Dec 23-24 storms OBS

[jaxjagman]

Figured it's time to start a thread,especially towards the 23-24 time frame.The models have shown since last evening into today some better PW's and convection even.The Euro is now showing the LLJ this afternoon at 50-55 kts.,0-6km shear is 65-70+ kts this coming Wednesday the 23rd this threat should be on going into the evening hours possible even without diurnal heating.But like all winter storms or any season in the Valley,we've seen what happens when we get convection further down south,we get pinched,we'll see.But this is looking more like a spring storm,look at the massive 591 ridge out in the Atlantic,rare event in the winter time

 

[ClicheVortex2014]

NWS Birmingham has a really alarming AFD this afternoon

 

 

NOW ON TO THE POSSIBLE HIGH IMPACT PART OF THE FORECAST...

MODELS ARE IN SIGNIFICANTLY BETTER AGREEMENT TODAY REGARDING THE
EVOLUTION OF THE UPPER-AIR PATTERN FOR WEDNESDAY...AND IT IS NOT
GOOD NEWS. SEVERAL HISTORIC COOL-SEASON SEVERE WEATHER ANALOGS ARE
SHOWING UP BASED ON THE FORECAST UPPER-AIR PATTERN. MODELS HAVE
TRENDED TOWARD THE ECMWF SOLUTION WITH MORE VORTICITY IN THE BASE
OF THE TROUGH ACROSS THE SOUTHERN PLAINS. THIS WILL CAUSE STRONG
SURFACE CYCLOGENESIS TO OCCUR TO OUR NORTHWEST AND SUBSTANTIAL
PRESSURE FALLS FARTHER SOUTH ACROSS INTO OUR AREA...LEADING TO
STRENGTHENING WIND FIELDS ACROSS A LARGE AREA. THE CONVECTIVE
EVOLUTION WITH THIS SYSTEM REMAINS A BIT UNCLEAR...BUT IT APPEARS
LESS LIKELY THAT COASTAL CONVECTION WILL BE A SIGNIFICANT
INHIBITING FACTOR IN POLEWARD MOISTURE ADVECTION. ONE POSSIBLE
SCENARIO IS THAT RAIN DEPARTS TO THE EAST DURING THE MORNING ON
WEDNESDAY...ALLOWING UNUSUALLY RICH GULF MOISTURE TO MOVE INLAND
FROM THE NORTHWESTERN GULF OF MEXICO. IF THIS OCCURS...CONDITIONS
COULD BECOME RIPE FOR A TORNADO OUTBREAK FROM THE LOWER MS VALLEY
EASTWARD INTO PARTS OF CENTRAL ALABAMA. FORECAST SOUNDINGS...
PARTICULARLY ACROSS THE NORTHERN AND WESTERN PARTS OF OUR AREA...
SHOW ABUNDANT LOW-LEVEL MOISTURE BENEATH STEEP MID-LEVEL LAPSE
RATES AND NEARLY TEXTBOOK WIND SHEAR PROFILES. IF THIS OCCURS...
SUPERCELLS WITH TORNADOES...DAMAGING WINDS...AND LARGE HAIL WOULD
BE POSSIBLE WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. IT IS
IMPOSSIBLE TO KNOW EXACTLY HOW MUCH GULF COAST CONVECTION WILL BE
PRESENT ON WEDNESDAY...AND IT MAY MAKE OR BREAK THIS FORECAST.

 

 

[jaxjagman]

NWS Birmingham has a really alarming AFD this afternoon

I was just checking out some discos and was going to post this,thanks Carver

[jaxjagman]

I know it's the NAM long range,STP is up to 2.8 Wed evening for us in Mid Tn

[HillsdaleMIWeather]

ECMWF at 12Z was showing alarmingly high instability for you folks, had a tornado outbreak on it.

[jaxjagman]

ECMWF at 12Z was showing alarmingly high instability for you folks, had a tornado outbreak on it.

Agree,the instability with the shear should not be over looked.I liked how it didnt show us getting crapvection down south

[jaxjagman]

NAM might be slower than most models but it still trended slower.Crazy dew points in the upper 60's,that's insane for winter in the Valley

 

Edit:Opps,thats not DP's but 2m's,dp's are in the lower 60's,my bad,got excited

[jaxjagman]

Kinda like i've been feeling looking at the latest NAM if the convection down south is toned down this will be a legit severe event in the Valley,the wind shear would make this a surreal threat into the afternoon into the evening

[jaxjagman]

Not as much convection down south,but there is still enough to throw a big wrench in for us in the Valley

[jaxjagman]

DAY 3 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   0229 AM CST MON DEC 21 2015

   VALID 231200Z - 241200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS WEDNESDAY ACROSS THE LOWER
   MISSISSIPPI VALLEY INTO PORTIONS OF THE TENNESSEE VALLEY...

   ...THERE IS A MRGL RISK OF SVR TSTMS WEDNESDAY INTO WEDNESDAY NIGHT
   ACROSS SURROUNDING AREAS OF THE MISSISSIPPI VALLEY...THE OHIO
   VALLEY...THE REMAINDER OF THE TENNESSEE VALLEY AND SOUTHERN
   APPALACHIANS...AND THE EASTERN GULF STATES...

   ...SUMMARY...
   SEVERE THUNDERSTORMS ARE POSSIBLE WEDNESDAY IN A CORRIDOR ACROSS THE
   LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE VALLEY.  THUNDERSTORMS
   MAY ALSO IMPACT PORTIONS OF THE MIDDLE MISSISSIPPI AND LOWER OHIO
   VALLEYS...AND EASTERN GULF COAST INTO SOUTHERN APPALACHIANS...WITH
   SOME RISK FOR SEVERE WEATHER.

