Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 210549
SWODY1
SPC AC 210547

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1247 AM CDT TUE APR 21 2015

VALID 211200Z - 221200Z

...THERE IS A MRGL RISK OF SVR TSTMS FROM THE SRN HIGH PLAINS TO THE
OZARK PLATEAU...

...SUMMARY...
MARGINALLY SEVERE HAIL/WIND MAY DEVELOP LATE AFTERNOON/EARLY EVENING
ACROSS PARTS OF SOUTHERN KANSAS/MISSOURI. ISOLATED SEVERE HAIL/WIND
IS ALSO POSSIBLE FROM LATE AFTERNOON INTO TONIGHT OVER THE SOUTHERN
HIGH PLAINS.

...SYNOPSIS...
A BROAD UPPER TROUGH WILL PERSIST OVER THE EAST THROUGH THE
PERIOD...WHILE A REX BLOCK REMAINS OVER THE WEST WITH AN UPPER RIDGE
IN THE PACIFIC NW AND A CUTOFF LOW ENTERING SRN CA. AT THE
SURFACE...A WEAK ANTICYCLONE WILL SHIFT E ACROSS THE DEEP SOUTH.
THIS WILL YIELD MODIFIED MOISTURE RETURN OVER THE SRN GREAT PLAINS
AHEAD OF A LEE TROUGH OVER ERN NM/SERN CO. A REINFORCING COLD FRONT
WILL SWEEP S/SE...LIKELY REACHING THE LOWER MO VALLEY TO KS BY
EVENING...BEFORE SETTLING INTO NRN AR TO THE NRN TX PANHANDLE NEAR
12Z/WED.

...SRN KS/MO...
A NARROW CORRIDOR OF MEAGER MLCAPE OF 250-500 J/KG SHOULD DEVELOP
ALONG A PRE-FRONTAL CONFLUENCE AXIS ON THE NRN PERIPHERY OF A
MODIFIED MOISTURE PLUME CHARACTERIZED BY MIDDLE TO UPPER 40S SURFACE
DEW POINTS. ALTHOUGH WEAK MID-LEVEL HEIGHT RISES ARE
ANTICIPATED...ROBUST DIABATIC HEATING SHOULD RESULT IN STEEP
TROPOSPHERIC LAPSE RATES AND AID IN ISOLATED TO PERHAPS WIDELY
SCATTERED LATE AFTERNOON/EARLY EVENING TSTMS. WITH 50-60 KT 500-MB
NWLYS...ELONGATED STRAIGHT-LINE HODOGRAPHS COULD SUPPORT A FEW
SPLITTING CELLS CAPABLE OF SEVERE HAIL/WIND. OVERALL RISK WILL
LIKELY BE LIMITED BY THE MARGINAL BOUNDARY LAYER MOISTURE.

...SRN HIGH PLAINS...
ALTHOUGH POLEWARD MOISTURE ADVECTION HAS COMMENCED...THIS WILL
INITIALLY BE CHARACTERIZED BY MODIFIED CP AIR WITH ONLY MIDDLE 40S
TO LOWER 50S SURFACE DEW POINTS EXPECTED INTO W TX BY LATE
AFTERNOON. THIS PLUME SHOULD BE DISPLACED E OF THE LEE TROUGH ALONG
THE HIGHER TERRAIN ACROSS ERN NM. RATHER ISOLATED TSTMS SHOULD FORM
NEAR THE LEE TROUGH LATE DAY AND MAY DEVELOP E INTO NW TX BEFORE THE
ONSET OF NOCTURNAL BOUNDARY LAYER COOLING WITH A HIGHLY LOCALIZED
WIND/HAIL RISK.

EARLY WED...A SLY LLJ WILL IMPINGE ON THE COLD FRONT DROPPING S FROM
THE CNTRL HIGH PLAINS. THIS SHOULD RESULT IN A FOCUSED CORRIDOR OF
ASCENT OVER THE OK/TX PANHANDLES WITH AT LEAST ISOLATED ELEVATED
CONVECTION LIKELY ROOTED AROUND 700 MB. ALTHOUGH MID-LEVEL LAPSE
RATES WILL BE STEEP...THE CLOSE PROXIMITY OF A MID-LEVEL RIDGE
SHOULD RESULT IN ONLY MODERATE EFFECTIVE SHEAR OF 30-35 KT. OVERALL
SETUP APPEARS TO FAVOR A MARGINAL RISK FOR MAINLY HAIL.

..GRAMS/COHEN.. 04/21/2015




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