Tuesday, October 6, 2009

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 061730
SWODY2
SPC AC 061728

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT TUE OCT 06 2009

VALID 071200Z - 081200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
WITHIN AN EVOLVING SPLIT UPPER FLOW PATTERN...A BROAD CLOSED LOW
APPEARS LIKELY TO BEGIN SHIFTING SOUTHWARD INTO THE CANADIAN
PRAIRIES DURING THIS FORECAST PERIOD...DOWNSTREAM OF A SHARP
NORTHERN BRANCH RIDGE OVER THE NORTHEAST PACIFIC. MODELS SUGGEST
THAT AN EMBEDDED IMPULSE DIGGING AROUND THE SOUTHERN/WESTERN
PERIPHERY OF THIS CIRCULATION MAY CONTRIBUTE TO THE INLAND
ACCELERATION OF A CLOSED LOW NOW FORMING NEAR CENTRAL/SOUTHERN
CALIFORNIA COASTAL AREAS. WHILE THIS MAY CONTRIBUTE TO GRADUAL
MID/UPPER HEIGHT FALLS ACROSS THE SOUTHERN AND CENTRAL PLAINS INTO
THE UPPER MIDWEST BY LATE WEDNESDAY NIGHT THROUGH EARLY
THURSDAY...UPPER RIDGING IS PROGGED TO BUILD THROUGH MUCH OF THE
EASTERN STATES...NORTH OF A SUBTROPICAL HIGH CENTER OVER THE FLORIDA
PENINSULA/BAHAMAS REGION...IN THE WAKE OF A VIGOROUS MID-LEVEL
TROUGH AND CYCLONE SHIFTING OFF THE NORTH ATLANTIC COAST.

DESPITE THE STRENGTH OF THE EASTERN SYSTEM...CONVECTIVE POTENTIAL
ACROSS THE ATLANTIC SEABOARD PROBABLY WILL BE LIMITED WEDNESDAY AS
LOW-LEVEL DRYING OCCURS ACROSS MOST AREAS WITH RAPID COLD FRONTAL
PASSAGE BY MID DAY. A QUICKLY DEVELOPING RETURN FLOW OFF THE
WESTERN GULF OF MEXICO...WHERE THE LOW-LEVEL ENVIRONMENT REMAINS
VERY MOIST...MAY...HOWEVER...RESULT IN INCREASING CONVECTIVE
POTENTIAL ACROSS PARTS OF THE PLAINS INTO THE LOWER MISSOURI VALLEY
BY LATE IN THE PERIOD. MUCH OF THE DAY WEDNESDAY... THUNDERSTORMS
ARE EXPECTED TO BE MOST NUMEROUS NEAR A STALLED FRONTAL ZONE ACROSS
THE UPPER TEXAS COASTAL PLAIN INTO CENTRAL GULF COASTAL AREAS.
WHILE THIS FRONT IS EXPECTED TO WEAKEN AND BEGIN RETREATING OR
REDEVELOPING NORTHWARD BENEATH THE UPPER RIDGE...MUCH OF THE LATER
PERIOD THUNDERSTORM ACTIVITY SHOULD BE BASED IN THE ELEVATED
MOISTURE RETURN TO THE NORTH OF THE SURFACE FRONT. DESPITE THE
LIKELIHOOD OF STRONG CONVECTIVE LAYER SHEAR ON THE NORTHERN
PERIPHERY OF THE UPPER RIDGE...A RELATIVELY WARM MID-LEVEL AIR
MASS...COUPLED WITH THE PRESENCE OF THE COOL STABLE BOUNDARY
LAYER...STILL SEEMS LIKELY TO MINIMIZE ANY SEVERE THREAT.

...SOUTHERN PLAINS...
MODELS ARE SUGGESTIVE THAT SUBSTANTIVE BOUNDARY LAYER
DESTABILIZATION IN THE PRESENCE OF MODERATE TO STRONG DEEP LAYER
SHEAR WILL BE CONFINED TO A RELATIVELY LOCALIZED AREA NEAR THE
INTERSECTION OF THE STALLING FRONT AND DRY LINE OVER SOUTHWEST
TEXAS. FORCING TO WEAKEN ANTICIPATED STRONG MID-LEVEL CAPPING
ACROSS THIS REGION IS STILL UNCLEAR...BUT AN ISOLATED STRONG/SEVERE
STORM OR TWO IS NOT OUT OF THE QUESTION IN THE VICINITY OF THE FORT
STOCKTON AREA WEDNESDAY AFTERNOON. OTHERWISE...INCREASING ASCENT
WITH THE APPROACHING SOUTHERN BRANCH TROUGH IS EXPECTED TO BECOME
FOCUSED NORTH OF THE FRONT BY WEDNESDAY EVENING...ACROSS PARTS OF
SOUTHWEST TEXAS/SOUTHEAST NEW MEXICO INTO THE TEXAS SOUTH
PLAINS...WHERE THERMODYNAMIC PROFILES MAY BE SUFFICIENT FOR MARGINAL
SEVERE HAIL.

...SOUTH CENTRAL PLAINS INTO LOWER MISSOURI VALLEY...
STRONGER CAPPING OF ELEVATED MOISTURE RETURN MAY NOT ALLOW
CONVECTIVE DEVELOPMENT SOUTH/SOUTHWEST OF THE LOWER MISSOURI VALLEY
UNTIL EARLY THURSDAY MORNING. BUT...IF STORMS ARE ABLE TO FORM
PRIOR TO 08/12Z ACROSS NORTHERN OKLAHOMA/SOUTHERN KANSAS INTO
SOUTHWEST MISSOURI...FORECAST THERMODYNAMIC PROFILES APPEAR A BIT
MORE SUPPORTIVE OF LARGE HAIL POTENTIAL THAN THOSE ACROSS NORTHEAST
KANSAS INTO NORTHERN/CENTRAL MISSOURI.

..KERR.. 10/06/2009

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