   ...SYNOPSIS...
   THERE HAS BEEN LITTLE CHANGE FROM PRIOR MODEL RUNS CONCERNING THE
   LARGE-SCALE PATTERN EVOLUTION THROUGH THIS PERIOD.  AMPLIFIED
   MID/UPPER TROUGHING ACROSS THE PLAINS IS EXPECTED TO DEAMPLIFY AS
   THE MOST PROMINENT EMBEDDED SHORT WAVE PERTURBATION ACCELERATES
   NORTHEASTWARD...FROM THE CENTRAL/SOUTHERN PLAINS THROUGH THE GREAT
   LAKES REGION.  THIS IS EXPECTED TO COINCIDE THE WESTWARD EXPANSION
   OF SUBTROPICAL RIDGING ACROSS THE WESTERN GULF OF MEXICO INTO THE
   SOUTHEASTERN U.S. BY EARLY CHRISTMAS EVE...AS ANOTHER SIGNIFICANT
   SHORT WAVE TROUGH...WITHIN THE MID-LATITUDE WESTERLIES...APPROACHES
   THE PACIFIC COAST.

   IN LOWER LEVELS...THE SURFACE CYCLONE EXPECTED TO REACH THE LOWER
   CENTRAL PLAINS BY 12Z WEDNESDAY IS FORECAST TO RAPIDLY MIGRATE NORTH
   NORTHEASTWARD ACROSS THE MIDDLE MISSISSIPPI VALLEY...INTO AND
   THROUGH THE UPPER GREAT LAKES REGION DURING THE DAY WEDNESDAY.  IT
   LIKELY WILL CONTINUE INTO ONTARIO WEDNESDAY NIGHT...WITH A TRAILING
   COLD FRONT ADVANCING THROUGH THE GREAT LAKES AND OHIO VALLEY...WHILE
   STALLING AND WEAKENING OVER THE OZARK PLATEAU AND SOUTH CENTRAL
   PLAINS.

   THE MOST PROMINENT STRENGTHENING OF LOWER/MID TROPOSPHERIC WIND
   FIELDS ACROSS THE WARM SECTOR OF THE CYCLONE IS EXPECTED FROM THE
   OZARK PLATEAU TOWARD THE LOWER GREAT LAKES REGION...WHERE A BELT OF
   90+ KT FLOW AROUND 500 MB MAY DEVELOP BY LATE WEDNESDAY NIGHT.
   HOWEVER...MID-LEVEL FLOW AS FAR SOUTH AS THE LOWER MISSISSIPPI
   VALLEY SHOULD REMAIN MORE THAN AMPLE FOR ORGANIZED SEVERE STORM
   DEVELOPMENT...AND MODELS SUGGEST IT WILL REMAIN AT LEAST BROADLY
   CYCLONIC OVER VIRTUALLY ALL BUT THE GULF AND SOUTH ATLANTIC COAST
   STATES THROUGH MUCH OF THE PERIOD.

   A BROAD AREA OF MODERATE TO STRONG SOUTHERLY LOW-LEVEL FLOW
   /INCLUDING 40-50+ KT AT 850 MB/ WILL MAINTAIN MOISTURE RETURN OFF A
   MOIST AND UNSTABLE BOUNDARY LAYER OVER THE GULF OF MEXICO...INTO THE
   WARM SECTOR.  HOWEVER...CLOUD COVER AND CONVECTIVE PRECIPITATION MAY
   BE IMPACTING MUCH OF THE WARM SECTOR EARLY IN THE PERIOD...PERHAPS
   STILL INCLUDING A CLUSTER OR TWO OF STORMS NEAR CENTRAL INTO EASTERN
   GULF COASTAL AREAS.  THE INFLUENCE OF THIS ACTIVITY ON SUBSEQUENT
   WARM SECTOR BOUNDARY LAYER DESTABILIZATION REMAINS UNCLEAR...AND
   THIS REMAINS THE PRIMARY UNCERTAINTY CONCERNING SEVERE WEATHER
   POTENTIAL FOR THIS PERIOD.

   ...LOWER MISSISSIPPI VALLEY INTO TENNESSEE VALLEY...
   THE RISK OF SEVERE STORMS STILL APPEARS MOST CERTAIN WITHIN A SWATH
   EAST NORTHEAST OF THE ARKLATEX THROUGH THE NORTHWEST MISSISSIPPI
   DELTA REGION.  THIS IS WHERE A DEVELOPING MID-LEVEL DRY SLOT...IN
   ADVANCE OF AN AREA OF ENHANCED MID-LEVEL FORCING FOR ASCENT
   ASSOCIATED WITH THE MID-LATITUDE WAVE...MAY ALLOW INSOLATION TO
   CONTRIBUTE TO WEAK TO MODERATE BOUNDARY LAYER CAPE BY MID-DAY.  WITH
   THE ONSET OF LARGE-SCALE ASCENT...ORGANIZED SEVERE STORM
   DEVELOPMENT...INCLUDING SUPERCELLS...APPEARS POSSIBLE.  LARGE
   HAIL...LOCALLY DAMAGING WIND GUSTS AND A COUPLE OF TORNADOES ALL
   APPEAR POSSIBLE...WITH ACTIVITY SPREADING EAST
   NORTHEASTWARD...PERHAPS INTO AND THROUGH PORTIONS OF THE TENNESSEE
   VALLEY BY LATE WEDNESDAY AFTERNOON.

