ACUS01 KWNS 211639
SWODY1
SPC AC 211637
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1137 AM CDT MON MAY 21 2007
VALID 211630Z - 221200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS A SWATH OF THE PLNS FROM
THE DAKOTAS S TO THE RIO GRANDE...
..SYNOPSIS...
POTENT ORE UPR LOW EXPECTED TO CONTINUE ESE INTO CNTRL ID THIS
AFTERNOON BEFORE TURNING MORE E INTO NW WY LATE TONIGHT/EARLY
TUESDAY. WHILE STRONGEST JET LIKELY WILL REMAIN ON SWRN SIDE OF LOW
THROUGH THE PERIOD...40 KT SSWLY 500 MB FLOW ON DOWNSTREAM SIDE OF
SYSTEM SHOULD OVERSPREAD THE WRN PARTS OF THE NRN PLNS BY EVENING.
WELL TO THE S...WEAKER SRN STREAM JET WILL PERSIST ACROSS NRN MEXICO
AND DEEP S TX. UPR TROUGH WITHIN THIS FLOW...NOW ENTERING SONORA
MEXICO...SHOULD WEAKEN AS IT HEADS E INTO NRN CHIHUAHUA EARLY
TUESDAY.
AT LWR LEVELS...EXPECT PRESSURES TO SLOWLY FALL OVER THE NRN PLNS...
WITH A LOW CONSOLIDATING OVER WRN SD TODAY AND THEN DEVELOPING NEWD
INTO ND TONIGHT. ANOTHER SFC CENTER MAY EVOLVE IN HEATED AREA OVER
ERN CO. ASSOCIATED STRENGTHENING OF SLY LLJ WITH THESE FEATURES
WILL ALLOW FOR CONTINUED MODEST NWD MOISTURE ADVECTION THROUGH THE
PLNS...BUT RICHER LOW LEVEL MOISTURE RETURN WILL BE CONFINED TO TX.
..DAKOTAS THIS AFTN INTO TONIGHT...
A LIMITED THREAT FOR SVR WILL EXIST ALONG AN EXTENDED SWATH ACROSS
THE PLNS FROM THE RIO GRANDE TO THE CANADIAN BORDER. IT APPEARS
..HOWEVER...THAT THE MOST FAVORABLE COMBINATION OF DEEP INSTABILITY
AND SHEAR FOR SUSTAINED SVR STORMS WILL BE OVER THE NRN PLNS AS
REGION HEATS AHEAD OF SLOWLY-ADVANCING COLD FRONT/LEE TROUGH
ASSOCIATED WITH DEVELOPING LEE LOWS.
STRONG SFC HEATING...EVAPOTRANSPIRATION AND MODEST MOISTURE
ADVECTION SHOULD CONTRIBUTE TO MLCAPE OF 1500-2000 J/KG THIS
AFTERNOON OVER CNTRL/ERN ND SWD INTO MUCH OF SD. THIS
DESTABILIZATION...COUPLED WITH CONVERGENCE ALONG COLD FRONT/LEE
TROUGH SEGMENTS...SHOULD SUPPORT TSTM DEVELOPMENT BY MID-LATE
AFTERNOON FROM N CNTRL ND SSW INTO WRN SD. 35-40 KT DEEP SSWLY
SHEAR ORIENTED ROUGHLY PARALLEL TO THE BOUNDARIES WILL BE SUFFICIENT
FOR A FEW SUPERCELLS AND/OR BOWING SEGMENTS WITH HAIL/HIGH WIND AND
PERHAPS A COUPLE TORNADOES. THE ACTIVITY SHOULD...HOWEVER...EVOLVE
INTO A MORE EXTENSIVE CONVECTIVE BAND BY EARLY EVENING...WITH A
GRADUALLY DIMINISHING SVR THREAT CONTINUING E ACROSS ERN ND/CNTRL SD
TONIGHT.
..MN...
APPARENT MCV /PER SATELLITE AND 12Z ABR RAOB/ THAT EVOLVED FROM
OVERNIGHT STORMS IN SD SHOULD CONTINUE SLOWLY ENE INTO CNTRL MN THIS
AFTERNOON. AS SYSTEM INTERACTS WITH SFC WARM FRONT OVER REGION AT
MAX HEATING TIME...NEW TSTMS MAY FORM. WHILE DEEP SHEAR WILL BE
MARGINAL FOR SUSTAINED ACTIVITY...ENHANCED LOW LEVEL SHEAR NEAR
FRONT AND UVV WITH MCV MAY LOCALLY HEIGHTEN SVR RISK.
