Nov 21-22 severe weather event

[janetjanet998]

since this event will likely involve multiple subforums lets try posting it in the "hard core" main thread and see how that goes.....

There is already a thread for the day two event here...mosty for the Texas/OK portion

http://www.americanw...sode-nov-21-22/

so perhaps this thread will be used mostly for the Tuesday event.

DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1200 AM CST SUN NOV 20 2011

VALID 211200Z - 221200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS W TX TO WRN AR...

...SYNOPSIS...

AS OF 20/05Z...MOISTURE CHANNEL IMAGERY INDICATED MID-UPPER LOW

ABOUT 125 NM WNW CAPE MENDOCINO...WITH SHORTWAVE TROUGH SWWD ACROSS

PAC. THIS POSITION IS MORE NLY THAN PROGGED BY MOST MODEL RUNS

DURING PREVIOUS DAYS...AS WILL BE INLAND TRACK OF SHORTWAVE TROUGH

THROUGH DAY-2 PERIOD. STG VORTICITY LOBE WILL MOVE S OF CURRENT

SYSTEM-RELATIVE LOW POSITION...RESULTING IN SOMEWHAT

NEGATIVELY-TILTED...HIGH-AMPLITUDE...OPEN-WAVE TROUGH FROM ERN NV TO

NRN GULF OF CA BY BEGINNING OF PERIOD. TROUGH SHOULD MOVE EWD TO

CENTRAL/SRN NM...FAR W TX AND NRN CHIHUAHUA BY 22/00Z...BECOMING

POSITIVELY TILTED FROM ERN KS TO W-CENTRAL TX BY 22/12Z.

STG SFC COLD FRONT NOW MOVING SEWD OVER ERN MO...S-CENTRAL OK AND

SWRN PANHANDLE OF TX WILL DECELERATE THROUGH DAY-1 PERIOD...BECOMING

QUASISTATIONARY BY 21/12Z OVER SRN KY...WRN TN...CENTRAL AR...AND

NERN THROUGH W-CENTRAL TX. OPERATIONAL SPECTRAL/NAM AND ALL SREF

MEMBERS RETREAT BOUNDARY SLOWLY NWD AS WARM FRONT ACROSS N-CENTRAL

TX AND SE OK DURING 21/18Z-22/00Z TIME FRAME. FRONTAL-WAVE LOW

SHOULD DEVELOP OVER W-CENTRAL TO N-CENTRAL TX AROUND 22/00Z...THEN

MOVE NEWD AND STRENGTHEN...REACHING SERN MO BY END OF PERIOD.

BEHIND THIS LOW...COLD FRONT SHOULD SURGE SEWD ACROSS W

TX...REACHING CENTRAL AR...NE TX...AND CENTRAL/SW TX BY 22/12Z. BY

MID-LATE AFTERNOON...SFC DRYLINE SHOULD EXTEND FROM FRONTAL

INTERSECTION OVER W-CENTRAL TX OR ERN PERMIAN BASIN REGION SWD INTO

NRN COAHUILA.

...SRN PLAINS TO MID-SOUTH REGION...

EARLY-PERIOD TSTMS ALONG AND N OF FRONT...FROM RED RIVER REGION

ENEWD ACROSS MID-SOUTH...MAY POST ISOLATED HAIL THREAT. POTENTIAL

FOR SPORADIC HAIL IN THIS REGIME WILL CONTINUE THROUGHOUT PERIOD AS

PLUME OF LOW-LEVEL WAA AND MOISTURE TRANSPORT EXTENDS EWD ACROSS TN.

