Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 190548
SWODY1
SPC AC 190546

DAY 1 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
1246 AM CDT SAT APR 19 2014

VALID 191200Z - 201200Z

...NO SVR TSTM AREAS FORECAST...

CORRECTED TORNADO PROBABILITY GRAPHIC

...SUMMARY...
ISOLATED STRONG STORMS ARE POSSIBLE TODAY ALONG FLORIDA AND GEORGIA
ATLANTIC COASTAL AREAS...ACROSS PARTS OF SOUTHWEST TEXAS AND
ADJACENT SOUTHEAST NEW MEXICO...AND ACROSS PARTS OF NORTH CENTRAL
KANSAS INTO SOUTHERN NEBRASKA.  SOME OF THESE COULD APPROACH OR
BRIEFLY EXCEED SEVERE LIMITS.

...SYNOPSIS...
LITTLE CHANGE TO THE LARGE-SCALE UPPER PATTERN IS EXPECTED THROUGH
THIS FORECAST PERIOD.  MID-LATITUDE WESTERLIES EMERGING FROM THE
PACIFIC WILL REMAIN SPLIT ACROSS THE U.S...WITH ONE ZONAL BRANCH
ACROSS THE NORTHERN TIER STATES REMAINING A BIT STRONGER AND MORE
PROGRESSIVE THAN THE SLIGHTLY MORE AMPLIFIED BUT WEAKER BRANCH
ACROSS THE SOUTHERN TIER.

IN THE WAKE OF THE FIRST OF A PAIR OF PROMINENT PERTURBATIONS WITHIN
THE SOUTHERN BRANCH...CONSIDERABLE DRYING IS ONGOING ACROSS MUCH OF
THE GULF COAST REGION INTO THE GULF OF MEXICO.  HOWEVER...WEAK TO
MODEST MOISTURE RETURN IS UNDERWAY IN A NARROW PLUME ACROSS PARTS OF
THE RIO GRANDE VALLEY...AHEAD OF THE UPSTREAM PERTURBATION...WHICH
IS FORECAST TO GRADUALLY MIGRATE EAST NORTHEASTWARD ACROSS THE FOUR
CORNER STATES AND NORTHERN MEXICAN PLATEAU TODAY AND TONIGHT.  SOME
MOISTENING ALSO IS EXPECTED TO CONTINUE IN A CORRIDOR ACROSS THE
CENTRAL HIGH PLAINS INTO THE MID MISSOURI VALLEY...AHEAD OF A LEE
SURFACE TROUGH...AND A WEAKENING COLD FRONT ASSOCIATED WITH ONE IN A
SERIES OF VIGOROUS NORTHERN STREAM IMPULSES.

OTHERWISE...MOISTURE LEVELS ACROSS MUCH OF THE NATION WILL REMAIN
SEASONABLY LOW...WITH RELATIVELY LOW CONVECTIVE POTENTIAL FOR THE
TIME OF YEAR.

...SOUTH ATLANTIC COASTAL AREAS...
MODELS GENERALLY SUGGEST THAT A BAND OF ENHANCED FORCING FOR UPWARD
VERTICAL MOTION...AND ASSOCIATED VIGOROUS THUNDERSTORM
ACTIVITY...WILL BE IN THE PROCESS OF SPREADING OFF SOUTHEAST FLORIDA
ATLANTIC COASTAL AREAS DURING THE 12-15Z TIME FRAME.  IN ITS
WAKE...MID-LEVEL SUBSIDENCE...ASSOCIATED LOWER/MID TROPOSPHERIC
DRYING...AND A VEERING OF LOW-LEVEL FLOW TO A MORE WESTERLY
COMPONENT LIKELY WILL DIMINISH CONVECTIVE POTENTIAL.
HOWEVER...NORTH OF THE MIAMI AREA...BETWEEN PALM BEACH AND
MELBOURNE...MID-LEVEL COOLING AND ASCENT ON THE SOUTHERN FRINGE OF
THE UPPER LOW COULD CONTRIBUTE TO NEW CONVECTIVE DEVELOPMENT DURING
THE AFTERNOON.  INLAND ADVANCEMENT OF THE SEA BREEZE STILL APPEARS
UNLIKELY...THOUGH...AND STRONG CONVECTIVE DEVELOPMENT MAY BE LIMITED
TO AREAS EAST OF THE COASTAL WATERS.

MEANWHILE...IN CLOSER PROXIMITY TO THE MID-LEVEL COLD CORE /WITH 500
MB TEMPS OF -16 TO -18C/...RESIDUAL LOW-LEVEL MOISTURE NEAR A WEAK
SURFACE LOW/TROUGH MAY CONTRIBUTE TO THERMODYNAMIC PROFILES
SUPPORTIVE OF STRONG THUNDERSTORMS CAPABLE OF PRODUCING HAIL AND
STRONG WIND GUSTS.  SOME OF THIS COULD APPROACH OR BRIEFLY EXCEED
SEVERE LIMITS AROUND JACKSONVILLE FL...NORTHWARD INTO SOUTHEAST
GEORGIA...DURING THE AFTERNOON HOURS.

...PARTS OF SOUTHWEST TEXAS AND ADJACENT SOUTHEAST NEW MEXICO...
MODELS SUGGEST THAT BOUNDARY LAYER WARMING AND MOISTENING WILL ONLY
SUPPORT WEAK TO MODEST CAPE THIS AFTERNOON.  HOWEVER...VEERING WINDS
WITH HEIGHT BENEATH 30-50 KT SOUTHWESTERLY 500 MB FLOW AHEAD OF THE
APPROACHING UPPER TROUGH LIKELY WILL CONTRIBUTE TO STRONG DEEP LAYER
SHEAR SUPPORTIVE OF ORGANIZED CONVECTION...POTENTIALLY INCLUDING
SUPERCELLS.  THIS APPEARS ENOUGH TO SUPPORT AT LEAST LOW
PROBABILITIES FOR SEVERE HAIL AND WIND LATE THIS AFTERNOON AND
EVENING.

...NORTH CENTRAL KANSAS INTO SOUTHERN NEBRASKA...
MODELS SUGGEST THAT STRONG SURFACE HEATING AND A FOCUSED AREA OF
LARGE-SCALE ASCENT SUPPORTED BY LOW-LEVEL WARM ADVECTION MAY PROVIDE
THE SUPPORT FOR VIGOROUS CONVECTIVE DEVELOPMENT LATE THIS AFTERNOON
AND EVENING.  MID/UPPER FLOW MAY BE RELATIVELY WEAK ACROSS THE
REGION...BUT THE EVOLUTION OF AT LEAST A SMALL STORM CLUSTER APPEARS
POSSIBLE.  AND A REMNANT 30 KT SOUTHERLY 850 MB JET...COUPLED WITH
THE EVOLUTION OF A RELATIVELY DEEP MIXED BOUNDARY LAYER...MAY
CONTRIBUTE TO THE RISK FOR A DOWNBURST OR TWO...AS WELL AS VIGOROUS
COLD POOL DEVELOPMENT ACCOMPANIED BY STRONG SURFACE GUSTS.  ISOLATED
SEVERE HAIL MAY ALSO NOT BE OUT OF THE QUESTION...BEFORE ACTIVITY
WEAKENS BY MID TO LATE EVENING.

..KERR/COHEN.. 04/19/2014



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