..WRN/SRN TX...
OVERNIGHT STORMS IN NRN CHIHUAHUA/SW TX APPEAR TO GENERATED AN MCV
NOW NEAR DRT THAT IS MAINTAINING ARC OF STORMS OVER S TX. THE STORM
ARC SHOULD CONTINUE E INTO WEAKLY CAPPED ENVIRONMENT LATER TODAY.
RELATIVELY RICH MOISTURE INFLOW MAY ENHANCE PRECIP LOADING/DOWNBURST
POTENTIAL...BUT ANVIL SHADING SHOULD LIMIT DESTABILIZATION AND
OVERALL SVR THREAT.
FARTHER W...A NEW ROUND OF STRONG TO SVR STORMS EXPECTED TO FORM IN
STRONGLY HEATED AREA OVER SW TX/THE DAVIS MTNS THIS AFTERNOON.
ACTIVITY MAY BE ENHANCED WITH TIME BY CONTINUED EWD MOTION OF SRN
STREAM TROUGH. COMBINATION OF SFC DEWPOINTS AROUND 60 F AND STEEP
LOW TO MID LEVEL LAPSE RATES SHOULD BOOST SBCAPE TO 2000 J/KG.
STRONGER FLOW ALOFT WITH SRN STREAM JET SHOULD YIELD A FEW ORGANIZED
STORMS/SUPERCELLS WITH LARGE HAIL/DAMAGING WIND AND PERHAPS A
TORNADO THROUGH THIS EVENING.
..WRN KS SSW INTO ERN TX PNHDL...
IN THE ERN TX PANHANDLE AND SW KS...PROFILER DATA ATTM SUGGEST
PRESENCE OF A N/S CONVERGENCE ZONE OVER THE REGION...PROBABLY
RELATED TO LONGER-LIVED VORT NOW CENTERED OVER THE WRN END OF THE OK
PANHANDLE. THE CONVERGENCE ZONE MAY SERVE AS A FOCUS FOR NEW STORMS
AS AREA HEATS IN WAKE OF OVERNIGHT DEBRIS LATER TODAY. ORIENTATION
OF SHEAR RELATIVE TO CONVERGENCE ZONE SUGGEST FAIRLY RAPID EVOLUTION
INTO A CONVECTIVE BAND...BUT SUFFICIENT INSTABILITY/SHEAR WILL BE
PRESENT FOR SVR HAIL/WIND AND PERHAPS AN ISOLATED TORNADO...MAINLY
PRIOR TO STORM MERGERS.
..NE CO/WRN NEB...
THREAT FOR SUSTAINED SVR ACTIVITY LOOKS MORE NEBULOUS IN NE CO INTO
WRN NEB RELATIVE TO POINTS FARTHER N AND S. NEVERTHELESS...
MODERATE INSTABILITY WILL DEVELOP WITH HEATING GIVEN EXISTING STEEP
MID LEVEL LAPSE RATES AND CONTINUING LOW LEVEL MOISTURE RETURN AHEAD
OF WRN TROUGH. LOW TO MID LEVEL WIND PROFILES WILL BE SUPPORTIVE OF
SUSTAINED UPDRAFTS AND AT LEAST SOME STORM ROTATION...WEAK AND
INCREASINGLY BACKED UPR WINDS WILL TEND TO MITIGATE POTENTIAL FOR
SUSTAINED DISCRETE STORMS AND OVERALL SVR THREAT.
..UT/WY...
SHARP...PROGRESSIVE LEADING EDGE OF HEIGHT FALLS ASSOCIATED WITH ORE
UPR LOW SUGGEST LIKELY DEVELOPMENT OF A CONVECTIVE BAND OVER PARTS
OF UT/WY WITH HEATING LATER TODAY. COUPLED WITH BAND OF 40-50 KT
MID LEVEL SW FLOW AND FAIRLY DEEPLY MIXED/INVERTED-VEE TYPE
PROFILES...SETUP MAY SUPPORT A FEW EMBEDDED AFTERNOON/EARLY EVENING
STORMS WITH HIGH WIND.
.CORFIDI/JEWELL.. 05/21/2007
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