Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 282007
SWODY1
SPC AC 282005

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0305 PM CDT FRI AUG 28 2015

VALID 282000Z - 291200Z

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS NRN MN...

...SUMMARY...
ISOLATED STORMS WITH LARGE HAIL AND DAMAGING WINDS WILL BE POSSIBLE
LATE THIS AFTERNOON AND EVENING ACROSS NORTHERN MINNESOTA.  OTHER
STRONG STORMS WITH GUSTY WINDS COULD OCCUR THIS AFTERNOON ACROSS
SOUTH GEORGIA AND NORTH FLORIDA...AND FROM NORTHEAST KANSAS INTO
NORTHWEST MISSOURI AND SOUTHEAST IOWA.

...DISCUSSION...
CURRENT FORECAST REASONING APPEARS TO REMAIN VALID...WITH ONLY MINOR
LINE TWEAKS APPEARING NECESSARY ATTM.  THE BIGGEST CHANGE THIS
FORECAST WILL BE TO SHIFT THE WRN FRINGE OF THE 5%/MRGL RISK AREA
EWD OUT OF ND...AS CAPPING APPEARS LIKELY TO HINDER STORM
DEVELOPMENT THIS AFTERNOON/EVENING ACROSS THIS REGION.

..GOSS.. 08/28/2015

.PREV DISCUSSION... /ISSUED 1130 AM CDT FRI AUG 28 2015/

...SYNOPSIS...
SLOW EWD PROGRESSION OF A MIDLEVEL TROUGH OVER IA IS
EXPECTED...LARGELY IN RESPONSE TO HEIGHT RISES OVER THE NRN PLAINS
WHICH WILL OCCUR DOWNSTREAM FROM ANOTHER PRONOUNCED SHORTWAVE TROUGH
THAT WILL APPROACH THE PAC NW COAST SAT MORNING.

...ERN ND/NRN MN THIS AFTERNOON/EVENING...
MORNING CONVECTION WITH AN INITIAL SPEED MAX HAS WEAKENED OVER THE
PAST COUPLE OF HOURS.  ADDITIONAL STORM DEVELOPMENT WILL BE POSSIBLE
LATE THIS AFTERNOON/EVENING ALONG A WEAK SURFACE TROUGH FROM ERN ND
INTO NW MN AS AFTERNOON SURFACE HEATING/MIXING WEAKENS CONVECTIVE
INHIBITION...AND A WEAK UPSTREAM SPEED MAX APPROACHES FROM SRN
SASKATCHEWAN.  STEEP LAPSE RATE PROFILES AND BOUNDARY LAYER
DEWPOINTS NEAR 60 F WITH MIXING WILL CONTRIBUTE TO MLCAPE AOA 2000
J/KG...WITH DEEP-LAYER VERTICAL SHEAR THAT WILL BE SUFFICIENT FOR
ORGANIZED MULTICELL CLUSTERS AND PERHAPS MARGINAL SUPERCELL
STRUCTURES.  ISOLATED LARGE HAIL AND DAMAGING OUTFLOW GUSTS WILL BE
POSSIBLE FOR A FEW HOURS LATE THIS AFTERNOON INTO THIS EVENING.

...N FL/S GA THIS AFTERNOON...
A MIDLEVEL LOW OVER THE N CENTRAL GULF OF MEXICO WILL MOVE
LITTLE...WITH A PLUME OF TROPICAL MOISTURE PERSISTING TO THE E OF
THE TROUGH OVER S GA/FL.  SCATTERED THUNDERSTORMS ARE EXPECTED
THROUGH THE AFTERNOON ALONG LOCAL SEA BREEZE CIRCULATIONS AND A
RESIDUAL FRONT.  MODIFIED 12Z SOUNDINGS SUPPORT AFTERNOON MLCAPE
NEAR 2500 J/KG ACROSS N FL/S GA...WHERE THERE WILL ALSO BE SOME
POTENTIAL FOR STRONG DOWNDRAFTS AND OUTFLOW WINDS GIVEN
PRECIPITATION LOADING IN AN ENVIRONMENT WITH DCAPE NEAR 1200 J/KG.
STILL...COVERAGE OF STRONG STORMS IS IN QUESTION...AND WILL NOT ADD
A 5% WIND AREA IN THIS UPDATE.

...NE KS/NW MO/SW IA THIS AFTERNOON...
PERSISTENT CLOUDS/RAIN IN THE WAA ZONE WITH THE IA SHORTWAVE TROUGH
HAVE REDUCED LAPSE RATES AND WILL LIMIT THE STRONGER SURFACE HEATING
TO A NARROW CORRIDOR FROM NE KS INTO SE NEB/NW MO/SW IA THIS
AFTERNOON.  THE HAIL AND DOWNBURST RISKS WITH ADDITIONAL STORM
DEVELOPMENT ALONG THE SURFACE COLD FRONT LATER THIS AFTERNOON WILL
BE TEMPERED BY THE POOR LAPSE RATES...AND BUOYANCY SHOULD REMAIN
LIMITED WHERE VERTICAL SHEAR WILL BE STRONGER IN THE WAA ZONE OVER
IA.  THUS...WILL NOT ADD ANY PROBABILITIES IN THIS UPDATE...BUT THIS
AREA WILL CONTINUE TO BE MONITORED THROUGH THE AFTERNOON.



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