   MID/UPPER FORCING FOR ASCENT BECOMES INCREASINGLY UNCLEAR IN THE
   WAKE OF THIS EARLY ACTIVITY...SOUTHWARD TOWARD THE GULF COAST.
   HOWEVER...LINGERING WEAK MID-LEVEL INHIBITION...COUPLED WITH SURFACE
   HEATING...AND PERHAPS WEAK LOW-LEVEL WARM ADVECTION...MAY ALLOW FOR
   DISCRETE STORM DEVELOPMENT WEDNESDAY AFTERNOON ACROSS PARTS OF
   NORTHEASTERN LOUISIANA INTO SOUTHWESTERN MISSISSIPPI.  THIS SHOULD
   BE MOSTLY ALIGNED ALONG/WEST OF THE LINGERING 40-50 KT SOUTHERLY 850
   MB JET AXIS...WHICH WILL CONTRIBUTE TO FAVORABLE SHEAR FOR
   SUPERCELLS CAPABLE OF PRODUCING TORNADOES...AND MAY TRACK ACROSS
   PARTS OF SOUTH CENTRAL THROUGH EASTERN MISSISSIPPI AND WESTERN
   ALABAMA INTO EARLY EVENING.

[jaxjagman]

Models keep bumping up the STP in the SW section of the Valley.The NAM is ugly if that were verify,PDS in S/Mid/TN.late night.But take this with a grain of salt it's the NAM long range.Hope it is anyways,wouldnt be good while people are sleeping

[jaxjagman]

 

[ClicheVortex2014]

Dr. Forbes says tornado outbreak is likely. All the models have some alarming parameters

 

WEDNESDAY
Tornado outbreak likely, probably ongoing in the morning, in east TX, LA, south, central, and northeast AR, southeast MO, south IL, southwest IN, west KY, west and middle TN, west half AL, west FL panhandle, MS. TORCON - 5 west TN, east AR, MS, LA, east TX; 4 - west AL, middle TN; 3 - rest of area. The severe threat continues overnight in AL, west FL panhandle, middle and east TN, central and east KY, south IN. TORCON - 3 to 4 

[nrgjeff]

Pattern match at upper levels and wind fields all levels suggests severe potential. I favor Euro with that southern stream energy. However surface details and timing of other rain offer still many questions. Looks like the average Day 3 winter situation in the South. I do not infer a major outbreak as I type on Monday. Looking for more certain clearing ahead of and along a pre-frontal surface trough. Sure thunder would be a nice gift, but huddling in the interior room with helmets and a mattress is not the kind of holiday family time I have in mind.

[ClicheVortex2014]

More strong wording from BMX

 

NATIONAL WEATHER SERVICE BIRMINGHAM AL
324 PM CST MON DEC 21 2015

.DISCUSSION...

THE SEVERE WEATHER THREAT FOR TUESDAY WAS REMOVED FROM THE
FORECAST. CONVECTION NEAR THE GULF COAST SHOULD LIMIT INSTABILITY
ACROSS OUR AREA THROUGH TUESDAY AFTERNOON.

THERE IS GROWING CONCERN REGARDING THE SEVERE WEATHER POTENTIAL
FOR WEDNESDAY INTO WEDNESDAY NIGHT. THE POTENTIAL FOR DISRUPTIVE
COASTAL CONVECTION CONTINUES TO DECREASE AS WE APPROACH THE EVENT.
IN FACT...THERE IS LITTLE TO NO CONVECTION TO BE FOUND ON THE 4KM
NAM...NMM...AND ARW MODELS AT 12Z WEDNESDAY. THIS IS EXTREMELY
CONCERNING BECAUSE A BROAD WARM SECTOR WILL DEVELOP WELL INLAND IF
THESE MODELS ARE ACCURATE. WITH UPPER-LEVEL SUPPORT REMOVED FROM
THE GULF COAST...AND STRAIGHT SOUTHERLY FLOW INDICATED BY THE
SURFACE ISOBARS...I BELIEVE REASON FOR WIDESPREAD MODEL QPF ALONG
THE COAST IS MAINLY DUE TO CONVECTIVE FEEDBACK IN GLOBAL MODELS.

THE LOW-AMPLITUDE NATURE OF THE TROUGH WILL ALLOW STEEP LAPSE
RATES TO OVERSPREAD A RICH WARM SECTOR. IF THIS WARM SECTOR
DEVELOPS...UPPER-LEVEL JET SUPPORT WOULD AID IN AIRMASS/CELLULAR
TYPE DEVELOPMENT WEDNESDAY AFTERNOON AND EVENING WITH AN
ENVIRONMENT SUFFICIENT FOR LONG-TRACK SUPERCELLS AND TORNADOES.
THE MOST FAVORABLE REGION FOR LONG-TRACK TORNADOES SHOULD BE
ACROSS THE NORTH AND WEST...NORTH OF THE 576 DM 500 MB HEIGHT
CONTOUR...WHERE 500 MB WINDS WILL EXCEED 60 KTS. WE WILL HOLD OUR
THREAT LEVELS STEADY FOR THIS UPDATE AND MAKE SURE WE DON`T JUMP
THE GUN. IF SHORT-RANGE MODELS TOMORROW AFTERNOON INDICATE LITTLE
TO NO GULF CONVECTION ON WEDNESDAY MORNING...AN UPGRADE TO THE
THREAT WILL BE NEEDED.

THE SEVERE THREAT SHOULD SLOWLY DIMINISH AFTER 03Z THURSDAY AS
THE BEST UPPER-LEVEL SUPPORT MOVES AWAY AND THE LOW-LEVEL JET
WEAKENS. HEIGHT RISES WILL OCCUR ON THURSDAY...BUT A VERY MOIST
AIRMASS COULD RESULT IN ISOLATED THUNDERSTORM DEVELOPMENT NEAR A
TRAILING CONFLUENCE ZONE. DEEP-LAYER SHEAR AND TALL CAPE PROFILES
WOULD SUPPORT A LOW-END THREAT FOR ISOLATED DAMAGING WINDS AND
HAIL IF STORMS DEVELOP.

