SPC AC 220552
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1252 AM CDT THU MAY 22 2008
VALID 221200Z - 231200Z
...THERE IS A MDT RISK OF SVR TSTMS PORTIONS SWRN NEB...WRN
KS...EXTREME NWRN OK...
...THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE FROM WRN NEB AND
EXTREME SERN WY TO PORTIONS NW TX/SW OK...
...SYNOPSIS...
PRIMARY UPPER AIR FEATURE FOR THIS OUTLOOK WILL BE
DEEP/LARGE
CYCLONE -- NOW DEVELOPING ACROSS GREAT BASIN FROM HIGH-AMPLITUDE
SYNOPTIC TROUGH. LATEST 00Z 250 MB ANALYSIS SHOWED 150 KT JET MAX
DIGGING SSEWD ALONG W SIDE OF THIS SYSTEM...ACROSS ORE...NERN CA AND
WRN NV. AS SEVERAL RELATIVELY LOW-AMPLITUDE VORTICITY LOBES REVOLVE
AROUND THIS GYRE...MEAN CIRCULATION CENTER SHOULD RETROGRADE ACROSS
SRN GREAT BASIN DURING THIS PERIOD.
AS THIS OCCURS...ELONGATED LOW PRESSURE ZONE -- PERHAPS WITH TWO OR
THREE LOCALIZED ISOBARIC MINIMA -- SHOULD DEVELOP ALONG SFC
BAROCLINIC ZONE FROM S-CENTRAL/SERN WY SEWD ACROSS NERN CO TO NWRN
KS. AFTERNOON DRYLINE WILL INTERSECT FRONT/LOW INVOF WRN PORTIONS
KS/NEB BORDER...AND EXTEND SWD ACROSS WRN KS...CENTRAL/ERN PORTIONS
TX/OK PANHANDLES...AND W-CENTRAL TX...WITH SLGT EWD MIXING EARLY-MID
AFTERNOON AND RETREAT BEGINNING BEFORE SUNSET. SHORT/BENT-BACK
DRYLINE SEGMENT MAY ARC NWWD ACROSS PORTIONS NWRN KS/SERN NEB/NERN
CO...PERMITTING NARROW CORRIDOR OF FAVORABLE MOISTURE ALONG WARM
FRONTAL ZONE OVER THOSE AREAS. FRONT IS FCST TO EXTEND FROM LOW
ESEWD ACROSS NERN KS AND W-CENTRAL/SWRN MO...WITH NET NWD DRIFT
THROUGHOUT PERIOD.
...CENTRAL/SRN HIGH PLAINS...
ANOTHER AMONG SEVERAL CONSECUTIVE DAYS OF SVR POTENTIAL IS EXPECTED
ACROSS HIGH PLAINS...WITH REGIONAL OUTBREAK OF
LARGE HAIL AND
TORNADOES BEING MOST PROBABLE ACROSS CATEGORICAL MDT RISK AREA.
CLIMATOLOGICALLY FAVORABLE REGIME WILL FEATURE DIURNALLY SLOSHING
DRYLINE...LOCATED BENEATH FAVORABLE SHEAR AND MOISTURE PROFILES...E
OF LARGE UPPER LEVEL LOW. SVR CONVECTION TODAY IS FCST TO BE MUCH
BETTER ORGANIZED AND POTENTIALLY MORE DANGEROUS THAN ON WEDNESDAY
THANKS TO GREATER MOISTURE...STRONGER DEEP-LAYER SHEAR AND MORE
INTENSE LOW LEVEL FOCI FOR ASCENT.
THERMODYNAMIC PROFILES WILL BE FAVORABLE WITH STG SFC HEATING IN
RICHLY MOIST AIR MASS...BETWEEN DRYLINE AND WARM FRONT. PRECURSORY
MOIST ADVECTION -- NOW WELL UNDERWAY -- SHOULD RESULT IN SFC DEW
POINTS UPPER 50S TO LOW 60S IN IMMEDIATE VICINITY
DRYLINE...INCREASING QUICKLY TO MID 60S EWD OVER MUCH OF CENTRAL/NRN
KS...AND UPPER 60S/LOW 70S OVER TX/OK MOIST SECTOR. BY MID
AFTERNOON...EXPECT POTENTIAL FOR SFC-BASED TSTMS TO DEVELOP INVOF
ELONGATED SFC LOW AND NEARBY DRYLINE AND WARM FRONTAL SEGMENTS.
THIS ACTIVITY SHOULD MOVE NNEWD TO NNWWD ACROSS WARM FRONTAL ZONE.
BECAUSE OF RELATIVELY BACKED FLOW INVOF WARM FRONT...EFFECTIVE BULK
SHEAR...LOW LEVEL SRH AND BOUNDARY LAYER VORTICITY EACH WILL BE
MAXIMIZED THERE...AND ANY MATURE STORMS INTERACTING WITH FRONTAL
ZONE MAY PRODUCE TORNADOES BUT THEN MOVE QUICKLY INTO UNFAVORABLE
SFC AIR MASS.
