Mar. 24-27th Plains Severe Weather, SPC Risk Level: Slight - Forecasts & OBS Options

[Chicago Storm]

http://www.spc.noaa.gov/products/outlook/

This post has been edited by Chicago Storm: Mar 27 2011, 12:56 PM

[The Snowman]

I couldn't find a SE thread, but here's a great radar image of a nice supercell.

[jdrenken]

I couldn't find a SE thread, but here's a great radar image of a nice supercell.

That's because Texas isn't in the SE.

[WeatherMonger]

SPC talks about that storm

MESOSCALE DISCUSSION 0270
NWS STORM PREDICTION CENTER NORMAN OK
0709 PM CDT THU MAR 24 2011

AREAS AFFECTED...PORTIONS OF W TX

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 250009Z - 250145Z

ONE SUPERCELL IS UNDERWAY IN SCURRY CO TEXAS...WITH ADDITIONAL
INITIATION POSSIBLE ALONG AND E OF THE DRYLINE IN THE NEXT 2-3 HRS.
A WW IS POSSIBLE IF ADDITIONAL CELLS BECOME ORGANIZED.

23Z SFC ANALYSIS INDICATES A DRYLINE ACROSS FAR W TX...WITH CU NOTED
RUNNING FROM AROUND LBB S TO NEAR AND JUST SW OF MAF. MEANWHILE...A
NW-TO-SE ORIENTED WARM FRONT RUNS FROM S OF LBB TO THE NE OF MAF.
WHILE MANY CELLS HAVE STRUGGLED TO SURVIVE AS THEY MOVE OFF THE
DRYLINE...ONE CELL HAS INTENSIFIED AND HAS ALREADY PRODUCED SEVERE
HAIL NE OF MAF. HOWEVER...THIS CELL HAS MOVED N OF THE WARM FRONT
AND SHOULD BEGIN TO WEAKEN AS IT ENCOUNTERS WEAKER BUOYANCY AND
STRONGER SFC-BASED INHIBITION.

ADDITIONAL CELLS MAY FORM FURTHER W ON THE DRYLINE IN THE NEXT 1-2
HRS BEFORE DIABATIC COOLING STABILIZES THE BOUNDARY LAYER. VERY
STEEP LAPSE RATES.../AS NOTED ON THE 00Z MAF SOUNDING/...MU CAPE OF
1000-1500 J/KG AND EFFECTIVE SHEAR OF 40-50 KTS WILL SUPPORT A LARGE
HAIL THREAT WITH ANY CELL THAT BECOMES ESTABLISHED. LARGE T/TD
SPREADS AND DCAPE OF AROUND 1500 J/KG WILL SUPPORT A THREAT OF
ISOLATED SEVERE WIND.

IF ADDITIONAL STORMS FORM FURTHER WEST ALONG THE DRYLINE AND HAVE
THE OPPORTUNITY TO STAY IN THE WARM SECTOR FOR AT LEAST AN HOUR OR
TWO...A WW MAY BECOME NECESSARY. CONVECTIVE TRENDS WILL CONTINUE TO
BE MONITORED.

..DEAN.. 03/25/2011

[jdrenken]

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1243 AM CDT FRI MAR 25 2011

VALID 251200Z - 261200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS ARKLATEX REGION TO
LOWER MS VALLEY...

...SYNOPSIS...
IN MIDDLE-UPPER LEVELS...SPLIT-FLOW PATTERN FCST TO PERSIST WELL
BEYOND THIS PERIOD. RIDGING WILL EXTEND SWD ACROSS ND FROM
ANTICYCLONE CENTERED OVER NERN SK...WHILE CONTINUOUS/QUASI-ZONAL
CURRENT COVERS MUCH OF CONUS FROM MIDDLE-SRN ATLANTIC COAST WWD
ACROSS CENTRAL/SRN ROCKIES. WELL-DEFINED CYCLONE -- NOW EVIDENT IN
MOISTURE CHANNEL IMAGERY OFFSHORE ORE -- IS FCST TO MOVE INLAND
EARLY THIS PERIOD. THIS FEATURE THEN SHOULD QUICKLY DEAMPLIFY INTO
WEAKENING OPEN-WAVE TROUGH OVER NRN ROCKIES...WHILE SECOND CYCLONE
DEVELOPS OFFSHORE PAC NW. SHORTWAVE TROUGH -- NOW MOVING INLAND
CENTRAL/NRN CA -- IS FCST TO MOVE EWD ACROSS GREAT BASIN AND CENTRAL
ROCKIES TO CENTRAL HIGH PLAINS BY 26/12Z. MEANWHILE...DOWNSTREAM
SHORTWAVE OVER CENTRAL PLAINS WILL MOVE EWD AND WEAKEN CONSIDERABLY
ACROSS CENTRAL APPALACHIANS TODAY...AMIDST CONFLUENT FLOW ALOFT
ASSOCIATED WITH CYCLONE OVER LOWER ST LAWRENCE VALLEY REGION.

