SWODY1
SPC AC 311609
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1109 AM CDT SUN MAY 31 2009
VALID 311630Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF MAINE...
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE NRN/CENTRAL PLAINS AND
UPPER MS VALLEY...
...NEW ENGLAND...
VIGOROUS POLAR VORTEX CROSSING SRN QUEBEC THIS AFTERNOON AND MAINE
EARLY TONIGHT WILL PUSH A COLD FRONT ACROSS NEW ENGLAND PRIOR TO
SUNSET. FRONT CURRENTLY EXTENDS SSWWD FROM NEAR BTV THRU ERN PA.
MOISTURE/INSTABILITY IN ADVANCE OF THE FRONT IS QUITE MEAGER AS
DEWPOINTS ARE GENERALLY LESS THAN 50F. HOWEVER WITH SOME HEATING
AND COOL STEEP LAPSE RATES...SBCAPES FROM 300-500 J/KG HAVE
DEVELOPED ACROSS MUCH OF ME. AT 16Z CINH WAS ABOUT GONE WITH
DEVELOPMENT OF LOW TOPPED CONVECTION ACROSS NRN ME. WILL CONTINUE A
LOW END SLIGHT RISK ACROSS MUCH OF ME THIS AFTERNOON AS STRONG/BRIEF
DAMAGING WINDS WILL BE POSSIBLE WITH STRONGER UPDRAFTS ALONG AND
AHEAD OF COLD FRONT AS DEEP LAYER SHEAR RAMPS UP AS 90-100KT 500MB
JET TRAVERSES SRN ENGLAND. ALSO GIVEN THE COOL LAPSE RATES...HAIL
WILL BE ASSOCIATED WITH MOST STRONGER UPDRAFTS.
...NRN-CNTRL PLNS/UPR MS VLY...
LATEST SFC AND SATELLITE/PW DATA SUGGEST THAT MOISTURE WILL REMAIN
QUITE SPARSE BY LATE MAY STANDARDS IN WARM SECTOR OVER THE NRN
PLNS/UPR MS VLY. BUT WITH STRONG HEATING...MID-LVL LAPSE RATES AOA
7 DEG C/KM...LOW/MID 50S SFC DEW POINTS SHOULD YIELD SBCAPE OF
1000-2000 J/KG OVER PARTS OF SD/WRN MN/NEB AND WRN IA BY LATE IN THE
DAY.
PERSISTENT CONVERGENCE NEAR SFC TRIPLE POINT/WRMFNT AND GLANCING
INFLUENCE OF LEAD IMPULSE CROSSING SRN MB/NRN MN...SHOULD SUPPORT
WDLY SCTD HIGH-BASED TSTM DEVELOPMENT OVER CNTRL/ERN SD AND PERHAPS
WRN MN/SE ND. OTHER STORMS MAY FORM SW ALONG PRE-FRONTAL TROUGH
ACROSS CNTRL NEB INTO NE CO.
SUFFICIENT DEEP SPEED AND DIRECTIONAL SHEAR /20-25 KT SWLY LOW LVL
FLOW VEERING TO 30-40 KT WNW FLOW AT 500 MB/ WILL BE PRESENT FOR
SUPERCELLS WITH LARGE HAIL AND...GIVEN SIZABLE TEMP-DEW POINT
SPREADS...HIGH WIND.
WARM ADVECTION ON THE STRENGTHENING LOW LEVEL JET THIS EVENING WILL
SUPPORT THE DEVELOPMENT OF AN MCS MOVING EWD ACROSS IA. PRIMARILY A
WIND DAMAGE THREAT WILL ACCOMPANY ANY MCS.
...W TX AND EXTREME SE NM...
WEAK HEIGHT FALLS OVER THE SRN RCKYS ASSOCIATED WITH LWR CO VLY UPR
LOW WILL INDUCE A MODEST SELY LOW LVL FLOW ACROSS SW TX. SFC DEW
POINTS WILL LIKELY MIX INTO THE 50S DURING THE AFTN...DESPITE
PRESENCE OF FAIRLY SUBSTANTIAL MOISTURE /PW TO 1.25 INCHES/ OVER THE
LWR RIO GRANDE. BUT PERSISTENT UPSLOPE FLOW...DIFFERENTIAL
HEATING...AND WEAK FORCING ALOFT LIKELY WILL YIELD HIGH-BASED STORMS
OVER THE TRANSPECOS REGION INTO SE NM BY MID/LATE AFTN. 30 KT DEEP
WNWLY SHEAR MAY PROVE SUFFICIENT FOR A FEW ORGANIZED/ SUSTAINED
STORMS WITH LARGE HAIL/LOCALLY STRONG WINDS.
..HALES/KERR.. 05/31/2009
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