SWODY1
SPC AC 082006
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0306 PM CDT WED JUL 08 2009
VALID 082000Z - 091200Z
...THERE IS A MDT RISK OF SVR TSTMS OVER FAR SERN MT...SRN ND AND
NRN/CNTRL SD...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE NRN/CNTRL
PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF SERN OK/NERN
TX...
...ERN MT/NERN WY ACROSS THE NRN PLAINS...
PREVIOUS FORECAST ON TRACK WITH LITTLE CHANGE NEEDED ATTM. ADJUSTED
WRN EXTENT OF SLGT RISK TO MATCH CURRENT POSITION OF COLD
FRONT/SURFACE LOW OVER ERN MT. REFER TO MCD 1489 FOR ADDITIONAL
SHORT-TERM INFORMATION.
...CNTRL/SRN PLAINS...
REMNANT LONG-LIVED TSTM CLUSTERS PERSIST OVER CNTRL OK AND E-CNTRL
KS. MODEL FORECASTS HAVE STRUGGLED WITH THE HANDLING OF THESE
CONVECTIVE AREAS AND LENDS TO UNCERTAINTY WITH REGARD TO THE
EVOLUTION OF THIS ACTIVITY THROUGH TONIGHT. NEVERTHELESS...WITH
INHIBITION WEAKENING AND DEEP-LAYER SHEAR SUFFICIENT FOR CONTINUED
UPDRAFT ORGANIZATION...THREAT FOR ISOLATED DAMAGING WINDS AND
MARGINAL SEVERE HAIL SHOULD CONTINUE. IN THE WAKE OF THIS
ACTIVITY...ADDITIONAL CONVECTIVE DEVELOPMENT SHOULD BE LARGELY
SUPPRESSED ACROSS CNTRL KS/NRN OK BY LACK OF CONVERGENCE AND STOUT
INHIBITION AS MID-LEVEL HEIGHTS RISE DOWNSTREAM OF VIGOROUS NRN
ROCKIES SHORT WAVE TROUGH. REFER TO MCD 1490 FOR ADDITIONAL
SHORT-TERM INFORMATION ON THE ERN KS CLUSTER.
...SOUTHEAST...
ONGOING PULSE TO LOOSELY ORGANIZED MULTICELL TSTMS MAY STILL POSE A
THREAT FOR ISOLATED WET MICROBURSTS INTO EARLY EVENING. VERY MOIST
THERMODYNAMIC PROFILES /WITH GPS PW VALUES AROUND 2 INCHES/ AND WEAK
LOW-LEVEL FLOW /PER AREA VWP DATA/ HAVE LIMITED POTENTIAL FOR A MORE
ORGANIZED THREAT. THUS...A SLGT RISK NO LONGER APPEARS WARRANTED.
...SRN NEW ENGLAND...
RELATIVELY COLD TEMPERATURES /-16 TO -18C AT 500 MB/ AND FAST WLY
FLOW IN THE MID-LEVELS WILL CONTINUE TO SUPPORT A FEW BRIEFLY
ORGANIZED UPDRAFTS WHERE SURFACE TEMPERATURES HAVE WARMED INTO THE
LOWER TO MIDDLE 70S. WITH ANEMIC LOWER-LEVEL FLOW /PER AREA VWP
DATA/...PRIMARY THREAT SHOULD BE MARGINAL SEVERE HAIL INTO EARLY
EVENING.
..GRAMS/DIAL.. 07/08/2009
.PREV DISCUSSION... /ISSUED 1134 AM CDT WED JUL 08 2009/
...ERN MT/NERN WY ACROSS THE NRN PLAINS...
WIDESPREAD SEVERE THUNDERSTORM EPISODE EXPECTED LATE THIS AFTERNOON
AND TONIGHT...
UPPER SHORT WAVE TROUGH NOW EVIDENT IN WATER VAPOR IMAGERY OVER ERN
PARTS OF WA AND OREGON IS FORECAST TO MOVE ENEWD ACROSS MT AND INTO
WRN ND BY THE END OF THE PERIOD. A STRONG MID/UPPER LEVEL JET
STREAK OVER THE NRN GREAT BASIN/INTERMOUNTAIN REGION IS EXPECTED TO
TRANSLATE ENEWD ACROSS THE NRN ROCKIES THIS AFTERNOON AND INTO THE
NRN HIGH PLAINS TONIGHT. AS THE UPPER LEVEL JET PROGRESSES
ENEWD...AN INTENSIFYING SOUTHERLY LOW LEVEL JET WILL DEVELOP LATE
THIS AFTERNOON INTO TONIGHT OVER THE CENTRAL/NRN PLAINS.
A SURFACE COLD FRONT CURRENTLY EXTENDS FROM ERN MT SWD INTO A LOW
OVER NERN WY...CONTINUING SWWD INTO NRN UT. THE LOW AND COLD FRONT
WILL MOVE SLOWLY EWD LATER THIS AFTERNOON AND EVENING TOWARD THE WRN
DAKOTAS BORDER...THEN ACCELERATING SOMEWHAT INTO THE ERN DAKOTAS BY
THE END OF THE PERIOD. LOW LEVEL CONVERGENCE NEAR THE LOW AND FRONT
IS EXPECTED TO PROVIDE THE PRIMARY FOCUS FOR SEVERE STORMS LATER
THIS AFTERNOON AND TONIGHT.