 

[Carvers Gap]

You all know the rule about thunder in the mountains during winter...I am telling ya, it generally is true.  Keep us updated all.  Good info.

[Reed Stough]

Just looking at the NAM-4K and it is getting a little scary to see some of the numbers coming in.  However, the last couple of severe weather events the models have been bullish and the events failed to really live up to what was forecasted.  So I am waiting for the actual day before getting too excited.

 

[jaxjagman]

...SHORT WAVE NEAR THE PACIFIC NORTHWEST MON...
...LOW PRESSURE FORMING OVER THE PLAINS/MIDWEST WED...

PREFERENCE: 12Z GFS/12Z ECMWF
CONFIDENCE: AVERAGE

THE 12Z NAM CONTINUES TO HAVE PROBLEMS RESOLVING THE SHORT WAVE
COMING INTO THE PACIFIC NORTHWEST MON...AND ITS TIMING OF THE
SHORT WAVE CROSSING THE NORTHERN PLAINS HEADED TO THE GREAT LAKES
HAS BEEN VARIABLE. BECAUSE OF THE TIMING ISSUES...THE 12Z NAM IS
NOT PREFERRED WITH THE SHORT WAVE...AND DEVELOPING SURFACE LOW
OVER KS (WHERE IS APPEARS TO BE TOO SLOW/DEEP...COMPARED TO THE
CONSENSUS). THE 12Z GFS APPEARS TO HAVE A BETTER HANDLE ON THE
SHORT WAVE ENERGY ENTERING THE PACIFIC NORTHWEST. THE 12Z UKMET IS
AGAIN FASTER AND FURTHER SOUTH WITH THE SURFACE LOW...WHILE THE
12Z CMC IS SLOWER AND WEAKER.

THE 12Z ECMWF IS A BIT SLOWER WITH THE SHORT WAVE ENERGY THAT
SPINS UP THE SURFACE LOW OVER NORTHERN MO AT THE END OF DAY
2...AND THE RESULTANT SURFACE LOW IS WEAKER AND SLOWER THAN THE
12Z GFS. THESE DIFFERENCES ARE NOT LARGE ENOUGH TO DROP THE 12Z
ECMWF FROM THE PREFERENCE...SO THE RECOMMENDATION REMAINS A BLEND
OF THE 12Z ECWMF/GFS.

...SHORT WAVE ACTIVITY PATTERN OVER THE OH AND TN VALLEYS INTO THE
EAST TUE/WED...

PREFERENCE: 12Z GFS/12Z ECMWF
CONFIDENCE: AVERAGE

THE 12Z NAM APPEARS TO BE HAVING DIFFICULTIES WITH THE SHORT WAVE
ENERGY IN THE TN/OH VALLEYS DURING THE TUE/WED TIME FRAME...AND
THIS COULD BE TIED TO THE DIFFICULTIES THE NAM IS EXPERIENCING
ACROSS THE PACIFIC NORTHWEST. THE 12Z GFS/12Z ECMWF ARE AT THE
CENTER OF THE MODEL CONSENSUS WITH THE SHORT WAVE ENERGY...WHILE
THE 00Z UKMET IS TOO FAST WITH THE SHORT WAVE ENERGY MOVING INTO

THE UPPER GREAT LAKES WED NIGHT.

http://www.wpc.ncep.noaa.gov/discussions/hpcdiscussions.php?disc=pmdhmd

[yoda]

DAY 2 CONVECTIVE OUTLOOK  

NWS STORM PREDICTION CENTER NORMAN OK  

1256 AM CST TUE DEC 22 2015  

 

VALID 231200Z - 241200Z  

 

...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PARTS OF THE MID-SOUTH  

AND TN VALLEY...  

 

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE ENH FROM PARTS  

OF THE LOWER GREAT LAKES REGION TO THE CNTRL GULF COAST...  

 

...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLGT FROM PARTS  

OF THE LOWER GREAT LAKES REGION TO THE CNTRL GULF COAST...  

   

..SUMMARY  

 

THE POTENTIAL FOR SEVERE THUNDERSTORMS WILL EXTEND FROM THE CENTRAL  

GULF COAST TO THE LOWER GREAT LAKES REGION ON WEDNESDAY INTO  

WEDNESDAY NIGHT. THE GREATEST POTENTIAL FOR SEVERE THUNDERSTORMS IS  

FORECAST FROM PORTIONS OF THE MID-SOUTH REGION TO THE TENNESSEE  

VALLEY...WHERE TORNADOES...SOME POSSIBLY SIGNIFICANT...ALONG WITH  

DAMAGING WINDS AND HAIL WILL BE POSSIBLE.  

   

..SYNOPSIS  

 

WITHIN A BELT OF BROADLY CYCLONIC MID-LEVEL FLOW COVERING MUCH OF  

THE WRN TWO-THIRDS OF THE CONUS...A SHORTWAVE TROUGH IS FORECAST TO  

QUICKLY PROGRESS FROM THE SRN GREAT PLAINS TO THE GREAT LAKES  

REGION. AS THIS OCCURS...A SFC CYCLONE WILL DEVELOP NEWD FROM THE  

CNTRL GREAT PLAINS TO LAKE SUPERIOR...WITH A STRONG LLJ IN THE WARM  

SECTOR ATTENDANT TO THE SFC CYCLONE. THIS WILL ENCOURAGE INLAND  

FLUXES OF GULF-MODIFIED MOISTURE...WITH A BROAD CORRIDOR OF 60S SFC  

DEWPOINTS BECOMING ESTABLISHED ACROSS THE SERN QUARTER OF THE CONUS  

EXTENDING AS FAR N AS THE OHIO VALLEY. THE WRN EXTENT OF THE RICHER  

MOISTURE WILL BE MARKED BY A BOUNDARY EXTENDING SWWD FROM THE  

AFOREMENTIONED SFC LOW TO S TX.  

