SWODY2
SPC AC 221728
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT SUN MAR 22 2009
VALID 231200Z - 241200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF ERN KS...NRN
OK...CNTRL OK...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE GREAT
PLAINS AND UPPER MIDWEST...
...NEBRASKA AND SOUTH DAKOTA...
A WELL-DEVELOPED UPPER-LEVEL TROUGH OVER THE FOUR CORNERS REGION
WILL CLOSE-OFF TONIGHT ACROSS COLORADO AND MOVE QUICKLY ENEWD INTO
CNTRL HIGH PLAINS MONDAY. AHEAD OF THE SYSTEM...A BROAD 50 TO 65 KT
LOW-LEVEL JET WILL BE IN PLACE FROM THE SRN PLAINS EXTENDING NWD
INTO THE MID-MO RIVER VALLEY. ELEVATED WARM ADVECTION THUNDERSTORMS
WITH SOME MARGINALLY SEVERE HAIL SHOULD BE ONGOING AT THE BEGINNING
OF THE PERIOD FROM WRN IA AND ERN NEB SSWWD ACROSS ERN KS INTO NRN
OK. AS THE UPPER-LEVEL SYSTEM APPROACHES THE GREAT PLAINS...A
POWERFUL 80 TO 100 KT MID-LEVEL JET WILL ROUND THE BASE OF THE
TROUGH AND EJECT NEWD INTO THE CNTRL PLAINS. THE LEFT EXIT REGION OF
THE JET ALONG WITH A PLUME OF STEEP MID-LEVEL LAPSE RATES IS
FORECAST TO SPREAD ACROSS NEBRASKA EARLY IN THE PERIOD. IN
RESPONSE...THE MODELS ARE IN GOOD AGREEMENT...DEVELOPING A
CONCENTRATED CLUSTER OF THUNDERSTORMS ACROSS WRN SD AND NW NEB
MONDAY MORNING. THIS ACTIVITY SHOULD SPREAD ENEWD INTO ERN SD BY
EARLY AFTERNOON EXPANDING SWD WITH TIME ACROSS NCNTRL AND ERN NEB.
AHEAD OF THE UPPER-LEVEL LOW...LARGE-SCALE ASCENT WILL BE QUITE
STRONG ACROSS THE WRN HALF OF NEB INTO SRN SD MONDAY MORNING.
FORECAST SOUNDINGS IN THIS AREA AT 15Z MONDAY SHOW STRONG VERTICAL
SHEAR /0-6 KM SHEAR OF 50-60 KT/ AND 850 TO 500 MB LAPSE RATES
AROUND 8.0 C/KM. THIS ALONG WITH THE STRONG LARGE-SCALE ASCENT
SHOULD BE SUPPORTIVE OF ISOLATED SUPERCELLS WITH HAIL. AS THE
COMPLEX MOVES NEWD INTO ERN SD AND DEVELOPS SWD ACROSS ERN NEB
MONDAY AFTERNOON...LARGE HAIL AND DAMAGING WINDS WILL BE POSSIBLE. A
FEW TORNADOES WILL ALSO BE POSSIBLE ESPECIALLY IF THE CONVECTION CAN
REMAIN DISCRETE.
...OKLAHOMA/KANSAS/NORTH TEXAS...
A WELL-DEVELOPED UPPER-LEVEL TROUGH OVER THE DESERT SOUTHWEST SUNDAY
NIGHT WILL MOVE INTO THE SRN ROCKIES MONDAY WITH SOUTHWEST FLOW IN
PLACE ACROSS THE SRN AND CNTRL PLAINS. AN IMPRESSIVE 80 TO 100 KT
MID-LEVEL JET WILL EJECT ENEWD ACROSS THE CNTRL PLAINS. SOUTH OF THE
AXIS OF THE JET...CONVECTION SHOULD NOT INITIATE THROUGH MUCH OF
MONDAY AFTERNOON DUE TO A CAPPING INVERSION. MODEL FORECASTS ARE IN
GOOD AGREEMENT WEAKENING THE CAP AND RAPIDLY INITIATING STORMS
BETWEEN 21Z AND 00Z ALONG THE INTERSTATE-35 CORRIDOR IN ERN KS WITH
THE CONVECTION DEVELOPING SSWWD INTO NRN AND CNTRL OK DURING THE
EARLY EVENING. DUE TO THE STRENGTH OF THE UPPER-LEVEL TROUGH AND
POSITION OF THE INSTABILITY AXIS...THERE IS SUBSTANTIAL CERTAINTY
THAT A LARGE AMOUNT OF THUNDERSTORMS WILL DEVELOP FROM NNE TO SSW
ACROSS THE REGION DURING THE EARLY TO MID-EVENING.
AS THE MID-LEVEL JET EJECTS ENEWD ACROSS THE CNTRL PLAINS...VERTICAL
SHEAR PROFILES WILL STRENGTHEN ACROSS THE SRN AND CNTRL PLAINS. BY
00Z TUESDAY...FORECAST SOUNDINGS SHOW 0-6 KM SHEAR VALUES RANGING
FROM AROUND 50 KT IN NCNTRL KS TO ABOUT 75 KT IN SRN OK. IN
ADDITION...MID-LEVEL LAPSE RATES WILL BE QUITE STEEP ALONG THE
INSTABILITY AXIS. THIS COMBINED WITH THE STRONG VERTICAL SHEAR
SHOULD BE FAVORABLE FOR SUPERCELLS WITH LARGE HAIL. THE MOST INTENSE
STORMS COULD PRODUCE VERY LARGE HAIL FROM SE KS SSWWD ACROSS WCNTRL
OK WITH ISOLATED LARGE HAIL ALSO POSSIBLE IN NORTH TX. IN
ADDITION...FORECAST SOUNDINGS BY EARLY EVENING ACROSS CNTRL OK AND
SRN KS SHOW 0-1 KM SHEAR VALUES IN THE 30 TO 40 KT RANGE SUGGESTING
TORNADOES WILL BE POSSIBLE WITH THE MORE ORGANIZED STORMS. A FEW
STRONG TORNADOES WILL BE POSSIBLE ALONG THE INTERSTATE-35 CORRIDOR
ESPECIALLY IF SUPERCELLS CAN REMAIN DISCRETE THROUGH THE EARLY
EVENING. IF A SQUALL-LINE RAPIDLY DEVELOPS BY EARLY EVENING...THEN
THE DOMINATE SEVERE THREATS WOULD LIKELY BE HAIL AND WIND DAMAGE.
ALTHOUGH UNCERTAINTY STILL EXISTS CONCERNING STORM MODE...THE
POTENTIAL FOR A CONCENTRATED AREA FOR SEVERE CONVECTION WARRANTS A
MODERATE RISK FROM ERN KS SSWWD ACROSS NRN AND CNTRL OK.
..BROYLES.. 03/22/2009
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