SWODY1
SPC AC 231231
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0731 AM CDT SUN MAY 23 2010
VALID 231300Z - 241200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL U.S. FROM MN
TO WEST TX...
...SYNOPSIS...
HIGHLY AMPLIFIED MID LEVEL FLOW PATTERN WILL CONTINUE ACROSS THE
CONUS WITH A SIGNIFICANT TROUGH DOMINATING THE WEST...AND A
DOWNSTREAM BLOCKING RIDGE TAKING FORM FROM THE MS VALLEY TO THE
GREAT LAKES. IN THE EAST...A WEAK CIRCULATION CENTER OVER PA/WV THIS
MORNING WILL SETTLE TOWARD THE MID ATLANTIC SEABOARD...EVENTUALLY
BECOMING ABSORBED INTO THE WRN FLANK OF LARGE OFFSHORE GYRE DRIFTING
WWD.
AS ONE STRONG DISTURBANCE IS EJECTED OUT OF THE WRN TROUGH AND LIFTS
INTO CNTRL CANADA...SHORT WAVE RIDGING AND HEIGHT RISES WILL DEVELOP
ATOP TRAILING FRONTAL ZONE FROM MN SWWD TO NRN KS. THE NEXT STRONG
SHORT WAVE WITHIN THE LARGER SCALE TROUGH WILL MOVE FROM SRN CA TO
THE FOUR CORNERS THIS PERIOD. HEIGHT FALLS AND STRENGTHENING
DEEP-LAYER SWLY/SLY FLOW WILL OVERSPREAD THE ROCKIES AND ADJACENT
HIGH PLAINS AND DRIVE CYCLOGENESIS OVER CO. RESULTANT SURFACE LOW
AND WARM FRONT WILL DEVELOP NWD FROM CO/KS LATE TODAY TO NEB/SD
BORDER AREA BY MONDAY MORNING. DIURNAL E-W OSCILLATIONS OF THE DRY
LINE...TRAILING SOUTH FROM ERN CO TO WEST TX...WILL REMAIN WITHIN A
NARROW RANGE GIVEN SIGNIFICANT MERIDIONAL COMPONENT TO THE LARGE
SCALE FLOW.
...UPPER MS VALLEY...
DESPITE LIMITED LARGE SCALE SUPPORT FOR ASCENT ALONG THE FRONT
MOVING INTO THIS AREA...RICH BOUNDARY LAYER MOISTURE /SURFACE
DEWPOINTS WELL INTO THE 60SF/ AND DIURNAL HEATING WILL CONTRIBUTE TO
MODEST TO LOCALLY STRONG DESTABILIZATION. IT SEEMS PROBABLE THAT
PERSISTENT CONVERGENCE ALONG THE FRONT...COMBINED WITH HEATING OF
THE DAY...MAY BE SUFFICIENT TO OVERCOME INHIBITION AND SUPPORT
SCATTERED CONVECTIVE INITIATION FROM THE ARROWHEAD OF MN SWD/SWWD
ACROSS MN/NWRN WI. STRONGER DEEP-LAYER SHEAR WILL LAG THE FRONTAL
ZONE BUT MAGNITUDE OF INSTABILITY SUGGESTS AT LEAST A LOW
PROBABILITY THREAT OF HAIL/WIND.
SEVERE WEATHER POTENTIAL MAY INCREASE AGAIN ACROSS WRN MN
LATE IN THE PERIOD AS THE NEXT SYSTEM APPROACHES AND LIFT ACROSS THE
WARM FRONT BRINGS ANOTHER CHANCE FOR DEEP CONVECTION.
...CNTRL PLAINS...
A DIFFICULT FORECAST CHALLENGE PRESENTS ITSELF ACROSS PARTS OF THE
PLAINS WHERE FRONTAL ZONE IS NOW STALLING FROM SERN CO TO NRN KS
BENEATH STRONG CAPPING INVERSION/EML. A WIDE ARRAY OF DETERMINISTIC
MODEL SOLUTIONS ARGUE THAT PREDICTABILITY IN THIS REGIME IS LOW.
