Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 250557
SWODY1
SPC AC 250556

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CDT MON MAY 25 2015

VALID 251200Z - 261200Z

...THERE IS AN ENH RISK OF SVR TSTMS TODAY ACROSS PARTS OF CENTRAL
INTO NORTHEAST TEXAS...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SURROUNDING AREAS OF THE
SOUTHERN PLAINS AND ADJACENT PORTIONS OF THE LOWER MISSISSIPPI
VALLEY...

...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON AND EVENING
ACROSS PARTS OF THE NORTH CENTRAL PLAINS AND MID MISSOURI VALLEY...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS MUCH OF THE REMAINDER OF
THE SOUTHERN AND CENTRAL PLAINS...AND A CORRIDOR EXTENDING ACROSS
THE MID MISSOURI VALLEY INTO THE GREAT LAKES REGION...

...SUMMARY...
SEVERE THUNDERSTORMS ARE LIKELY TODAY INTO TONIGHT ACROSS MUCH OF
CENTRAL AND EASTERN TEXAS INTO PARTS OF THE LOWER MISSISSIPPI
VALLEY...AS WELL AS ACROSS PARTS OF THE CENTRAL PLAINS INTO THE
MIDDLE MISSOURI VALLEY.  STRONGEST STORMS WILL BE CAPABLE OF
PRODUCING LARGE HAIL AND POTENTIALLY DAMAGING WIND GUSTS.  A FEW
TORNADOES ARE ALSO POSSIBLE.

...SYNOPSIS...
SUBTROPICAL RIDGING APPEARS LIKELY TO REMAIN PROMINENT ALONG
ATLANTIC COASTAL AREAS THROUGH THIS PERIOD.  MODELS DO INDICATE THAT
UPPER FLOW ACROSS THE WESTERN INTO CENTRAL U.S. MAY BEGIN TO
DEAMPLIFY A BIT...BUT BROAD UPPER TROUGHING IS FORECAST TO
PERSIST...WITH A NUMBER OF SIGNIFICANT EMBEDDED SHORT WAVE
PERTURBATIONS.  SEVERAL OF THESE WILL CONTINUE TO PROGRESS EAST OF
THE ROCKIES...WITHIN SOUTHWESTERLY MID/UPPER FLOW ACROSS THE
PLAINS...MISSISSIPPI/OHIO VALLEYS...AND GREAT LAKES REGION...ABOVE A
PERSISTENT SOUTHERLY RETURN FLOW.

THIS INCLUDES ONE IMPULSE WHICH IS EXPECTED TO PIVOT NORTHEAST OF
THE MID/LOWER MISSOURI VALLEY...THROUGH THE UPPER MIDWEST EARLY
TODAY...BEFORE BECOMING ABSORBED WITHIN INCREASINGLY CONFLUENT FLOW
ACROSS AND NORTHEAST OF THE GREAT LAKES REGION.  UPSTREAM...THE
REMNANTS OF A COMPACT...BUT SIGNIFICANT...MID-LEVEL CIRCULATION /NOW
PROGRESSING INTO SOUTHWEST TEXAS/ ARE EXPECTED TO TURN NORTHEASTWARD
ACROSS THE SOUTHERN PLAINS RED RIVER VALLEY DURING THE DAY TODAY.
GUIDANCE INDICATES THAT IT WILL THEN CONTINUE THROUGH THE LOWER
MISSOURI VALLEY TONIGHT...JUST AHEAD OF THE REMNANTS OF THE CLOSED
LOW NOW BEGINNING TO PROGRESS EAST OF THE FRONT RANGE OF THE
ROCKIES.

...SOUTHERN PLAINS...
MODELS GENERALLY INDICATE THAT A 30-50 KT LOWER/MID TROPOSPHERIC JET
WILL ACCOMPANY THE IMPULSE EMERGING FROM THE SOUTHWEST.  THIS
FEATURE APPEARS LIKELY TO NOSE NORTH/NORTHEAST OF THE BIG BEND
REGION AFTER 12Z THIS MORNING.  ASSOCIATED FORCING FOR
ASCENT...COUPLED WITH RETURNING MOISTURE BENEATH AT LEAST MODESTLY
STEEP MID-LEVEL LAPSE RATES...MAY ALREADY BE IN THE PROCESS OF
SUPPORTING VIGOROUS CONVECTIVE DEVELOPMENT ACROSS PARTS OF THE TEXAS
SOUTH PLAINS AND EDWARDS PLATEAU.  THIS ACTIVITY IS EXPECTED TO
CONTINUE...GRADUALLY INCREASING IN COVERAGE AND INTENSITY WHILE
DEVELOPING EAST NORTHEASTWARD THROUGH EARLY AFTERNOON...AS INFLOW
BECOMES INCREASINGLY ROOTED IN A DESTABILIZING BOUNDARY LAYER.