   

..CNTRL GULF COAST TO THE OHIO VALLEY  

 

AS THE BROAD WARM/MOIST SECTOR BECOMES ESTABLISHED FROM PORTIONS OF  

THE GREAT LAKES REGION TO THE CNTRL GULF COAST AND COINCIDES WITH  

AMPLE DEEP SHEAR...A LONG-DURATION/SPATIALLY EXTENSIVE SVR RISK WILL  

EXIST THROUGH THE D2/WED PERIOD. MULTIPLE CORRIDORS OF STRONG TO SVR  

TSTMS WILL BE LIKELY ACROSS THE WARM SECTOR...FOCUSED IN A VARIETY  

OF REGIMES. DCVA PRECEDING THE SHORTWAVE TROUGH AND RELATED  

DESTABILIZATION WILL ENHANCE TSTM ACTIVITY FROM PARTS OF THE MID-MS  

VALLEY TO PORTIONS OF THE LOWER GREAT LAKES AND OHIO VALLEY  

REGION...WHERE BUOYANCY WILL BE RELATIVELY MARGINAL.  

MEANWHILE...AMPLE LOW-LEVEL MOISTURE CHARACTERIZED BY LOWER/MIDDLE  

70S SFC DEWPOINTS CURRENTLY RESIDES OFF THE GULF COAST. GIVEN  

ANTICIPATED NWD TRANSPORT OF THE RICH MOISTURE...AT LEAST ISOLATED  

SVR TSTMS WILL BE POSSIBLE SWD TO THE GULF COAST THROUGH THE PERIOD.  

 

THE OVERLAP OF STRONGER DEEP ASCENT PERIPHERAL TO THE SHORTWAVE  

TROUGH...AND MLCAPE OF 500-1250 J/KG AIDED BY SFC DEWPOINTS AROUND  

63-66F...IS FORECAST TO EXIST FROM PARTS OF THE LOWER MS VALLEY TO  

THE TN VALLEY AND VICINITY DURING PEAK HEATING. WITH AT LEAST  

POCKETS OF INSOLATION SUPPORTING STEEPENING LOW-LEVEL LAPSE RATES  

ACROSS THIS AREA...AND AN INFLUX OF MODESTLY STEEP MID-LEVEL LAPSE  

RATES...DIURNAL SUPERCELL DEVELOPMENT WILL BE MORE LIKELY IN THIS  

REGION. THIS WILL BE AIDED BY 50-60 KT OF DEEP SHEAR ORIENTED WITH  

AT LEAST SOME ORTHOGONAL COMPONENT TO THE SFC BOUNDARY. WITH 60-70  

KT OF H7 FLOW ABOVE 45-55 KT OF H85 FLOW...LOW-LEVEL SHEAR WILL BE  

ADEQUATE FOR TORNADOES...SOME POTENTIALLY SIGNIFICANT. DMGG WIND  

GUSTS AND HAIL MAY ALSO ACCOMPANY THIS ACTIVITY. SVR-TSTM POTENTIAL  

WILL BE MORE ISOLATED FARTHER S TOWARD THE GULF COAST AS DEEP ASCENT  

WILL BE MORE LACKING...THOUGH STRONGER INSTABILITY WILL BE AIDED BY  

RICHER LOW-LEVEL MOISTURE IN PROXIMITY TO THE COAST.  

 

THE SVR TSTM POTENTIAL -- INCLUDING RISK FOR TORNADOES AND DMGG  

WINDS -- WILL SPREAD EWD/ENEWD ACROSS THE RISK AREAS THROUGH WED  

NIGHT. SVR TSTM POTENTIAL MAY LAST WELL INTO THE OVERNIGHT HOURS  

FROM THE TN VALLEY SWD...WHERE NOCTURNAL GAINS IN MLCINH WILL BE  

LIMITED BY THE RETURNING LOW-LEVEL MOISTURE.

[yoda]

[John1122]

Whew, this will be a rocky one, you're going to have a ton of last minute shoppers and things like that out and about. The highest risk area is basically the most deadly area of the entire country for tornadoes as well. 

 

[jaxjagman]

NAM,still is sticking with this crazy and wild set up.Euro looks in between and the GFS looks the weaker out of the three.Euro during the early morning/afternoon has the strong LLJ 60+ KTS over La that quickly moves into the Valley by late afternoon,early evening.Plenty of 0-1(km) shear 35-40kts from the gulf into the great lakes.Shear at 0-6(km) is best in the middle and west parts of the valley 70+ kts and lesser towards the east but shouldn't matter it looks ample enough for severe if something fires up.

[jaxjagman]

Euro last night showed some of the best PW's yet from that model .Maybe a hair less to the west but 1.4"+ for the rest going west to east.Showalter shows good convection from south of Birmingham into the parts/all of the Mid Valley,slight lesser to the far west late/ afternoon,early evening then -2/-3 into the evening for the east.But this could change today.,anything can

[jaxjagman]

That would be a good light show towards Lawrenceburg.K index at 41 in the early evening on the 4k NAM,pretty ugly hodo as well

[jaxjagman]

DAY 2 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   1130 AM CST TUE DEC 22 2015

   VALID 231200Z - 241200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS FROM THE LOWER MS VALLEY INTO
   THE TN VALLEY...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CNTRL GULF COAST TO
   JUST SOUTH OF CHICAGO...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLGT RISK FROM
   THE UPPER TX COAST TO SRN LOWER MI...

