[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 032015
SWODY1
SPC AC 032013

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0313 PM CDT MON APR 03 2006

VALID 032000Z - 041200Z

...THERE IS A MDT RISK OF SVR TSTMS PORTIONS SERN/S-CENTRAL
VA...EXTREME S-CENTRAL MD...NC...NRN SC...

...THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE FROM SRN AL TO
CENTRAL PA...

...SYNOPSIS...
HIGH AMPLITUDE TROUGH -- EVIDENT IN MOISTURE CHANNEL IMAGERY FROM
SRN ONT SWD TO ERN TN -- SHOULD MOVE NEWD OVER CENTRAL APPALACHIANS
THROUGH REMAINDER PERIOD AS UPPER LEVEL LOW DIGS SEWD FROM NWRN ONT.
 SMALLER SHORTWAVE NOW MOVING THROUGH BASE OF BROADER SCALE TROUGH
OVER SRN APPALACHIANS WILL EJECT NEWD OVER ERN NC/SERN VA EARLY
TONIGHT.  ASSOCIATED/OCCLUDED SFC LOW WILL MOVE NEWD TOWARD SERN
QUE. OCCLUDED FRONT - NOW ANALYZED FROM SRN ONT ACROSS NWRN PA --
SHOULD MOVE EWD ACROSS NY AND NRN PA THROUGH EVENING...WHILE
TRAILING COLD FRONT MOVES ACROSS MUCH OF REMAINDER
MID-ATLANTIC...VA...CAROLINAS...NRN GA AND AL. WARM FRONT --
ANALYZED FROM SWRN PA SEWD ACROSS ERN VA TO SRN CHESAPEAKE
BAY...SHOULD MOVE NEWD ACROSS POTOMAC RIVER AND INTO PORTIONS
SRN/CENTRAL MD.

...TIDEWATER REGION THROUGH CAROLINAS/GA...
REF WW 147 AND RELATED MESOSCALE DISCUSSIONS FOR NOWCAST SITUATION
ACROSS PORTIONS SRN APPALACHIANS AND ADJACENT PIEDMONT ZONES OF
GA/CAROLINAS.  REF MESOSCALE DISCUSSION 421 AND WW 148 FOR NEAR-TERM
POTENTIAL FROM CENTRAL/NRN NC INTO SRN VA.

DAMAGING WIND POTENTIAL WILL CONTINUE THROUGH THIS EVENING WITH
CONVECTION AHEAD OF FRONT...AND TORNADOES STILL ARE A CONCERN FROM
COASTAL NC INTO PORTIONS VA/SRN MD TIDEWATER REGION.  SFC ANALYSIS
INDICATES SUBSTANTIAL MIXING-OUT OF BOUNDARY LAYER MOISTURE AHEAD OF
PRIMARY CONVECTIVE BAND -- WITH DEW POINTS UPPER 40S TO MID 50S F
NOW COMMON ACROSS MUCH OF PIEDMONT FROM VA-GA. SUCH DRYING IN
PROSPECTIVE SUBCLOUD LAYER MAY RESULT IN TORNADO POTENTIAL BEING
REDUCED...BY ENCOURAGING EVAPORATIVELY COOLED OUTFLOW PLUMES IN
SUBCLOUD LAYERS. HOWEVER...THIS ALSO ENCOURAGES DOWNDRAFT
ACCELERATION THROUGH BOUNDARY LAYER...AND ENHANCED POTENTIAL FOR
DAMAGING GUSTS.  THEREFORE WE WILL MAINTAIN MDT RISK...WHOSE
THRESHOLD ALREADY WAS BASED ON DAMAGING WIND PROBABILITIES.

DEEP-LAYER SHEAR WILL REMAIN FAVORABLE FOR SEVERE ACROSS ENTIRE
REGION -- EVEN WHERE FLOW HAS VEERED TO SWLY -- GIVEN STRENGTH OF
MID/UPPER LEVEL WINDS. HOWEVER...GREATEST COMBINATION OF
INSTABILITY...MOISTURE AND SHEAR SHOULD BE FROM ERN NC THROUGH ERN
VA AND PERHAPS SRN MD. LARGEST TORNADO PROBABILITIES WILL BE
SHUNTED EWD TOWARD MORE ROBUST MOISTURE INVOF COAST AND NEAR WARM
FRONT...WHERE RELATIVELY BACKED SFC FLOW ALSO ENHANCES DEEP-LAYER
SHEAR...AND SFC DEW POINTS SHOULD REMAIN IN UPPER 50S TO LOW 60S IN
MANY AREAS.

EARLIER MCS HAS LEFT BEHIND POOL OF OUTFLOW AIR IN ERN NC THAT IS
BEING HEATED/MODIFIED ATTM.  LOW LEVEL DRY ADVECTION AND MIXING WILL
ERODE WRN EDGE OF THIS PLUME SOMEWHAT...BUT VORTICITY/SHEAR SHOULD
REMAIN MAXIMIZED FROM THIS PLUME NWD TO WARM FRONTAL ZONE.  ANY
RELATIVELY DISCRETE ACTIVITY DEVELOPING IN WARM SECTOR AHEAD OF MAIN
CONVECTIVE BAND MAY INTERACT WITH EITHER FAVORABLY MODIFIED OUTFLOW
AIR OR WARM FRONT...WHERE BACKED FLOW...ENLARGED HODOGRAPHS...AND
LOWER LCL ARE EXPECTED.  VIS IMAGERY SHOWS BOUNDARY LAYER BILLOWS
OVER E-CENTRAL VA ATTM...INDICATING CAPPING...HOWEVER...AIR MASS
SHOULD CONTINUE TO DESTABILIZE WITH INSOLATION OCCURRING IN WAKE OF
MORNING CONVECTIVE/CLOUD AREA.

..N-CENTRAL APPALACHIANS/MID-ATLANTIC...
ORGANIZED LINE OF TSTMS...INVOF OCCLUDED/COLD FRONTAL ZONE...SHOULD
CONTINUE MOVING EWD ACROSS PORTIONS PA/WRN NY THROUGH REMAINDER
AFTERNOON INTO EARLY EVENING.  MAIN THREAT IS WIND DAMAGE.  GIVEN
STRENGTH OF VERTICAL SHEAR ACROSS THIS REGION... ISOLATED HAIL AND A
TORNADO OR TWO ALSO REMAIN POSSIBLE...PARTICULARLY IN ASSOCIATION
WITH EMBEDDED BOWS/MESOCYCLONES.  REF WW 146 AND ASSOCIATED
MESOSCALE DISCUSSIONS FOR NEAR TERM SITUATION. ACTIVITY SHOULD
DIMINISH THIS EVENING AS IT MOVES INTO LOW THETAE BOUNDARY LAYER
THAT WILL CONTINUE TO CHARACTERIZE MUCH OF ERN PA...CENTRAL NY AND
BEYOND.

..EDWARDS.. 04/03/2006