Wednesday, July 15, 2009

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 152001
SWODY1
SPC AC 151958

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT WED JUL 15 2009

VALID 152000Z - 161200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM A PORTION OF SRN KS AND
NRN OK INTO THE TN VALLEY...

...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE SRN HIGH
PLAINS...

...SYNOPSIS...


...SRN PLAINS THROUGH LOWER MS AND TN VALLEY...

A COLD FRONT EXTENDS FROM ERN WI SWWD THROUGH SWRN MO...EXTREME NRN
OK AND SRN KS WHERE IT HAS BECOME STATIONARY. A FEW STORMS CONTINUE
OVER SRN KS WITHIN REGION OF MODEST ISENTROPIC LIFT ALONG BAROCLINIC
ZONE. OTHER STORMS ARE DEVELOPING ALONG OUTFLOW BOUNDARY OVER SRN MO
JUST AHEAD OF EWD MOVING MCV AND ALONG OUTFLOW BOUNDARY FARTHER EAST
ACROSS NRN TN. STRONGER DIABATIC HEATING IS OCCURRING ON THE SRN
PERIPHERY OF ONGOING CONVECTION...AND STORMS HAVE SHOWN AN INCREASE
IN INTENSITY AS THE SURFACE LAYER DESTABILIZES. ACTIVITY WILL REMAIN
EMBEDDED WITHIN MODEST BULK SHEAR ON SRN FRINGE OF STRONGER WLYS. A
FEW STORMS MAY BECOME CAPABLE OF PRODUCING ISOLATED DAMAGING WIND
AND LARGE HAIL THIS AFTERNOON. OTHER STORMS ARE EXPECTED TO DEVELOP
OVERNIGHT ACROSS SRN KS AS STRENGTHENING SLY LOW LEVEL JET INTERACTS
WITH BAROCLINIC ZONE. ISOLATED LARGE HAIL WILL BE THE MAIN THREAT
WITH THIS ACTIVITY.


...SRN HIGH PLAINS...

PREVIOUS FORECAST STILL APPEARS ON TRACK. STORMS ARE IN THE PROCESS
OF DEVELOPING ALONG THE FRONT RANGE WITHIN ELY UPSLOPE REGIME.
ISOLATED DAMAGING WIND AND HAIL WILL BE POSSIBLE AS ACTIVITY MOVES
EWD THROUGH THE DESTABILIZING BOUNDARY LAYER.


...WRN SD AND NEB...

BRANCH OF THE LOW LEVEL JET IS FORECAST TO DEVELOP OVER THE CNTRL
HIGH PLAINS AHEAD OF SECONDARY FRONTAL SURGE...CONTRIBUTING TO NWD
ADVECTION OF 50S LOW-LEVEL DEWPOINTS BENEATH STEEP MID LEVEL LAPSE
RATES. MUCAPE FROM 500-1000 J/KG WILL BE POSSIBLE IN THIS AREA.
INCREASING FORCING FOR ASCENT RESULTING FROM THE LOW LEVEL JET
INTERACTING WITH THE SWD ADVANCING BAROCLINIC ZONE WILL PROBABLY
CONTRIBUTE TO THE DEVELOPMENT OF A FEW STORMS LATER TONIGHT. THE
THERMODYNAMIC ENVIRONMENT APPEARS SUFFICIENT FOR A THREAT OF
ISOLATED HAIL.

...OH VALLEY...

