SWODY1
SPC AC 241249
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0749 AM CDT SUN MAY 24 2009
VALID 241300Z - 251200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A RELATIVELY BENIGN FLOW REGIME PERSISTS OVER THE CONUS WITH THE
PRIMARY POLAR JET TO THE N ACROSS SRN CANADA...AND THE SUBTROPICAL
JET TO THE S ACROSS NRN MEXICO AND THE GULF OF MEXICO. A SERIES OF
SLOW-MOVING VORTICES WILL CONTINUE IN BETWEEN THE PRIMARY FLOW
STREAMS...ONE OF WHICH WILL MOVE NWWD ACROSS AR...AND ANOTHER OVER
UT WILL MOVE NEWD AND GRADUALLY PHASE WITH A SEPARATE SHORTWAVE
TROUGH PROGRESSING EWD FROM THE PAC NW. A BROAD SWATH OF THE CONUS
WILL BE SUBJECTED TO WIDELY SCATTERED THUNDERSTORMS /MAINLY DIURNAL/
WITHIN THE DEEP MOISTURE PLUMES ACCOMPANYING THE LOWER MS VALLEY AND
INTERMOUNTAIN W MID LEVEL TROUGHS.
...SRN NEW ENGLAND THIS AFTERNOON...
A COLD FRONT WILL MOVE SLOWLY SEWD ACROSS NEW ENGLAND/NY/PA IN
ASSOCIATION WITH A NRN STREAM SHORTWAVE TROUGH CROSSING QUEBEC.
PRE-FRONTAL MOISTENING /BOUNDARY LAYER DEW POINTS IN THE 60S/ AND
SURFACE HEATING WILL RESULT IN A BELT OF WEAK-MODERATE INSTABILITY
FROM PA EWD INTO SRN NEW ENGLAND...AND THUNDERSTORM DEVELOPMENT IS
EXPECTED BY EARLY AFTERNOON ALONG AND IN ADVANCE OF THE FRONT.
MLCAPE VALUES OF 1000-1500 J/KG...0-6 KM BULK SHEAR OF 30-40 KT AND
RELATIVELY STRAIGHT HODOGRAPHS /ALONG THE SRN FRINGE OF THE STRONGER
MID-UPPER WLYS/ WILL BE SUPPORTIVE OF ORGANIZED CLUSTERS AND
POSSIBLY SPLITTING SUPERCELLS CAPABLE OF PRODUCING ISOLATED DAMAGING
WINDS AND MARGINALLY SEVERE HAIL. THE PRIMARY LIMITING FACTOR FOR A
MORE SUBSTANTIAL SEVERE THREAT WILL BE WEAK FLOW BELOW 700 MB...IN
COMBINATION WITH RATHER MODEST INSTABILITY.
...LOWER TX COAST THIS AFTERNOON...
AN INITIAL THUNDERSTORM COMPLEX HAS MOVED OFFSHORE AND IS
WEAKENING...WHILE CLOUD DEBRIS WILL CLEAR S TX BY MID MORNING AND
ANY LINGERING COLD POOL WILL DISSIPATE WITH DAYTIME HEATING. BY
EARLY AFTERNOON...EXPECT LOCAL SEA BREEZE CIRCULATIONS TO BECOME
ESTABLISHED IN AN ENVIRONMENT WITH MODERATE INSTABILITY INLAND
/MLCAPE VALUES NEAR 1500 J/KG/. MEANWHILE...AN EMBEDDED MID LEVEL
CYCLONIC VORTICITY CENTER NEAR DRT WILL CONTINUE TO PROGRESS ESEWD
TOWARD THE MATAGORDA BAY AREA. THIS VORT MAX IS WITHIN THE BELT OF
STRONGER MID-UPPER WLY/WNWLY FLOW OVER NRN MEXICO AND S TX...WHICH
WILL MAINTAIN SUFFICIENT DEEP LAYER VERTICAL SHEAR FOR ORGANIZED
THUNDERSTORM CLUSTERS...AND PERHAPS STORMS WITH SUPERCELL
STRUCTURES. A FEW STORMS SHOULD DEVELOP THIS AFTERNOON ALONG THE
SEA BREEZE...WITH THE POSSIBILITY OF ISOLATED HAIL/DAMAGING WINDS.
...NRN HIGH PLAINS THIS AFTERNOON INTO TONIGHT...
THE NEWD EJECTION OF THE MID LEVEL TROUGH OVER UT AND ITS PHASING
WITH A SEPARATE TROUGH APPROACHING THE NRN ROCKIES WILL INDUCE LEE
CYCLOGENESIS ACROSS WY/SE MT...AND A STRENGTHENING SELY LLJ THIS
AFTERNOON/EVENING ACROSS THE NRN HIGH PLAINS. THIS WILL RESULT IN
WAA AND THE NWD RETREAT OF A BAROCLINIC ZONE ACROSS THE CENTRAL HIGH
PLAINS OF KS/NE/CO...AS WELL AS NWWD TRANSPORT OF BOUNDARY LAYER DEW
POINTS IN THE MID 50S. HOWEVER...WIDESPREAD CLOUDS AND POOR MID
LEVEL LAPSE RATES WILL LIMIT THE DEGREE OF INSTABILITY ...AND WEAK
FLOW ALOFT WILL LIMIT DEEP LAYER VERTICAL SHEAR. THE RESULTANT
MOIST/WEAKLY UNSTABLE PROFILES WITH CURVED LOW-LEVEL HODOGRAPHS BUT
WEAK FLOW ALOFT COULD SUPPORT A FEW STORMS THAT ROTATE BRIEFLY
BEFORE BECOMING OUTFLOW DOMINANT.
...TN VALLEY INTO THE MID SOUTH TODAY...
THE SUBTROPICAL LOW WILL CONTINUE TO PROGRESS WNWWD ACROSS AR TODAY.
A BELT OF ENHANCED LOW-LEVEL ELY/SELY FLOW AND STRONGER LOW-LEVEL
SHEAR WILL ALSO TRANSLATE WNWWD FROM AL ACROSS NRN MS/WRN TN/NE AR.
PER A COMPARISON OF THE 00Z/12Z BMX SOUNDINGS...VWP TRENDS...AND
SHORT TERM MODEL FORECASTS...IT APPEARS THAT THE STRONGER LOW-LEVEL
SHEAR WILL NO LONGER BE PHASED WITH THE RICHER LOW-LEVEL
MOISTURE/INSTABILITY ACROSS AL AFTER ABOUT MID MORNING. INSTABILITY
WILL LIKELY REMAIN LIMITED FARTHER TO THE W TOWARD THE MS RIVER.
ANY POTENTIAL FOR ROTATING STORMS APPEARS TO BE LESS THAN YESTERDAY
AND TOO SMALL TO WARRANT THE ADDITION OF LOW TORNADO PROBABILITIES.
..THOMPSON/SMITH.. 05/24/2009
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