   ...SUMMARY...
   THE POTENTIAL FOR SEVERE THUNDERSTORMS WILL EXTEND FROM THE CENTRAL
   GULF COAST TO THE LOWER GREAT LAKES REGION ON WEDNESDAY INTO
   WEDNESDAY NIGHT. THE GREATEST POTENTIAL FOR SEVERE THUNDERSTORMS IS
   FORECAST FROM PORTIONS OF THE MID-SOUTH REGION TO THE TENNESSEE
   VALLEY...WHERE TORNADOES...SOME SIGNIFICANT...ALONG WITH DAMAGING
   WINDS AND HAIL WILL BE POSSIBLE.

   ...DISCUSSION...

   STRONG HIGH-LEVEL FLOW IS FORECAST TO TRANSLATE ALONG A CORRIDOR
   FROM THE GREAT BASIN...INTO THE BASE OF CNTRL U.S. TROUGH OVER
   TX...THEN NEWD INTO THE GREAT LAKES EARLY IN THE PERIOD.  FOCUSED
   12HR MID-LEVEL HEIGHT FALLS WILL SHIFT FROM KS/OK INTO THE UPPER
   GREAT LAKES BY LATE AFTERNOON AS SFC CYCLONE SHIFTS FROM NERN KS
   INTO THE U.P. OF MI.  IN RESPONSE TO THIS LARGE-SCALE
   ADJUSTMENT...STRONG WARM ADVECTION WILL BE RESPONSIBLE FOR LATE DAY1
   INTO EARLY DAY2 CONVECTION ACROSS MUCH OF THE GULF STATES AND
   MID-SOUTH REGION.  THIS EARLY PERIOD TSTM ACTIVITY WILL INHIBIT
   DESTABILIZATION WITHIN BROADER RECOVERY PORTIONS OF THE OH/ERN TN
   VALLEY.

   LATEST THINKING IS A PW SURGE WILL ADVANCE NWD ACROSS ERN TX/OK LATE
   DAY1 AHEAD OF SURGING COLD FRONT.  THIS MOISTURE PLUME SHOULD SHIFT
   INTO THE LOWER/MID MS VALLEY BY MID DAY AND THE MOST SIGNIFICANT
   DESTABILIZATION IS EXPECTED ALONG WRN FRINGE OF AFOREMENTIONED WARM
   ADVECTION TSTM ACTIVITY.  LATEST MODEL GUIDANCE SUGGESTS STRONGEST
   BOUNDARY LAYER HEATING AND STEEPEST LOW-LEVEL LAPSE RATES WILL
   EVOLVE FROM CNTRL AR...NEWD INTO IL.  IF SUFFICIENT LOW-LEVEL
   MOISTURE CAN RETURN INTO THIS CORRIDOR THEN A MORE CONCENTRATED AREA
   OF STRONG/SEVERE TSTMS CAN BE EXPECTED AHEAD OF COLD FRONT.  AT THIS
   TIME IT APPEARS ROBUST UPDRAFTS WILL DEVELOP BY MID DAY ACROSS
   AR/NRN LA THEN TRACK NEWD INTO THE WRN TN VALLEY.  VERY STRONG SHEAR
   ALONG SRN FRINGES OF MID-LEVEL HEIGHT FALL REGION APPEARS TO BE THE
   FAVORED CORRIDOR FOR POTENTIAL LONG-LIVED SUPERCELLS AND PERHAPS A
   FEW STRONG TORNADOES.

   IF SUFFICIENT BUOYANCY CAN DEVELOP FARTHER NORTH ACROSS IL/IND THEN
   A DAMAGING SQUALL LINE COULD EVOLVE WITH SEVERE WIND GUSTS.  STRONG
   FORCING WILL BE MORE SUPPORTIVE OF A LINEAR MCS ACROSS THE OH VALLEY
   AS 90KT 500MB SPEED MAX EJECTS INTO THIS REGION DURING THE EVENING
   HOURS.  FOR THIS REASON HAVE EXPANDED SEVERE PROBS A BIT NORTH TO
   ACCOUNT FOR STRONG FORCING.

   ..DARROW.. 12/22/2015

[jaxjagman]

Nashville disco

 

THE 1ST EVENT WILL OCCUR TOMORROW AFTERNOON AND EVENING AS A COLD
FRONT APPROACHES OUR AREA FROM THE WEST. THE MOST IMPRESSIVE FEATURE
WITH THIS SYSTEM WILL BE THE LOW LEVEL WIND ENERGY AND SHEAR.
HELICITY VALUES ARE GOING TO BE QUITE STRONG...AND LLJ-OMEGA
INTERACTION IS EXPECTED WITHIN AN INCREASINGLY UNSTABLE AIRMASS. THE
LIKELIHOOD FOR WIDESPREAD SEVERE WEATHER IS ENHANCED AS IT
STANDS...AND MAY BE UPGRADED BY SPC INTO THE MODERATE RANGE BY
TOMORROW MORNING. THE TIMEFRAME LOOKS TO BE BETWEEN 4PM AND
MIDNIGHT...BUT CANNOT RULE OUT A FEW STRONG STORMS AS EARLY AS THE
LATE MORNING HOURS IN ADVANCE OF THE MAIN ASSAULT. I WILL INCLUDE
SEVERE STORM WORDING IN THE ZONES AND GFE. THIS WILL INCLUDE
DAMAGING WINDS AND THE POTENTIAL FOR TORNADIC DEVELOPMENT AS WELL.

