SWODY3
SPC AC 220704
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0204 AM CDT SUN MAR 22 2009
VALID 241200Z - 251200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF ERN OK/TX INTO
THE LOWER MS VALLEY...
...SYNOPSIS...
MID/UPPER-LEVEL LOW INITIALLY OVER SD/NEB WILL EVOLVE INTO AN OPEN
WAVE TUESDAY AS ASSOCIATED JET STREAK DEVELOPS NNEWD FROM THE LOWER
MO VALLEY INTO UPPER GREAT LAKES. AS THIS PROCESS OCCURS...A
SECONDARY VORTICITY MAXIMUM AND ATTENDANT MID/HIGH-LEVEL JET STREAKS
WILL INITIALLY SHIFT EWD ACROSS OK AND NRN TX...AND THEN MORE NEWD
INTO THE MID MO VALLEY. DCVA IN ADVANCE OF THIS FEATURE IN CONCERT
WITH A COUPLED UPPER-LEVEL JET STREAK STRUCTURE WILL RESULT IN A
ZONE OF STRONG DEEP-LAYER FORCING FOR ASCENT FROM THE MID MS VALLEY
SWD INTO THE ARKLATEX AND LOWER MS VALLEY.
AT THE SURFACE...DEEPLY OCCLUDED SURFACE LOW WILL DEVELOP NEWD FROM
SERN SD ACROSS SRN MN...NWRN WI TO LAKE SUPERIOR. TRAILING COLD
FRONT WILL PUSH EWD THROUGH THE UPPER MIDWEST AND MID MS
VALLEY...AND MORE SEWD THROUGH THE ARKLATEX INTO LOWER MS VALLEY. A
MARINE/WARM FRONT WILL LIFT NWD THROUGH PORTIONS OF LA/MS IN ADVANCE
OF THE COLD FRONT.
...ERN PARTS OF OK/TX INTO THE MIDDLE AND LOWER MS VALLEYS...
PERSISTENT LOW-LEVEL RIDGING ALONG THE E COAST /IN ASSOCIATION WITH
DEEP-LAYER CYCLONE OVER THE WRN ATLANTIC/ WILL CONTINUE TO LIMIT THE
BREADTH OF PREFRONTAL WARM SECTOR...PARTICULARLY OVER THE MID MS
VALLEY INTO UPPER MIDWEST. FARTHER S...FURTHER AIR MASS
MODIFICATION WILL OCCUR OVER THE WRN GULF BASIN WITH DEWPOINTS
GRADUALLY INCREASING THROUGH THE 60S AHEAD OF COLD FRONT FROM ERN TX
INTO THE LOWER MS VALLEY. THIS MOISTURE WILL COINCIDE WITH MODESTLY
STEEP MIDLEVEL LAPSE RATES...CONTRIBUTING TO POCKETS OF MODERATE
CONVECTIVE INSTABILITY ACROSS THE SLIGHT RISK AREA WHERE MLCAPE MAY
APPROACH 1000-1500 J/KG. MORE WIDESPREAD CLOUDINESS AND DRIER
BOUNDARY LAYER CONDITIONS WILL LIMIT MLCAPE TO AOB 500 J/KG FROM THE
OZARK PLATEAU INTO MID MS VALLEY.
CLUSTERS OF TSTMS OR A LINEAR CONVECTIVE SYSTEM WILL LIKELY BE
ONGOING ALONG FRONT TUESDAY MORNING FROM THE LOWER MO VALLEY INTO
NRN TX. INCREASED LARGE-SCALE FORCING IN ADVANCE OF SECONDARY
IMPULSE /AS MENTIONED IN SYNOPSIS/ IS EXPECTED TO SUPPORT A GRADUAL
INCREASE IN STORM INTENSITY THROUGH THE DAY...PARTICULARLY ACROSS
THE SLIGHT RISK AREA WHERE STRONGER AIR MASS DESTABILIZATION WILL
OCCUR. IN ADDITION TO THE COLD FRONTAL ACTIVITY...OTHER STORMS MAY
DEVELOP WITHIN OPEN WARM SECTOR OR ALONG RETREATING WARM/MARINE
FRONT OVER THE LOWER MS VALLEY TUESDAY AFTERNOON.
THE COMBINATION OF THE MODERATE INSTABILITY AND MODERATE TO STRONG
VERTICAL SHEAR SUGGESTS THE POTENTIAL FOR EMBEDDED SUPERCELL AND/OR
BOWING STRUCTURES WITH THE THREAT FOR DAMAGING WINDS...TORNADOES AND
SOME HAIL. FARTHER N OVER THE OZARKS INTO MID MS VALLEY....VERTICAL
SHEAR WILL BE QUITE STRONG OWING TO THE COLLOCATION OF 50-60 KT LLJ
AND 70-80 KT MIDLEVEL FLOW. CURRENTLY...IT APPEARS THAT THE VERY
MARGINAL INSTABILITY WILL PRECLUDE A MORE SUBSTANTIAL/ORGANIZED
SEVERE THREAT. THEREFORE...ONLY LOW SEVERE PROBABILITIES HAVE BEEN
INCLUDED FOR THESE AREAS.
..MEAD.. 03/22/2009
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