Sunday, October 11, 2009

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 111714
SWODY2
SPC AC 111712

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1212 PM CDT SUN OCT 11 2009

VALID 121200Z - 131200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...

LARGE-SCALE PATTERN WILL REMAIN PROGRESSIVE THROUGH THE DAY TWO
PERIOD...FEATURING THE EWD TRANSLATION OF A NRN BRANCH SHORT WAVE
TROUGH THROUGH THE GREAT LAKES REGION. A WEAKER...SRN STREAM
IMPULSE WILL LIKELY PRECEDE THE FORMER...SHIFTING RAPIDLY EWD FROM
THE LOWER MS VALLEY TO OFF THE CAROLINA COASTS. UPSTREAM...ANOTHER
SHORT WAVE TROUGH WILL MOVE FROM THE ERN PACIFIC INTO THE GREAT
BASIN.

AT THE SURFACE...A WEAK CYCLONE IS FORECAST TO ACCOMPANY GULF STATES
IMPULSE EWD...TRACKING FROM CNTRL MS ENEWD THROUGH THE CAROLINAS. A
WARM FRONT WILL RETREAT NWD IN ADVANCE OF THIS FEATURE WHILE A
TRAILING COLD FRONT PUSHES SWD TOWARD THE GULF COAST.

...CNTRL GULF STATES TO SERN ATLANTIC COAST...

A MOIST WARM SECTOR AIR MASS WILL BECOME ESTABLISHED INLAND IN
ADVANCE OF ABOVE-MENTIONED SURFACE WAVE WITH DEWPOINTS INCREASING
THROUGH THE 60S INTO LOWER 70S TO THE S OF WARM FRONT. LAPSE RATES
WILL REMAIN WEAK...EFFECTIVELY LIMITING MLCAPE TO LESS THAN 500-
1000 J/KG. NONETHELESS...THIS MARGINAL INSTABILITY COUPLED WITH
ZONE OF ENHANCED FORCING FOR ASCENT ATTENDANT TO SHORT WAVE TROUGH
SHOULD SUPPORT A GENERAL INCREASE IN STORM COVERAGE AND INTENSITY
THROUGH THE DIURNAL HEATING CYCLE.

11/12Z MODEL GUIDANCE SUGGESTS THAT THE STRONGEST FORCING AND
VERTICAL SHEAR WILL LIKELY REMAIN TO THE N OF WARM FRONT WITHIN A
STABLE AIR MASS. HOWEVER...FORECAST SOUNDINGS WITHIN WARM SECTOR
/AND ESPECIALLY ALONG LOW TRACK/ SUGGEST THAT SUFFICIENT LOW AND
DEEP-LAYER SHEAR WILL EXIST FOR MARGINAL SUPERCELL STRUCTURES
CAPABLE OF LOCALLY DAMAGING WIND GUSTS AND PERHAPS A BRIEF TORNADO.

..MEAD.. 10/11/2009

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