THE 2ND EVENT WILL OCCUR ON FRIDAY AS A WARM FRONT LIFTS NORTHWARD
ACROSS THE AREA. CAPES AND SHOWALTER VALUES WILL ELEVATE BY FRIDAY
AFTERNOON. LOTS OF ENERGY TO WORK WITH AS TEMPS FRIDAY MORNING TO
THE NORTH OF THE BOUNDARY WILL BE A GOOD 15 TO 20 DEGREES ABOVE
NORMAL. BY AFTERNOON...OMEGA FIELDS WILL ALIGN WITH WITH A 30-40 KT
LLJ TO ALLOW THE DEVELOPMENT OF STRONG THUNDERSTORMS. THE SEVERE
THRESHOLD LOOKS LIKE IT WILL BE HELD IN CHECK FOR NOW. W-E FRONTAL
CONFIGURATIONS GENERALLY BRING A LESSER THREAT OF SEVERE WEATHER.
NEVERTHELESS...THE INSTABILITY WILL BE IN PLACE.

THE 3RD EVENT WILL OCCUR SUN NT AND MONDAY. THOUGH WE ARE NOT
CURRENTLY OUTLOOKED...THIS SYSTEM WILL NEED TO BE CLOSELY MONITORED
AS WELL. ITS ORIGINS WILL OCCUR OVER THE WESTERN TX AREA. A POWERFUL
WINTER SYSTEM COULD SPREAD MASSIVE HEADACHES ACROSS CENTRAL AND
SOUTHERN PLAINS AREA. THE ASSOCIATED SFC LOW WILL TRACK NORTHEAST
TOWARD THE MIDWEST. A STRONG TRAILING COLD FRONT WILL REACH AND MOVE
ACROSS THE MID STATE SOMETIME ON MONDAY. WITH PRE-FRONTAL FORCING
LIKELY AND A VERY IMPRESSIVE WARM WEDGE IN PLACE...ANOTHER SEVERE
THREAT COULD BE IN THE CARDS FOR SUNDAY NT AND MONDAY. WILL NEED
TO AWAIT SPC`S VIEW ON THIS IN FUTURE RUNS.

ON TUESDAY...PACIFIC AIRMASS WILL BUILD IN. MAYBE...AND I MEAN
MAYBE...WE COULD COOL TO NEAR SEASONAL.

HANG ON TO YOUR HATS ALL...COULD BE A ROUGH HOLIDAY RIDE AHEAD.

http://forecast.weather.gov/product.php?site=OHX&issuedby=OHX&product=AFD&format=CI&version=1&glossary=1

[jaxjagman]

Memphis

 

.DISCUSSION...

...THE POTENTIAL FOR A SIGNIFICANT SEVERE THUNDERSTORM OUTBREAK
ACROSS THE ENTIRE MIDSOUTH CONTINUES TO INCREASE STRONG TORNADOES
ARE POSSIBLE...

AN ABNORMAL WEATHER PATTERN IS IN PLACE ACROSS THE
MIDSOUTH...FEATURING VERY UNSTABLE CONDITIONS AND WHAT LOOKS TO BE
AN ADEQUATE AMOUNT OF SHEAR TO BALANCE THE THERMODYNAMICS.
TEMPERATURES ARE IN THE MIDDLE 60S TO LOW 70S ACROSS THE
REGION...AROUND 25 DEGREES ABOVE NORMAL. DEW POINTS ARE IN THE
UPPER 50S TO LOW 60S...BUT SOUTHERLY WIND WILL KEEP DEWPOINTS
RISING AS GULF MOISTURE FLOODS THE MIDSOUTH. OVER THE NEXT 24
HOURS OR SO A VERY BROAD TROUGH WILL SHIFT ACROSS THE PLAINS.  LATE
TONIGHT INTO EARLY TOMORROW ITS AXIS SHOULD BE OVER CENTRAL
OKLAHOMA...WITH A NEGATIVELY TILTED SHORTWAVE APPROACHING THE
MISSISSIPPI RIVER VALLEY. ONE OF THE MORE SIGNIFICANT CHANGES IN
MODEL GUIDANCE OVER THE LAST 24 HOURS IS THE DEVELOPMENT OF
DIURNAL THUNDERSTORMS ALONG AND WEST OF THE MISSISSIPPI RIVER
TONIGHT. BOTH THE NAM AND GFS INDICATE IN EXCESS OF 1000 J/KG CAPE
IN PLACE AS THE SHORTWAVE APPROACHES. A STRONG LLJ NEAR 100KT IS
ALREADY IN PLACE...STREAMING FROM THE SOUTHWEST GULF OF MEXICO
ACROSS THE MIDSOUTH. IF THUNDERSTORMS DEVELOP...THEY WOULD ALMOST
CERTAINLY QUICKLY STRENGTHEN TO SEVERE LIMITS. SIGNIFICANT HEIGHT
FALLS...ON THE ORDER OF 4DM/12HR WILL BEGIN AROUND MIDNIGHT...WITH
AS MUCH AS 8DM/12HR MY MIDDAY TOMORROW. THE STORM PREDICTION
CENTER HAS INCLUDED MOST OF THE MIDSOUTH WEST OF THE MISSISSIPPI
RIVER IN AN ENHANCED OUTLOOK FOR SEVERE THUNDERSTORMS TONIGHT.

