ACUS01 KWNS 030601
SWODY1
SPC AC 030559
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT THU APR 03 2008
VALID 031200Z - 041200Z
..THERE IS A MDT RISK OF SVR TSTMS LATE THIS AFTN INTO TONIGHT
ACROSS PARTS OF CNTRL/NRN TEXAS INTO SE OK...WRN AND CNTRL AR....
..THERE IS A SLGT RISK OF SVR TSTMS TODAY...SURROUNDING THE
MODERATE RISK AREA...ACROSS THE SRN PLAINS AND OZARK PLATEAU INTO
PARTS OF THE LWR OH VALLEY....
..SYNOPSIS...
A COMPLEX SPLIT UPPER FLOW PATTERN APPEARS LIKELY TO PERSIST ACROSS
THE EASTERN PACIFIC INTO THE WESTERN U.S. THROUGH THIS FORECAST
PERIOD. AND...EMBEDDED SHORT WAVE IMPULSES NOW OVER THE
INTERMOUNTAIN WEST AND SOUTHWESTERN STATES ARE EXPECTED TO REMAIN
PROGRESSIVE...AS A SIGNIFICANT UPSTREAM SHORT WAVE TROUGH APPROACHES
THE PACIFIC NORTHWEST COAST.
WITHIN THE STREAM EMANATING FROM THE NORTHERN PACIFIC...MODELS
INDICATE THAT A SIGNIFICANT SHORT WAVE TROUGH WILL DIG SOUTHEAST OF
THE NORTHERN INTERMOUNTAIN REGION INTO THE MID MISSOURI VALLEY BY
12Z FRIDAY. THIS SYSTEM IS PROGGED TO BE PRECEDED BY A COUPLE OF
SIGNIFICANT SHORT WAVE IMPULSES EMERGING FROM THE TROUGH IN THE
SOUTHERNMOST POLAR STREAM...NOW OVER THE SOUTHWESTERN STATES. THE
WEAKER INITIAL IMPULSE IS PROGGED TO LIFT OUT ACROSS THE MIDDLE
MISSISSIPPI VALLEY BY LATE THIS AFTERNOON...BEFORE CONTINUING
THROUGH THE OHIO VALLEY TONIGHT...WHILE AN INCREASINGLY
SHEARED...BUT MORE SIGNIFICANT IMPULSE SHIFTS ACROSS THE SOUTHERN
ROCKIES INTO THE SOUTHERN PLAINS.
MODELS INDICATE THAT THE LACK OF STRONGER/MORE FOCUSED MID/UPPER
FORCING WILL PRECLUDE STRONG SURFACE CYCLOGENESIS ALONG A FRONTAL
ZONE NOW DEVELOPING ACROSS THE SOUTH CENTRAL PLAINS INTO THE LOWER
OHIO/TENNESSEE VALLEYS. BUT...DESTABILIZATION ASSOCIATED WITH
EAST/NORTHEASTWARD MOISTURE RETURN AND STEEPENING LAPSE RATES IN THE
PRESENCE OF MODERATE TO STRONG DEEP LAYER SHEAR IS EXPECTED TO
SUPPORT FAIRLY WIDESPREAD STRONG/SEVERE THUNDERSTORM ACTIVITY ALONG
AND AHEAD OF THE FRONTAL ZONE.
..CNTRL/SRN PLAINS THROUGH THE LOWER OHIO VALLEY...
CONSIDERABLE STRONG/ISOLATED SEVERE THUNDERSTORM ACTIVITY MAY BE
ONGOING AT 12Z TODAY ACROSS THE OZARK PLATEAU...AIDED BY STRONG
LOWER/MID TROPOSPHERIC WARM ADVECTION BENEATH DIVERGENT UPPER FLOW
FIELD IN THE RIGHT ENTRANCE REGION OF A STRONG HIGH LEVEL JET
STREAK. THIS ACTIVITY SHOULD BE MOSTLY ELEVATED ABOVE THE WARM
FRONTAL INVERSION...WELL IN ADVANCE OF A WEAK FRONTAL WAVE EXPECTED
TO MIGRATE EAST NORTHEASTWARD OUT OF THE TEXAS/OKLAHOMA PANHANDLE
REGION THIS MORNING. TOWARD MID DAY...INTO THE AFTERNOON HOURS...AS
INITIAL UPPER WAVE LIFTS TOWARD THE MID MISSISSIPPI VALLEY...WARM
ADVECTION STORMS ARE EXPECTED TO WEAKEN/LIFT NORTHEASTWARD OUT OF
EASTERN OKLAHOMA/ARKANSAS. BUT...BREAKS IN CLOUD COVER AND THE
APPROACH OF SURFACE WAVE COULD SUPPORT ADDITIONAL ISOLATED STORM
DEVELOPMENT ACROSS THE OZARK PLATEAU...ON THE NORTHEASTERN FRINGE OF
A CAPPING ELEVATED MIXED LAYER EMANATING FROM THE PLATEAU REGION.
IF THIS OCCURS...WEAK TO MODERATE INSTABILITY...STRONG DEEP LAYER
SHEAR AND LARGE LOW-LEVEL HODOGRAPHS NEAR A 40-50 KT SOUTHWESTERLY
LOW-LEVEL JET WILL SUPPORT POTENTIAL FOR SUPERCELLS WITH
TORNADOES...IN ADDITION TO LARGE HAIL/DAMAGING WINDS.
FARTHER TO THE WEST/SOUTHWEST...INHIBITION IS EXPECTED TO BE STRONG
ENOUGH TO PRECLUDE CONVECTIVE DEVELOPMENT UNTIL AT LEAST LATE
AFTERNOON...WHEN FORCING NEAR A COLD FRONT/DRY LINE INTERSECTION
ACROSS SOUTH CENTRAL OKLAHOMA COULD BECOME SUFFICIENT FOR THE
INITIATION OF THUNDERSTORMS. ALTHOUGH LOW-LEVEL SHEAR APPEARS
LIKELY TO BE INITIALLY WEAK ACROSS THIS REGION...STRONG DEEP LAYER
SHEAR AND MODERATE TO STRONG INSTABILITY ASSOCIATED WITH A MOIST
BOUNDARY LAYER AND STEEP LAPSE RATES ARE EXPECTED TO BE SUFFICIENT
FOR SUPERCELLS. VERY LARGE HAIL...LOCALLY DAMAGING WIND GUSTS AND A
FEW TORNADOES WILL ALL BE POSSIBLE.
INTO THE EVENING HOURS...WITH THE APPROACH OF THE MAIN SOUTHERN
STREAM IMPULSE...A RAPID INCREASE IN SEVERE THUNDERSTORMS IS
EXPECTED ACROSS MUCH OF CENTRAL/NORTHERN TEXAS INTO AREAS NEAR/
NORTHWEST OF THE ARKLATEX. WITH THE BOUNDARY LAYER EXPECTED TO BE
SLOW TO COOL...WIDESPREAD MIXED LAYER CAPE IN EXCESS OF 2000 J/KG
..AND ENLARGING LOW-LEVEL HODOGRAPHS ASSOCIATED WITH A
STRENGTHENING LOW-LEVEL JET...COULD SUPPORT INCREASING TORNADIC
POTENTIAL...BEFORE TRANSITIONING TO A DAMAGING WIND THREAT WITH
POSSIBLE UPSCALE GROWTH INTO A QUASI LINEAR CONVECTIVE SYSTEM LATE
THIS EVENING.
.KERR/GRAMS.. 04/03/2008
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