SPC AC 200522
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1222 AM CDT WED APR 20 2011
VALID 201200Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN TX ENEWD ACROSS THE
MID SOUTH...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE MID-ATLANTIC
REGION...
...SYNOPSIS...
RELATIVELY FLAT UPPER TROUGH CROSSING THE CENTRAL U.S. EARLY IS
FORECAST TO SHIFT INTO/ACROSS THE NORTHEAST THIS PERIOD...WITH MORE
ZONAL/WLY FLOW ALOFT LEFT ACROSS MUCH OF THE COUNTRY IN ITS WAKE.
MEANWHILE...A TROUGH PROGRESSING TOWARD THE WRN U.S. IS EXPECTED TO
REACH THE COAST LATE IN THE PERIOD.
AT THE SURFACE...A COLD FRONT IS PROGGED TO CROSS THE NRN AND
CENTRAL APPALACHIANS THROUGH THE AFTERNOON...WHILE SHIFTING MORE
SLOWLY SEWD ACROSS THE MID SOUTH INTO THE GULF COAST STATES/SWD INTO
TX. BY THE END OF THE PERIOD...THE NRN PORTION OF THE FRONT WILL
LIE OVER THE WRN ATLANTIC OFF NEW ENGLAND AND THE MID-ATLANTIC
REGION...WHILE STRETCHING WWD ACROSS THE GULF COAST STATES INTO TX.
...ERN TX ENEWD ACROSS THE GULF COAST STATES...
STORMS SHOULD BE ONGOING AT THE START OF THE PERIOD INVOF THE
SURFACE FRONT...AND EXPECT PERSISTENT REDEVELOPMENT TO OCCUR THROUGH
THE AFTERNOON AS DIURNAL HEATING/DESTABILIZATION INCREASE -- DESPITE
THE LACK OF A FORCING MECHANISM ALOFT.
WHILE FLOW ALOFT SHOULD ALSO SLACKEN ACROSS THIS REGION A BIT DURING
THE AFTERNOON...PRESENCE OF THE FRONT AND AMPLY MOIST/UNSTABLE
AIRMASS SUGGEST STRONGER STORMS WILL BE CAPABLE OF LOCALLY DAMAGING
WINDS AND MARGINAL HAIL INTO THE EVENING.
...MID-ATLANTIC REGION...
POTENTIAL FOR CONVECTIVE DEVELOPMENT REMAINS A QUESTION ATTM...AS
WEAKENING CONVECTION EARLY IN THE PERIOD SHOULD RESULT IN EXPANSIVE
CLOUD COVER ACROSS THIS REGION. WHILE MODELS FORECAST AFTERNOON
DESTABILIZATION AHEAD OF THE ADVANCING FRONT...ATTM IT APPEARS THAT
WITH STRONGER FORCING ALOFT SHIFTING NE OF THIS REGION AND THE
LIKELIHOOD FOR CLOUDINESS TO RETARD HEATING...CONVECTIVE DEVELOPMENT
MAY BE LESS WIDESPREAD/VIGOROUS THAN EXPECTED EARLIER.
HOWEVER...WILL MAINTAIN SLIGHT RISK FOR WIND...AS ANY POCKETS OF
HEATING COULD PERMIT STORM DEVELOPMENT ALONG/AHEAD OF THE FRONT
WHICH -- GIVEN STRENGTH OF THE FLOW FIELD ALOFT -- WOULD LIKELY
RESULT IN LOCALLY DAMAGING WINDS.
...OK AND VICINITY...
STRENGTHENING SLY LOW-LEVEL JET AND RESULTING ISENTROPIC UPGLIDE MAY
RESULT IN ELEVATED CONVECTIVE DEVELOPMENT LATE IN THE PERIOD. WITH
STEEP LAPSE RATES ALOFT...INSTABILITY SHOULD BE SUFFICIENT -- IN
CONJUNCTION WITH MODERATE WLYS ALOFT -- TO YIELD A FEW STRONGER
STORMS. THUS...WILL MAINTAIN LOW PROBABILITY HAIL THREAT ACROSS
THIS REGION.
..GOSS/COHEN.. 04/20/2011
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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