Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS02 KWNS 281712
SWODY2
SPC AC 281711

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1211 PM CDT WED SEP 28 2016

VALID 291200Z - 301200Z

...THERE IS A MRGL RISK OF SVR TSTMS THURSDAY ACROSS THE PIEDMONT OF
CAROLINAS AND VIRGINIA...AND THE CENTRAL APPALACHIANS INTO THE UPPER
OHIO VALLEY...

...SUMMARY...
THUNDERSTORMS ARE EXPECTED ACROSS THE PIEDMONT OF THE CAROLINAS AND
VIRGINIA...AND THE CENTRAL APPALACHIANS INTO THE UPPER OHIO
VALLEY...ON THURSDAY...ACCOMPANIED BY AT LEAST SOME RISK FOR SEVERE
HAIL AND LOCALLY STRONG SURFACE GUSTS.

...SYNOPSIS...
A DEEP CLOSED LOW NOW DIGGING INTO THE OHIO VALLEY...TO THE WEST OF
THE CENTRAL APPALACHIANS...HAS BECOME INCREASINGLY CUT OFF FROM THE
STRONGER MID-LATITUDE WESTERLIES.  LITTLE CHANGE APPEARS LIKELY
THROUGH THIS FORECAST PERIOD.  A CONTINUED GRADUAL FILLING OF THE
LOW IS POSSIBLE...BUT LITTLE NET EASTWARD PROGRESSION IS EXPECTED.
ANY MOVEMENT LIKELY WILL BE SUBTLE...AND GENERALLY IN RESPONSE TO
SHORT WAVE PERTURBATIONS PIVOTING AROUND THE MID-LEVEL CIRCULATION
CENTER.  TO ITS NORTHWEST AND NORTH...BROAD UPPER RIDGING WITHIN THE
PRIMARY BELT OF WESTERLIES IS EXPECTED TO CONTINUE TO BUILD ACROSS
PARTS OF THE NORTHERN ROCKIES AND CANADIAN PRAIRIES...WHILE
EXPANDING EASTWARD ACROSS ONTARIO AND QUEBEC...DOWNSTREAM OF
AMPLIFIED TROUGHING NEAR/WEST  OF THE PACIFIC COAST.

IN RESPONSE TO THESE DEVELOPMENTS...SOME CONTINUED SOUTHWARD
PROGRESSION OF A SURFACE COLD FRONT ACROSS THE GULF COAST REGION IS
POSSIBLE.  ADVANCEMENT ACROSS THE SOUTHERN APPALACHIANS AND SOUTH
ATLANTIC COAST REGION MAY OCCUR BY THE END OF THE PERIOD...BUT
MODELS INDICATE THAT THE FRONTAL ZONE WILL REMAIN STALLED SOUTH OF
NEW ENGLAND COASTAL AREAS INTO THE MID ATLANTIC COAST REGION.
HIGHER MOISTURE CONTENT AIR WILL BE CONFINED TO AREAS
ALONG/SOUTHEAST OF THE FRONT...BUT SUBSTANTIVE MOISTURE  WILL
CONTINUE TO WRAP AROUND THE NORTHEASTERN AND NORTHERN PERIPHERY OF
THE  LOW...ACROSS PARTS OF THE CENTRAL APPALACHIANS/OHIO VALLEY AND
GREAT LAKES REGION.  AT THE SAME TIME...AT  LEAST MODEST MOISTENING
MAY CONTINUE ON SOUTHERLY MEAN FLOW ACROSS PARTS OF THE
INTERMOUNTAIN WEST AND ROCKIES.

...MID ATLANTIC/CENTRAL APPALACHIANS/UPPER OHIO VALLEY...
THE MID-LEVEL COLD CORE OF THE CUT-OFF LOW APPEARS LIKELY TO REMAIN
LARGELY WEST OF THE CREST OF THE CENTRAL APPALACHIANS THROUGH THIS
PERIOD.  HOWEVER...ON ITS EASTERN PERIPHERY /ACROSS THE PIEDMONT OF
THE CAROLINAS AND VIRGINIA...NORTHWARD ACROSS THE APPALACHIANS INTO
THE UPPER OHIO VALLEY/ BREAKS IN CLOUD COVER BENEATH THE MID-LEVEL
DRY SLOT PROBABLY WILL ALLOW FOR SUFFICIENT INSOLATION TO CONTRIBUTE
TO WEAK TO MODEST BOUNDARY LAYER DESTABILIZATION BY THURSDAY
AFTERNOON.  BENEATH RELATIVELY STRONG SOUTHERLY MID TO UPPER LEVEL
FLOW /INCLUDING 40-50 KT AROUND 500 MB/...THE ENVIRONMENT PROBABLY
WILL BECOME AT LEAST MARGINALLY CONDUCIVE TO ORGANIZED SEVERE STORM
DEVELOPMENT...PERHAPS INCLUDING SUPERCELLS.  LOW-LEVEL HODOGRAPHS IN
THE AREAS WITH THE MOST APPRECIABLE BOUNDARY LAYER DESTABILIZATION
MAY REMAIN RATHER MODEST IN SIZE...AND TEND TO LIMIT TORNADIC
POTENTIAL...BUT SEVERE HAIL AND LOCALLY STRONG SURFACE GUSTS WILL BE
POSSIBLE IN STRONGEST STORMS.  AT THIS POINT...DUE TO SOME LINGERING
UNCERTAINTIES...SLIGHT RISK PROBABILITIES WILL NOT BE
INTRODUCED...BUT PROBABILITIES MAY NEED TO BE UPGRADED IN LATER
OUTLOOKS FOR THIS TIME PERIOD.

..KERR.. 09/28/2016

$$



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