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Tn Valley Storms Dec 25-31


jaxjagman

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Since it looks like we are heading into a unsettled pattern the next few days,figured we won't derail the winter thread.Slight risk tomorrow for the south

 

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DAY 1 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   1159 PM CST THU DEC 24 2015

   VALID 251200Z - 261200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE ARKLAMISS AND TN
   VALLEY...

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM THE ARKLATEX TO THE
   SOUTHERN APPALACHIANS...

   ...SUMMARY...
   ISOLATED SEVERE STORMS ARE POSSIBLE ACROSS PARTS OF THE DEEP SOUTH
   TO SOUTHERN APPALACHIANS ON CHRISTMAS DAY AND NIGHT.

   ...ARKLAMISS/TN VALLEY TO SOUTHERN APPALACHIANS...
   LARGE-SCALE TROUGH AMPLIFICATION WILL OCCUR OVER THE GREAT
   BASIN/SOUTHERN ROCKIES TODAY...WHILE A MODERATELY STRONG BELT OF
   MID/HIGH-LEVEL SOUTHWESTERLY WINDS WILL LARGELY PARALLEL A FRONTAL
   BOUNDARY FROM THE ARKLATEX/MID-SOUTH TO TN VALLEY/APPALACHIANS.
   NEAR/SOUTHEAST OF THIS FRONT...A SEASONALLY MOIST BOUNDARY LAYER
   WITH MIDDLE 60S TO LOWER 70S F DEWPOINTS WILL EXIST WITHIN THE WARM
   SECTOR. THUNDERSTORMS ARE LIKELY TO CONTINUALLY INCREASE EARLY TODAY
   WITHIN A SOUTHWEST/NORTHEAST-ORIENTED NEAR-FRONTAL CORRIDOR ACROSS
   THE ARKLAMISS REGION AND TN VALLEY. VERY MOIST/CONFLUENT LOW-LEVEL
   FLOW WILL CONTRIBUTE TO THE DEVELOPMENT/PERSISTENCE OF WHAT MAY BE
   UPSCALE-GROWING LINEAR CLUSTERS/EMBEDDED BOWS DURING THE DAY...BUT
   ALSO THE POSSIBILITY OF SEMI-DISCRETE SUPERCELLS WITHIN THE
   EFFECTIVE-FRONT-ADJACENT WARM SECTOR AS LOW-LEVEL LAPSE RATES
   DIURNALLY STEEPEN IN AN ENVIRONMENT CHARACTERIZED BY MODERATE
   LOW-LEVEL SHEAR/SRH. ISOLATED INSTANCES OF DAMAGING WINDS SHOULD BE
   THE MOST COMMON PROBABLE TODAY...BUT A TORNADO OR TWO COULD ALSO
   OCCUR.

   ...ARKLATEX/MID-SOUTH FRIDAY NIGHT...
   A SOMEWHAT SEPARATE SCENARIO MAY BE FOR RENEWED STORM DEVELOPMENT
   LATE TONIGHT/EARLY SATURDAY ACROSS THE REGION IN RESPONSE TO
   INCREASING WARM ADVECTION/FORCING FOR ASCENT NEAR/NORTH OF THE
   NORTH-NORTHWESTWARD SHIFTING SURFACE BOUNDARY. THE POTENTIAL WILL
   EXIST FOR WHAT SHOULD BE SLIGHTLY ELEVATED STORMS CAPABLE OF SOME
   HAIL/POSSIBLY WIND AS MID-LEVEL LAPSE RATES WILL BE STEEPENING
   ACROSS THE REGION.

 

 

A large area of flood watches so far

 

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It looks like the boundary that started all of this rain yesterday is finally about to push back north of the area. I'm not sure that I ever remember such a long period of sustained convection in winter. 4.5" here, and I feel lucky. It could have been a lot worse, and in some places it was.

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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NASHVILLE TN
1203 PM CST SAT DEC 26 2015

.UPDATE...
FOR MORNING AND 18Z AVIATION DISCUSSION.

&&

.DISCUSSION...

