AM CST MON NOV 28 2016

   VALID 011200Z - 061200Z

   ...DISCUSSION...
   THE POTENTIAL MID/UPPER FLOW EVOLUTION ACROSS THE EASTERN PACIFIC
   INTO NORTH AMERICA LATE THIS WEEK THROUGH EARLY NEXT WEEK IS
   BECOMING MORE UNCLEAR.  INCREASING SPREAD IS EVIDENT AMONG THE
   MEDIUM-RANGE MODELS...PERHAPS MOST NOTABLY IN ASSOCIATION WITH
   TROUGHING FORECAST TO DIG INLAND OF THE PACIFIC COAST BY EARLY
   THURSDAY.

   THE PAST FEW DAYS...GUIDANCE IN GENERAL HAS SUGGESTED THAT A
   SIGNIFICANT EMBEDDED IMPULSE WILL SPLIT OFF THE MAIN BELT OF
   WESTERLIES...AND DIG SOUTHWARD THROUGH SOUTHERN CALIFORNIA AND BAJA
   BY NEXT WEEKEND...BEFORE TURNING EAST NORTHEASTWARD ACROSS NORTHERN
   MEXICO LATE NEXT WEEKEND INTO EARLY NEXT WEEK.  PRECEDING THE
   EASTWARD ACCELERATION OF THIS FEATURE...CONFLUENT DOWNSTREAM FLOW
   WOULD ALLOW SURFACE RIDGING WITH POTENTIALLY COOL/COLD AIR TO
   DEVELOP EAST SOUTHEASTWARD ACROSS MOST AREAS EAST OF THE ROCKIES...AS
   FAR SOUTH AS THE GULF COAST.  THIS WOULD MAINTAIN GENERALLY STABLE
   CONDITIONS WITH NEGLIGIBLE CONVECTIVE POTENTIAL.

   RECENT RUNS OF THE GFS/NCEP MREF GENERALLY MAINTAIN THIS SCENARIO. 
   HOWEVER...OTHER MEDIUM-RANGE GUIDANCE...INCLUDING THE ECMWF/ECENS...
   HAVE TRENDED MORE PROGRESSIVE WITH THE VIGOROUS SOUTHERN STREAM
   IMPULSE.  AT THE OTHER EXTREME OF THE SPECTRUM...COMPARED TO THE GFS...
   THE 28/00Z DETERMINISTIC ECMWF INDICATES A SOLUTION THAT MAY SUPPORT
   STRONG CYCLOGENESIS INLAND OF THE LOUISIANA/MISSISSIPPI GULF COAST...
   THROUGH THE OHIO VALLEY AND GREAT LAKES...LATE THIS WEEKEND INTO
   EARLY NEXT WEEK.  TRENDS WILL NEED TO BE MONITORED.  IF THIS OUTPUT
   COMES CLOSE TO VERIFYING...IT WOULD PROBABLY BE ACCOMPANIED BY
   CONSIDERABLE SEVERE THUNDERSTORM POTENTIAL ACROSS AT LEAST THE
   CENTRAL GULF STATES THROUGH MUCH OF THE SOUTHEAST.

   ..KERR.. 11/28/2016

[jaxjagman]

DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0659 AM CST MON NOV 28 2016

   VALID 281300Z - 291200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS FROM THE NORTHERN PARTS OF THE
   TEXAS/LOUISIANA BORDER AREA TO NORTHERN MISSISSIPPI...

   ...THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE FROM EAST TEXAS TO
   WESTERN PARTS OF TENNESSEE AND ALABAMA...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLIGHT RISK
   FROM EAST TEXAS TO ALABAMA AND WESTERN KENTUCKY...

   ...SUMMARY...
   THUNDERSTORMS WILL SHIFT FROM EAST TEXAS AND THE ARKLATEX REGION
   ACROSS THE LOWER MISSISSIPPI VALLEY AND MID SOUTH.  THE SEVERE-STORM
   THREAT COULD REACH THE TENNESSEE VALLEY OVERNIGHT.  DAMAGING WINDS
   WILL BE THE PRIMARY THREAT...WITH A FEW TORNADOES ALSO POSSIBLE. 
   OTHER DAYTIME STORMS OVER PARTS OF MISSOURI MAY PRODUCE HAIL
   APPROACHING SEVERE LIMITS.