GREATER SVR THREAT IS FCST TO DEVELOP FROM AROUND MIDDAY

ONWARD...NEAR FRONT. THIS WILL OCCUR AS STG LARGE-SCALE ASCENT AND

INTENSIFYING DEEP-LAYER SHEAR PRECEDE MID-UPPER TROUGH IMPINGE ON

PROGRESSIVELY MORE MOIST/BUOYANT AIR MASS ON BOTH SIDES OF SFC

FRONT. SCATTERED-NUMEROUS TSTMS ARE LIKELY ALONG AND N OF SFC FRONT

DURING AFTERNOON AND EVENING...AMIDST STG DEEP-LAYER ASCENT. SFC

BAROCLINIC ZONE WILL REMAIN QUITE STG EVEN AS IT BECOMES MORE

SHALLOW...BENEATH ELEVATED LOW-LEVEL WAA REGIME THAT WILL PRECEDE

SWRN CONUS TROUGH. AS SUCH...SFC-BASED EFFECTIVE LIFTED PARCELS

WILL DISAPPEAR WITHIN VERY SHORT DISTANCE N OF FRONT...ALTHOUGH

CONSIDERABLE ELEVATED INSTABILITY IS EXPECTED IN PRE-STORM

ENVIRONMENT. SFC DEW POINTS MID-60S F ALREADY HAVE REACHED PORTIONS

N-CENTRAL/NE TX. MID-UPPER 60S DEW POINTS SHOULD BE COMMON ALONG

AND S OF FRONT BY EARLY DAY-2...SUPPORTING 1500-2000 J/KG MLCAPE IN

MOIST SECTOR. ALONG AND S OF FRONT...CORRIDOR OF MULTI-MODAL SVR

THREAT IS EXPECTED...INCLUDING POTENTIAL FOR SUPERCELLS AND BOW

ECHOES...WITH LARGE HAIL...DAMAGING WIND AND THREAT FOR TORNADOES AS

WELL. LARGEST LOW-LEVEL HODOGRAPHS ARE FCST ALONG FRONT...WITH 0-1

KM SRH POTENTIALLY REACHING 200-250 J/KG.

ACTIVITY N OF FRONT WILL POSE THREAT FOR LARGE HAIL...GENERALLY

DECREASING IN PROBABILITY NWD. 50-60 KT EFFECTIVE SHEAR MAGNITUDE

AND ELEVATED MUCAPE 1000-1500 J/KG ARE EXPECTED IN THAT REGIME.

FARTHER S...LINE OF TSTMS SHOULD DEVELOP ALONG COLD FRONT DURING

LATE EVENING/OVERNIGHT HOURS...POTENTIALLY BUILDING SWD INTO

PORTIONS CENTRAL/E TX WITH WIND/HAIL THREAT.

..EDWARDS.. 11/20/2011

VALID 221200Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL/WRN GULF COAST

TO SRN APPALACHIANS AND OH VALLEY...

...SYNOPSIS...

STG SHORTWAVE TROUGH AND EMBEDDED MID-UPPER LOW -- NOW EVIDENT IN

MOISTURE CHANNEL IMAGERY OFFSHORE CA -- IS FCST TO MOVE EWD ACROSS

GREAT BASIN...SRN ROCKIES AND SRN HIGH PLAINS THROUGH DAY-2. BY

START OF PERIOD...THIS SYSTEM SHOULD ASSUME POSITIVE TILT AT 500

MB...ROUGHLY FROM ERN KS SWWD TO W-CENTRAL TX. ALTHOUGH OPERATIONAL

MODELS AND SREF MEMBERS START TO DIVERGE WITH AMPLITUDE AND SPEED OF

THIS PERTURBATION LATE DAY-2 INTO EARLY DAY-3...DIFFERENCES NOW

APPEAR MESOSCALE IN NATURE THROUGH THIS PERIOD. MID-UPPER TROUGH

SHOULD EXTEND FROM CENTRAL/SRN IL TO CENTRAL/ERN TX BY 23/00Z...AND

FROM OH SWWD OVER AL BY 23/12Z.

AT SFC...FRONTAL-WAVE CYCLONE SHOULD MOVE FROM SERN MO ENEWD ACROSS

LOWER GREAT LAKES/NRN APPALACHIANS REGION THROUGH PERIOD. COLD

FRONT SHOULD EXTEND FROM LOW SWWD ACROSS SERN OK AND CENTRAL/SW TX

BY 22/12Z...THEN FROM SRN INDIANA TO WRN/MID TN AND CENTRAL/SRN LA

BY 23/00Z. FRONT SHOULD REACH CENTRAL/SRN APPALACHIANS AND WRN FL

PANHANDLE BY END OF PERIOD.

...CENTRAL/WRN GULF COAST TO SRN APPALACHIANS AND OH VALLEY...