SEE PREVIOUS DISCUSSION

..DIAL.. 07/15/2009

.PREV DISCUSSION... /ISSUED 1129 AM CDT WED JUL 15 2009/

...SRN PLAINS TO TN VALLEY THIS AFTERNOON THROUGH TONIGHT...
THE PRIMARY NRN STREAM SHORTWAVE TROUGH CONTINUES TO PROGRESS EWD
OVER THE GREAT LAKES WHILE AN ASSOCIATED COLD FRONT MOVES EWD FROM
MO/IA/WI AS OF LATE MORNING TO IL/INDIANA/MI BY TONIGHT. THE WRN
EXTENT OF THIS FRONT IS DRIFTING SWD ACROSS SRN KS/NRN OK.
MEANWHILE...SEVERAL OVERNIGHT THUNDERSTORMS CLUSTERS AND REMNANT
MCV/S PERSIST AS OF LATE MORNING...ONE OF WHICH IS MOVING SEWD INTO
CENTRAL KY...AND ANOTHER IS MOVING EWD FROM ERN KS INTO WRN MO.
STRONG SURFACE HEATING AND AN INFLUX OF 70-75 F BOUNDARY LAYER
DEWPOINTS WILL CONTRIBUTE TO AFTERNOON MLCAPE VALUES IN THE
1500-3000 J/KG RANGE ALONG THE SRN/SWRN FRINGES OF THE ONGOING
CONVECTION...AND ADDITIONAL THUNDERSTORM DEVELOPMENT WILL BE
POSSIBLE THIS AFTERNOON ALONG THE RESIDUAL CONVECTIVE OUTFLOWS. THE
COMBINATION OF MODERATE-STRONG INSTABILITY AND MARGINAL DEEP LAYER
SHEAR ON THE SRN FRINGE OF THE WESTERLIES WILL SUPPORT A FEW
MULTICELL CLUSTERS CAPABLE OF PRODUCING A FEW DAMAGING GUSTS AND
LARGE HAIL.

OVERNIGHT...A 20-30 KT LLJ WILL AGAIN DEVELOP OVER THE SRN PLAINS
AND RESULT IN STRENGTHENING LOW-LEVEL WAA ON THE IMMEDIATE COOL SIDE
OF THE STALLED FRONT NEAR THE KS/OK BORDER. THIS SHOULD SUPPORT THE
FORMATION OF ANOTHER CLUSTER OF STORMS ALONG THE BOUNDARY
OVERNIGHT...WITH AN ATTENDANT THREAT FOR AT LEAST ISOLATED DAMAGING
WINDS/HAIL FROM SRN KS/NRN OK EWD INTO SW MO/NW AR.

...HIGH PLAINS OF CO/NM THIS AFTERNOON/EVENING...
LOW-LEVEL UPSLOPE FLOW WITH BOUNDARY LAYER DEWPOINTS IN THE MID 50S
AND STRONG SURFACE HEATING WILL SUPPORT THE DEVELOPMENT OF A FEW
THUNDERSTORMS THIS AFTERNOON IN PROXIMITY TO THE RATON MESA...AND
STORMS WILL SPREAD EWD OVER THE HIGH PLAINS DURING THE EVENING.
VERTICAL SHEAR AND INSTABILITY WILL BE MARGINALLY SUFFICIENT FOR
ORGANIZED MULTICELL CLUSTERS...AND PERHAPS SOME BRIEF SUPERCELL
STRUCTURES...ALONG WITH THE POTENTIAL FOR AT LEAST ISOLATED LARGE
HAIL/DAMAGING WINDS THROUGH LATE EVENING.

...IL/INDIANA/LOWER MI THROUGH EARLY TONIGHT...
SOME DESTABILIZATION IS EXPECTED THIS AFTERNOON IN ADVANCE OF THE
COLD FRONT AND TO THE N OF THE ONGOING CLOUDS/CONVECTION FARTHER S
ACROSS SRN IL/INDIANA/KY. HOWEVER...MID LEVEL LAPSE RATES ARE
RATHER POOR OVER THIS AREA...AND THE MAGNITUDE OF INSTABILITY SHOULD
REMAIN SOMEWHAT MARGINAL THROUGH THE AFTERNOON /MLCAPE OF 500-1000
J/KG/. GIVEN ONLY ISOLATED THUNDERSTORM DEVELOPMENT EXPECTED ALONG
THE FRONT...ALONG WITH RATHER MODEST INSTABILITY AND UNIDIRECTIONAL
WIND PROFILES...THE SEVERE THREAT APPEARS TO BE LIMITED TO ONLY
ISOLATED STRONG WIND GUSTS AND MARGINALLY SEVERE HAIL THIS
AFTERNOON/EVENING.

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