   ...SYNOPSIS...
   A PRONOUNCED...STACKED...DEEP-TROPOSPHERIC CYCLONE -- CURRENTLY
   CENTERED OVER NORTHEASTERN SOUTH DAKOTA -- WILL REMAIN THE DOMINANT
   SYNOPTIC FEATURE TODAY AND TONIGHT...WITH CYCLONIC FLOW FROM THE
   PACIFIC COAST TO THE SOUTHERN/CENTRAL APPALACHIANS.  THE DEEP-LAYER
   LOW ITSELF IS FORECAST TO DRIFT ERRATICALLY NORTHWARD OVER THE
   EASTERN DAKOTAS AND WEST-CENTRAL/NORTHWESTERN MINNESOTA THROUGH THE
   PERIOD...BECOMING EVER MORE DEEPLY OCCLUDED IN LOW LEVELS.  THE BASAL
   SHORTWAVE TROUGH FOR THIS SYSTEM -- NOW EVIDENT IN MOISTURE-CHANNEL
   IMAGERY OVER FAR WEST TEXAS AND EASTERN NEW MEXICO -- IS EXPECTED TO
   EJECT RAPIDLY NORTHEASTWARD ACROSS NORTH TEXAS AND OKLAHOMA TODAY...
   REACHING NORTHERN ARKANSAS AND EASTERN MISSOURI BY 00Z.  THIS
   PERTURBATION WILL CONTINUE NORTHEASTWARD TO SOUTHERN ONTARIO BY 12Z.
    MEANWHILE...AN INITIALLY WEAKER SHORTWAVE TROUGH -- CURRENTLY
   POSITIONED OVER THE INLAND PACIFIC NORTHWEST...WILL DIG SOUTHEASTWARD
   TO PARTS OF ARIZONA AND NEW MEXICO BY THE END OF THE PERIOD.

   AT THE SURFACE...THE SOUTHERN PLAINS COLD FRONT LARGELY HAS OVERTAKEN
   ITS PRECEDING DRYLINE...AND EXTENDS FROM A NEBULOUS WARM-FRONTAL
   INTERSECTION IN SOUTHEASTERN KANSAS SOUTHWESTWARD ACROSS CENTRAL
   OKLAHOMA AND SOUTHWEST TEXAS.  THE OCCLUDED FRONT WAS DRAWN FROM
   THERE NORTHWARD TO THE EASTERN DAKOTAS LOW.  A WARM FRONT WAS
   ANALYZED NEAR THE LOUISIANA COAST...ARCHING NORTHWARD OVER EAST TEXAS
   TOWARD THE TEXARKANA AREA...BECOMING ILL-DEFINED AMIDST STRONGER
   BAROCLINIC INFLUENCES OF CONVECTION FARTHER NORTH.  THE COLD FRONT
   SHOULD PROCEED SOUTHEASTWARD TODAY...REACHING PARTS OF NORTHERN
   MISSISSIPPI...CENTRAL/SOUTHWESTERN LOUISIANA AND SOUTH TEXAS DURING
   LATE AFTERNOON.  MEANWHILE THE WARM FRONT WILL MOVE ERRATICALLY
   NORTHEASTWARD ACROSS PORTIONS OF LOUISIANA...SOUTHERN ARKANSAS AND
   MISSISSIPPI.

   ...EAST TEXAS TO THE TENNESSEE VALLEY REGION...
   SCATTERED THUNDERSTORMS ARE ONGOING ACROSS PARTS OF NORTH-CENTRAL
   AND NORTHEAST TEXAS INTO WESTERN ARKANSAS...IN A REGIME WHERE SBCAPE
   DWINDLES AND SBCINH INCREASES WITH NORTHEASTWARD EXTENT.  THE
   WARM-ADVECTION/CONFLUENT-FLOW REGIME IN LOW LEVELS OVER EAST TEXAS
   ALSO SHOULD SUPPORT SLOWLY INCREASING THUNDERSTORM COVERAGE AND
   INTENSITY FROM NOW THROUGH THE AFTERNOON...AS BOTH REGIMES SHIFT
   EASTWARD AND PERHAPS MERGE.  THE TEXAS PART OF THESE PROCESSES MAY
   POSE AN INCREASING SEVERE THREAT THROUGH LATE MORNING AS THEY SHIFT
   OVER THE ARKLATEX REGION INTO MIDDAY; A RELATED MESOSCALE DISCUSSION
   (NUMBER 1826) WILL ADDRESS THE NEAR-TERM DETAILS.

   OTHERWISE...THE SEVERE-STORM THREAT IS EXPECTED TO SHIFT EASTWARD AND
   RAMP UP THROUGH THE DAYLIGHT HOURS -- PRIMARILY WIND DAMAGE...BUT
   ALSO WITH ISOLATED HAIL AND A FEW TORNADOES POSSIBLE.  THE FOREGOING
   WARM SECTOR WILL DESTABILIZE GRADUALLY FROM A BLEND OF THETA-E
   ADVECTION AND DIABATIC SURFACE HEATING...THE LATTER RENDERED GRADUAL
   AND PATCHY BY CLOUD/PRECIP FIELDS.  THE MAIN UNCERTAINTY IS THE
   EXTENT OF FAVORABLE SURFACE-BASED DESTABILIZATION NORTHEASTWARD
   TOWARD THE LOWER OHIO VALLEY IN A NARROW AND VERY MARGINAL WARM
   SECTOR...FOLLOWING ONGOING CLOUDS AND PRECIP...AND RESULTING IN LOWER
   UNCONDITIONAL SEVERE PROBABILITIES IN THAT AREA COMPARED TO FARTHER
   SOUTH.  WITH SOUTHWARD EXTENT NEAR THE GULF COAST AND INTO THE MORE
   FAVORABLE MOISTURE...LIFT WILL BE MORE QUESTIONABLE BENEATH STRONGER
   CAPPING -- AS EVIDENT UPSTREAM IN THE 12Z CRP SOUNDING -- WHILE THE
   MAIN CYCLONE OCCLUDES AND OVERALL MASS RESPONSE PEAKS FARTHER NORTH.