LATE DAY-2 INTO EARLY DAY-3...EXPECT BAND OF TSTMS TO BUILD SWWD

ALONG SFC COLD FRONT...WITH ATTENDANT RISK FOR OCNL DAMAGING GUSTS

AND ISOLATED HAIL FROM OZARKS TO CENTRAL/ERN TX. THROUGH LATE

AFTERNOON...SVR RISK SHOULD SHIFT EWD...WHILE EXPANDING NWD OVER OH

VALLEY IN STEP WITH EXPANDING WARM-SECTOR REGIME OF AT LEAST MRGL

BUOYANCY. CONVECTION ALSO SHOULD BACKBUILD ALONG/AHEAD OF FRONT

TOWARD COASTAL SE TX AND LA. DAMAGING TSTM GUSTS SHOULD REMAIN

MOST PREVALENT SVR MODE DURING AFTERNOON/EVENING...THOUGH TORNADOES

AND ISOLATED HAIL ALSO ARE POSSIBLE. MAIN UNCERTAINTIES RESULT FROM

DIFFERENCES IN PROGS OF SYSTEM SPEED...AND INVOLVE BOTH TIMING OF

SVR THREAT AREA-WIDE...AND NWD EXTENT OF SVR THREAT INTO OH VALLEY

REGION. SVR THREAT THEREFORE IS MORE CONDITIONAL WITH NWD AND EWD

EXTENT WHERE AVAILABILITY OF SFC-BASED EFFECTIVE LIFTED PARCELS IS

PROGRESSIVELY MORE QUESTIONABLE.

WARM-SECTOR AIR MASS WILL DESTABILIZE DIURNALLY FROM COMBINATION OF

BOUNDARY-LAYER THETAE ADVECTION AND POCKETS OF SFC DIABATIC HEATING.

EXPECT SFC DEW POINTS RANGING FROM LOWER 60S NEAR OH RIVER TO UPPER

60S/LOW 70S OVER COASTAL AREAS OF LA/MS/AL. FCST SOUNDINGS SUGGEST

THIS WILL OFFSET MODEST MIDLEVEL LAPSE RATES ENOUGH FOR MLCAPE

1000-1500 J/KG FROM GULF COAST TO TN VALLEY REGION...DIMINISHING TO

BELOW 500 J/KG OVER OH RIVER. DOMINANT CONVECTIVE MODE SHOULD

REMAIN QUASI-LINEAR...AS WINDS ALOFT PRECEDING POSITIVELY-TILTED

TROUGH CROSS LOW-LEVEL CONVERGENCE ZONE AT SMALL ANGLE.

HOWEVER...WITH LACK OF SIGNIFICANT ELEVATED MIXED-LAYER AIR MASS

AHEAD OF FRONT...MLCINH SHOULD BE RATHER SMALL. THIS MAY PERMIT

DISCRETE OR CLUSTERED DEVELOPMENT AHEAD OF MAIN LINE...WITH ENOUGH

DEEP-LAYER SHEAR TO SUPPORT CONDITIONAL SUPERCELL POTENTIAL AHEAD OF

MAIN BAND...IN ADDITION TO ANY EMBEDDED SUPERCELLS/BOWS/MESOVORTICES

IN QLCS.

CONVECTIVE REGIME WILL SHIFT EWD ACROSS LOWER DELTA...MID-SOUTH...OH

VALLEY AND TN VALLEY REGIONS THROUGH EVENING...IN STEP WITH OR

SLIGHTLY AHEAD OF SFC COLD FRONT. DURING LATE EVENING AND OVERNIGHT

HOURS...FAVORABLE BUOYANCY WILL BE OVERTAKEN FROM N-S AS MAIN TSTM

BAND ENCOUNTERS MORE STABLE BOUNDARY-LAYER TRAJECTORIES EMANATING

FROM RIDGING OVER ATLANTIC COAST REGION. SVR POTENTIAL ACCORDINGLY

SHOULD DIMINISH OVER NRN PORTIONS OF OUTLOOK AREA...AND BECOME MORE

CONDITIONAL/MRGL EWD ACROSS ERN PORTIONS AL/TN INTO WRN GA.

[janetjanet998]

day

3

[Ed Lizard]

Besides severe, Kanas-Indiana heavy rain threat looks possible.

NAM suggests limited warm sector action in Texas Monday, may be more a hail threat than anything else IMHO.

[Hoosier]

Doubtful about how far north the instability axis will reach but shear (including low level shear) is very good near and north of the Ohio River. Conditional tornado threat there and backed up by the modest probs on that outlook.

[Thundersnow12]

popping a 30 now on the 15z run

[janetjanet998]

ooz NAM is slower, stronger and more north with the system Tuesday then 12z run ...500mb closes off for a bit over IL at 18z tuesday low at 1002 MB by 00z over N IND

[andyhb]

ooz NAM is slower, stronger and more north with the system Tuesday then 12z run ...500mb closes off for a bit over IL at 18z tuesday low at 1002 MB by 00z over N IND

Pretty large reservoir of 60+ sfc dews/ 65-70+ sfc temps on that run.