LIFT ACROSS THE FRONT WILL INCREASE DURING THE SECOND HALF OF THE
FORECAST PERIOD AS SIGNIFICANT SHORT WAVE TROUGH APPROACHES AND MASS
ADJUSTMENT COMMENCES. UNTIL THEN...DESPITE PRONOUNCED DIURNAL
DESTABILIZATION...STRONG CAP AND WEAK/NEUTRAL HEIGHT FALLS MAY
PRECLUDE STORM INITIATION.
PROBABILITY OF THUNDERSTORMS INCREASES SUBSTANTIALLY BETWEEN 21Z AND
00Z NEAR AND NORTH OF TRIPLE POINT AND DEVELOPING WARM FRONT FROM
NWRN KS/ERN CO INTO NEB. MAGNITUDE OF INSTABILITY AND SHEAR IN THESE
AREAS WILL BE MORE THAN ADEQUATE FOR INTENSE/SUSTAINED CONVECTIVE
DEVELOPMENT. SUPERCELLS WITH TORNADO POTENTIAL APPEAR QUITE POSSIBLE
EARLY IN THIS DEVELOPMENT PROCESS...ESPECIALLY NEAR THE DEVELOPING
WARM FRONT FROM NWRN KS/SRN NEB NWWD TO EXTREME SERN WY. FAST NEWD
STORM MOTION SUGGESTS THAT SOME CELLS MAY MOVE FASTER THAN WARM
FRONTAL RETREAT ACROSS THESE AREAS...BECOMING DECOUPLED FROM
BOUNDARY LAYER INFLOW AND PRESENTING MORE OF A LARGE HAIL THREAT
WITH TIME.
SEVERE WEATHER THREAT IN THE FORM OF HAIL/WIND AND PERHAPS TORNADOES
IS FORECAST TO EXPAND NWD OVER THE NRN PLAINS AND ADJACENT HIGH
PLAINS THROUGH THE NIGHT AND INTO EARLY MONDAY AS STRONG FORCING FOR
ASCENT ACCOMPANYING VIGOROUS TROUGH SPREADS NWD/EWD...LOW LEVEL JET
INTENSIFIES...AND ABUNDANT INSTABILITY FUELS WIDESPREAD/ORGANIZED
CONVECTION.
...SRN HIGH PLAINS...
AT LEAST SCATTERED ROBUST CONVECTIVE DEVELOPMENT APPEARS LIKELY
ALONG EXTENSIVE DRY LINE FROM CO/KS BORDER TO NM/TX BORDER THROUGH
EARLY EVENING. STORMS WILL EXIST AMIDST CAPE AROUND 2000 J/KG AND
SUFFICIENT SHEAR FOR SUPERCELLS. THIS DEVELOPMENT IS LIKELY TO BE
SUSTAINED IN SOME FORM WELL AFTER DARK WITH THE APPROACH OF MORE
SUBSTANTIAL FORCING FOR ASCENT WITH THE UPPER TROUGH MOVING EAST.
THUS...THE PROBABILITY OF SEVERE HAIL AND WIND ACROSS THESE AREAS
HAS BEEN INCREASED IN THIS OUTLOOK.
...CAROLINAS...
SITUATION APPEARS SIMILAR TO YESTERDAY WITH PERHAPS SLIGHTLY GREATER
DESTABILIZATION POSSIBLE DUE TO HIGHER BOUNDARY LAYER THETA-E AND
COOLER TEMPS ALOFT. NWLY TO NLY FLOW OF 20-30KT AROUND THE BASE OF
WEAK CIRCULATION DROPPING SOUTH ACROSS THE AREA COULD RESULT IN A
COUPLE MORE ORGANIZED OR PERSISTENT CLUSTERS OF CONVECTION WITH SOME
HAIL AND DAMAGING WIND POTENTIAL.
..CARBIN/ROGERS.. 05/23/2010
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