Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS02 KWNS 291732
SWODY2
SPC AC 291730

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT FRI JUL 29 2016

VALID 301200Z - 311200Z

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS A PORTION OF THE CENTRAL
AND NORTHERN HIGH PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF VA...CENTRAL
AND WESTERN MD...EASTERN WV PANHANDLE AND FAR SOUTHERN PA...

...SUMMARY...
ISOLATED STRONG STORMS ARE POSSIBLE ACROSS PARTS OF THE CENTRAL HIGH
PLAINS AND MID-ATLANTIC REGION SATURDAY AFTERNOON AND EVENING.

...HIGH PLAINS...
A BAND OF MID-LEVEL NORTHWESTERLY WINDS OF 25-30 KT IS EXPECTED TO
EXTEND FROM THE NORTHERN ROCKIES/HIGH PLAINS THROUGH THE CENTRAL
PLAINS...WHILE SOUTHERLY LOW-LEVEL WINDS GRADUALLY STRENGTHEN
THROUGH THIS FORECAST PERIOD.  THE LATTER FLOW WILL SUPPORT POLEWARD
MOISTURE RETURN ACROSS THE FULL EXTENT OF THE GREAT PLAINS.  DESPITE
SOME BOUNDARY-LAYER MIXING ACROSS THE HIGH PLAINS...SURFACE DEW
POINTS IN THE UPPER 50S TO LOWER 60S ARE EXPECTED IN THE MARGINAL
SEVERE-WEATHER THREAT AREA SATURDAY AFTERNOON.  THIS COMBINED WITH
DIABATIC HEATING BENEATH STEEP MIDLEVEL LAPSE RATES WILL RESULT IN
MUCAPE OF 1000-2000 J/KG.  THIS DESTABILIZATION WITHIN AN
ENVIRONMENT WITH VERTICALLY VEERING WINDS SUGGESTS ANY STORMS THAT
DEVELOP AND MOVE OFF THE HIGHER TERRAIN SHOULD BE ORGANIZED.  A
MARGINAL SEVERE RISK WILL BE MAINTAINED...SINCE THIS REGION WILL
HAVE A LACK OF STRONGER FORCING ALOFT...RESULTING IN A LOW COVERAGE
FOR SEVERE STORMS.  GREATER STORM COVERAGE MAY OCCUR LATER SATURDAY
NIGHT AS TWO BRANCHES OF THE SOUTHERLY LOW-LEVEL JET FOCUS
MOISTURE/WARM AIR ADVECTION ACROSS THE DAKOTAS AND KS.  MODERATE
ELEVATED INSTABILITY COULD RESULT IN A COUPLE OF STRONGER TO SEVERE
STORMS...THOUGH COVERAGE OF THAT POTENTIAL IS EXPECTED TO BE
SUFFICIENT TO EXPAND THE MARGINAL RISK AT THIS TIME.

...MID-ATLANTIC REGION...
A MIDLEVEL SHORTWAVE TROUGH IS EXPECTED TO MOVE FROM THE MID
MS/LOWER OH VALLEYS TOWARD SOUTHERN ONTARIO/LOWER GREAT LAKES
REGION...WITHIN A REGIME OF BROAD CYCLONIC MID- TO UPPER-LEVEL FLOW
AND WEAK TO NEUTRAL HEIGHT RISES ACROSS THE NORTHEAST QUARTER OF THE
UNITED STATES.  MODELS MAINTAIN A CORRIDOR OF STRONGEST CYCLONIC
FLOW TO AROUND 30 KT EXTENDING FROM THE CENTRAL PLAINS THROUGH THE
OH VALLEY TO THE MID-ATLANTIC STATES.  RESIDUAL RICH BOUNDARY-LAYER
MOISTURE IS EXPECTED IN THIS MARGINAL RISK AREA...BOUNDED BY THE
HIGHER TERRAIN AND LEE TROUGH TO THE WEST AND A BOUNDARY DRAPED FROM
THE UPPER OH VALLEY THROUGH NORTHERN TO SOUTHEAST VA. DESPITE THE
PRESENCE OF WEAK MIDLEVEL LAPSE RATES EAST OF THE PLAINS STATES...
THE AVAILABLE MOISTURE AND SOME SURFACE HEATING WILL RESULT IN
MODERATE INSTABILITY.  THIS COMBINED WITH ENHANCED DEEP-LAYER SHEAR
PER MODERATELY STRONG WESTERLY FLOW REGIME ALOFT WILL PROVIDE A
FAVORABLE CAPE/SHEAR PARAMETER SPACE FOR ORGANIZED STORMS.  THIS
OUTLOOK HAS EXPANDED THE MARGINAL SEVERE-WEATHER RISK AREA EAST AS
THE BREADTH OF DESTABILIZATION SHOULD EXTEND INTO CENTRAL MD AS
WELL.  A SOUTHWARD EXTENSION IS TO ACCOUNT FOR DEVELOPMENT NEAR THE
LEE TROUGH.  THE LACK OF STRONGER MIDLEVEL FORCING FOR ASCENT AND
THE PRESENCE OF NEUTRAL TO WEAK HEIGHT RISES SUGGEST OVERALL
COVERAGE OF SEVERE STORMS SHOULD BE LOW.  THUS...THIS OUTLOOK WILL
MAINTAIN A LOW SEVERE PROBABILITY...WITH ISOLATED DAMAGING WINDS THE
GREATEST THREAT.

...AZ TO SOUTHERN AND NORTHERN CA...
STORMS WILL BE POSSIBLE ALONG THE FULL EXTENT OF THE SIERRAS AND
ALSO THE MOUNTAINS OF SOUTHERN CA.  MEANWHILE...FARTHER EAST INTO
AZ...MODELS CONTINUE TO SUGGEST WEAKER EASTERLY 500-MB WINDS THAN
EXPECTED DURING DAY 1.  THUS...WILL NOT INTRODUCE SEVERE
PROBABILITIES AT THIS TIME.

..PETERS.. 07/29/2016

$$


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