Tuesday's discussion from JAN:

THE MAIN WEATHER STORY FOR THIS WEEK WILL COME TUESDAY AND TUESDAY

NIGHT. IT APPEARS THAT THE GFS AND ECMWF ARE IN PRETTY GOOD

AGREEMENT. THE ECMWF IS A LITTLE BIT SLOWER BUT OVERALL REMAINS IN

RATHER GOOD AGREEMENT. BY TUESDAY MORNING...THE UPPER TROUGH WILL BE

LOCATED OVER SOUTHEAST KANSAS DOWN THROUGH NORTHEAST TEXAS. A SFC

LOW WILL BE ACROSS SOUTHWEST MISSOURI...WHICH WILL PUSH THE

PREVIOUSLY STALLED COLD FRONT INTO AND THROUGH OUR REGION TUESDAY.

GIVEN THAT THE REGION WILL HAVE BEEN SITUATED IN GOOD GULF RETURN

FLOW FOR SEVERAL DAYS...THIS WILL ALLOW FOR ENOUGH MOISTURE TO BE

PRESENT AHEAD OF THE FRONT. MODELS CONTINUE TO INDICATE THAT WE

SHOULD HAVE MID 60 DEWPOINTS ACROSS THE CWA. THERE WILL BE STRONG

ATMOSPHERIC FORCING WITH THIS SYSTEM...ESPECIALLY WITH THE

FRONT...ALONG WITH AN INCOMING 55-60KT 850MB JET...60-70KT 500MB JET

AND COUPLED UPPER LEVEL JET STRUCTURE...WHICH WOULD LEAD TO RATHER

GOOD UPPER DIVERGENCE OVER THE REGION. HELICITY VALUES LOOK GOOD

ENOUGH TO SUPPORT THE IDEA OF TORNADOES AS WELL AS DAMAGING WINDS.

THE BEST COMBINATION OF WIND AND HELICITY AS WELL AS UPPER FORCING

LOOKS MOST LIKELY NORTH OF I-20 BUT STILL THINK THERE IS THE RISK OF

SEVERE STORMS EVERYWHERE ON TUESDAY. WHILE THE PRIMARY MODE SHOULD

BE SQUALL LINE...I CANT RULE OUT THE POTENTIAL FOR ISOLATED

STORMS/SUPERCELLS AHEAD OF THE LINE GIVEN NEARLY 50KTS OF DEEP LAYER

SHEAR AND 35-40KTS OF LOWER LEVEL SHEAR. THE COLD FRONT...AND

ASSOCIATED SQUALL LINE...LOOKS TO ENTER THE DELTA REGION AT SOMETIME

IN THE LATE MORNING AND CONTINUE INTO CENTRAL PORTIONS OF THE CWA BY

MID AFTERNOON AND EXITING THE SOUTHEAST IN THE EVENING HOURS...MOST

LIKELY BEFORE MIDNIGHT. WILL ALSO INCLUDE MENTION OF LOCALLY HEAVY

RAIN IN THE HWO AS PW VALUES REACH 1.8-1.9 INCHES WITH THE FRONT.

[andyhb]

BMX:

A FEW CHANGES SINCE YESTERDAY CONCERNING THE SHORTWAVE EJECTING

OUT FROM THE WEST ON TUESDAY. THE GFS HAS COME IN WITH SLIGHTLY

HIGHER INSTABILITY AND BETTER SHEAR AS WELL. THIS PROMPTED THE MID

SHIFT TO GO WITH SEVERE WORDING IN THE HWO. THE 12Z RUN REALLY

HAS NOT BACKED OFF ANY WITH BULK SHEAR STILL AROUND 50 KTS AHEAD

OF THE MAIN LINE. 0-1KM AND 0-3KM HELICITY SHOW SOME POTENTIAL

FOR ROTATING SUPERCELLS IF ANYTHING CAN DEVELOP AHEAD OF THE MAIN

LINE. WILL BE CURIOUS TO SEE IF THERE WILL BE ANY POCKETS OF SUN

BREAK OUT ON TUESDAY. GUIDANCE TEMPERATURES ARE VERY WARM WITH

HIGHS CLOSE TO 80 AND THEY ARE UNDER FORECASTING THE DEW POINTS

THUS FAR BY A FEW DEGREES. AT LEAST LOOKING LIKE A QUASI-LINEAR

BAND WITH BOWING SEGMENTS AND POTENTIAL FOR EMBEDDED SUPERCELLS.

AS FOR TIMING...THE FRONT APPEARS TO ENTER NORTHWEST ALABAMA

AROUND 23Z TUESDAY AND PUSHES OUT OF CENTRAL ALABAMA BETWEEN 03Z

AND 06Z WEDNESDAY. IF THEY DEVELOP...PREFRONTAL STORMS HAVE THE

POTENTIAL TO DEVELOP AS EARLY AS 18Z.

