SPC AC 231954
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0254 PM CDT WED APR 23 2008
VALID 232000Z - 241200Z
...THERE IS A MDT RISK OF SVR TSTMS LATE THIS AFTN/EVE ACROSS PARTS
OF NORTHWEST/NORTH CENTRAL TEXAS INTO SOUTHWEST OKLAHOMA...
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK
AREA...ACROSS A LARGE PART OF THE CNTRL/SRN PLAINS....
...SOUTHERN PLAINS INTO LWR/MID MO VALLEY...
MODERATE INSTABILITY IS ALREADY PREVALENT OVER A BROAD AREA OF THE
CENTRAL/SOUTHERN PLAINS...WHERE LOW-LEVELS HAVE MOISTENED BENEATH
STEEP MID-LEVEL LAPSE RATES. AND...THIS HAS ALREADY CONTRIBUTED TO
EXTENSIVE CONVECTIVE DEVELOPMENT FROM THE TEXAS SOUTH PLAINS INTO
EASTERN KANSAS...SUPPORTED BY A DIVERGENT UPPER FLOW FIELD
DOWNSTREAM OF A SHORT WAVE IMPULSE EMANATING FROM THE SUBTROPICAL
PACIFIC. LOW-LEVEL FOCUS FOR CONVECTION IS NOT STRONG...AND DEEP
LAYER SHEAR STILL FAIRLY WEAK...SO STORMS TO THIS POINT HAVE
REMAINED DISORGANIZED.
HOWEVER...THE STRONGER MID/UPPER JET STREAK ASSOCIATED WITH THE
SUBTROPICAL SYSTEM IS ALREADY NOSING INTO THE TEXAS SOUTH
PLAINS...AND PROGGED TO CONTINUE TOWARD THE ARKLATEX REGION LATE
THIS AFTERNOON AND TONIGHT. AS THIS OCCURS...THE MID/UPPER CYCLONIC
VORTICITY CENTER IS EXPECTED TO DEVELOP EAST NORTHEASTWARD OUT OF
NEW MEXICO...ACROSS THE RED RIVER VALLEY BY THIS EVENING.
AND...MODELS GENERALLY AGREE THAT A SOUTHERLY LOW-LEVEL JET WILL
STRENGTHEN FROM 30-50 KT ACROSS CENTRAL TEXAS LATE THIS AFTERNOON
AND EVENING.
IT SEEMS PROBABLE THAT A CONVECTIVELY ENHANCED/GENERATED BOUNDARY
WILL BECOME BETTER DEFINED ACROSS EXTREME NORTHERN TEXAS INTO THE
SOUTHERN TEXAS PANHANDLE LATE THIS AFTERNOON...AND THE FOCUS FOR
INTENSIFYING THUNDERSTORM ACTIVITY. MIXED LAYER CAPE INCREASING IN
EXCESS OF 2000 J/KG WILL BECOME SUPPORTIVE OF INTENSE UPDRAFTS
CAPABLE OF PRODUCING VERY LARGE HAIL IN THE PRESENCE OF STRONG DEEP
LAYER SHEAR. AND...LOW-LEVEL HODOGRAPHS NEAR THE SURFACE BOUNDARY
MAY BECOME SUFFICIENTLY LARGE TO SUPPORT A FEW TORNADOES.
AN INCREASINGLY ORGANIZED CLUSTER OF STORMS ACCOMPANIED BY A RISK
FOR DAMAGING WINDS APPEARS POSSIBLE THIS EVENING ACROSS PARTS OF
SOUTHERN OKLAHOMA/NORTHERN AND WEST CENTRAL TEXAS. BUT...A WARM
ELEVATED MIXED LAYER ADVECTING OFF THE ROCKIES/PLATEAU REGION IN THE
WAKE OF THE UPPER IMPULSE IS EXPECTED TO EVENTUALLY SUPPRESS
ACTIVITY OVERNIGHT. TOWARD 12Z THURSDAY...PRIMARY THUNDERSTORM
ACTIVITY MAY CONSOLIDATE IN AN ELEVATED WARM ADVECTION REGIME ON THE
EASTERN EDGE OF THE CAP ACROSS PARTS OF THE EASTERN SOUTHERN PLAINS
INTO THE OZARK PLATEAU/LOWER AND MID MISSOURI VALLEY. THE RISK FOR
LARGE HAIL WILL BECOME THE PRIMARY SEVERE THREAT WITH THIS ACTIVITY.
...NORTH CENTRAL HIGH PLAINS INTO THE UPPER MISSISSIPPI VALLEY...
MOISTURE RETURN IS UNDERWAY...AND SURFACE HEATING IS CONTRIBUTING TO
A NARROW CORRIDOR OF MODERATE INSTABILITY NEAR THE LEE SURFACE
TROUGH...ACROSS EASTERN COLORADO INTO THE VICINITY OF A STATIONARY
FRONTAL ZONE NEAR THE BLACK HILLS REGION. THE FRONT BISECTS SOUTH
DAKOTA IN A SOUTHWEST THROUGH NORTHEAST FASHION...ALONG WHICH MODELS
INDICATE THE PRIMARY SURFACE LOW WILL TRACK OUT OF SOUTHEAST WYOMING
LATER TODAY/TONIGHT. THIS IS FORECAST TO OCCUR AS A SHORT WAVE
IMPULSE WITHIN THE POLAR STREAM LIFTS NORTHEAST OF THE GREAT BASIN
LATE THIS AFTERNOON...IN ADVANCE OF THE PRIMARY UPPER SYSTEM STILL
NEAR THE PACIFIC COAST.
LARGE-SCALE ASCENT WILL AID STORM DEVELOPMENT ALONG THE SURFACE
TROUGH THROUGH EARLY EVENING...IN THE PRESENCE OF A MODERATE TO
STRONGLY SHEARED CYCLONIC FLOW REGIME SUPPORTIVE OF SUPERCELLS
CAPABLE OF PRODUCING LARGE HAIL/DAMAGING WIND GUSTS. ISOLATED
TORNADOES WILL ALSO BE POSSIBLE AS A SOUTHERLY LOW-LEVEL JET
STRENGTHENS FROM 30 TO 50 KTS TO THE EAST OF SURFACE TROUGH.
CONVECTION IS EXPECTED TO PERSIST LATE THIS EVENING INTO THE
OVERNIGHT HOURS ACROSS PARTS OF THE NORTHERN PLAINS...MAINLY IN A
FAVORABLE ELEVATED WARM ADVECTION REGIME TO THE NORTHEAST OF THE
SURFACE LOW. BUT...THE LOSS OF HIGH PLAINS DAYTIME HEATING...AND
WEAKER DESTABILIZATION EASTWARD TOWARD THE UPPER MISSISSIPPI VALLEY
IS TO LIMIT FURTHER SEVERE POTENTIAL.
...NORTHEAST...
WEAK DESTABILIZATION AHEAD OF A COLD FRONT...ASSOCIATED WITH A SHORT
WAVE TROUGH DIGGING WITHIN INCREASINGLY NORTHWESTERLY FLOW TOWARD
NEW ENGLAND...COULD BECOME SUPPORTIVE OF SCATTERED STRONG STORMS TO
THE LEE OF THE LOWER GREAT LAKES LATE THIS AFTERNOON. SOME OF THIS
ACTIVITY MAY BE CAPABLE OF PRODUCING SOME SMALL HAIL AND GUSTY
WINDS.
..KERR.. 04/23/2008
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