National Weather Service Weather Forecast Office

Severe Storm Outlook Narrative (ac)

000
ACUS01 KWNS 270530
SWODY1
SPC AC 270529

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1129 PM CST THU NOV 26 2009

VALID 271200Z - 281200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
MODELS CONTINUE TO INDICATE THAT UPPER TROUGH AMPLIFICATION ACROSS
THE EASTERN U.S. WILL BE SHORT-LIVED.  A SIGNIFICANT EMBEDDED SHORT
WAVE IMPULSE IS ALREADY IN THE PROCESS OF LIFTING OUT OF THE
SOUTHEASTERN STATES...AND AN ASSOCIATED DEEPENING LOW/MID-LEVEL
CYCLONE IS PROGGED TO LIFT NORTHWARD ALONG OR NEAR NORTH ATLANTIC
COASTAL AREAS INTO THE CANADIAN MARITIMES BY EARLY SATURDAY MORNING.
 IN THE WAKE OF THIS SYSTEM...STRONGER BELTS OF POLAR AND
SUBTROPICAL WESTERLIES ARE EXPECTED TO REMAIN LARGELY OUT OF
PHASE...WITH A SIGNIFICANT SUBTROPICAL IMPULSE LIFTING ACROSS THE
RIO GRANDE VALLEY INTO THE WESTERN GULF STATES...AS A STRONGER SHORT
WAVE TROUGH DIGS FROM THE PACIFIC NORTHWEST.  THIS LATTER FEATURE IS
PROGGED TO EVOLVE INTO A DEEPENING CLOSED LOW OVER CENTRAL/SOUTHERN
CALIFORNIA DURING THE LATTER HALF OF THIS FORECAST PERIOD.

ALTHOUGH A SURFACE HIGH CENTER MAY BEGIN TO RETREAT EASTWARD OUT OF
THE WESTERN GULF COAST REGION IN RESPONSE TO THE EVOLVING UPPER
PATTERN...RIDGING WILL REMAIN PROMINENT WITH LITTLE IN THE WAY OF
SUBSTANTIVE BOUNDARY LAYER MOISTENING AND DESTABILIZATION ACROSS THE
WESTERN GULF OF MEXICO.  AS A RESULT...STABLE CONDITIONS ARE
EXPECTED TO PERSIST ACROSS MOST AREAS EAST OF THE ROCKIES...AS WELL
AS MUCH OF THE WEST...WITH GENERALLY LOW OR NEGLIGIBLE RISK FOR
THUNDERSTORM ACTIVITY.

...MIDDLE ATLANTIC COAST INTO NEW ENGLAND...
AS THE STRONG SHORT WAVE IMPULSE SHIFTS EAST OF MID ATLANTIC COASTAL
AREAS EARLY IN THE DAY...PRIMARY CONVECTIVE DEVELOPMENT FOR THIS
PERIOD APPEARS LIKELY TO BECOME FOCUSED OVER THE GULF STREAM.
HOWEVER...IT STILL APPEARS A POSSIBILITY THAT DESTABILIZATION WITHIN
AN ELEVATED WARM ADVECTION ZONE TO THE NORTH/NORTHWEST OF THE
DEEPENING CYCLONE COULD BECOME SUFFICIENT FOR CONVECTION WITH
EMBEDDED THUNDERSTORMS...FROM SOUTHERN NEW ENGLAND COASTAL AREAS
AROUND 12Z THIS MORNING...THROUGH DOWNEAST MAINE BY LATE AFTERNOON.

...CALIFORNIA...
DESPITE THE LIKELIHOOD OF STRONG FORCING FOR UPWARD VERTICAL MOTION
ASSOCIATED WITH THE DEVELOPING UPPER SYSTEM...GUIDANCE CURRENTLY
SUGGESTS THAT POTENTIAL FOR SUBSTANTIVE DESTABILIZATION SUPPORTIVE
OF THUNDERSTORM ACTIVITY IS TOO LOW FOR A CATEGORICAL OUTLOOK.

..KERR.. 11/27/2009