STILL FEEL LIKE THE MOST WIDESPREAD AND STRONGEST STORMS WILL BE
TOMORROW...WITH THE HIGHEST THREAT ALONG THE SOUTH OF THE INTERSTATE
40 CORRIDOR...BUT SEVERE WEATHER IS POSSIBLE ACROSS ALL OF THE
MIDSOUTH. THE STRONG LLJ WILL BRING A COASTAL AIRMASS ACROSS THE
MIDSOUTH TOMORROW AFTERNOON. DEW POINTS WILL CERTAINLY BE IN THE
MIDDLE 60S ACROSS MOST OF THE AREA...AND MAY CLIMB INTO THE UPPER
60S IN NORTH MISSISSIPPI. RESULTING SURFACE BASED INSTABILITY
COULD EXCEED 1200J/KG. LOW LEVEL LAPSE RATES ON THE ORDER OF 6C
AND 30-40 DEGREES OF DIFFLUENCE ALOFT SHOULD HELP MAINTAIN
SUSTAINED HEALTHY UPDRAFTS. 0-3KT SRH WILL BE IN EXCESS OF
300M^2/S^2 IN NORTH MISSISSIPPI TOMORROW AT MIDDAY...WEAKENING
ONLY SLIGHTLY TO AROUND 250M^2/S^2 BY SUNSET. AS A RESULT A FEW
STRONG TORNADOES ARE POSSIBLE...ESPECIALLY IN NORTH MISSISSIPPI.
IN ADDITION...DAMAGING WIND AND LARGE HAIL ARE THREATS AREA WIDE
TOMORROW. THE SEVERE THREAT SHOULD DIMINISH AFTER SUNSET.

THURSDAY SHOULD BE MOSTLY DRY...ALTHOUGH A FEW SHOWERS MAY LINGER
IN FAR EASTERN PORTIONS OF THE MIDSOUTH NEAR THE ALABAMA STATE
LINE AND TENNESSEE RIVER.

WE WILL REMAIN IN AN ACTIVE PATTERN
AFTER TOMORROW. FRIDAY THROUGH MONDAY...LONG RANGE MODELS INDICATE
THE FRONT WILL BEGIN TO RETURN BACK NORTH AS A WARM FRONT ACROSS
THE FORECAST AREA ON CHRISTMAS DAY. THIS WILL RESULT IN THE
DEVELOPMENT OF ADDITIONAL SHOWERS AND THUNDERSTORMS ACROSS THE MID
SOUTH THURSDAY NIGHT AND ESPECIALLY ON FRIDAY. ADDITIONAL STRONG
TO SEVERE THUNDERSTORMS MAY BE POSSIBLE ON CHRISTMAS DAY. LONG
TERM MODELS BEGIN TO DIVERGE GREATLY WITH RUN TO RUN CONTINUITY AS
AN UPPER LEVEL LOW MOVES FROM THE PLAINS INTO THE MISSISSIPPI
VALLEY TOWARDS EARLY NEXT WEEK. THUS OVERALL CONFIDENCE IN
PRECIPITATION CHANCES MAY NEED TO BE ADJUSTED IN SUBSEQUENT
FORECASTS FOR THIS WEEKEND AND ESPECIALLY EARLY NEXT WEEK.

30

[dwagner88]

Very surprised at the lack of information from MRX about this event. I realize we are on the edge of the severe threat, but I also imagine that the whole CWA needs to be in a flood watch. They have no products out at all right now, just a mention of possible thunderstorms tomorrow night.

[Reed Stough]

I am beginning to question this event.  It is only the NAM 4KM that is showing no GOM convection.  Other models including the HRRR, NAM, and RAP are showing somekind of GOM convection.  If that occurs the Enhanced Risk will be gone tomorrow and it will bust. 

[jaxjagman]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NASHVILLE TN
226 AM CST WED DEC 23 2015

.DISCUSSION...

...SEVERE STORMS WITH TORNADOES POSSIBLE IN THE MID STATE THIS
AFTERNOON AND EVENING...

...SREF HAS SIGNIFICANT TORNADO PARAMETER AT 5 FOR MID STATE THIS
AFTERNOON AND EVENING...

...THE LAST TIME A TORNADO OCCURRED IN THE MONTH OF DECEMBER IN
TENNESSEE WAS BACK IN 2000 IN LINCOLN COUNTY...AND BEFORE THAT IN
1988 IN WILLIAMSON COUNTY...DECEMBER TORNADOES ARE SOMEWHAT
RARE...

FOR DISCUSSION PURPOSES WILL CONCENTRATE ON TODAY AND TONIGHT.
MADE ONLY MINOR TWEAKS TO THE EXTENDED. LONG WAVE TROUGH ACROSS
CENTRAL U.S. WILL AMPLIFY AS STRONG HEIGHT FALL CENTER IN EXCESS
OF 90 METERS PUSHES ACROSS NORTH TEXAS DURING THE DAY. UPPER
TROUGH WILL TAKE ON NEGATIVE TILT AS IT WORKS INTO OUR AREA THIS
AFTERNOON AND EVENING AS EMBEDDED SHORT WAVE SWINGS THIS WAY.
STRONG MOISTURE TRANSPORT WILL GET UNDERWAY DURING THE DAY FROM
GULF REGION DRIVING PRECIPITABLE WATER WELL ABOVE CLIIMATOLOGY FOR
THIS TIME OF THE YEAR. 60 DEGREE DEWPOINTS ALREADY IN PLACE WITH
CURRENT TEMPS IN THE LOW 60`S. 986 MBAR SURFACE LOW CENTER
CURRENTLY OVER WESTERN PANHANDLE OF OKLAHOMA...WARM FRONT DRAPED
FROM LOW CENTER ACROSS NORTHERN MISSOURI...SOUTHERN ILLINOIS THEN
UP INTO SOUTHERN INDIANA AND NORTHERN OHIO. MID STATE WILL BE IN
WARM SECTOR FOR THIS SEVERE WEATHER EVENT WITH MUCAPES ON THE
ORDER OF 500 TO 750 JOULES PER KILOGRAM AT 00Z TODAY. LIFTED
INDICES GO TO -4 THIS AFTERNOON/EVENING AS 850 MBAR JET CLIMBS TO
50-70 KNOTS AT 00Z. AS IF THIS IS NOT ENOUGH THE 700 MBAR TO 500
MBAR LAPSE RATES OFF 00Z OHX SOUNDING AT 7.7 DEGS CELSIUS PER
KILOMETER.