   GIVEN THESE CONSTRAINTS...THE MOST FAVORABLE PARAMETRIC JUXTAPOSITION
   APPEARS TO BE IN AND NEAR THE ENHANCED RISK...WHERE MODIFIED RAOBS
   AND FORECAST SOUNDINGS SUGGEST THAT THE MLCAPE WILL RISE TO THE
   500-1000 J/KG RANGE BETWEEN I-10 AND I-20 AND 300-800 J/KG NORTHWARD
   OVER SOUTHERN ARKANSAS AND NORTHERN MISSISSIPPI.  DEEP SHEAR
   GENERALLY WILL BE STRONGEST OVER THE NORTHERN PART OF THE
   CATEGORICAL SLIGHT AND ENHANCED RISK AREAS...BENEATH A 150-170-KT
   250-MB JET AND A BROAD SWATH OF 80-100-KT 500-MB FLOW.  LOW-LEVEL
   SHEAR WILL BE STRONG OVER THE ENTIRE OUTLOOK BUT GREATEST NEAR THE
   WARM FRONT...WHERE FLOW IS MORE SOUTHERLY TO SOUTHEASTERLY...
   SUPPORTING GREATER DIRECTIONAL SHEAR.  EFFECTIVE SRH GENERALLY
   SHOULD REACH THE 300-500 J/KG RANGE AND LOCALLY HIGHER...BEFORE
   SURFACE WINDS VEER SOUTHWESTERLY.  ANY SUPERCELLS IN THIS
   ENVIRONMENT WILL POSE A RISK FOR TORNADOES AS WELL.  A MORE
   CONCENTRATED/SUBSTANTIAL TORNADO THREAT MAY BECOME APPARENT AS
   MESOSCALE DETAILS BECOME LESS NEBULOUS...GIVEN FAVORABLE STORM MODES.
    WITH TIME THE DOMINANT STORM MODE WILL BECOME QUASI-LINEAR...GIVEN
   THE PERSISTENT GEOMETRY OF DEEP-LAYER FLOW BEING LARGELY PARALLEL TO
   THE SOUTHWEST-NORTHEAST-ALIGNED ZONE OF STRONGEST LOW-LEVEL FORCING
   FOR CONVECTION.

   THE DOMINANT...QUASI-LINEAR BAND OF CONVECTION SHOULD WEAKEN FROM
   NORTH TO SOUTH THIS EVENING AND OVERNIGHT AS ITS NORTHERN EXTENT
   OUTRUNS THE SURFACE WARM SECTOR.  SOME SEVERE THREAT MAY PERSIST
   LATE TONIGHT OVER MIDDLE TENNESSEE AND ALABAMA WHERE THETA-E WILL BE
   HIGHER.

[nrgjeff]

No concerns for Tennessee. However I think North Alabama and North Mississippi could get really active late Tuesday night. IFF they can reach high temps in the 70s Tuesday, the stage would be set for low-moderate instability overnight. Tuesday night into Wednesday morning could become a classic low CAPE high shear severe weather outbreak. Note I write could, not will and not even should. Conditional at the moment, but it is definitely something to watch. SPC hatched their slight valid for Tuesday night.

[jaxjagman]

 DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1154 PM CST MON NOV 28 2016

   VALID 291200Z - 301200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS ACROSS ERN LA...MUCH OF
   MS...PARTS OF SRN TN...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SABINE RIVER NEWD INTO
   SRN KY...

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM THE CENTRAL GULF COAST
   NEWD INTO KY...

   ...SUMMARY...
   SEVERE STORMS ARE EXPECTED ACROSS PARTS OF THE LOWER MISSISSIPPI
   VALLEY AND ADJACENT GULF COASTAL AREAS...AND EXTENDING NORTHEASTWARD
   INTO TENNESSEE AND KENTUCKY. THE THREAT SHOULD PEAK TUESDAY EVENING
   AND OVERNIGHT.  STORMS MAY BE ACCOMPANIED BY TORNADOES...HAIL...AND
   DAMAGING WIND...WITH A FEW STRONG TORNADOES POSSIBLE.