NOW THAT THE SHOWERS AND THUNDERSTORMS HAVE COMPLETELY PUSHED
NORTH OUT OF THE AREA THIS MORNING...IT`S TIME TO CUE ON THE
DAYTIME HEATING. IN FACT...NASHVILLE AIRPORT HAS ALREADY REACHED
74 DEGREES BREAKING TODAY`S HIGH TEMPERATURE RECORD WELL BEFORE
NOON. WITH MORE BREAKS IN THE CLOUDS EXPECTED...SEE NO REASON WHY
TEMPERATURES WILL NOT EASILY REACH THE MID TO UPPER 70S MOSTLY AREA
WIDE...SO HAVE BUMPED UP FORECAST HIGH TEMPERATURES SEVERAL
DEGREES. ALSO REMOVED MENTION OF SHOWERS AND THUNDERSTORMS ACROSS
AREAS SOUTH OF INTERSTATE 40 FOR THIS AFTERNOON.

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DAY 1 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   1143 PM CST SUN DEC 27 2015

   VALID 281200Z - 291200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF WRN AND MIDDLE
   TN...NRN AND ERN MS AND AL...

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER TO
   MID MS VALLEY...LOWER OH VALLEY AND GULF COAST STATES OUTSIDE OF THE
   SLIGHT RISK AREA...

   ...SUMMARY...
   A LINE OF SHOWERS AND THUNDERSTORMS WILL SPREAD EAST-NORTHEAST FROM
   THE LOWER MISSISSIPPI VALLEY ACROSS THE TENNESSEE VALLEY TODAY. A
   FEW STORMS MAY POSE THE RISK FOR ISOLATED DAMAGING WIND GUSTS AND
   PERHAPS A COUPLE TORNADOES THIS MORNING INTO THE AFTERNOON.

   ...CNTRL GULF COAST STATES/TN VALLEY...
   AN UPPER-LEVEL LOW AND NEGATIVELY-TILTED UPPER-LEVEL TROUGH WILL
   MOVE NEWD ACROSS THE MID MS VALLEY TODAY. AT THE SFC...A LOW WILL
   MOVE NNEWD FROM THE OZARKS INTO THE MID MS VALLEY AS A TRAILING COLD
   FRONT ADVANCES EWD ACROSS THE LOWER MS VALLEY INTO THE CNTRL GULF
   COAST STATES. A LINE OF THUNDERSTORMS WILL BE ONGOING ALONG THE
   FRONT AT THE START OF THE PERIOD WITH THIS LINE MOVING EWD ACROSS
   MS...TN AND AL FROM THIS MORNING INTO EARLY AFTERNOON. SFC DEWPOINTS
   AHEAD OF THE LINE IN THE UPPER 60S TO NEAR 70 F SHOULD CREATE ENOUGH
   INSTABILITY FOR STRONG UPDRAFTS WITH THE BETTER ORGANIZED SEGMENTS
   OF THE LINE.

   FORECAST SOUNDINGS IN ERN MS AND WRN AL AT 15Z TO 18Z SHOW MUCAPE
   VALUES FROM 800 TO 1200 J/KG WITH 0-6 KM SHEAR NEAR 50 KT. THE WIND
   PROFILE HAS STRONG SPEED SHEAR IN THE LOWEST 2 KM AGL WITH SOME
   DIRECTIONAL SHEAR BELOW 850 MB. THIS SHOULD BE ENOUGH FOR A WIND
   DAMAGE THREAT WITH BOWING LINE SEGMENTS. IN ADDITION...0-3 KM STORM
   RELATIVE HELICITIES AT OR ABOVE 400 M2/S2 SHOULD RESULT IN AN
   ISOLATED TORNADO THREAT LATE THIS MORNING FROM SW TN SWD ACROSS NE
   MS AND NW AL WITH ROTATING CELLS EMBEDDED IN THE LINE OR WITH
   DISCRETE CELLS AHEAD OF THE LINE. THE SEVERE THREAT IS EXPECTED TO
   CONTINUE INTO THE EARLY TO MID AFTERNOON AS THE LINE MOVES INTO
   MIDDLE TN AND ERN AL. HOWEVER...THE UPPER-LEVEL LOW WILL MOVE AWAY
   FROM THE WARM SECTOR AND SLIGHT RISK AREA RESULTING IN A GRADUAL
   DOWNTREND OF THE SEVERE THREAT BY THIS EVENING.

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DAY 1 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   0647 AM CST MON DEC 28 2015

   VALID 281300Z - 291200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM WEST TN INTO THE CENTRAL
   GULF COAST REGION...

   ...THERE IS A MRGL RISK OF SVR TSTMS OVER PARTS OF THE TN VALLEY AND
   GULF COAST STATES...

