DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 011224
SWODY1
SPC AC 011222

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0722 AM CDT MON APR 01 2013

VALID 011300Z - 021200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTN AND EVE ACROSS PARTS
OF THE SOUTHERN PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS TODAY ACROSS PARTS OF THE
SOUTHEAST FLORIDA COAST...

...SYNOPSIS...
WITHIN THE MORE PROMINENT NORTHERN BRANCH OF SPLIT MID-LATITUDE
WESTERLIES...UPPER TROUGHING OVER THE EASTERN U.S. MAY BEGIN TO LOSE
SOME AMPLITUDE AND SHIFT SLOWLY EASTWARD...AS THE MOST SIGNIFICANT
EMBEDDED SHORT WAVE IMPULSE PIVOTS EAST OF THE GREAT LAKES
REGION...TOWARD THE CANADIAN MARITIMES DURING THIS PERIOD. THE
CONFLUENCE OF THE TWO BRANCHES OF FLOW APPEARS LIKELY TO LINGER
ACROSS THE PLAINS. BUT UPPER FLOW IS EXPECTED TO BECOME
INCREASINGLY DIFLUENT...AND PERHAPS DIVERGENT...ACROSS PARTS OF THE
CENTRAL AND SOUTHERN HIGH PLAINS...AS THE MAJOR AXIS OF THE
ELONGATED SOUTHERN BRANCH LOW PIVOTS FROM WEST-EAST TO SOUTHWEST-
NORTHEAST ACROSS THE GREAT BASIN...AND SHORT WAVE RIDGING BUILDS TO
THE LEE OF THE CENTRAL ROCKIES. AT THE SAME TIME...BROAD SOUTHERN
STREAM TROUGHING IS EXPECTED TO CONTINUE GRADUALLY SHIFTING EASTWARD
ACROSS THE EASTERN GULF OF MEXICO...FLORIDA PENINSULA AND ADJACENT
WESTERN ATLANTIC.

IN LOWER LEVELS...A SIGNIFICANT COLD INTRUSION ASSOCIATED WITH THE
NORTHERN BRANCH TROUGH IS FORECAST TO CONTINUE AN EASTWARD
ADVANCEMENT ACROSS THE NORTHERN AND MID ATLANTIC SEABOARD...AND
SOUTHWARD INTO THE GULF STATES AND SOUTH CENTRAL PLAINS BY 12Z
TUESDAY. THIS WILL REINFORCE COOLING/DRYING ASSOCIATED WITH AN
INITIAL COLD INTRUSION WHICH HAS ALREADY IMPACTED AREAS AS FAR SOUTH
AS THE SOUTH ATLANTIC AND GULF COAST STATES. SUBSTANTIVE MOISTENING
TODAY APPEARS LIKELY TO BE CONFINED TO A SOUTHERLY RETURN FLOW NEAR
SOUTHEAST FLORIDA COASTAL AREAS...AND ACROSS THE LOWER RIO GRANDE
VALLEY INTO THE SOUTHERN HIGH PLAINS.

THE PRIMARY CONVECTIVE POTENTIAL FOR THIS PERIOD IS EXPECTED TO BE
ASSOCIATED WITH THESE LATTER TWO REGIMES...BUT A POCKET OF COLD AIR
ALOFT ASSOCIATED WITH THE REMNANT LOW OVER THE GREAT BASIN IS
EXPECTED TO CONTINUE TO CONTRIBUTE TO SUFFICIENT DESTABILIZATION FOR
SCATTERED THUNDERSTORM ACTIVITY.

