SWODY3
SPC AC 010755
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0255 AM CDT FRI APR 01 2011
VALID 031200Z - 041200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID MS VALLEY TO SRN
PLAINS...
...SYNOPSIS...
00Z GFS/ECMWF ARE IN FAIR AGREEMENT WITH THE MID-UPPER LEVEL TROUGH
MOVING INTO THE WRN U.S. ON DAY 2 WHICH WILL UNDERGO FURTHER
AMPLIFICATION AS IT PROGRESSES EWD AND EXTENDS NEWD FROM THE SRN
ROCKIES TO THE NRN PLAINS AS A POSITIVELY-TILTED TROUGH. TWO
PRIMARY SHORTWAVE TROUGHS COMPRISING THIS SYSTEM WILL REMAIN IN
PHASE...WITH ONE TRACKING EWD FROM THE NRN ROCKIES TO THE UPPER
MIDWEST...AND THE SECOND DIGGING SEWD TOWARD NM BY 12Z MONDAY.
AT THE SURFACE...AN AREA OF LOW PRESSURE INITIALLY LOCATED OVER THE
CENTRAL PLAINS SHOULD MOVE ENEWD INTO IA BY SUNDAY EVENING AND THEN
TRACK TOWARD THE WRN GREAT LAKES SUNDAY NIGHT. A TRAILING COLD
FRONT WILL ADVANCE SSEWD THROUGH THE CENTRAL AND SRN PLAINS AND
INTERSECT THE NRN EXTENT OF THE DRY LINE IN ERN KS SUNDAY AFTERNOON.
THE DRY LINE WILL EXTEND SWD THROUGH CENTRAL OK TO CENTRAL TX SUNDAY
AFTERNOON. MEANWHILE...A WARM FRONT WILL LIFT NEWD FROM THE LOWER
MO VALLEY INTO THE OH VALLEY ON DAY 2.
...OH VALLEY/SRN GREAT LAKES SWWD TO CENTRAL/SRN PLAINS...
ELEVATED TSTMS ARE EXPECTED TO BE ONGOING...ALONG AND E OF THE WARM
FRONT...FROM ERN MO N/NWWD INTO IA WITHIN THE NOSE OF A STRONG SWLY
LLJ /50-60 KT/. LOW LEVEL MOISTENING/WAA WITHIN THIS REGIME BENEATH
STEEP MIDLEVEL LAPSE RATES WILL BE PROMOTING AT LEAST AN ISOLATED
SEVERE HAIL THREAT AT 12Z SUNDAY. THIS ISOLATED SEVERE THREAT
SHOULD PERSIST THROUGH SUNDAY MORNING AS ACTIVITY ADVANCES INTO IL
ALONG NOSE OF LLJ. THIS JET WILL SHIFT EWD INTO THE LOWER OH VALLEY
SUNDAY BENEATH PLUME OF STEEP MIDLEVEL LAPSE RATES ALSO SPREADING
EWD...RESULTING IN WIDESPREAD CLOUDS/SHOWERS N OF THE WARM FRONT.
MODELS SUGGEST CONVECTION SHOULD DIMINISH IN COVERAGE/INTENSITY BY
SUNDAY AFTERNOON...GIVEN HEIGHT RISES AND LACK OF STRONGER FORCING
ALOFT NEGATING ADDITIONAL TSTM INITIATION. RE-STRENGTHENING OF THE
OH VALLEY LLJ EXPECTED SUNDAY NIGHT WILL SUPPORT AN INCREASE IN
ELEVATED TSTMS ACROSS THIS REGION INTO THE SRN GREAT LAKES.
MARGINAL INSTABILITY WITH EWD EXTENT AND INCREASING EFFECTIVE BULK
SHEAR N OF THE WARM FRONT MAY SUPPORT A FEW STRONGER STORMS...SOME
SEVERE.
MEANWHILE...THE STRONG EML OVER THE WARM SECTOR SHOULD LIMIT
DIURNAL TSTM DEVELOPMENT ALONG AND E OF THE DRY LINE THROUGH MUCH OF
THE AFTERNOON. STRONG SLY LOW LEVEL FLOW THIS PERIOD FROM THE SRN
PLAINS TO LOWER MO VALLEY WILL TRANSPORT MOISTURE NWD BENEATH A
PLUME OF STEEP MIDLEVEL LAPSE RATES RESULTING IN A CORRIDOR OF
MODERATE INSTABILITY EXTENDING EWD FROM THE DRY LINE INTO WRN AR AND
THE MID MS VALLEY. THIS COMBINED WITH EFFECTIVE BULK SHEAR /35-50
KT/ WILL SUPPORT ORGANIZED STRONG TO SEVERE /SUPERCELLULAR/ STORMS.
LARGE HAIL...DAMAGING WINDS AND INCREASING LOW LEVEL SHEAR ALONG A
SECONDARY LLJ FROM OK TO MO WILL SUPPORT A TORNADO THREAT. 00Z
ECMWF AND 21Z SREF SUGGEST ISOLATED STRONG TO SEVERE STORMS
/SUPERCELLS/ WILL BE POSSIBLE LATE SUNDAY AFTERNOON...AS THE COLD
FRONT ENCOUNTERS THE DRY LINE AND SWD ALONG THE DRY LINE WHERE
SURFACE HEATING WILL BE MAXIMIZED. TSTM COVERAGE IS EXPECTED TO
INCREASE SUNDAY NIGHT AND SPREAD E AND SE ALONG AND AHEAD OF THE
COLD FRONT. MODERATE INSTABILITY INTO THE OVERNIGHT PERIOD COMBINED
WITH BACKING SHEAR VECTORS SUGGESTS STORMS SHOULD EVOLVE INTO A
LINEAR MODE.
..PETERS.. 04/01/2011
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