IN RESPONSE TO THE DEVELOPING LOW LEVEL JET...MOISTURE IS LIKELY TO
BE TRANSPORTED NWD IN ADVANCE OF THE COLD FRONT WITH SURFACE DEW
POINTS IN THE LOW/MID 60S EXPECTED THIS AFTERNOON. PLUME OF STEEP
MID LEVEL LAPSE RATES EVIDENT IN THE RAP AND RIW SOUNDINGS IS
EXPECTED TO SPREAD EWD ACROSS PARTS OF THE NRN PLAINS...AND WHEN
COUPLED WITH INCREASING MOISTURE AND STRONG DIABATIC HEATING FROM
SERN MT INTO THE DAKOTAS WILL RESULT IN MODERATE INSTABILITY WITH
MLCAPE FROM 1500-2500 J/KG.
ISOLATED STRONG ELEVATED THUNDERSTORMS ARE OCCURRING THIS MORNING
OVER NERN MT AND EXTREME WRN ND. THESE STORMS WILL BE MONITORED AS
THEY PROGRESS EWD THROUGH THE LATE MORNING HOURS AS THEY HAVE
POTENTIAL TO PRODUCE HAIL AND POSSIBLE STRONG WIND GUSTS. PRIMARY
SEVERE THREAT IS EXPECTED TO DEVELOP LATER THIS AFTERNOON AND
EVENING...WITH INITIAL DISCRETE CELLS DEVELOPING OVER PARTS OF SOUTH
CENTRAL/ERN MT AND NERN WY. THESE STORMS WILL BE ON THE NOSE OF THE
UPPER LEVEL JET...AND WITHIN AN ENVIRONMENT CHARACTERIZED BY 35-45
KT OF DEEP LAYER SHEAR THAT WILL BE SUPPORTIVE OF SUPERCELLS. THESE
WILL BE CAPABLE OF LARGE HAIL...DAMAGING WIND GUSTS AND A FEW
TORNADOES. THUNDERSTORMS ARE EXPECTED TO GRADUALLY SPREAD EWD INTO
THE WRN DAKOTAS THIS EVENING...WITH ACTIVITY LIKELY GROWING UPSCALE
INTO A FORWARD PROPAGATING MCS WITH EMBEDDED BOW ECHO STRUCTURES.
ALTHOUGH POTENTIAL FOR LARGE HAIL AND ISOLATED TORNADOES WILL
CONTINUE...THE PRIMARY SEVERE WEATHER THREAT IS EXPECTED TO
TRANSITION TO WIDESPREAD DAMAGING WIND GUSTS AS THE BOW ECHO SYSTEM
MOVES EWD ACROSS PARTS OF THE DAKOTAS.
...CENTRAL/SRN PLAINS...
ELEVATED STRONG THUNDERSTORMS CONTINUE TO MOVE SSEWD ACROSS SERN NEB
AND PARTS OF NRN/ERN OK WITHIN BAND OF STRONGER NWLY FLOW ALOFT.
RADAR ANALYSIS INDICATES THAT UPDRAFT CORES HAVE BEEN PULSING TO
SOME EXTENT. HOWEVER...OVERALL PERSISTENCE OF CONVECTION INTO THE
LATE MORNING SUGGESTS THAT STORMS HAVE POTENTIAL TO BECOME
SURFACE-BASED THIS AFTERNOON. HAIL AND POSSIBLY STRONG WIND GUSTS
WILL BE POSSIBLE WITH THE STORMS.
ADDITIONAL CONVECTION IS EXPECTED TO DEVELOP ALONG THE LEE TROUGH
OVER THE HIGH PLAINS OF NEB AND POSSIBLY NWRN KS LATE THIS AFTERNOON
AND EVENING...AND WOULD MOVE SEWD ACROSS PARTS OF THE CENTRAL PLAINS
INTO THE OVERNIGHT HOURS. LARGE HAIL AND DAMAGING WIND WILL BE
POSSIBLE WITH STRONGER CELLS GIVEN ENVIRONMENT CHARACTERIZED BY
MLCAPE OF 1500-2000 J/KG AND DEEP LAYER SHEAR OF 40-45 KT.
...SERN STATES...
A BAND OF STRONG STORMS IS OCCURRING OVER THE NRN GULF OF MEXICO AND
EWD INTO NRN FL. NORTH OF THIS ACTIVITY...STORMS ARE LIKELY TO
REDEVELOP WITHIN VERY MOIST AIR MASS FROM PARTS OF AL EWD INTO GA
AND SC. STORM INTENSITY WILL BE ENHANCED BY DYNAMIC FORCING IN
ADVANCE OF A SHORT WAVE TROUGH MOVING EWD FROM THE LOWER MS VALLEY.
THERE IS SUFFICIENT WESTERLY FLOW ALOFT AND VERTICAL SHEAR TO AID IN
STORM ORGANIZATION...WITH STRONGER CELLS CAPABLE OF PRODUCING WET
MICROBURSTS AND POSSIBLY HAIL.
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