SPC AC 270730
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT FRI MAR 27 2009
VALID 291200Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS ERN PORTIONS CAROLINAS/VA TO
DELMARVA...
...SYNOPSIS...
MID-UPPER LEVEL CYCLONE -- NOW PIVOTING SEWD FROM 4-CORNERS REGION
-- WILL EJECT FROM 29/12Z POSITION OVER INDIANA/OH. CONSIDERABLE
SPREAD AND UNCERTAINTY IS EVIDENT AMONG SREF MEMBERS AND OPERATIONAL
SPECTRAL/NAM/UKMET REGARDING TRACK SPECIFICS AFTER BEGINNING OF
PERIOD. PROGGED TRACKS OVERLAY IN SPRAY PATTERN ACROSS SRN ONT...ST
LAWRENCE VALLEY AND NY...WITH VARYING AMPLITUDES FROM
PROGRESSIVE/OPEN-WAVE TO TIGHTLY CLOSED VORTEX.
DESPITE THAT MUCH SPREAD WITH UPPER AIR SOLUTION IN NERN
CONUS...PROGS ARE MORE CONSISTENT IN DEVELOPING
OCCLUSION/TRIPLE-POINT LOW OVER CENTRAL APPALACHIANS LATE DAY-2 INTO
EARLY THIS PERIOD...THEN MOVING IT ENEWD TO NEWD ACROSS MID-ATLANTIC
STATES AND SERN NEW ENGLAND BEFORE 30/12Z. TRAILING COLD FRONT
SHOULD SWEEP EWD ACROSS CAROLINAS/VA/MD THROUGH FIRST HALF OF
PERIOD...MOVING OFFSHORE TIDEWATER AREA AROUND 30/00Z.
...CAROLINAS TO DELMARVA AREA...
STG-SVR TSTMS ARE EXPECTED PRIOR TO FROPA...BOTH IN ORGANIZED
CONVECTIVE BAND NEAR SFC COLD FRONT...AND WITH ANY LINE SEGMENTS OR
SUPERCELLS THAT DEVELOP AHEAD OF QLCS. VERTICAL SHEAR PROFILES WILL
BE FAVORABLE FOR ALL MODES OF SVR...WITH MODIFIED NAM-KF SOUNDINGS
SHOWING INTENSE DEEP-TROPOSPHERIC WIND FIELDS AND EFFECTIVE SHEAR
VALUES ABOVE 50 KT OVER WARM SECTOR. MAIN UNCERTAINTIES ATTM
CONCERN CONVECTIVE MODE AND EXTENT/MAGNITUDE OF DIURNAL
DESTABILIZATION IN WARM SECTOR. NARROW AREA OF MORE
CONCENTRATED/LARGER SVR PROBABILITIES IS POSSIBLE...ONCE
AFOREMENTIONED UNCERTAINTIES ARE BETTER RESOLVED.
...FL...
TRAILING QLCS IS POSSIBLE INITIALLY OVER WRN/NRN FL THEN MOVING EWD
WITH STG-SVR GUSTS BEING MAIN CONCERN. LINE IS FCST TO WEAKEN WITH
TIME AS STRONGEST ISALLOBARIC FORCING LIFTS NEWD ACROSS NERN CONUS
AND WELL AWAY FROM THIS REGION...RESULTING IN VEERING PREFRONTAL
WINDS AND WEAKENING CONVERGENCE.
..EDWARDS.. 03/27/2009
CLICK TO GET WUUS03 PTSDY3 PRODUCT
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z
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