   ...SYNOPSIS...
   THE UPPER AIR PATTERN WILL FEATURE A STATIONARY UPPER LOW CENTERED
   OVER THE NORTHERN PLAINS AND UPPER MS VALLEY...WITH BROAD AREA OF
   CYCLONIC FLOW FROM THE ROCKIES ACROSS THE SOUTHERN PLAINS AND LOWER
   MS VALLEY AND INTO THE LOWER GREAT LAKES. EARLY IN THE DAY...A
   LEADING SHORTWAVE TROUGH WILL DISSIPATE AS IT MOVES FROM THE OH
   VALLEY ACROSS THE NORTHEASTERN STATES WITH SLIGHT HEIGHT RISES TO
   THE SOUTHWEST. HOWEVER...BY LATE TUESDAY EVENING...A LARGER SHORTWAVE
   TROUGH WILL ROTATE EASTWARD ACROSS THE SOUTHERN PLAINS AND WILL
   APPROACH THE MS RIVER INTO WEDNESDAY MORNING. 

   AT THE SURFACE...A LOW PRESSURE TROUGH WILL EXTEND FROM THE MIDDLE MS
   VALLEY SOUTHWARD TOWARD THE SABINE RIVER BY 00Z...WITH A SECONDARY
   SURFACE LOW MOVING FROM AR ACROSS TN...KY...AND INTO SOUTHERN OH BY
   WEDNESDAY MORNING. EXTENDING SOUTHWESTWARD FROM THE LOW WILL BE AN
   INTENSIFYING COLD FRONT WHICH WILL SWEEP EASTWARD TO AN EASTERN KY
   TO SOUTHEAST LA LINE BY WEDNESDAY MORNING. AHEAD OF THIS FRONT...
   RAPID WARM AIR ADVECTION WILL OCCUR IN THE LOW-LEVELS DURING THE DAY
   AS A WARM FRONT PUSHES NORTHWARD...WITH 850 MB FLOW INCREASING TO 50
   KT BY 00Z. A MOISTENING AND DESTABILIZING AIR MASS WILL MATERIALIZE
   ACROSS THE WARM SECTOR WITH MID 60S F DEWPOINTS APPROACHING THE
   SOUTHERN BORDER OF TN BY EVENING AND NEAR 70 F DEWPOINTS ACROSS LA
   AND MS.

   LIFT ALONG THE COLD FRONT...WITH INCREASING SHEAR PROFILES AND
   FAVORABLE LARGE-SCALE SUPPORT SHOULD ALLOW FOR A CORRIDOR OF
   SIGNIFICANT SEVERE WEATHER POTENTIAL ACROSS THE ENHANCED RISK AREA.

   ...EASTERN AR AND NORTHERN LA...MS...NORTHERN AL...TN...KY...
   SUBSTANTIAL LOW-LEVEL MOISTURE IS ALREADY IN PLACE ACROSS THE
   CENTRAL GULF COAST WITH DEWPOINTS NEAR 70 F OVER LA AS OF MONDAY
   EVENING. AS THE WARM FRONT SHIFTS NORTHWARD DURING THE DAY...
   MOISTENING WILL OCCUR AND SOME MODELS SUCH AS THE WRF-ARW AND THE
   HRRR SHOW SCATTERED THUNDERSTORMS DEVELOPING IN THE WARM ADVECTION
   ZONE FROM NEAR THE SABINE RIVER EASTWARD ACROSS LA AND PERHAPS INTO
   CENTRAL MS. IF THIS OCCURS...THESE WOULD LIKELY TAKE THE FORM OF
   SUPERCELLS AS SHEAR PROFILES WILL BE QUITE STRONG ALOFT...WITH
   MODERATE SRH OF 200-300 M2/S2 PRESENT ALONG THE WARM FRONT. HAIL AND
   A TORNADO ARE CONDITIONALLY POSSIBLE WITH THE EARLY/MIDDAY ACTIVITY.


   IN THE WAKE OF ANY EARLY ACTIVITY...AND PRECEDING THE COLD FRONT...
   MOISTENING AND DESTABILIZATION WILL CONTINUE...WITH FORECAST
   SOUNDINGS SHOWING A SMALL CAPPING INVERSION AROUND 800 MB.  THIS
   SHOULD ENSURE THAT WARM SECTOR DEVELOPMENT IS FOCUSED ALONG THE COLD
   FRONT...WHICH WILL ALSO LIMIT THE NUMBER OF STORMS INITIALLY AND BE
   FAVORABLE FOR SUPERCELLS.  INSTABILITY WILL BE STRONGER THAN THE
   PREVIOUS DAY...AND SHEAR WILL REMAIN VERY STRONG WITH HODOGRAPHS
   FAVORING TORNADIC SUPERCELLS AS WELL AS HAIL AND WIND. THE
   LIKELIHOOD OF DISCRETE SUPERCELLS...AMPLE MOISTURE...AND VERY STRONG
   SHEAR ALL SUGGEST A COUPLE TORNADOES MAY BE STRONG.