AT SFC...WEAK NW TX/SWRN OK LOW IS EXPECTED ALONG WARM FRONTAL ZONE
EARLY IN PERIOD...WITH FRONT ESEWD ACROSS ARKLATEX TO CENTRAL/SRN
LA. FRONT SHOULD LIFT NWD INTO SERN OK AND SRN AR BY
26/00Z...EXTENDING WNWWD ACROSS SRN TX PANHANDLE REGION. BY THAT
TIME...DRYLINE SHOULD EXTEND FROM SERN OK SWWD ACROSS N-CENTRAL TX
TO SRN HILL COUNTRY...THEN RETREAT SLIGHTLY WWD DURING EVENING.
ANOTHER SFC LOW MAY DEVELOP OVERNIGHT ALONG FRONT INVOF SWRN OK/NW
TX AND MOVE EWD...WITH RELATED VEERING OF SFC WINDS TO ITS S AND SW
RESULTING IN EWD OSCILLATION OF DRYLINE AGAIN BEFORE 26/12Z.

...ARKLATEX REGION TO LOWER MS VALLEY...
AREA OF STG-SVR TSTMS IS EXPECTED TO DEVELOP...EXPAND AND MOVE EWD
FROM NE TX/SERN OK/SWRN AR AREA DURING EVENING...AMIDST INCREASING
LOW-LEVEL MOISTURE AND FAVORABLE DEEP-LAYER SHEAR PROFILES TO
SUPPORT SVR RISK. SUPERCELLS WITH LARGE HAIL AND SVR GUSTS ARE
POSSIBLE...AND THREAT FOR TORNADOES ALSO MAY EXIST INVOF
WARM-FRONTAL ZONE.

PROGS ARE IN VERY STG AGREEMENT REGARDING GENERAL EVOLUTION/LOCATION
OF SCENARIO...HOWEVER TIMING OF INITIATION REMAINS QUITE
UNCERTAIN...ESPECIALLY POTENTIAL FOR DIURNAL/SFC-BASED DEVELOPMENT
BEFORE 00Z. THIS IS BECAUSE OF STG CAPPING RELATED TO
ANTECEDENT/ELEVATED MIXED LAYER...COMBINED WITH ONLY SUBTLE/SHALLOW
WARM-FRONTAL LIFT AND LACK OF SIGNIFICANT MID-UPPER PERTURBATION
NEARBY. THIS REGION WILL BE TOO REMOVED FROM GREAT BASIN/CENTRAL
ROCKIES SHORTWAVE TROUGH TO EXPERIENCE DIRECT EFFECTS.
HOWEVER...BROAD/LOW-LEVEL WAA REGIME ALREADY IN PLACE OUGHT TO
STRENGTHEN OVERNIGHT ACROSS LOWER MS VALLEY REGION...RESULTING IN
INCREASING THETAE WITH TIME FOR INFLOW PARCELS IN AND N OF SFC
WARM-FRONTAL ZONE. TIME WINDOW FOR SFC-BASED CONVECTION SHOULD
EXIST DURING EVENING NEAR WARM FRONT BEFORE SUBSTANTIAL SFC
COOLING...AS LOW-LEVEL HODOGRAPH EXPANDS BENEATH STRENGTHENING LLJ.
THIS WILL BOOST SRH AND TORNADO POTENTIAL FOR SEVERAL HOURS...BEFORE
ACTIVITY MOVES EWD INTO MORE STABLE AIR MASS. ADDITIONAL
DEVELOPMENT MAY OCCUR OVERNIGHT IN EARLIER STORM GENESIS REGION OF
SERN OK/NE TX...MAINTAINING SVR THREAT BEHIND INITIAL ACTIVITY.

...WRN OZARKS REGION...
CLUSTER OF SCATTERED/ELEVATED TSTMS MAY BE ONGOING EARLY IN PERIOD
OVER PORTIONS NERN OK/SERN KS...ROOTED IN 750-850 MB LAYER BASED ON
RUC/ETA-KF FCST SOUNDINGS. ALTHOUGH BUOYANCY IS EXPECTED TO BE
RATHER UNSPECTACULAR...WITH MUCAPE 400-800 J/KG...40-50 KT EFFECTIVE
SHEAR INDICATES CONVECTION MAY BE ORGANIZED ENOUGH FOR MRGL HAIL
POTENTIAL. THIS ACTIVITY SHOULD WEAKEN THROUGH MID-LATE MORNING AS
IT MOVES EWD OVER AR/MO OZARKS AND INITIALLY SUPPORTIVE LLJ
DIMINISHES.

..EDWARDS/DEAN.. 03/25/2011