...FLORIDA...
ONE OR TWO SOUTHERN STREAM IMPULSES APPEAR LIKELY TO CONTRIBUTE TO
THE RISK FOR THUNDERSTORM ACTIVITY TODAY. THIS PROBABLY WILL BE
CONFINED TO PORTIONS OF EAST CENTRAL AND SOUTHEAST COASTAL
AREAS...WHERE SEA BREEZE CONVERGENCE WILL BECOME ENHANCED...AS
LOW-LEVEL FLOW TAKES ON AN INCREASINGLY WESTERLY COMPONENT ACROSS
THE REMAINDER OF THE PENINSULA BY MIDDAY. MODERATELY LARGE CAPE IS
EXPECTED TO DEVELOP WITH DAYTIME HEATING...FROM MIAMI TO PALM BEACH.
AS MID-LEVEL COOLING ERODES INHIBITION...THE INITIATION OF SCATTERED
STORMS APPEARS PROBABLE BY 18-21Z. IN THE PRESENCE OF MODERATE TO
STRONG DEEP LAYER SHEAR BENEATH 30+ KT 500 MB FLOW /50+ KT AT
HIGH-LEVELS/...SUPERCELLS ARE POSSIBLE. AIDED BY FAIRLY COOL
THERMODYNAMIC PROFILES ALOFT...STORMS MAY BE CAPABLE OF PRODUCING
SEVERE HAIL. THE RISK FOR A TORNADO MAY NOT BE COMPLETELY
NEGLIGIBLE.

GUIDANCE ALSO INDICATES POTENTIAL FOR ADDITIONAL SCATTERED STORM
DEVELOPMENT LATER THIS AFTERNOON...NORTHWARD TOWARD VERO BEACH...
PERHAPS MELBOURNE. HOWEVER...SURFACE DEW POINTS MAY REMAIN LOWER
ACROSS THIS AREA...AND UNCERTAINTY CONCERNING DESTABILIZATION
REMAINS TOO LARGE FOR SLIGHT RISK PROBABILITIES AT THE PRESENT TIME.

...SOUTHERN HIGH PLAINS...
LARGE-SCALE ASCENT AND ASSOCIATED DESTABILIZATION ALOFT IS ALREADY
CONTRIBUTING TO WEAK THUNDERSTORM ACTIVITY ACROSS PARTS OF THE
EASTERN TEXAS PANHANDLE AND NORTHWEST OKLAHOMA. THIS ACTIVITY MAY
PERSIST AND SLOWLY INCREASE THROUGH THE DAY...BUT VIGOROUS
CONVECTIVE DEVELOPMENT WILL AWAIT SUBSTANTIVE BOUNDARY LAYER
DESTABILIZATION ASSOCIATED WITH STRONG DAYTIME HEATING AND MODEST
MOISTURE RETURN THROUGH THE TEXAS SOUTH PLAINS.
ULTIMATELY...STRONGEST CONVECTIVE DEVELOPMENT IS EXPECTED TO OCCUR
NEAR THE INTERSECTION OF THE SOUTHWARD ADVANCING COLD FRONT AND THE
SHARPENING DRYLINE SOMETIME LATE THIS AFTERNOON OR EVENING. THIS
MAY BE FAIRLY LOCALIZED INITIALLY. BUT DEEP LAYER SHEAR BENEATH
35-40 KT WEST NORTHWESTERLY 500 MB FLOW IS EXPECTED TO BE SUFFICIENT
FOR SUPERCELLS...AND STEEP MID-LEVEL LAPSE RATES WILL CONTRIBUTE TO
THE RISK FOR LARGE HAIL.

FORCING ASSOCIATED WITH SOUTHERLY LOW-LEVEL JET STRENGTHENING ACROSS
THE SOUTH PLAINS INTO NORTHWEST TEXAS MAY SUPPORT UPSCALE CONVECTIVE
GROWTH WITH ADDITIONAL MOISTENING THIS EVENING. IF THIS OCCURS...A
PERIOD WITH INCREASING POTENTIAL FOR SEVERE WIND GUSTS APPEARS
PROBABLE...BEFORE CONVECTION WEAKENS IN WANING INSTABILITY LATER
TONIGHT.

..KERR/LEITMAN.. 04/01/2013

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