DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 030537
SWODY1
SPC AC 030535

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1135 PM CST SAT FEB 02 2008

VALID 031200Z - 041200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
MODELS INDICATE THAT THE AMPLIFICATION WITHIN THE MAIN BELT OF POLAR
WESTERLIES EMANATING FROM THE NORTHERN PACIFIC WILL CONTINUE TO
TRANSLATE EASTWARD INTO THE U.S. DURING THIS FORECAST PERIOD. THE
BROAD TROUGH OVER THE WESTERN STATES IS PROGGED TO SHARPEN...
DOWNSTREAM OF A BUILDING UPPER RIDGE SLOWLY EDGING TOWARD PACIFIC
COASTAL AREAS. AT THE SAME TIME...AN UPPER RIDGE IS FORECAST TO
BUILD ACROSS MOST AREAS EAST OF THE MISSISSIPPI VALLEY...
PARTICULARLY DURING THE LATTER HALF OF THE PERIOD...AS THE MOST
PROMINENT POLAR SHORT WAVE IMPULSE DIGS INTO THE SOUTHERN PLATEAU.

A WEAKER POLAR IMPULSE...NOW SHIFTING ACROSS THE SOUTHERN ROCKIES
INTO THE SOUTH CENTRAL HIGH PLAINS...AND A LOW AMPLITUDE SUBTROPICAL
WAVE LIFTING THROUGH THE LOWER RIO GRANDE VALLEY...ARE PROGGED TO
CONTINUE NORTHEASTWARD. BOTH FEATURES WILL EVENTUALLY WEAKEN WITHIN
A BROADER SCALE ANTICYCLONIC SOUTHWESTERLY UPPER FLOW REGIME.
BUT...THIS IS NOT EXPECTED TO OCCUR BEFORE ASSOCIATED FORCING FOR
UPWARD VERTICAL MOTION CONTRIBUTES TO AT LEAST SCATTERED
THUNDERSTORM ACTIVITY FROM PARTS OF THE EASTERN PLAINS INTO THE
VICINITY OF THE APPALACHIANS.

A MOISTENING RETURN FLOW OFF THE WESTERN GULF OF MEXICO IS ALREADY
UNDERWAY. THOUGH THE BOUNDARY LAYER OVER THE GULF IS STILL
MODIFYING FROM A RECENT COLD INTRUSION...SURFACE DEW POINTS HAVE
INCREASED INTO THE LOWER/MID 60S ALONG THE TEXAS COAST...WITH 50S
INLAND ACROSS MUCH OF CENTRAL/EASTERN TEXAS AND LOUISIANA.
MOISTENING OVER THE GULF OF MEXICO WILL CONTINUE THROUGH THIS
PERIOD...WITH MOISTURE ADVECTION OCCURRING THROUGH A BROAD AREA OF
THE SOUTH CENTRAL U.S...AS A DEEP SURFACE CYCLONE BEGINS TO DEVELOP
TO THE LEE OF THE CENTRAL ROCKIES.

..EASTERN PLAINS THROUGH THE APPALACHIANS...
SHOWERS ARE ALREADY FORMING WITHIN MOIST BROAD ISENTROPIC ASCENT
..DOWNSTREAM OF THE SUBTROPICAL IMPULSE...ACROSS PARTS OF EASTERN
TEXAS INTO THE LOWER MISSISSIPPI VALLEY. THE BULK OF MODEL GUIDANCE
HAS BEEN SUGGESTIVE THAT FORCING WILL WEAKEN INHIBITION SUFFICIENTLY
FOR THE INITIATION OF THUNDERSTORMS NEAR THE LOWER MISSISSIPPI
VALLEY BETWEEN 03/12-18Z. ENOUGH DESTABILIZATION MAY OCCUR ABOVE A
RESIDUAL COOL/STABLE BOUNDARY LAYER FOR A FEW STRONG STORMS WITH
HAIL...BEFORE ACTIVITY SPREADS TOWARD THE UPPER TENNESSEE VALLEY AND
WEAKENS LATER IN THE PERIOD. THE TENDENCY MAY THEN BE FOR MID LEVEL
WARMING TO SUPPRESS DEEP CONVECTION ACROSS EAST TEXAS INTO THE LOWER
MISSISSIPPI VALLEY...BUT SCATTERED STORMS COULD LINGER ON THE EDGE
OF THE STRONGER CAP... NEAR THE RIVER. AND...THE RISK FOR AN
ISOLATED STORM OR TWO ACROSS UPPER TEXAS COASTAL AREAS INTO
LOUISIANA MAY NOT BE COMPLETELY NEGLIGIBLE.

FARTHER NORTH...THE POLAR SHORT WAVE IMPULSE IS EXPECTED TO ENHANCE
LIFT WITHIN THE BAROCLINIC ZONE NORTH OF A RETREATING WARM
FRONT...WHERE MOISTENING ABOVE THE FRONTAL INVERSION IS PROGGED TO
CONTRIBUTE TO CONDITIONAL/CONVECTIVE INSTABILITY SUFFICIENT FOR AT
LEAST WEAK THUNDERSTORMS. THE PRIMARY ACTIVITY SEEMS MOST LIKELY TO
INITIATE ACROSS THE OZARKS BY MIDDAY...BEFORE SPREADING EAST
NORTHEASTWARD THROUGH THE LOWER OHIO VALLEY. THUNDERSTORMS PROBABLY
WILL DIMINISH EAST OF THE LOWER OHIO VALLEY TONIGHT...AS MID-LEVEL
FORCING WEAKENS/OUTRUNS BETTER LOW-LEVEL MOISTURE RETURN.

..CALIFORNIA INTO THE INTERMOUNTAIN WEST...
DESPITE A COOL LOW-LEVEL ENVIRONMENT...MODELS INDICATE THAT WEAK
DESTABILIZATION WILL OCCUR ACROSS A RATHER BROAD AREA...BENEATH A
MID-LEVEL THERMAL TROUGH WITH A 500 MB COLD CORE AROUND -30C.
SCATTERED CONVECTION IS LIKELY ACROSS MUCH OF THE REGION...BUT SOME
UNCERTAINTY EXISTS CONCERNING HOW MUCH WILL BE CAPABLE OF PRODUCING
LIGHTNING. MOST THUNDERSTORMS WILL PROBABLY BE SHORT- LIVED AND
SPARSE IN COVERAGE. THE GREATEST CONCENTRATION IS EXPECTED IN
RESPONSE TO AGEOSTROPHIC FORCING IN THE LEFT EXIT REGION OF A
DIGGING MID/UPPER JET STREAK...EAST SOUTHEAST OF THE SOUTHERN
SIERRA NEVADA INTO THE SOUTHERN GREAT BASIN.

SUFFICIENT FORCING/INSTABILITY MAY LINGER INTO THE PEAK AFTERNOON
HEATING HOURS FOR A FEW THUNDERSTORMS WEST OF THE SIERRA NEVADA...
MAINLY ACROSS PARTS OF THE SAN JOAQUIN VALLEY.

.KERR.. 02/03/2008

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