Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS01 KWNS 190605
SWODY1
SPC AC 190603

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0103 AM CDT SUN APR 19 2015

VALID 191200Z - 201200Z

...THERE IS AN ENH RISK OF SVR TSTMS OVER PARTS OF THE S-CNTRL
STATES...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN GREAT PLAINS TO
THE SOUTHEAST...

...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLGT RISK AND
INCLUDING THE LOWER OH VALLEY...

...SUMMARY...
SCATTERED SEVERE THUNDERSTORMS ARE EXPECTED OVER PARTS OF THE
SOUTH-CENTRAL STATES MAINLY THIS AFTERNOON AND EVENING...WITH VERY
LARGE HAIL...DAMAGING WINDS...AND A FEW TORNADOES. ISOLATED SEVERE
STORMS MAY ALSO OCCUR OVER PARTS OF THE SOUTHEAST STATES THROUGH THE
PERIOD.

...SYNOPSIS...
A BROAD UPPER TROUGH WILL GRADUALLY SHIFT E AND AMPLIFY OVER THE
CNTRL CONUS WITH A FEW EMBEDDED SHORTWAVE IMPULSES. OF PARTICULAR
CONVECTIVE INTEREST IS AN IMPULSE CURRENTLY OVER THE CNTRL HIGH
PLAINS THAT SHOULD REACH THE CONFLUENCE OF THE MS/OH RIVERS EARLY
MON. CONVECTIVELY INDUCED IMPULSES FROM E TX TO THE NRN GULF MAY
EVOLVE NE WITHIN THE BROADER CYCLONIC FLOW REGIME. MEANWHILE...AN
INTENSE UPPER-LEVEL JET WILL BECOME CENTERED FROM NW MEXICO
BISECTING TX AND INTO LA. A COMPLEX SURFACE EVOLUTION IS EXPECTED
GIVEN THE MULTITUDE OF MID-LEVEL IMPULSES. A WEAK SURFACE CYCLONE
SHOULD TRACK ALONG THE RED RIVER TODAY WHILE LARGE-SCALE
CYCLOGENESIS SHOULD OCCUR PRIMARILY LATE IN THE PERIOD OVER PARTS OF
THE MIDWEST. A DRYLINE WILL LIKELY MIX E INTO E TX AND BE OVERTAKEN
BY A COLD FRONT THAT SHOULD REACH THE LOWER MS VALLEY TO TX GULF
COAST BY 12Z/MON.

...S-CNTRL STATES...
IN THE WAKE OF DECAYING EARLY MORNING CONVECTION AND AHEAD OF THE
CNTRL HIGH PLAINS SHORTWAVE IMPULSE...DIABATIC HEATING SHOULD BE
PRONOUNCED. WITH A GRADUALLY EWD-EXPANDING EML PLUME ATOP RESIDUAL
60S SURFACE DEW POINTS EMANATING FROM S TX/LA...A MODERATELY TO
STRONGLY UNSTABLE AIR MASS SHOULD DEVELOP BY LATE DAY IN THE
ARKLATEX AREA. INITIAL DIURNALLY DRIVEN TSTM DEVELOPMENT WILL
PROBABLY OCCUR IMMEDIATELY AHEAD OF THE SHORTWAVE IMPULSE OVER PARTS
OF CNTRL OK WITH THE MAIN HAZARD BEING SEVERE HAIL. ADDITIONAL
STORMS SHOULD DEVELOP ALONG THE DRYLINE NEAR THE WEAK SURFACE
CYCLONE BY LATE AFTERNOON AS MLCIN WEAKENS. SETUP SHOULD YIELD
INITIALLY DISCRETE SUPERCELLS WITH PRIMARY HAZARDS OF VERY LARGE
HAIL AND A COUPLE TORNADOES. STRENGTHENING 700-500 MB W/SWLYS DURING
THE EVENING AND PREDOMINANT VEERED LOW-LEVEL WINDS SHOULD TEND TO
FAVOR UPSCALE GROWTH AND BOWING STRUCTURES WITH A CORRESPONDINGLY
INCREASE IN THE DAMAGING WIND RISK TOWARDS THE LOWER MS VALLEY.

...SOUTHEAST STATES...
WIDESPREAD CLOUDINESS AND ABUNDANT SHOWERS WITH EMBEDDED TSTM
ACTIVITY ARE EXPECTED TO BE ONGOING AT 19/12Z...AIDED BY LARGE-SCALE
HEIGHT FALLS AND A FEW MID-LEVEL VORTICITY MAXIMA. THIS ALONG WITH
POOR MID-LEVEL LAPSE RATES SAMPLED BY 19/00Z RAOBS ACROSS THE REGION
WILL HAMPER DIURNAL DESTABILIZATION. NEVERTHELESS...A BELT OF
STRENGTHENING LOW-LEVEL SLYS FROM THE FL PANHANDLE TOWARDS THE CNTRL
APPALACHIANS SHOULD YIELD ENLARGED LOW-LEVEL HODOGRAPHS AND
POTENTIAL FOR A COUPLE TORNADOES AND ISOLATED DAMAGING WINDS.
GREATER DIABATIC HEATING IS ANTICIPATED FARTHER W OVER PARTS OF
MS/AL WHERE A REMNANT MCV FROM A DECAYING MCS OVER E TX MAY FOCUS
AFTERNOON/EVENING TSTM DEVELOPMENT AND PROVIDE SUFFICIENT DEEP SHEAR
FOR ORGANIZED UPDRAFTS.

..GRAMS/COHEN.. 04/19/2015



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