090
ACUS02 KWNS 040532
SWODY2
SPC AC 040531
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1231 AM CDT SAT JUL 04 2009
VALID 051200Z - 061200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MS VALLEY INTO
THE CAROLINAS...
..THERE IS A SLGT RISK OF SVR TSTMS OVER THE CENTRAL HIGH PLAINS
..SYNOPSIS
UPPER FLOW PATTERN IS FORECAST TO AMPLIFY ON SUNDAY AS A JET STREAK
DIGS SEWD ACROSS THE UPPER MS VALLEY AND SRN GREAT LAKES...RESULTING
IN THE DEVELOPMENT OF ANOTHER LOW OVER SRN ONTARIO...AND MAINTENANCE
OF THE LONG WAVE TROUGH OVER THE ERN STATES. IN THE WEST...THE
RIDGE IS FORECAST TO BUILD FROM THE SRN PLATEAU INTO THE CANADIAN
ROCKIES AS AN UPSTREAM LOW OVER THE ERN PACIFIC MOVES EWD...REACHING
THE PACIFIC NW COAST BY THE END OF THE PERIOD. A BROAD REGION OF
NWLY/WLY FLOW ALOFT WILL AFFECT MUCH OF THE US EAST OF THE
CONTINENTAL DIVIDE.
AT THE SURFACE...A LOW INITIALLY OVER ERN KY WILL MOVE EWD ALONG A
QUASI-STATIONARY FRONT EXTENDING ACROSS SRN VA DURING THE DAY AND
CONTINUE EWD INTO THE ATLANTIC SUNDAY NIGHT. A COLD FRONT TRAILING
WSWWD FROM THE LOW WILL SLOWLY MOVE SWD INTO THE SERN STATES...LOWER
MS VALLEY...AND CENTRAL TX.
..LOWER MS VALLEY INTO THE CAROLINAS
SCATTERED CONVECTION IS EXPECTED TO BE ONGOING EARLY IN THE PERIOD
FROM PARTS OF VA WSWWD ACROSS THE CENTRAL APPALACHIANS AND TN VALLEY
INTO THE SRN PLAINS ALONG/AHEAD OF THE AFOREMENTIONED FRONTAL
BOUNDARY. EXTENSIVE CLOUDS/PRECIPITATION NEAR THE FRONT IS EXPECTED
TO LIMIT DIURNAL HEATING AND SUBSEQUENT DESTABILIZATION...ALTHOUGH
SOME BREAKS IN CLOUD COVER MAY PERMIT LOCALIZED AREAS OF STRONGER
HEATING. MORE WIDESPREAD HEATING WILL BE POSSIBLE ALONG AND SOUTH
OF THE SRN EDGE OF THE AGGREGATE CLOUD SHIELD...WHERE A DIFFERENTIAL
HEATING BOUNDARY MAY BECOME ESTABLISHED THAT WILL ENHANCE INITIATION
OF NEW CONVECTION.
DESPITE RELATIVELY WARM MID LEVEL TEMPERATURES...SURFACE DEW POINTS
IN THE UPPER 60S/LOWER 70S COUPLED WITH TEMPERATURES WARMING ABOVE
90 WILL RESULT IN MLCAPE OF 1000-2000 J/KG. THUNDERSTORMS ARE
EXPECTED TO INCREASE IN COVERAGE BY EARLY AFTERNOON AS HEATING AND
LOW LEVEL CONVERGENCE WEAKEN THE CAP. WNWLY/WLY WINDS OF 30-35 KT
ABOVE 2-3 KM AGL WILL RESULT IN SUFFICIENT VERTICAL SHEAR TO AID IN
STORM ORGANIZATION...INCLUDING DEVELOPMENT OF SMALL SCALE BOW
STRUCTURES. FORECAST SOUNDINGS SHOW LOW-LEVEL INVERTED-V PROFILES
AND MODERATE DCAPE VALUES SUGGESTING POTENTIAL FOR STRONGER STORMS
TO PRODUCE DAMAGING WIND GUSTS...WITH A LESSER THREAT FOR LARGE
HAIL...PRIMARILY DURING THE AFTERNOON AND EARLY EVENING HOURS.
..CENTRAL HIGH PLAINS
WEAK UPSLOPE FLOW IS EXPECTED TO DEVELOP DURING THE AFTERNOON WITH
SURFACE DEW POINTS REMAINING IN THE 50S ACROSS THE AREA. ALTHOUGH
THE STEEPER MID LEVEL LAPSE RATES ARE FORECAST TO REMAIN PRIMARILY
OVER THE HIGHER TERRAIN...STRONG DIURNAL HEATING WILL CONTRIBUTE TO
AN UNSTABLE ENVIRONMENT WITH MLCAPE OF 1000-1500 J/KG.
THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER THE ERN SLOPES OF THE
ROCKIES AND ADJACENT HIGH PLAINS DURING THE MID/LATE AFTERNOON AND
SPREAD SEWD WITHIN 25-35 KT WNWLY MID LEVEL FLOW. FORECAST
SOUNDINGS SHOW WINDS VEERING AND INCREASING WITH HEIGHT WITH
SUFFICIENT SHEAR TO SUPPORT ORGANIZED STORMS...INCLUDING A FEW
SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WIND GUSTS.
THE SEVERE THREAT IS LIKELY TO DIMINISH SEVERAL HOURS AFTER SUNSET.
..NRN/CNTRL TX INTO ERN NM
STRONG STORMS ARE EXPECTED TO MOVE SEWD/SWD ACROSS PARTS OF NRN TX
DURING THE MORNING IN ADVANCE OF THE COLD FRONT. THERE IS POTENTIAL
FOR CONVECTION TO INTENSIFY DURING THE AFTERNOON AS STRONG
HEATING/DESTABILIZATION OCCURS INTO CNTRL/SWRN TX. ADDITIONAL
STRONG STORMS ARE EXPECTED TO DEVELOP OVER PARTS OF ERN NM DURING
THE AFTERNOON...MOVING SEWD INTO PARTS OF NWRN TX BY EVENING.
ISOLATED SEVERE STORMS WILL BE POSSIBLE BUT OVERALL COVERAGE IS
EXPECTED TO BE LIMITED BY WEAK FLOW/VERTICAL SHEAR.
..WEISS.. 07/04/2009
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