   SOME DIFFERENCES EXIST IN TERMS OF HOW FAR EAST OR WEST THE COLD
   FRONT DEVELOPMENT WILL TAKE PLACE...BUT GENERAL MODEL CONSENSUS IS
   NEAR THE MS RIVER ALONG THE AR/MS BORDER...AND EXTENDING
   SOUTHWESTWARD THROUGH THE EVENING ACROSS EASTERN LA AND OVER MUCH OF
   MS. THE INITIAL DEVELOPMENT AROUND 00Z MAY MOVE FROM EASTERN
   AR/NORTHERN MS INTO MIDDLE TN AND EVENTUALLY SOUTHERN KY WITH A
   TORNADO AND WIND THREAT. FURTHER DEVELOPMENT IS ALSO EXPECTED AROUND
   03Z FROM CENTRAL LA INTO CENTRAL MS...EITHER JUST AHEAD OF THE FRONT
   OR IN A PRE-FRONTAL CONFLUENCE LINE. HERE...DEWPOINTS WILL BE IN THE
   UPPER 60S F...AND INSTABILITY WILL BE ON THE ORDER OF 1000 J/KG WHICH
   WILL CLEARLY BE SUFFICIENT FOR SUPERCELLS AND A FEW TORNADOES GIVEN
   THE AMPLE MOISTURE.

   ..JEWELL/LEITMAN.. 11/29/2016

[jaxjagman]

 DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0654 AM CST TUE NOV 29 2016

   VALID 291300Z - 301200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS FROM EASTERN LOUISIANA TO
   NORTHWESTERN ALABAMA AND SOUTHERN MIDDLE TENNESSEE...

   ...THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE FROM SOUTHEAST TEXAS
   TO SOUTH-CENTRAL KENTUCKY AND CENTRAL/NORTHERN ALABAMA...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLIGHT RISK....

   ...SUMMARY...
   SEVERE STORMS ARE EXPECTED MAINLY THIS EVENING AND TONIGHT ACROSS
   PARTS OF THE LOWER MISSISSIPPI VALLEY AND ADJACENT GULF COASTAL
   AREAS...AND EXTENDING NORTHEASTWARD INTO TENNESSEE AND KENTUCKY.
   DAMAGING WIND...ISOLATED HAIL...AND A FEW STRONG TORNADOES ARE
   POSSIBLE.

   ...SYNOPSIS...
   THE DOMINANT UPPER-AIR FEATURE FOR THIS FORECAST PERIOD WILL REMAIN
   A LARGE...STACKED...OCCLUDED CYCLONE...NOW CENTERED OVER THE EASTERN
   PART OF THE SOUTH DAKOTA/NORTH DAKOTA LINE.  THE DEEP-LAYER LOW IS
   EXPECTED TO MEANDER ERRATICALLY AND VERY SLOWLY EASTWARD ACROSS
   CENTRAL MINNESOTA THROUGH TOMORROW MORNING.  MEANWHILE...A BASAL
   SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE-CHANNEL IMAGERY OVER
   PARTS OF NEW MEXICO AND ARIZONA -- WILL PIVOT EASTWARD OVER PARTS OF
   OKLAHOMA...NORTHWEST TEXAS AND SOUTHERN NEW MEXICO BY 00Z.  BY 12Z...
   THIS PERTURBATION SHOULD REACH THE OZARKS...NORTH-CENTRAL AND
   WEST-CENTRAL TEXAS...MAINTAINING A PRONOUNCED POSITIVE TILT. 

   AT THE SURFACE...A QUASISTATIONARY FRONTAL ZONE WAS DRAWN FROM A WEAK
   LOW OVER SOUTH-CENTRAL TEXAS EAST-NORTHEASTWARD ACROSS THE
   MIDDLE/UPPER TEXAS COASTAL PLAIN...SOUTHWESTERN/CENTRAL LOUISIANA...
   AND CENTRAL/NORTHERN MISSISSIPPI...ARCHING NORTHWARD AND
   NORTHWESTWARD TOWARD THE DEEP-LAYER CYCLONE.  THE FRONT BECAME MORE
   ILL-DEFINED WITH NORTHWARD EXTENT FROM THE COASTAL OUTFLOW BOUNDARY.
    THE OUTFLOW BOUNDARY...PRODUCED AND REINFORCED BY PRIOR/OVERNIGHT
   CONVECTION...WAS ANALYZED ACROSS THE GULF COASTAL PLAIN...FROM
   NORTHEASTERN GEORGIA SOUTHWESTWARD ACROSS EXTREME SOUTHERN ALABAMA
   AND MISSISSIPPI...THEN SOUTH-CENTRAL/SOUTHWESTERN LOUISIANA...BEFORE
   INTERSECTING THE FRONT NORTH OF THE GOLDEN TRIANGLE AREA OF EXTREME
   SOUTHEAST TEXAS. THE OUTFLOW BOUNDARY IS EXPECTED TO RETREAT
   NORTHEASTWARD ACROSS THE MISSISSIPPI DELTA REGION AND MUCH OF
   MISSISSIPPI AND ALABAMA THROUGHOUT TODAY...THEN NORTHERN ALABAMA...
   MUCH OF WESTERN/MIDDLE TENNESSEE...AND PERHAPS INTO SOUTHERN KENTUCKY
   THIS EVENING AND OVERNIGHT.  EXCEPT WHERE LOCAL...CONVECTIVE
   REINFORCEMENTS OCCUR...THE BAROCLINIC GRADIENT WITH THE OUTFLOW
   BOUNDARY ALSO WILL BECOME MORE DIFFUSE WITH TIME. 

