DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 290532
SWODY1
SPC AC 290529

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1129 PM CST WED NOV 28 2007

VALID 291200Z - 301200Z

..NO TSTM AREAS FORECAST...

..SYNOPSIS...

UPPER TROUGH FROM THE UPPER MS VALLEY INTO THE CNTRL PLAINS WITHIN
PROGRESSIVE FLOW REGIME WILL ADVANCE EWD THROUGH THE OH VALLEY AND
NERN STATES THURSDAY. THIS WILL PROVIDE IMPETUS FOR A COLD FRONT
FROM THE GREAT LAKES INTO THE SRN PLAINS TO CONTINUE EAST AND SEWD
AND OFF THE ATLANTIC SEABOARD AND GULF COAST DURING THE DAY. HIGH
PRESSURE WILL BUILD INTO ERN THIRD OF THE NATION WITH OFFSHORE FLOW
OVER THE GULF MUCH OF THE DAY. FARTHER WEST...ANOTHER IN A SERIES OF
IMPULSES WILL DROP INTO THE PACIFIC NW. A LARGE CUTOFF LOW WILL
PERSIST WEST OF BAJA.

..PACIFIC NW REGION...

COLD UPPER LEVEL TEMPERATURES WITH -34C AT 500 MB ACCOMPANYING A
SHORTWAVE TROUGH DROPPING INTO THE PACIFIC NW WILL RESULT IN STEEP
MID LEVEL LAPSE RATES. HOWEVER...LIMITED LOW LEVEL MOISTURE WILL
MAINTAIN ONLY MARGINAL INSTABILITY. SCATTERED CONVECTION WILL LIKELY
DEVELOP WITHIN THIS STEEP LAPSE RATE ENVIRONMENT...BUT CURRENT
THINKING IS THAT THUNDERSTORM COVERAGE WILL REMAIN LESS THAN 10%.
BEST CHANCE FOR A FEW STRIKES WILL BE NEAR THE COAST WHERE PRESENCE
OF THE MARINE LAYER MAY RESULT IN SLIGHTLY GREATER INSTABILITY.

..ERN AZ THROUGH NM...

IMPULSES EJECTING NEWD ALONG ERN PERIPHERY OF UPPER TROUGH...PLUME
OF MID-HIGH LEVEL MOISTURE AND OROGRAPHIC LIFT WILL CONTRIBUTE TO
THE DEVELOPMENT OF AREAS OF PRECIPITATION OVER PARTS OF AZ THROUGH
NM. HOWEVER...LAPSE RATES AND INSTABILITY ARE EXPECTED TO REMAIN TOO
LIMITED FOR SIGNIFICANT LIGHTNING ACTIVITY.

..OK...

ZONAL FLOW WILL BECOME ESTABLISHED OVER THE CNTRL AND SRN PLAINS
THURSDAY IN WAKE OF INITIAL SHORTWAVE TROUGH WITH A LEE TROUGH AND
40-50 KT SWLY LOW LEVEL JET FORECAST IN THIS REGION BY THURSDAY
EVENING. WARM ADVECTION AND LIFT ASSOCIATED WITH THE LOW LEVEL JET
AND NEWD EJECTING IMPULSES WILL CONTRIBUTE TO THE DEVELOPMENT OF
PRECIPITATION OVERNIGHT. HOWEVER...WEAK MID LEVEL LAPSE RATES AND
INSUFFICIENT LOW LEVEL MOISTURE RETURN SUGGEST INSTABILITY WILL
REMAIN TOO MARGINAL FOR THUNDERSTORMS.

.DIAL.. 11/29/2007

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