Friday, November 30, 2012

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 301256
SWODY1
SPC AC 301254

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0654 AM CST FRI NOV 30 2012

VALID 301300Z - 011200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
IN THE MID/UPPER LEVELS...A LARGE PACIFIC GYRE WILL REMAIN ANCHORED
OVER THE EAST PACIFIC WATERS OFF THE NWRN CONUS/BRITISH COLUMBIA
COAST. IMPULSES PIVOTING AROUND THE SRN SEMICIRCLE OF THE GYRE WILL
BE ASSOCIATED WITH A THREAT FOR ISOLATED THUNDERSTORMS ACROSS THE
COAST OF WA/ORE/NRN CA. ELSEWHERE ACROSS THE LOWER 48 STATES...
LOW-AMPLITUDE/PREDOMINANTLY ZONAL FLOW WILL BE PRESENT AND SUPPORT
SFC LEE TROUGHING OVER THE HIGH PLAINS. A SFC RIDGE AXIS WILL
PERSIST ACROSS PARTS OF THE MID ATLANTIC AND SERN UNITED STATES.
HIGHER PW SOUTH OF THE RIDGE AXIS WILL COMBINE WITH WEAK ASCENT
ACCOMPANYING A SHORTWAVE TROUGH CURRENTLY CROSSING THE MIDDLE GULF
OF MEXICO TO MAINTAIN A CHANCE FOR THUNDERSTORMS OVER THE STRAITS OF
FL...ONE OR TWO OF WHICH COULD GRAZE THE LOWER FL KEYS.

...COAST OF WA/ORE/NRN CA TODAY THROUGH TONIGHT...
SCATTERED LOW-TOPPED CONVECTION...OCCASIONALLY ORGANIZED IN SHORT
QUASI-LINEAR SEGMENTS...CONTINUES MOVING ASHORE IN ASSOCIATION WITH
AN IMPULSE PIVOTING AROUND THE AFOREMENTIONED GYRE. LIGHTNING
STRIKES HAVE BEEN DETECTED OVER THE COASTAL/OFFSHORE WATERS AND
IMMEDIATELY ADJACENT INLAND LOCATIONS EARLY THIS MORNING. THE THREAT
FOR STORMS WILL LESSEN TO SOME EXTENT BY LATE MORNING AS THE LOBE OF
ASCENT ACCOMPANYING THE IMPULSE BECOMES DISPLACED FROM ANY MARGINAL
INSTABILITY NEAR THE COAST.

FARTHER UPSTREAM...WATER VAPOR DATA AROUND 12Z INDICATE TWO CLOSELY
SPACED IMPULSES LOCATED APPROXIMATELY ALONG 133W/134W AND ALONG
139W/140W OFF THE PACIFIC NW COAST. BANDS OF LOW-TOPPED CONVECTION
ASSOCIATED WITH THESE FEATURES WILL AFFECT THE COAST...MAINLY AFTER
22Z AND CONTINUING INTO THE OVERNIGHT HOURS. LIGHTNING WILL BE
POSSIBLE WITH THIS ACTIVITY AMIDST STRONG DEEP FORCING...STRONG
VERTICAL WIND SHEAR...AND LIMITED INSTABILITY. VERTICAL MOMENTUM
TRANSPORT IN THUNDERSTORMS COULD AUGMENT STRONG BACKGROUND FLOW TO
POTENTIALLY ENHANCE THE THREAT FOR STRONG CONVECTIVE WIND GUSTS.
HOWEVER...THE VERY MEAGER AMOUNT OF BOUNDARY-LAYER BUOYANCY
INDICATED BY FORECAST SOUNDINGS SHOULD MINIMIZE THE POTENTIAL FOR
SVR-WIND-PRODUCING STORMS. AS SUCH...SVR PROBABILITIES HAVE NOT BEEN
INCLUDED AT THIS TIME.

..COHEN/CORFIDI.. 11/30/2012

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