   ...SOUTHEAST TEXAS AND LOUISIANA TO WESTERN/MIDDLE TENNESSEE...
   SOME WESTWARD ADJUSTMENT HAS BEEN MADE TO THE MARGINAL-RISK
   PROBABILITIES IN DEFERENCE TO THE POTENTIAL FOR DIURNAL CONVECTION
   TO DEVELOP NEAR OR EVEN SOMEWHAT POLEWARD OF A WAVY SEGMENT OF THE
   FRONT OVER SOUTHEAST TEXAS...BEFORE THE BAROCLINIC ZONE ACCELERATES
   SOUTHEASTWARD.  EITHER THIS CONVECTION...OR ADDITIONAL DEVELOPMENT
   LATER THIS AFTERNOON AND EVENING OVER LOUISIANA AND SOUTHEAST
   ARKANSAS NEAR THE FRONT...WILL MOVE NORTHEASTWARD AND BECOME
   SURFACE-BASED AS THE WARM SECTOR RETURNS INLAND.  ADDITIONAL
   THUNDERSTORMS SHOULD FORM THROUGHOUT THIS EVENING ACROSS PARTS OF
   LOUISIANA AND MISSISSIPPI...WHETHER ON THE FRONT OR IN WARM-SECTOR
   CONVERGENCE ZONES...MOVING NORTHEASTWARD TOWARD ALABAMA AND
   WESTERN/MIDDLE TENNESSEE.  COLLECTIVELY...THIS ACTIVITY SHOULD EVOLVE
   INTO THE PRIMARY...SOUTHWEST/NORTHEAST-ORIENTED BELT OF CONVECTION
   OVERNIGHT.  SUPERCELLS AND SMALL BOWS EACH ARE POSSIBLE.  DAMAGING
   GUSTS MAY BE THE MOST NUMEROUS EVENT TYPE...BUT TORNADOES (SOME
   CAPABLE OF SIGNIFICANT DAMAGE) ALONG WITH ISOLATED SEVERE HAIL WILL
   BE POSSIBLE. 

   THE ENVIRONMENT ALONG AND SOUTH OF THE RETREATING OUTFLOW BOUNDARY
   WILL BECOME MORE FAVORABLE FROM MID AFTERNOON INTO THE EARLY
   OVERNIGHT HOURS...AS THE LOW-LEVEL JET INTENSIFIES AND HODOGRAPHS
   ENLARGE...AMIDST FAVORABLY RICH BOUNDARY-LAYER MOISTURE AND MINIMAL
   CINH.  INCREASING LOW-LEVEL MOISTURE WILL BE MANIFEST BY SURFACE DEW
   POINTS MID/UPPER 60S F ALONG THE RETREATING BOUNDARY AND 70S NEAR
   THE GULF...WITH WARM-SECTOR PW OF 1.25-1.5 INCHES BEING COMMON.  OVER
   THE DELTA REGION AND EASTWARD TOWARD WESTERN ALABAMA...THIS WILL
   OFFSET NOCTURNAL/DIABATIC COOLING STABILIZATION ENOUGH TO MAINTAIN
   EFFECTIVELY SURFACE--BASED INFLOW WELL INTO THE OVERNIGHT HOURS...
   WITH MLCAPE AROUND 1500-2000 J/KG NEAR I-10 AND 500-1000 J/KG IN
   NORTHERN PORTIONS OF MISSISSIPPI/ALABAMA AND SOUTHERN TENNESSEE. 
   THE SEVERE THREAT WILL SHIFT EASTWARD ACROSS THE OUTLOOK AREAS
   OVERNIGHT AND MAY PERSIST TO THE END OF THE PERIOD AS THE CONVECTIVE
   PLUME REACHES EASTERN TENNESSEE...NORTHWESTERN GEORGIA...AND
   EASTERN/SOUTHERN ALABAMA.  

