Severe Storm Outlook Narrative (AC)
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ACUS02 KWNS 271705
SWODY2
SPC AC 271705

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1205 PM CDT TUE SEP 27 2016

VALID 281200Z - 291200Z

...THERE IS A MRGL RISK OF SVR TSTMS LATE WEDNESDAY AFTERNOON AND
EVENING ACROSS THE PIEDMONT OF VIRGINIA AND NORTH CAROLINA...

...SUMMARY...
THUNDERSTORMS MAY POSE SOME SEVERE WEATHER POTENTIAL ACROSS THE
PIEDMONT OF VIRGINIA AND NORTH CAROLINA LATE WEDNESDAY AFTERNOON AND
EVENING.

...SYNOPSIS...
MODELS CONTINUE TO INDICATE THAT LARGE-SCALE RIDGING WITHIN THE
MID-LATITUDE WESTERLIES WILL REBUILD ACROSS THE NORTHERN ROCKIES AND
CENTRAL CANADIAN/U.S. BORDER DURING THIS PERIOD.  EXPANSION EASTWARD
ACROSS ONTARIO AND QUEBEC ALSO APPEARS LIKELY...AROUND THE
NORTHWESTERN AND NORTHERN PERIPHERY OF THE DEEP CLOSED LOW NOW OVER
THE UPPER GREAT LAKES REGION.  AS IT BECOMES INCREASINGLY CUT OFF
FROM THE WESTERLIES...A GRADUAL FILLING OF CYCLONE STILL APPEARS
PROBABLE...WITH THE CENTER OF THE MID-LEVEL CIRCULATION EXPECTED TO
REDEVELOP SOUTH SOUTHEASTWARD INTO THE MIDDLE OHIO VALLEY...TO THE
WEST OF THE CENTRAL APPALACHIANS...BY LATE WEDNESDAY NIGHT.  THIS
WILL LARGELY OCCUR AS A SIGNIFICANT IMPULSE DIGS AROUND ITS
SOUTHWESTERN INTO SOUTHERN PERIPHERY...ACROSS THE LOWER OHIO
VALLEY...TOWARD THE SOUTHERN APPALACHIANS.  IN RESPONSE TO THESE
DEVELOPMENTS...ANOTHER INTRUSION OF COOL AIR IS EXPECTED TO PROGRESS
SOUTHEAST OF THE MIDDLE MISSISSIPPI VALLEY/CENTRAL PLAINS REGION
TOWARD THE GULF COAST.  AN INITIAL STALLING SURFACE
FRONT...EXTENDING ACROSS THE MID ATLANTIC COAST AND CAROLINA/GEORGIA
PIEDMONT INTO THE CENTRAL GULF COAST...IS EXPECTED TO WEAKEN FURTHER
IN THE WAKE OF A WEAK LOW MIGRATING NORTHEASTWARD OFF THE MID
ATLANTIC COAST.  MORE UNCERTAINTY EXISTS CONCERNING SURFACE PRESSURE
FALLS AND NEW LOW DEVELOPMENT TO THE LEE OF THE SOUTHERN
APPALACHIANS LATE WEDNESDAY AFTERNOON INTO EARLY THURSDAY.

...SOUTHERN MID ATLANTIC COAST REGION...
SUBSTANTIVE MID-LEVEL HEIGHT FALLS AND THE MID/UPPER JET CORE
ASSOCIATED WITH THE APPROACHING CUT-OFF LOW MAY NOT BEGIN TO SPREAD
EAST OF THE CREST OF THE CENTRAL/ SOUTHERN APPALACHIANS UNTIL LATE
WEDNESDAY NIGHT.  HOWEVER...SHARPLY CYCLONIC AND DIFLUENT MID/UPPER
FLOW TO THE EAST OF THE DIGGING LOW COULD PROVIDE SUPPORT FOR
INCREASING THUNDERSTORM ACTIVITY NEAR THE BLUE RIDGE MOUNTAINS INTO
THE VIRGINIA AND NORTHERN CAROLINA PIEDMONT BY THE 29/00-03Z TIME
FRAME...IF NOT A BIT BEFORE.  IF THIS OCCURS...PERHAPS COINCIDING
WITH THE ONSET OF AT LEAST WEAK MID-LEVEL COOLING...IT APPEARS
POSSIBLE THE RESIDUAL MODEST BOUNDARY LAYER INSTABILITY DRIVEN BY
DAYTIME HEATING OF A SEASONABLY MOIST AIR MASS COULD CONTRIBUTE TO
VIGOROUS CONVECTIVE ACTIVITY.  GUIDANCE SUGGESTS CAPE UP TO 1000+
J/KG IS POSSIBLE.  BENEATH 30-40 KT SOUTHERLY TO SOUTHWESTERLY
LOWER/MID TROPOSPHERIC FLOW...IT MAY NOT BE OUT OF THE QUESTION THAT
THE ENVIRONMENT COULD BECOME MARGINALLY CONDUCIVE TO AN ISOLATED
SUPERCELL OR TWO...BEFORE INSTABILITY WANES OVERNIGHT.

..KERR.. 09/27/2016

$$


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