HUN:

THE MAIN STORY FOR THIS FORECAST THEN LIES WITH THE PROGRESSION OF

THE LOW CURRENTLY OFF THE COAST OF CALIFORNIA. THE SURFACE WAVE WILL

WEAKEN OVER THE NEXT DAY OR SO BUT THE ASSOCIATED SHORTWAVE WILL

TRACK ACROSS THE SOUTHERN ROCKIES AND LEAD TO LEE CYCLOGENESIS ALONG

THE REMAINS OF THE FRONTAL BOUNDARY. THE LOW WILL RAPIDLY DEEPEN AND

TRACK NORTHEAST TOWARD LAKE ERIE...DRAGGING A COLD FRONT ACROSS THE

SOUTHEAST ON TUESDAY. DUE TO SHEAR PROFILES...ANTICIPATE QUASI-LINEAR

CONVECTION TO DEVELOP ASSOCIATED WITH THE FRONT WITH THE POTENTIAL

FOR SOME DISCRETE DEVELOPMENT AHEAD OF THE FRONT ON TUESDAY. STRONG

WIND SHEAR AND A LL JET (40-50KTS AT 850MB) AHEAD OF THE FRONT...PLUS

LOW-MOD MLCAPE VALUES (200-600 J/KG)...SOME DECENT DCAPE AND 0-3 SRH

ARND 200 M2/S2 INDICATE THE POTENTIAL FOR DAMAGING WINDS AND A FEW

TORNADOES (IF WE GET BREAKS IN THE LINE OR HAVE DISCRETE DEVELOPMENT

AHEAD OF THE LINE). THE BEST PARAMETERS REMAIN OFF TO OUR SW (TOWARD

JACKSON MS) BUT A SLIGHT CHANCE FOR SEVERE WEATHER WILL EXIST AS

THIS SYSTEM MOVES ACROSS THE CWA. PRIMARY TIME FRAME CURRENTLY LOOKS

TO BE BETWEEN 18Z TUESDAY AND 06Z WEDNESDAY...WITH 00Z BEING THE

FOCUS FOR THE MAIN THREAT.

MEG:

THE FRONT WILL RETREAT BACK NORTH QUICKLY MONDAY NIGHT WITH GUSTY

WINDS AND A DEEPENING LOW OVER EASTERN OKLAHOMA. THIS LOW WILL

TRACK ACROSS SOUTHERN MISSOURI TO CENTRAL INDIANA BY TUESDAY

EVENING. THE COLD FRONT LOOKS LIKE IT WILL BE CROSSING THE

WESTERN CWA BORDER AROUND 18Z TUESDAY. VERY IMPRESSIVE WIND FIELDS

WILL OVERSPREAD THE WARM SECTOR BY EARLY AFTERNOON WITH 0-6 KM

BULK SHEAR AROUND 50 KTS AND 0-3 KM AROUND 35 KTS...0-3 KM SRH

VALUES AROUND 150 M2/S2...AND MLCAPE VALUES OF AT LEAST 1000 J/KG.

LITTLE CAPPING WILL BE IN PLACE...SO SOME STORMS MAY FORM IN THE

WARM SECTOR AHEAD OF THE MAIN LINE AS SHOWN IN THE QPF FIELDS.

HODOGRAPHS ARE LINEAR...INDICATIVE OF MULTI-CLUSTER LINE SEGMENTS

AND SPLITTING SUPERCELLS. AT THIS POINT GIVEN THE MOIST

ATMOSPHERE...WIND DAMAGE WILL BE THE MAIN THREAT ALTHOUGH IF WINDS

CAN BACK A BIT MORE AT THE SURFACE...A FEW TORNADOES WILL ALSO BE

POSSIBLE WITH DISCRETE SUPERCELLS. ANOTHER LINE OF STORMS WILL

FORM ALONG THE COLD FRONT...PROBABLY AS A QLCS AND TRACK ACROSS

THE MIDSOUTH TUESDAY AFTERNOON. WIND DAMAGE ALSO LOOKS LIKE THE

MAIN THREAT WITH THIS. MOST OF THE ACTIVITY WILL BE EAST OF THE

NATCHEZ TRACE PARKWAY BY 00Z WEDNESDAY.

Keep in mind that the models have been underestimating shear and instability recently until what seems like the very last minute.

[Ed Lizard]

Really not sure there'll be warm sector action in Texas tomorrow judging by the models. GFS looks a touch more favorable for that. If the cap can break, helicities look impressive.

[TheWeatherPimp]

00z GFS appears to be suffering from some major convective feedback fwiw.