   ...NORTHERN TENNESSEE TO CENTRAL KENTUCKY...
   SCATTERED THUNDERSTORMS ARE EXPECTED TO PASS ACROSS THIS AREA
   ROUGHLY AFTER 03Z...IN TWO EPISODES THAT MAY MERGE ON THE NORTHERN
   END:  
   1.  NORTHEASTWARD-MOVING...MAINLY ELEVATED ACTIVITY IN A STRONG
   WARM-ADVECTION PLUME ALONG AND NORTHEAST OF THE RETREATING OUTFLOW
   BOUNDARY...AND 
   2.  THE NORTHEAST SEGMENT OF THE PRIMARY SW-NE CONVECTIVE BAND
   SHIFTING EAST-NORTHEASTWARD INTO WHATEVER REMAINS OF THE WARM
   SECTOR.  

   FAVORABLE SURFACE-BASED DESTABILIZATION THIS EVENING...BEHIND THE
   RETREATING OUTFLOW AIR AND PRIOR TO PASSAGE OF THE MAIN NEAR-FRONTAL
   THUNDERSTORM BAND...BECOMES MORE UNCERTAIN WITH NORTHEASTWARD EXTENT
   FROM MIDDLE TENNESSEE ACROSS CENTRAL/SOUTHERN KENTUCKY.  ASSORTED
   PLANAR PROGS AND MODEL FORECAST SOUNDINGS VARY CONSIDERABLY ON THE
   MAGNITUDE OF AVAILABLE BUOYANCY FOR CONVECTION -- MAINLY RELATED TO
   TIMING OF EROSION OF STATIC STABILITY FROM RAIN-COOLED ANTECEDENT
   AIR.  HOWEVER THERE IS REASONABLE AGREEMENT IN PRINCIPLE ON A
   NORTHEASTWARD DIMINISHING OF BOTH AVAILABLE THETA-E AND DURATION OF
   WARM-SECTOR INFLOW FOR ANY CONVECTION THAT DOES MOVE ACROSS THIS
   AREA.  TO REFLECT THESE UNCERTAINTIES...UNCONDITIONAL SEVERE
   PROBABILITIES DECREASE STEADILY NORTHEASTWARD ACROSS KENTUCKY...
   THOUGH THE ACTUAL SEVERE THREAT LIKELY WILL HAVE A SHARP NORTHERN
   BOUND SOMEWHERE IN THAT PROBABILITY GRADIENT.

   ..EDWARDS/MOSIER.. 11/29/2016

[jaxjagman]

NAM4k..S/MID/TN Valley 

[nrgjeff]

No heart for severe wx today, not even a desk chase overnight. Was looking for downed trees and power lines on the OBS thread. Figure we are all horrified by what we see in/around Gatlinburg.

Anyway we have another safety issue tonight, with a late night nocturnal severe wx threat for MS/AL, perhaps southern middle Tenn. Nobody should chase that crap at night. The following is more for the information and safety.

Warm front lifting north is dangerous. People will goto bed in what feels like stable conditions. In fact the soundings may be fairly stable early, before quickly destabilizing. Deep layer and low level shear will both be very high. CAPE is somewhat conditional, but surging dews will bring low LCLs either way. Low CAPE high shear tornado event is possible/probable. Tornado event would be localized, so I am not using outbreak language.

Looking at models the EHI numbers are pretty impressive for a low CAPE deal. The shear numbers are quite high for any time of year. Throw a boundary in there and we have a volatile situation overnight. Some research shows the rate of destabilization is more important than the final number. Some high-res models going linear; however, beware in Dixie. Models are programmed for the Plains. Cells will start discrete, perhaps remaining so for a few hours. Also possible an initial line actually breaks up into cells. People need 2-3 ways to be notified, ways that can wake up someone sleeping.

Bottom line: Hatched 10% tornado is clearly justified. A small 15% hatched area would not surprise me in later outlooks.

[jaxjagman]

3 hours ago, nrgjeff said:

No heart for severe wx today, not even a desk chase overnight. Was looking for downed trees and power lines on the OBS thread. Figure we are all horrified by what we see in/around Gatlinburg.

Anyway we have another safety issue tonight, with a late night nocturnal severe wx threat for MS/AL, perhaps southern middle Tenn. Nobody should chase that crap at night. The following is more for the information and safety.

Warm front lifting north is dangerous. People will goto bed in what feels like stable conditions. In fact the soundings may be fairly stable early, before quickly destabilizing. Deep layer and low level shear will both be very high. CAPE is somewhat conditional, but surging dews will bring low LCLs either way. Low CAPE high shear tornado event is possible/probable. Tornado event would be localized, so I am not using outbreak language.

Looking at models the EHI numbers are pretty impressive for a low CAPE deal. The shear numbers are quite high for any time of year. Throw a boundary in there and we have a volatile situation overnight. Some research shows the rate of destabilization is more important than the final number. Some high-res models going linear; however, beware in Dixie. Models are programmed for the Plains. Cells will start discrete, perhaps remaining so for a few hours. Also possible an initial line actually breaks up into cells. People need 2-3 ways to be notified, ways that can wake up someone sleeping.

