Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 290554
SWODY1
SPC AC 290552

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1252 AM CDT THU SEP 29 2016

VALID 291200Z - 301200Z

...THERE IS A MRGL RISK OF SVR TSTMS FROM A PORTION OF THE CAROLINAS
INTO THE CNTRL APPALACHIANS AND UPPER OH VALLEY...

...THERE IS A MRGL RISK OF SVR TSTMS FROM SERN AZ INTO SWRN NM...

...SUMMARY...
THUNDERSTORMS ARE EXPECTED ACROSS THE PIEDMONT OF THE
CAROLINAS...VIRGINIA...AND THE CENTRAL APPALACHIANS INTO THE UPPER
OHIO VALLEY ON THURSDAY. A FEW OF THE STORMS WILL BE ACCOMPANIED BY
AT LEAST SOME RISK FOR HAIL...LOCALLY STRONG WIND GUSTS AND PERHAPS
A BRIEF TORNADO. OTHER STRONG STORMS WITH POTENTIAL FOR A FEW
DOWNBURST WINDS WILL DEVELOP OVER SOUTHEAST ARIZONA AND SOUTHWEST
NEW MEXICO.

...SYNOPSIS...

BLOCKING PATTERN WILL PERSIST TODAY WITH PRIMARY FEATURE OF INTEREST
BEING A NEARLY STATIONARY UPPER LOW CIRCULATION OVER THE ERN STATES.
FARTHER WEST A SHORTWAVE TROUGH WILL EJECT NEWD INTO THE SWRN
STATES...WHILE AN UPPER TROUGH APPROACHES THE PACIFIC NW. AT THE SFC
A QUASISTATIONARY FRONT WILL LINGER ACROSS CNTRL/SRN VA WHILE A COLD
FRONT ADVANCES SLOWLY EWD THROUGH A PORTION OF THE CAROLINAS.


...CNTRL THROUGH NWRN NC INTO THE CNTRL APPALACHIANS AND UPPER OH
VALLEY...

MOIST WARM SECTOR IS IN PLACE FROM CNTRL VA SWD THROUGH THE CNTRL
AND ERN CAROLINAS. ONGOING THUNDERSTORMS EARLY THIS MORNING WILL
GRADUALLY SHIFT EWD...BUT WIDESPREAD CLOUDS MAY LINGER FROM A
PORTION OF ERN NC INTO ERN VA. ATMOSPHERE MAY DESTABILIZE IN A
NARROW CORRIDOR NEAR AND WEST OF COLD/OCCLUDED FRONT FROM WRN NC
THROUGH WRN VA AND WV WHERE DIABATIC WARMING OF THE BOUNDARY LAYER
WILL OCCUR IN WAKE OF EARLY CONVECTIVE DEBRIS...BUT WEAK MID-LEVEL
LAPSE RATES SHOULD LIMIT MLCAPE TO AOB 1000 J/KG. THUNDERSTORMS
SHOULD INCREASE THIS AFTERNOON AS THE ATMOSPHERE DESTABILIZES AND AS
ANOTHER IN A SERIES OF VORTICITY MAXIMA ROTATE THROUGH BASE OF UPPER
TROUGH AND INTO THE SRN APPALACHIANS. WINDS ALOFT WITH 40+ KT AOA
600 MB WILL SUPPORT 40+ KT EFFECTIVE BULK SHEAR...SUFFICIENT FOR A
FEW ORGANIZED STORMS INCLUDING POTENTIAL FOR SUPERCELLS. THOUGH
MID-LEVEL UPDRAFT ROTATION MAY BOOST UPDRAFT STRENGTH IN A FEW
STORMS...WEAK MID-LEVEL LAPSE RATES MIGHT PROVE TO BE A LIMITING
FACTOR FOR A MORE ROBUST HAIL THREAT. A BRIEF TORNADO OR TWO CANNOT
BE RULED OUT...MAINLY IN A NARROW ZONE AS STORMS MOVE NWD AND
INTERACT WITH STALLED FRONT ACROSS VA BEFORE CROSSING INTO THE MORE
STABLE REGIME. DUE TO POTENTIAL LIMITING FACTORS ASSOCIATED WITH AN
EXPECTED MARGINAL THERMODYNAMIC ENVIRONMENT...WILL MAINTAIN MARGINAL
RISK THIS UPDATE...BUT CONTINUE TO EVALUATE FOR A POSSIBLE SLIGHT
RISK.

...SERN AZ THROUGH SWRN NM...

DEWPOINTS GENERALLY IN THE 50S WILL SUPPORT 400-800 J/KG MLCAPE AS
THE BOUNDARY LAYER DESTABILIZES DURING THE DAY. FORCING FOR ASCENT
ASSOCIATED WITH NEWD-EJECTING SHORTWAVE TROUGH AND DIABATIC WARMING
OVER THE HIGHER TERRAIN WILL PROMOTE THE DEVELOPMENT OF
THUNDERSTORMS. INVERTED-V BOUNDARY LAYERS SUGGEST AT LEAST A FEW
STORMS COULD PRODUCE DOWNBURST WIND GUSTS DURING THE AFTERNOON.

..DIAL/COHEN.. 09/29/2016

$$



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