[andyhb]

Day 1:

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1145 PM CST SUN NOV 20 2011

VALID 211200Z - 221200Z

...THERE IS A SLGT RISK OF SVR TSTMS TX/SRN OK EWD INTO CENTRAL

AR...

...SYNOPSIS...

A SHORTWAVE TROUGH...CURRENTLY LOCATED IN THE CA/NV REGION...IS

FORECAST TO SHIFT RAPIDLY EWD INTO NM TODAY...AND THEN ENEWD INTO

ERN KS OVERNIGHT. THIS UPPER SYSTEM WILL BECOME NEGATIVELY TILTED

DURING THE SECOND HALF OF THE PERIOD AS A 70-80 KT MID LEVEL JET MAX

MOVES FROM THE BASE ONTO THE EAST SIDE OF THE TROUGH.

...TX/SRN OK EWD INTO CENTRAL AR...

THE SEVERE FORECAST THIS FORECAST WILL BE COMPLICATED BY THE

PRESENCE OF AN EXISTING COLD SHALLOW AIR MASS...WITH THE LEADING

EDGE CURRENTLY EXTENDING FROM NERN AR SWWD INTO CENTRAL TX. MODELS

ARE CONSISTENT IN MAINTAINING SURFACE RIDGE ACROSS MUCH OF OK SWD

INTO CENTRAL TX TODAY AND GIVEN CONTINUED SLOW SWD MOTION OF FRONT

AND WEAK PRESSURE RISES...EXPECT FRONT IN CENTRAL TX TO REMAIN

QUASI-STATIONARY THROUGH MUCH OF THE DAY. HOWEVER...THE PORTION OF

THE FRONT IN AR/ERN TX MAY RETREAT SLOWLY WWD... POSSIBLY TO NEAR AN

AUS -HRO LINE BY EVENING...AS THE UPPER TROUGH APPROACHES.

GIVEN THE ABOVE FRONTAL LOCATION...THE GREATER HEIGHT

FALLS/DYNAMICAL FORCING WILL OCCUR NORTH AND WEST OF THE FRONT

THROUGH THE DAY. THE FORCING IS EXPECTED TO RESULT IN ELEVATED

STORMS FORMING EARLY IN THE DAY IN WRN TX...SPREADING RAPIDLY ENEWD

ACROSS NRN TX AND OK. DESPITE THE COLD BOUNDARY LAYER... MUCAPES

AROUND 1000 J/KG AND 50 KT DEEP LAYER SHEAR ABOVE THE BOUNDARY LAYER

WILL BE SUFFICIENT FOR SOME ROTATING STORMS...WITH HAIL THE PRIMARY

THREAT. AS THE STORMS PROGRESS AND APPROACH THE WARMER AND MORE

UNSTABLE BOUNDARY LAYER...THE POTENTIAL FOR WIND DAMAGE WILL

INCREASE FROM FAR ERN OK SWD INTO ERN TX. AS THE UPPER WAVE BECOMES

NEGATIVELY TILTED...A SURFACE WAVE SHOULD DEVELOP ALONG THE FRONT IN

AR MONDAY EVENING...AND THEN SHIFT NEWD INTO MO OVERNIGHT. ONCE THIS

HAPPENS...THE FRONT WILL BEGIN MOVING EWD WITH THE POTENTIAL FOR

MORE LINEAR STORMS TO DEVELOP ALONG IT. INSTABILITY IS NOT FORECAST

TO BE PARTICULARLY STRONG...THOUGH THE STRENGTH OF THE WIND FIELDS

AND SHEAR WILL BE FAVORABLE FOR WIND DAMAGE AND PERHAPS EVEN A

TORNADO OR TWO ...ESPECIALLY IN AR NEAR DEVELOPING SURFACE LOW.

ALSO...DURING THE AFTERNOON...THE UPPER FORCING MAY BRUSH THE

STATIONARY FRONT IN CENTRAL TX. THE FORECAST SOUNDINGS SHOW A WEAK

CAPPING INVERSION AROUND 700 MB...BUT IF SURFACE BASED STORMS CAN

DEVELOP NEAR THIS PORTION OF THE FRONT...MLCAPES NEAR 1500

J/KG...DEEP LAYER SHEAR AT 60 KT AND 1 KM SRH AOA 200 M2/S2 WILL BE

FAVORABLE FOR SUPERCELLS...INCLUDING TORNADOES. THE SEVERE THREAT

WILL DECREASE DURING THE EVENING AS THE FORCING LIFTS NWD OUT OF THE

REGION.

