SWODY1
SPC AC 231247
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0747 AM CDT WED MAY 23 2007
VALID 231300Z - 241200Z
..THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT FOR
THE NE TX PANHANDLE...NW OK...AND SRN KS...
..THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK...FROM
THE SRN HIGH PLAINS TO THE MID MO VALLEY...
..SYNOPSIS...
AN INITIAL SHORTWAVE TROUGH OVER THE WRN DAKOTAS WILL LIFT NEWD OVER
MANITOBA AS AN UPSTREAM TROUGH OVER SRN UT/NRN AZ MOVES EWD TO NRN
NM/SRN CO THIS EVENING AND THEN WRN KS LATE TONIGHT. AT THE
SURFACE...A COLD FRONT WILL SLOW ITS SEWD MOVEMENT ACROSS SRN KS/NW
OK/TX PANHANDLE THIS MORNING...AND STALL BY EARLY AFTERNOON. THE
FRONT WILL THEN BEGIN A SLOW RETREAT TO THE N THIS AFTERNOON/EVENING
IN RESPONSE TO CYCLOGENESIS OVER THE HIGH PLAINS IN ADVANCE OF THE
GREAT BASIN SHORTWAVE TROUGH. THIS SURFACE LOW WILL THEN DEVELOP
NEWD INTO NRN KS ALONG THE BAROCLINIC ZONE DURING THE OVERNIGHT
HOURS. THE PRIMARY SEVERE STORM THREAT AREAS SHOULD BE ENE OF THE
DEVELOPING SURFACE LOW ALONG THE RETREATING SURFACE FRONT LATE THIS
AFTERNOON...AND TO THE W ACROSS THE HIGH PLAINS WITH THE EJECTING
MID LEVEL WAVE BY EARLY TONIGHT.
..NRN TX PANHANDLE/NW OK/SRN KS THIS AFTERNOON INTO TONIGHT...
THE PRIMARY UNCERTAINTIES THIS AREA WILL BE THE EVENTUAL LOCATION OF
THE SURFACE FRONT BY THIS AFTERNOON...AND THE COVERAGE OF CONVECTION
ALONG THE BOUNDARY BY THIS EVENING. SURFACE OBSERVATIONS SHOW THAT
THE COLD FRONT IS A LITTLE FARTHER SE THAN THE MOST AGGRESSIVE MODEL
FORECASTS...THOUGH OBSERVATIONAL TRENDS OVER THE PAST 2-3 HOURS
SUGGEST THAT MOTION OF THE FRONT HAS SLOWED SUBSTANTIALLY. THERE
ARE ALSO SOME DISCREPANCIES IN HOW QUICKLY THE BOUNDARY RETREATS
LATER TODAY INTO EARLY TONIGHT...WHILE ALMOST ALL MODELS BUT THE 4
KM WRF NMM GENERATE CONVECTION ALONG THE RETREATING FRONT LATE THIS
AFTERNOON.
REGIONAL SOUNDINGS AND SURFACE OBSERVATIONS IN THE WARM SECTOR SHOW
BOUNDARY LAYER DEWPOINTS OF 64-67 F NEAR AND JUST UPSTREAM FROM THE
MDT RISK AREA. WITH THIS MOISTURE COMES THE POSSIBILITY OF STRATUS
LINGERING INTO THE AFTERNOON ACROSS MUCH OF THE WARM SECTOR...WHICH
MAY DELAY SURFACE HEATING. STILL...AFTERNOON TEMPERATURES IN THE
MID-UPPER 70S WITH MID 60S DEWPOINTS...BENEATH MODEST MID LEVEL
LAPSE RATES...SHOULD RESULT IN MLCAPE VALUES OF 2000-2500 J/KG ALONG
THE SURFACE BOUNDARY BY MID-LATE AFTERNOON. MODEL FORECAST
SOUNDINGS...AS WELL AS MODIFIED 12Z SOUNDINGS... SUGGEST THAT SOME
CONVECTIVE INHIBITION WILL PERSIST OVER MUCH OF THE WARM SECTOR.
GIVEN THAT THE STRONGER LARGE SCALE FORCING FOR ASCENT WILL REMAIN
FARTHER W/NW ACROSS NRN NM AND SRN CO...LOW-LEVEL ASCENT ALONG THE
RETREATING FRONT WILL BE NECESSARY FOR STORM INITIATION LATER THIS
AFTERNOON. THE MOST PROBABLE AREA FOR STORM DEVELOPMENT WILL BE
IMMEDIATELY ENE OF THE SURFACE TRIPLE POINT IN THE TX PANHANDLE
AFTER 21Z...WITH CONVECTION EXPECTED TO DEVELOP ENEWD ALONG THE
FRONT INTO NW OK AND SW KS.
A GRADUAL INCREASE IN MID-UPPER LEVEL SWLY FLOW AND BACKING/
STRENGTHENING LOW-LEVEL FLOW DURING THE EVENING WILL CONTRIBUTE TO
AN INCREASINGLY FAVORABLE ENVIRONMENT FOR SUPERCELLS FROM ABOUT
21-03Z. EXPECT STORMS TO MOVE ALONG THE BOUNDARY DURING THE
EVENING...WITH THE POTENTIAL TO PRODUCE TORNADOES...VERY LARGE
HAIL...AND DAMAGING WINDS. A COUPLE OF STRONG TORNADOES MAY OCCUR
THIS EVENING GIVEN THE EXPECTED MAGNITUDE OF THE LOW-LEVEL SHEAR
WITH AT LEAST MID 60S BOUNDARY LAYER DEWPOINTS.
..NE NM/SE CO INTO WRN KS THIS EVENING INTO TONIGHT...
IN ASSOCIATION WITH THE EJECTING MID LEVEL WAVE AND DEVELOPING
SURFACE CYCLONE...FORCING FOR ASCENT WILL INCREASE OVER THE HIGH
PLAINS THIS EVENING INTO TONIGHT. AT THE SAME TIME...MOISTURE WILL
ATTEMPT TO SPREAD BACK TO THE W/NW. INSTABILITY WILL LIKELY REMAIN
FAIRLY LIMITED OVER THE HIGH PLAINS...BUT STRONG ASCENT AND VERTICAL
SHEAR WILL BOTH HELP COMPENSATE AND SUPPORT A LARGE CONVECTIVE
CLUSTER BEGINNING LATE THIS AFTERNOON IN NM/CO...AND CONTINUING INTO
WRN KS TONIGHT. A MIXTURE OF BOWING SEGMENTS AND EMBEDDED
SUPERCELLS CAN BE EXPECTED WITHIN THE LARGER MCS...AND THE STRONGER
STORMS COULD PRODUCE LARGE HAIL..DAMAGING WINDS...AND PERHAPS A
TORNADO OR TWO.
.THOMPSON/GRAMS.. 05/23/2007
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