Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 271924
SWODY1
SPC AC 271923

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0223 PM CDT TUE SEP 27 2016

VALID 272000Z - 281200Z

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF THE WESTERN
CAROLINAS AND ADJACENT NORTHEAST GEORGIA...

...SUMMARY...
THUNDERSTORMS MAY BE ACCOMPANIED BY LOCALLY STRONG SURFACE GUSTS
ACROSS PARTS OF THE WESTERN CAROLINAS AND ADJACENT NORTHEAST GEORGIA
LATE THIS AFTERNOON.

...20Z OUTLOOK UPDATE...
SOME CHANGES TO CATEGORICAL AND PROBABILISTIC LINES HAVE BEEN MADE
TO ACCOUNT FOR  ONGOING TRENDS CONCERNING APPARENT DESTABILIZATION.

MODEST DESTABILIZATION AND LARGE-SCALE ASCENT ALONG SOUTHERN
PORTIONS OF THE BLUE RIDGE MOUNTAINS HAVE CONTRIBUTED TO THE
INITIATION OF SCATTERED THUNDERSTORMS THIS AFTERNOON.  THIS IS
OCCURRING GENERALLY WITHIN A STALLING/WEAKENING FRONTAL ZONE...BUT
WELL SOUTH OF THE STRONGER DEEP LAYER MEAN WIND FIELDS ON THE
SOUTHERN PERIPHERY OF THE BROAD CLOSED LOW NOW STILL CENTERED OVER
THE UPPER GREAT LAKES REGION.  HOWEVER...SOME STRENGTHENING OF MEAN
WESTERLY LOWER/MID TROPOSPHERIC FLOW FROM AROUND 20 KT TOWARD 30 KT
STILL APPEARS POSSIBLE PRIOR TO THE ONSET OF BOUNDARY LAYER
COOLING...WITHIN A NARROW CORRIDOR TO THE LEE OF THE BLUE RIDGE
MOUNTAINS.  THIS IS WHERE BOUNDARY LAYER HEATING/MIXING SEEMS MOST
CONDUCIVE TO ALLOW THE DOWNWARD TRANSFER OF HIGHER MOMENTUM TO THE
SURFACE.  STRONGEST GUSTS COULD AT LEAST APPROACH SEVERE LIMITS NEAR
THE MOST VIGOROUS CONVECTION.

..KERR.. 09/27/2016

.PREV DISCUSSION... /ISSUED 1105 AM CDT TUE SEP 27 2016/

...CAROLINAS...
WATER VAPOR LOOPS SHOWS A LARGE UPPER LOW CENTERED NEAR LAKE
SUPERIOR...WITH CYCLONIC FLOW ALOFT OVER THE OH/TN VALLEYS...CENTRAL
APPALACHIANS...AND MID ATLANTIC STATES.  THE NORTHERN EDGE OF
SUBSTANTIAL LOW LEVEL MOISTURE AND MODERATE CAPE EXTENDS FROM
SOUTHEAST VA INTO WESTERN NC/SC...THEN SOUTHEASTWARD INTO GA/AL.
THIS BOUNDARY IS EXPECTED TO BE THE FOCUS FOR ISOLATED-SCATTERED
AFTERNOON AND EVENING THUNDERSTORMS.  12Z MODEL GUIDANCE SUGGESTS
THE CORRIDOR ACROSS THE WESTERN CAROLINAS HAS THE HIGHEST
PROBABILITY OF STORMS.  THIS AREA WILL ALSO SEE SUFFICIENT WESTERLY
FLOW ALOFT AND 500MB TEMPERATURES AOB -9C...SUGGESTING A LOW RISK OF
A FEW BRIEFLY SEVERE STORMS.  LOCALLY DAMAGING WINDS GUSTS ARE THE
MAIN THREAT...BUT FORECAST SOUNDINGS CONFIRM SOME RISK OF HAIL AS
WELL.

ELSEWHERE ACROSS THE COUNTRY...AN ISOLATED STRONG STORM OR TWO
CANNOT BE RULED OUT OVER PARTS OF SOUTHEAST AZ...AND OVER SOUTH FL.
HOWEVER...WILL MAINTAIN LESS THAN 5 WIND/HAIL PROBABILITIES IN THESE
AREAS DUE TO LACK OF CONFIDENCE IN AN ORGANIZED SEVERE THREAT.

$$


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