VERTICAL SHEAR INCREASINGLY WILL
FAVOR SUPERCELLS/TORNADOES FARTHER
S IN WRN PORTION OF MOIST SECTOR WITH TIME AS WELL...AS CAPPING
WEAKENS ALONG DRYLINE. THIS ESPECIALLY IS A CONCERN LATE AFTERNOON
INTO EARLY EVENING WHEN LIFTED PARCELS STILL ARE SFC-BASED AND
STRENGTHENING LLJ GREATLY ENLARGES HODOGRAPHS IN ENVIRONMENT OF ANY
EXISTING SUPERCELLS. POTENTIAL WILL BUILD SWD ALONG KS SEGMENT OF
DRYLINE THROUGH AFTERNOON.
STRONG MERIDIONAL COMPONENT OF MEAN FLOW AND POTENTIAL FOR
SCATTERED-NUMEROUS TSTM COVERAGE PROVIDES SOME STORM-SCALE
UNCERTAINTIES PRECLUDING GREATER SIGNIFICANT HAIL/TORNADO
PROBABILITIES ATTM. HOWEVER...THERE SHOULD BE SUFFICIENT SBCINH --
E.G. 2000-2500 J/KG OVER MUCH OF WRN KS AND PERHAPS SMALL PART OF
SWRN NEB -- TO SUPPORT POTENTIAL FOR SEVERAL
DISCRETE/CYCLIC/TORNADIC SUPERCELLS DURING AFTERNOON AND EARLY
EVENING HOURS...ALSO PRODUCING DESTRUCTIVE HAIL. THOUGH
SUPERCELLS/TORNADO POTENTIAL MAY PERSIST WELL INTO NIGHTTIME
HOURS...OVERALL MODE SHOULD BECOME MORE LINEAR WITH TIME AFTER DARK.
INCREASING/ELEVATED TSTM COVERAGE WELL N OF WARM FRONT -- ACROSS
N-CENTRAL PLAINS...WILL RESULT IN POTENTIAL FOR SVR HAIL AS FAR N AS
PORTIONS SD.
...SRN HIGH PLAINS...
STRONGER BUOYANCY -- E.G. 3000-4000 J/KG MLCAPE -- AND GREATER
MLCINH EACH ARE FCST SWD OVER ERN PANHANDLES AND WRN OK...COMPARED
TO FARTHER N...LIMITING POTENTIAL COVERAGE. THREAT THEREFORE
BECOMES MORE ISOLATED AND CONDITIONAL WITH SWD EXTENT ACROSS SRN
HIGH PLAINS...HENCE SWD REDUCTION IN SVR PROBABILITIES.
HOWEVER...
VERY LARGE HAIL AND PERHAPS A FEW TORNADOES WILL BE
POSSIBLE WITH ANY STORMS THAT CAN FORM OVER THIS AREA. SOME FCST
SOUNDINGS REASONABLY INDICATE SLGT INCREASE IN BULK SHEAR -- E.G.
55-60 KT OVER WRN OK OR ABOUT 5-10 KT MORE THAN S OF WARM FRONT IN
KS -- THANKS TO MORE WLY COMPONENT OF FLOW ALOFT.
...ARKLATEX AREA...ERN OK...
SCATTERED TSTMS ARE EXPECTED TO DEVELOP THIS AFTERNOON IN ZONE OF
WEAK LARGE SCALE ASCENT/DESTABILIZATION ALOFT...JUXTAPOSED WITH STG
DIURNAL HEATING...RICH BOUNDARY LAYER MOISTURE...AND RELATIVELY WEAK
SBCINH. MAIN LIMITING FACTOR WILL BE LACK OF SUBSTANTIAL LOW LEVEL
FOCI...ESPECIALLY PRIOR TO DEVELOPMENT OF ANY OUTFLOW BOUNDARIES.
FCST SOUNDINGS INDICATE ENLARGED LOW LEVEL HODOGRAPHS...ESPECIALLY
IN NARROW ZONE OF SELY SFC WINDS IMMEDIATELY AHEAD OF UPPER LOW AND
S OF WARM FRONTAL ZONE. ALTHOUGH MID-UPPER LEVEL FLOW SHOULD BE
RELATIVELY WEAK...MESSY/TEMPORARY SUPERCELL ORGANIZATION IS POSSIBLE
AMONG MORE PREDOMINANT MULTICELLULAR MODES. THEREFORE WILL INCLUDE
MRGL PROBABILITIES FOR HAIL AND DAMAGING CONVECTIVE GUSTS.
SPC upgraded to Moderate Risk for Thursday..
Main Threat: Southwest Nebraska, West-Central Kansas, Central Oklahoma, and Central Texas
Read
MikeDeFino Blog for insight and discussion on this possible severe weather..As he pointed out the strong threat of possible strong tornadoes on the areas above..
Major Severe Threat Thread 
Linear Mode
