Friday, May 11, 2007

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 110554
SWODY2
SPC AC 110553

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1253 AM CDT FRI MAY 11 2007

VALID 121200Z - 131200Z

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NRN
ROCKIES/PLAINS...

..NRN ROCKIES/HIGH PLAINS...

LATE EVENING MODEL GUIDANCE SUGGESTS UPPER RIDGE WILL FLATTEN ACROSS
THE NRN ROCKIES/HIGH PLAINS BEFORE TOTALLY SHUNTING EAST INTO THE
PLAINS LATE IN THE PERIOD IN RESPONSE TO PACIFIC NW SHORTWAVE
TROUGH. TIMING OF UPPER TROUGH WILL LIKELY HAVE MINIMAL INFLUENCE
ON DIURNAL CONVECTIVE POTENTIAL EAST OF THE ROCKIES OVER THE PLAINS
OF MT...ALTHOUGH LARGE SCALE ASCENT WILL UNDOUBTEDLY ENHANCE
THUNDERSTORM DEVELOPMENT ACROSS THE NRN ROCKIES FROM ERN OR...NEWD
INTO WRN MT. MOISTURE CONTENT ACROSS THE INTERIOR NRN ROCKIES IS
NOT PARTICULARLY HIGH...NOR SHOULD IT INCREASE MARKEDLY. INCREASED
ASCENT AND DEEP CONVERGENCE WILL HOWEVER MAINTAIN A ZONE OF
PRECIPITABLE WATER VALUES APPROACHING 0.75 WHICH WILL PROVE MORE
THAN ADEQUATE FOR DEEP CONVECTION. GIVEN THE DEEP LAYER SHEAR
WITHIN STRONG BAROCLINIC ZONE...STORM ROTATION/ORGANIZATION IS
POSSIBLE...ESPECIALLY GIVEN STEEP LAPSE RATE ENVIRONMENT. HAIL IS
THE GREATEST RISK WITH THIS ACTIVITY.

FARTHER DOWNSTREAM...INTENSE HEAT ACROSS SCNTRL MT...COUPLED WITH
WEAK/NEUTRAL FORCING...MAY RESULT IN A FEW LATE AFTERNOON
THUNDERSTORMS ACROSS THE PLAINS OF MT. AT THIS TIME IT APPEARS
ROBUST UPDRAFTS MAY NOT ORGANIZE UNTIL EARLY EVENING WHEN AFFECT OF
UPPER TROUGH BEGINS TO FLATTEN UPPER RIDGE. AS THIS OCCURS...LLJ
WILL INCREASE ACROSS THE WRN DAKOTAS INTO ERN MT. ANY STORMS THAT
CAN MIGRATE OFF THE HIGHER TERRAIN INTO ERN MT WILL ENCOUNTER
INCREASINGLY MOIST PROFILES AND STRONGER SHEAR...MORE CONDUCIVE FOR
SUPERCELL DEVELOPMENT. LARGE HAIL AND DAMAGING WINDS ARE THE MAIN
SEVERE RISKS WITH SUPERCELLS...AND POSSIBLE BOW-TYPE STRUCTURES THAT
SPREAD ACROSS THE PLAINS OF MT TOWARD THE WRN DAKOTAS AFTER 00Z.

..SD/MID MO VALLEY...

UPPER RIDGING WILL DOMINATE THE PLAINS SATURDAY. AS A
RESULT...INTENSE SFC HEATING WILL PROVE THE PRIMARY DAYTIME
MECHANISM FOR ANY THUNDERSTORM DEVELOPMENT ALONG THE BOUNDARY ACROSS
SRN SD...ESPECIALLY NEAR THE BLACK HILLS. ANOTHER AREA FOR POSSIBLE
STORM GENERATION WILL BE WITHIN WEAK WARM ADVECTION ZONE ALONG THE
MO RIVER OVER SERN SD INTO NWRN IA. AS LLJ INCREASES AFTER DARK
ELEVATED CLUSTERS OF STRONG STORMS MAY EVOLVE ACROSS THIS REGION
INTO THE ERN DAKOTAS AND WRN MN. HAIL IS THE PRIMARY THREAT WITH
THIS ACTIVITY.

..MIDDLE ATLANTIC TO CENTRAL GULF COAST...

PORTIONS OF THE MIDDLE ATLANTIC WILL NEED TO BE CLOSELY MONITORED
FOR STRONG/SEVERE THUNDERSTORMS ON SATURDAY. UPPER SPEED MAX WILL
DIG SEWD ACROSS THE OH VALLEY TOWARD VA LATE IN THE PERIOD.
ADDITIONALLY...HEIGHTS WILL FALL ACROSS THIS REGION AS TROUGH DIGS
INTO THE NERN U.S. IT APPEARS SFC FRONT WILL SHARPEN ALONG THE EAST
SLOPES OF THE CNTRL APPALACHIANS...THEN PLUNGE SEWD AFTER DARK INTO
THE CAROLINAS. IF SUFFICIENT MOISTURE/INSTABILITY CAN EVOLVE THERE
IS REASON TO BELIEVE ORGANIZED STORMS COULD DEVELOP ACROSS THIS
REGION. 00Z MODELS SUGGEST SUFFICIENT DEEP LAYER SHEAR FOR
SUPERCELLS WHICH WOULD MOVE SEWD ALONG/AHEAD OF ADVANCING SFC
BOUNDARY. AT THIS TIME WILL HOLD OFF ISSUING A SLIGHT RISK BUT AN
UPGRADE MAY BE WARRANTED IN LATER OUTLOOKS.

..ELSEWHERE...

MUCH WEAKER SHEAR WILL DOMINATE THE GULF STATES...SWD INTO THE FL
PENINSULA AS REMNANTS OF UPPER TROUGH SAG SEWD INTO THE ERN GULF OF
MEXICO. RELATIVELY COOL MID LEVEL TEMPERATURES WILL ENHANCE THE
PROSPECT FOR DEEP CONVECTION...ESPECIALLY ALONG WEAK ZONE OF
CONFLUENCE THAT WILL STRETCH FROM CNTRL SC...WWD INTO CNTRL MS.
THIS ZONE OF LIKELY INITIATION WILL GRADUALLY SAG SWD DURING THE
DAY...ESPECIALLY AS CONVECTION/OUTFLOW PROPAGATE TOWARD THE COASTAL
REGIONS.

ANOTHER POSSIBLE AREA FOR STRONG STORMS WILL BE IN ASSOCIATION WITH
FL SEA BREEZE. PENINSULA SHOULD HEAT NICELY DURING THE DAY AS
COLDEST MID LEVEL TEMPERATURES SAG INTO THE SRN PORTIONS OF THE
STATE. WLY COMPONENT WOULD FAVOR EAST COAST CONVERGENCE
ZONE...THOUGH STORM MOTIONS WOULD LIKELY PROPAGATE SEWD. HAIL AND
GUSTY WINDS MAY BE NOTED WITH THE STRONGEST UPDRAFTS ACROSS THE GULF
STATES...INCLUDING FL.

.DARROW.. 05/11/2007

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