SWODY1
SPC AC 220600
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT TUE APR 22 2008
VALID 221200Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF NW TX INTO THE
TX PANHANDLE AND FAR WRN OK TONIGHT...
...SYNOPSIS...
AN UPPER TROUGH WILL MOVE NEWD ACROSS THE UPPER MS VALLEY/NRN GREAT
LAKES REGION TODAY REACHING ONTARIO BY 12Z WEDNESDAY. IN THE WAKE
OF THIS TROUGH...UPPER FLOW IS EXPECTED TO BECOME MORE AMPLIFIED AS
A PACIFIC TROUGH DEEPENS AND MOVES INLAND IN THE WEST AND SUPPORTS
DOWNSTREAM RIDGE BUILDING NEWD FROM E TX/LOWER MS VALLEY INTO THE
MID MS/OH VALLEYS. A WEAK IMPULSE IN THE SRN STREAM SHOULD MOVE
ESEWD ACROSS E TX/LOWER MS VALLEY THIS MORNING INTO THE AFTERNOON.
MODELS REMAIN FAIRLY CONSISTENT SHOWING A STRONGER SRN STREAM SHORT
WAVE TROUGH WILL TRACK ENEWD ACROSS NWRN MEXICO LATER TONIGHT
REACHING FAR W TX BY 12Z WEDNESDAY.
IN THE LOW LEVELS...COLD FRONT ATTENDANT WITH UPPER MS VALLEY TROUGH
WILL MOVE EWD INTO THE WRN GREAT LAKES REGION AND MID MS VALLEY.
SRN EXTENT IS EXPECTED TO MOVE SLOWLY SWD THROUGH OK AND SHOULD
STALL FROM SRN MO/NWRN AR TO SRN OK AND NW TX BY LATE THIS
AFTERNOON. THIS WILL OCCUR AS LOW LEVEL MASS FIELDS WEAKEN ACROSS
ERN OK/E TX INTO THE LOWER AND MID MS VALLEY...AND RESPOND WWD TO
THE SRN/CENTRAL HIGH PLAINS WITH APPROACH OF SRN STREAM IMPULSE AND
WRN TROUGH.
...MID MS VALLEY SWD INTO AR THROUGH THIS AFTERNOON...
MODELS SUGGEST TSTMS...SOME STRONG TO SEVERE...SHOULD BE ONGOING
ACROSS SWRN MO INTO ERN IA/WRN IL AT 12Z TODAY. ALTHOUGH STRONGER
FORCING FOR ASCENT IS EXPECTED TO REMAIN N OF THIS REGION TODAY...
LOW LEVEL CONVERGENCE ALONG THE COLD FRONT AND ANY OUTFLOW
BOUNDARIES SHOULD SUPPORT ADDITIONAL TSTM DEVELOPMENT INTO THE
AFTERNOON. SURFACE HEATING WITHIN A MOIST AIR MASS IS EXPECTED TO
BECOME MODERATELY UNSTABLE SUPPORTING THE CONVECTIVE DEVELOPMENT.
MODEST DEEP LAYER SHEAR /AROUND 30 KT/ SUGGESTS TSTMS SHOULD BE
MULTICELLULAR WITH A POTENTIAL FOR ISOLATED HAIL AND STRONGER WIND
GUSTS. ADDITIONAL DEVELOPMENT IS POSSIBLE SWD INTO AR ALONG SRN
EXTENT OF ONGOING MORNING ACTIVITY WITH SIMILAR THREATS INTO THE
AFTERNOON.
...PARTS OF ERN TX INTO LA THROUGH THIS AFTERNOON...
AIR MASS IS EXPECTED TO BECOME MODERATELY UNSTABLE ACROSS THIS
REGION TODAY. MODELS ARE FAIRLY CONSISTENT SHOWING TSTMS DEVELOPING
BY LATE MORNING/EARLY AFTERNOON ACROSS MUCH OF E TX AND WRN LA AS
ASCENT ATTENDANT TO WEAK LEAD SRN STREAM IMPULSE SPREADS ESEWD
ACROSS THIS REGION DURING THIS TIME PERIOD. ALTHOUGH SLY LOW LEVEL
WINDS ARE FORECAST TO WEAKEN BY LATE MORNING...25-30 KT NWLY MID
LEVEL WINDS WILL PROVIDE SUFFICIENT EFFECTIVE BULK SHEAR AROUND 30
KT TO SUPPORT A FEW ORGANIZED STORMS. HOWEVER...GIVEN THE
LIKELIHOOD FOR WEAK FORCING...PRESENT INDICATIONS SUGGEST SEVERE
WEATHER THREAT COVERAGE SHOULD BE SPORADIC RESULTING IN LOW SEVERE
PROBABILITIES.
...WRN AR/CENTRAL/SRN OK TO WRN N TX THIS AFTERNOON/EVENING...
STRONG SURFACE HEATING WITHIN A MOIST AIR MASS RESIDING ALONG THE
STALLED FRONT THIS AFTERNOON WILL RESULT IN MLCAPE VALUES RANGING
FROM 2000-3000 J/KG. ALTHOUGH FORCING FOR ASCENT SHOULD BE WEAK
GIVEN BUILDING RIDGE OVER THIS REGION...MODELS SUGGEST CONVERGENCE
ALONG BOUNDARY AND SURFACE HEATING SHOULD PROVE SUFFICIENT TO
OVERCOME CAP AND SUPPORT TSTM DEVELOPMENT. WEAK DEEP LAYER SHEAR
WILL RESULT IN GENERALLY UN-ORGANIZED TO MULTICELL STORMS WITH
ISOLATED HAIL AND STRONG WIND GUSTS POSSIBLE WITH THE STRONGER
STORMS.
...PARTS OF W TX NWD TO WRN KS THIS EVENING AND TONIGHT...
SELY LOW LEVEL WINDS ARE EXPECTED TO STRENGTHEN TO 40-45 KT THIS
EVENING ACROSS THE SRN/CENTRAL HIGH PLAINS IN RESPONSE TO HEIGHT
FALLS AHEAD OF WRN LONGWAVE TROUGH. THIS WILL RESULT IN INCREASING
MOIST/WARM AIR ADVECTION INTO THIS REGION WITH THE POTENTIAL FOR
TSTM DEVELOPMENT THIS EVENING THROUGH TONIGHT. STEEP LAPSE RATES
SPREADING NEWD ACROSS THIS REGION AFTER 23/00Z ATOP THE MOISTURE
RETURN WILL RESULT IN STRONG INSTABILITY. EFFECTIVE BULK SHEAR UP
TO 50 KT WILL FAVOR SUPERCELL STRUCTURES WITH HAIL AND WIND BEING
THE PRIMARY THREATS. SOME STORMS MAY DEVELOP FARTHER NWD OVERNIGHT
INTO WRN KS.
..PETERS/GRAMS.. 04/22/2008
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