..IMY/LEITMAN.. 11/21/2011

Day 2:

DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1226 AM CST MON NOV 21 2011

VALID 221200Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL/WRN GULF COAST

TO SRN APPALACHIANS AND OH VALLEY...

...SYNOPSIS...

HIGH-AMPLITUDE SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL

IMAGERY FROM NRN CA SWD ACROSS SRN CA OFFSHORE WATERS -- IS FCST TO

MOVE EWD ACROSS SWRN CONUS AND SRN/CENTRAL HIGH PLAINS DAY-1. BY

22/12Z...TROUGH SHOULD ASSUME POSITIVE TILT FROM ERN KS TO W-CENTRAL

TX...IN STG AGREEMENT WITH PAST FEW RUNS OF OPERATIONAL PROGS AND

SREF CONSENSUS THAT...IN TURN...HAVE AGREED WELL WITH EACH OTHER.

MODELS DIVERGE WITH SHAPE/AMPLITUDE OF THIS SYSTEM EARLY DAY-2...BUT

REMAIN IN GEN AGREEMENT WITH TROUGH POSITION FROM LM/LOWER MI AREA

TO N-CENTRAL TX BY 23/00Z. BY END OF PERIOD...TROUGH SHOULD EXTEND

FROM LOWER GREAT LAKES SWWD ACROSS MS...ITS NRN PERIPHERY PHASING

WITH NRN-STREAM TROUGH NOW LOCATED OFFSHORE PAC NW COAST.

AT SFC...STG COLD FRONT WAS ANALYZED AT 21/05Z FROM LOWER OH VALLEY

SWWD ACROSS CENTRAL AR...CENTRAL TX BETWEEN ACT-CLL...BECOMING

QUASISTATIONARY ACROSS SRN HILL COUNTRY AND SERN EDWARDS PLATEAU

REGION TO NEAR DRT. FRONTAL-WAVE CYCLONE SHOULD DEVELOP ALONG THIS

BOUNDARY OVER N TX DURING DAY-1...DEEPENING AND MOVING NEWD ACROSS

SERN MO BY 22/12Z. LOW WILL CONTINUE TO STRENGTHEN THROUGH MOST OF

PERIOD...REACHING INTERIOR MID-ATLANTIC/NRN APPALACHIANS REGION BY

END OF PERIOD. BY 23/00Z...COLD FRONT SHOULD EXTEND FROM INDIANA/OH

LOW SWWD NEAR MEM-CRP LINE. BY 23/12Z...FRONT SHOULD EXTEND FROM

CENTRAL/ERN PA SWWD DOWN APPALACHIANS...ACROSS NRN GA...TO SWRN AL

AND NWRN GULF.

...CENTRAL/WRN GULF COAST TO SRN APPALACHIANS AND OH VALLEY...

BAND OF TSTMS SHOULD BE ONGOING AT START OF PERIOD INVOF SFC COLD

FRONT...BACKBUILDING THROUGH MORNING TOWARD TX GULF COASTAL PLAIN.

ALTHOUGH FCST SOUNDINGS SUGGEST SFC-BASED EFFECTIVE-INFLOW

PARCELS...RELATIVE MORNING MIN IN BOUNDARY-LAYER INSTABILITY

SUGGESTS AT LEAST MRGL POTENTIAL FOR DAMAGING WIND...CONCENTRATED

LOCALLY WITH EMBEDDED BOW/LEWP FORMATIONS.

SVR POTENTIAL IS EXPECTED TO INCREASE FROM MIDDAY THROUGH AT LEAST

LATE AFTERNOON...SHIFT EWD ACROSS DELTA/TN VALLEY REGION...AND

EXPAND NWD TO OH VALLEY REGION. PRIMARY SVR TYPE WILL BE DAMAGING

WIND...THOUGH TORNADOES AND ISOLATED HAIL ALSO ARE POSSIBLE. BAND

OF CONVECTIVE FORCING IS FCST TO ENCOUNTER PROGRESSIVELY MORE MOIST

AND UNSTABLE WARM SECTOR THROUGH DAYLIGHT HOURS. SFC DEW POINTS

RANGING FROM UPPER 60S TO NEAR 70 NEAR I-10 IN MS/LA/AL...TO MID 60S

TN VALLEY...SHOULD OFFSET WEAK MID-UPPER LEVEL LAPSE RATES ENOUGH TO

SUPPORT MLCAPE 500-1500 J/KG. SOME WLY SFC WIND COMPONENT IS

PROGGED OVER THAT CORRIDOR...ALONG WITH 2-4 KM AGL LAYER CONTAINING

SOME BACKING WITH HEIGHT. STILL...LOW-LEVEL HODOGRAPHS SHOULD BE

LARGE ENOUGH TO SUPPORT EFFECTIVE SRH 150-300 J/KG AND POTENTIAL FOR

EMBEDDED SUPERCELLS/BOWS...AS WELL AS CONDITIONAL RISK FOR

SUPERCELLS FOR ANY SUSTAINED DEVELOPMENT THAT CAN OCCUR AHEAD OF

MAIN TSTM LINE.