THE RISK FOR LARGE HAIL APPEARS THE PRIMARY SEVERE THREAT INITIALLY.
 EVENTUALLY...A GRADUAL CONSOLIDATION OF CONVECTION AND ASSOCIATED
OUTFLOW IS EXPECTED TO LEAD TO EVOLUTION OF AN INCREASINGLY
ORGANIZED FORWARD PROPAGATING CONVECTIVE SYSTEM.  ALTHOUGH AMBIENT
LOW-LEVEL WIND FIELDS MAY BE INITIALLY MODEST...AT LEAST SOME
INTENSIFICATION DURING THE DAY...COUPLED WITH COLD POOL
STRENGTHENING...MAY CONTRIBUTE TO AN INCREASING RISK FOR POTENTIALLY
DAMAGING WIND GUSTS.  GIVEN THE SEASONABLY MOIST BOUNDARY LAYER
/CHARACTERIZED BY SURFACE DEW POINTS NEAR 70F/...MESOVORTICES
DEVELOPING ALONG THE GUST FRONT MAY BE ACCOMPANIED BY THE RISK FOR
TORNADOES OR LOCALLY ENHANCED SURFACE GUSTS AS ACTIVITY SPREADS
TOWARD THE ARKLATEX REGION AND SABINE VALLEY THROUGH EARLY EVENING.

IN THE WAKE OF THIS INITIAL CONVECTIVE ACTIVITY...ADDITIONAL
STRONG/SEVERE STORM DEVELOPMENT APPEARS POSSIBLE DURING THE LATE
AFTERNOON AND EVENING ALONG THE DRYLINE ACROSS THE PANHANDLE REGION
INTO WEST CENTRAL TEXAS.  THIS SHOULD BE MORE WIDELY SCATTERED IN
NATURE...BUT MAY INCLUDE DISCRETE SUPERCELLS.

...CENTRAL PLAINS INTO THE MID MISSOURI VALLEY...
LOW-LEVEL MOISTURE ALONG/AHEAD OF AN INCREASINGLY BETTER DEFINED
SURFACE FRONTAL ZONE WILL BE MORE LIMITED THAN ACROSS THE SOUTHERN
PLAINS.  BUT...THE NORTHEASTWARD ADVECTION OF A PLUME OF STEEP
MID-LEVEL LAPSE RATES IS EXPECTED TO CONTRIBUTE TO MODERATELY LARGE
CAPE BY LATE AFTERNOON.  STORMS MAY INITIATE FIRST NEAR THE
DRYLINE...ON THE NOSE OF STRONGER SURFACE HEATING  ACROSS NORTH
CENTRAL KANSAS...WHERE VERTICAL SHEAR SHOULD BE SUFFICIENT FOR
SUPERCELLS.  THEREAFTER...A MORE SUBSTANTIVE INCREASE IN STORM
DEVELOPMENT ALONG THE FRONT...EAST NORTHEASTWARD ACROSS THE MIDDLE
MISSOURI VALLEY...IS EXPECTED TO AWAIT BETTER FORCING ASSOCIATED
WITH IMPULSE PROGRESSING EAST OF THE FRONT RANGE.  THIS MAY NOT BE
UNTIL THE 26/00-03Z TIME FRAME...BUT THE ENVIRONMENT SHOULD STILL BE
CONDUCIVE TO THE DEVELOPMENT OF SUPERCELLS...PERHAPS AN ORGANIZING
STORM CLUSTER OR TWO.  LARGE HAIL...DAMAGING WIND GUSTS AND A COUPLE
OF TORNADOES ALL APPEAR POSSIBLE.

..KERR/PICCA.. 05/25/2015



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