   ...SUMMARY...
   A LINE OF SHOWERS AND THUNDERSTORMS WILL SPREAD EAST-NORTHEAST FROM
   THE LOWER MISSISSIPPI VALLEY ACROSS THE TENNESSEE VALLEY TODAY. A
   FEW STORMS MAY POSE THE RISK FOR ISOLATED DAMAGING WIND GUSTS AND
   PERHAPS A COUPLE TORNADOES THIS MORNING INTO THE AFTERNOON.

   ...TN VALLEY INTO CENTRAL GULF COAST REGION...
   A SQUALL LINE EXTENDING FROM MID-SOUTH TO SOUTHEAST MS WITH
   PRECEDING DISCRETE/SEMI-DISCRETE CONVECTION CLOSER TO THE GULF
   COAST WILL CONTINUE PROGRESSING EWD THROUGH THE DAY WITHIN AN
   UNSEASONABLY WARM/HUMID AIR MASS. THIS ACTIVITY LIES WITHIN THE WARM
   SECTOR OF A DEEP SFC CYCLONE WHOSE CENTER IS TRACKING FROM ARKANSAS
   TO LAKE MICHIGAN...AND IS FORECAST TO OCCLUDE THROUGH THE DAY.
   MODEST DIURNAL HEATING IN ADVANCE OF ONGOING CONVECTION WILL SUPPORT
   MLCAPE FROM 250 TO 1000 J/KG FROM PARTS OF THE TN VALLEY TO THE
   CNTRL GULF COAST...SUPPORTING CONVECTIVE SUSTENANCE THROUGH AT LEAST
   MID-DAY ACROSS PARTS OF TN...AL...AND THE FL PANHANDLE. DESPITE ONLY
   MODEST MID-LEVEL LAPSE RATES...STRONG VERTICAL SHEAR PROFILES WITHIN
   THE WARM SECTOR WILL SUPPORT THE POTENTIAL FOR DMGG WIND GUSTS AND
   POSSIBLY A COUPLE OF TORNADOES. EVEN LESS INSTABILITY WITH NWD
   EXTEND AHEAD OF THE LINE WILL FURTHER MARGINALIZE THE SVR RISK INTO
   PARTS OF THE OHIO VALLEY.

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MESOSCALE DISCUSSION 2100
   NWS STORM PREDICTION CENTER NORMAN OK
   0838 AM CST MON DEC 28 2015

   AREAS AFFECTED...NRN AL / WRN-MIDDLE TN

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

   VALID 281438Z - 281545Z

   PROBABILITY OF WATCH ISSUANCE...60 PERCENT

   SUMMARY...THE THREAT FOR A TORNADO OR TWO...IN ADDITION TO ISOLATED
   DAMAGING WINDS...WILL INCREASE BY LATE THIS MORNING INTO THE EARLY
   AFTERNOON.

   DISCUSSION...RADAR MOSAIC SHOWS A SEVERE SQUALL LINE LOCATED OVER
   NERN MS INTO WRN TN/MO BOOTHEEL REGIONS.  A COMPACT/INTENSE
   MID-LEVEL LOW AND ASSOCIATED SPEED MAX OVER THE ARKLATEX THIS
   MORNING ARE FORECAST TO MOVE NNEWD INTO THE OZARK PLATEAU BY MIDDAY
   WITH 75 KT H5 FLOW MOVING NEWD FROM MS INTO THE TN VALLEY.  VERY
   STRONG LOW-LEVEL MASS FLUX/MOISTURE TRANSPORT INTO THE AREA
   ASSOCIATED WITH A 60+ KT LLJ IS CONTRIBUTING TO A DESTABILIZING
   AIRMASS DESPITE INITIALLY POOR TO MARGINAL BUOYANCY.  MODEL GUIDANCE
   SHOWS THE DEVELOPMENT OF 200-400 J/KG MLCAPE POSSIBLY DEVELOPING
   IMMEDIATELY AHEAD OF THE LINE AS IT MOVES ACROSS THE TN VALLEY
   DURING THE NEXT SEVERAL HOURS.  STRONG LOW-LEVEL SHEAR WILL
   CONDITIONALLY SUPPORT THE THREAT FOR ISOLD WIND DAMAGE AND PERHAPS A
   TORNADO OR TWO...ESPECIALLY WITH ANY CELLULAR ELEMENTS EMBEDDED
   WITHIN THE CONVECTIVE LINE.

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