Bottom line: Hatched 10% tornado is clearly justified. A small 15% hatched area would not surprise me in later outlooks.

 

[jaxjagman]

 

15% added to the SW Valley

 

http://www.spc.noaa.gov/products/exper/day4-8/#

[nrgjeff]

Stout southern stream upper level short-wave comes out Saturday, but most of the low level kinematics is well east due to the main northern stream system. Possibly some of the strong upper level winds mix down again. Regardless it is totally veered off everywhere, good news if you do not like tornadoes. Could be some straight line winds Saturday.

SPC does mention the possibility of anafrontal which would shut down severe. Looks like storms will at least try to go in the warm sector. However shallow arctic air could undercut the storms. Despite being a weekend I am not at all excited about the set-up. At least we can catch up some more on much needed rainfall.

In other news the KC Chiefs will host the Tennessee Titans in an ice bowl on Sunday. Cheers!

[jaxjagman]

NAM don't look bad.Might be doing what it does best at this range ,over doing it.GFS isn't horrid as it also shows a tornado threat.Believe though IF the GFS sticks to what it's showing recently that slight risk box will be expanded further N and E the next update.Either way,that's going to be a potent line coming through with some heavy rain.

[jaxjagman]

Went N and E,thought it'd make it to Nashville

 

Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1129 AM CST Fri Dec 16 2016

   Valid 171200Z - 181200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SATURDAY AFTERNOON
   INTO SATURDAY NIGHT ACROSS THE LOWER MISSISSIPPI VALLEY...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS
   SURROUNDING AREAS FROM THE GULF COAST INTO THE LOWER OHIO VALLEY...

   ...SUMMARY...
   Severe storms are possible Saturday afternoon into Saturday night
   across the lower Mississippi Valley.  Potentially damaging wind
   gusts may be the primary threat, but a couple of tornadoes are not
   out of the question.

   ...Synopsis...
   A pair of significant short wave impulses, emerging from split
   branches of westerlies across the eastern Pacific/western North
   American, appear likely to continue to come increasingly in phase as
   they turn east northeast of the Rockies through an increasingly
   confluent regime across the Mississippi Valley during this period. 
   Consolidation of strongest mid-level height falls may not occur
   until late Saturday evening into early Sunday across the Great
   Lakes.  With a significant reinforcing intrusion of arctic air
   already ongoing early Saturday across much of the northern and
   central Plains (in association with the northern branch impulse),
   surface frontal wave development to the lee of the Rockies may
   remain relatively subdued, at least until it reaches the lower Great
   Lakes/St. Lawrence Valley late in the period.

   Still, as the increasingly sheared southern branch impulse
   accelerates northeast of the Four Corners region, models generally
   suggest that pre-frontal south southwesterly 850 mb flow will
   restrengthen to 50-70 kt across southeastern portions of the Ozark
   Plateau/Mid South through the Ohio Valley late Saturday afternoon
   into Saturday Night.  This is expected to occur on the southern
   periphery of strong mid/upper jet intensification, including
   110-130+ kt at 500 mb, in a belt across the middle Mississippi
   Valley into the lower Great Lakes region.

   Coinciding with these developments, models also all generally
   indicate a substantive Gulf moisture return in a plume ahead of the
   arctic front, across the lower Mississippi Valley, through the Ohio
   Valley and western slopes of the Appalachians.

   ...lower Mississippi Valley into Ohio Valley...
   Boundary layer moistening, characterized by lower/mid 60s surface
   dew points, is expected to contribute to substantive destabilization
   in at least a pre-frontal corridor across the lower Mississippi
   Valley.  CAPE on the order of 500-1000 J/kg appears likely, in the
   presence of strong deep layer vertical shear supportive of organized
   severe storm development.

   By late afternoon, the southern fringe of strongest mid-level
   forcing for ascent appears likely to overspread areas near/ahead of
   a developing wave along the surface frontal zone across parts of
   eastern Arkansas into western Tennessee.  This is expected to
   provide the support for the initiation of the most significant
   thunderstorm development.  This could include supercells initially,
   but frontal forcing and largely unidirectional low/mid-level wind
   profiles may allow for rapid upscale evolution of a squall line,
   with damaging wind gusts the primary severe weather threat.  This
   activity is expected to tend to develop northeastward and eastward
   into portions of the Ohio and Tennessee Valleys through Saturday
   night, where/when the extent of the erosion of an initially
   cool/cold surface based layer remains the primary uncertainty
   concerning continuing severe weather potential.

   Otherwise, despite weaker mid/upper forcing for ascent farther to
   the south, mid-level inhibition may gradually weaken enough to allow
   for additional thunderstorm development Saturday night along a
   pre-frontal low-level confluence zone across parts of Louisiana into
   Mississippi.  This may include discrete supercells, at least
   initially, with more clockwise curved low-level hodographs appearing
   to support somewhat greater potential for a couple of tornadoes.