SWODY1
SPC AC 191622
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1122 AM CDT THU MAY 19 2011
VALID 191630Z - 201200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE SOUTHERN
AND CENTRAL PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS FROM DELMARVA NWD INTO NY...
...CENTRAL/SOUTHERN PLAINS...
SATELLITE IMAGERY THE PAST 6 HOURS SHOWS THE UPPER WINDS HAVE
STARTED TO BACK ACROSS THE SRN/CENTRAL HIGH PLAINS...IN RESPONSE TO
ONE SHORTWAVE TROUGH LIFTING NWWD FROM THE CENTRAL PLAINS TOWARD THE
NRN ROCKIES...AND AN IMPRESSIVE SHORTWAVE TROUGH MOVING ESEWD
THROUGH SRN CA TOWARD AZ. THIS SHOULD RESULT IN THE DRYLINE TO NOT
MIXING AS FAR EAST AS WED...PERHAPS ONLY TO NEAR A DDC-GAG-ABI LINE
BY LATE AFTERNOON. WV IMAGERY SUGGESTS A WEAK WAVE IS MOVING INTO
WRN NM AND PRIMARY LIFT WILL SPREAD TOWARD ERN CO/WRN KS LATE IN THE
DAY...BUT THE DYNAMICAL FORCING SHOULD BE WEAK OVER MOST OF THE
WARM SECTOR. MOST MODELS...INCLUDING THE HIGH RESOLUTION
VERSIONS...ARE CONSISTENT IN STORMS DEVELOPING 21-00Z IN AREA OF
STRONGER LOW LEVEL CONVERGENCE NEAR INTERSECTION OF DRYLINE AND WARM
FRONT IN CENTRAL KS. THE APPROACHING WAVE MAY ALSO AID STORM
DEVELOPMENT SWD ALONG DRYLINE INTO NWRN OK. MODERATE INSTABILITY AND
DEEP LAYER SHEAR AT 50-60 KT WILL FAVOR SUPERCELLS. THIS COMBINATION
OF SHEAR AND INSTABILITY SHOULD SUPPORT HAIL IN EXCESS OF 2
INCHES...WIND DAMAGE AND TORNADOES...ESPECIALLY CLOSER TO THE WARM
FRONT IN KS.
...SWRN OK SWWD INTO SWRN TX...
DRYLINE WILL RETREAT WWD DURING THE NIGHT AND MAY PROVIDE FOCUS FOR
THUNDERSTORMS TO DEVELOP...AFTER 06Z...AS LARGE SCALE FORCING
INCREASES FROM THE WEST. THE COMBINATION OF DEWPOINTS CLIMBING BACK
INTO THE MID 60S...STEEP MID LEVEL LAPSE RATES AND MID LEVEL SPEED
MAX AT 50 KT WILL PROVIDE SUFFICIENT SHEAR AND INSTABILITY FOR
SUPERCELLS. GIVEN THE TIME OF NIGHT AND SLIGHTLY STABLE BOUNDARY
LAYER...EXPECT SEVERE HAIL TO BE THE MAIN THREAT... THOUGH STRONG
DOWNDRAFTS MAY ALSO RESULT IN WIND DAMAGE.
...MID ATLANTIC STATES INTO SOUTHERN NEW ENGLAND...
THE UPPER LOW IS CURRENTLY LOCATED OVER FAR NRN WV AND IS FORECAST
TO SHIFT EWD ACROSS NRN MD THROUGH THE DAY. AT MID MORNING...WV
IMAGERY SHOWS AN IMPRESSIVE SHORTWAVE MOVING NEWD AROUND UPPER LOW
FROM NRN VA TOWARD ERN PA/NJ. CONVECTION HAS RECENTLY DEVELOPED
AHEAD OF THIS FEATURE IN ERN PA AND SHOULD MOVE/SPREAD NWD THROUGH
THE DAY ACROSS ERN PA/NJ AND NY. ALTHOUGH INSTABILITY IS NOT
PARTICULARLY STRONG...SOME WARMING HAS RESULTED IN MLCAPES TO AROUND
500 J/KG. THIS INSTABILITY COMBINED WITH DEEP LAYER SHEAR AROUND 30
KT AND MID LEVEL LAPSE RATES BETWEEN 6.5-7.0 C/KM FAVOR MULTICELL
STORMS WITH HAIL AND STRONG GUSTY WINDS.
ANOTHER IMPULSE WAS LOCATED NEAR THE KY/WV BORDER AND ALL MODELS ARE
SUGGESTIVE OF CONVECTION DEVELOPING LATER THIS AFTERNOON IN THE
DELMARVA AREA WITH THIS SYSTEM. STORMS THAT DEVELOP WILL BE
WITHIN A SLOWLY DRYING BOUNDARY LAYER AND WHEN COMBINED WITH WLY
WINDS ALOFT AND STEEPENING LOW LEVEL LAPSE RATES...STRONG AND
POSSIBLY SEVERE WIND GUSTS ARE POSSIBLE.
..IMY.. 05/19/2011
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