CAPE IS EXPECTED TO DIMINISH WITH NWD EXTENT OVER KY AND OH VALLEY

PORTIONS OF OUTLOOK...WITH MORE LIMITED TIME WINDOW OF OPPORTUNITY

FOR THETAE ADVECTION AND DIURNAL HEATING TO DESTABILIZE BOUNDARY

LAYER BEFORE FROPA. BUOYANCY ALSO WILL DIMINISH WITH TIME AND EWD

EXTENT AFTER DARK...ACROSS CENTRAL/SRN APPALACHIANS INTO ERN AL/WRN

GA. THEREFORE SVR POTENTIAL IN EACH REGIME BECOMES MORE

CONDITIONAL...THOUGH STG FRONTAL FORCING CAN YIELD POTENTIAL FOR SVR

EVEN IN PRESENCE OF NEAR-NEUTRAL MIDLEVEL LAPSE RATES AND MLCAPE

BELOW 500 J/KG. WITH RESPECT TO CINH...LOW-LEVEL FORCING SHOULD

LESSEN WITH SWD EXTENT...MAKING SVR POTENTIAL LOWER ALONG IMMEDIATE

COAST RELATIVE TO FARTHER N AND NE.

..EDWARDS.. 11/21/2011

[Srain]

BULLETIN - EAS ACTIVATION REQUESTED

TORNADO WARNING

NATIONAL WEATHER SERVICE LAKE CHARLES LA

831 AM CST TUE NOV 22 2011

THE NATIONAL WEATHER SERVICE IN LAKE CHARLES HAS ISSUED A

* TORNADO WARNING FOR...

EASTERN VERNON PARISH IN WEST CENTRAL LOUISIANA...

THIS INCLUDES...SLAGLE...LEESVILLE...FORT POLK...

* UNTIL 900 AM CST

* AT 828 AM CST...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A

SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO NEAR FORT

POLK...MOVING NORTHEAST AT 45 MPH.

* THE TORNADO WILL BE NEAR...

SLAGLE BY 840 AM CST...

LACAMP BY 850 AM CST...

[isohume]

Last night's Bufkit CONRAD signatures showed a high potential for right-moving supercells across the western Carolinas tonight. It's still looking like embedded mini-SCs are possible with a few even developing ahead of the line. It doesn't take much SBCAPE for tornadic storms around here...strongly curved shear is more important. Perhaps there will be more intense activity than the SPC has envisioned and I'm glad I have tonight off.

[Srain]

BULLETIN - EAS ACTIVATION REQUESTED

TORNADO WARNING

NATIONAL WEATHER SERVICE LAKE CHARLES LA

930 AM CST TUE NOV 22 2011

THE NATIONAL WEATHER SERVICE IN LAKE CHARLES HAS ISSUED A

* TORNADO WARNING FOR...

WEST CENTRAL AVOYELLES PARISH IN CENTRAL LOUISIANA...

THIS INCLUDES BUNKIE...

NORTH CENTRAL EVANGELINE PARISH IN CENTRAL LOUISIANA...

SOUTHEASTERN RAPIDES PARISH IN CENTRAL LOUISIANA...

THIS INCLUDES...GLENMORA...CHENEYVILLE...

* UNTIL 1000 AM CST

* AT 927 AM CST...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A

SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO NEAR GLENMORA...

MOVING EAST AT 40 MPH.

* THE TORNADO WILL BE NEAR...

LECOMPTE BY 945 AM CST...

CHENEYVILLE BY 955 AM CST...

BUNKIE AND ECHO BY 1000 AM CST...

[Bryan Wood]

SPC removed Southern Ohio & Indiana from Slight Risk, which is a good call. We've had thick cloud cover and rain all morning. CAPE is going to be hard to come by here.

[tornadotony]

Last night's Bufkit CONRAD signatures showed a high potential for right-moving supercells across the western Carolinas tonight. It's still looking like embedded mini-SCs are possible with a few even developing ahead of the line. It doesn't take much SBCAPE for tornadic storms around here...strongly curved shear is more important. Perhaps there will be more intense activity than the SPC has envisioned and I'm glad I have tonight off.

Yeah your area is the one I'm actually most concerned about with this system at this point.