Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS02 KWNS 271700
SWODY2
SPC AC 271659

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1159 AM CDT MON JUL 27 2015

VALID 281200Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE UPPER MIDWEST...

...THERE IS A MRGL RISK OF SVR TSTMS FROM THE UPPER MIDWEST/GREAT
LAKES TO THE SOUTH-CENTRAL PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS NEW ENGLAND...

...SUMMARY...
SEVERE THUNDERSTORMS WILL BE POSSIBLE TUESDAY OVER PORTIONS OF THE
UPPER MIDWEST...LOWER/MIDDLE MISSOURI VALLEY...AND NEW ENGLAND.

...SYNOPSIS...

A PROGRESSIVE UPPER PATTERN WILL BRING A TROUGH EASTWARD FROM THE
NORTHERN HIGH PLAINS TO THE UPPER MS VALLEY BY 12Z WED. A SURFACE
COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL TRACK EAST SOUTHEAST
ACROSS THE NORTHERN AND CENTRAL PLAINS DURING THE MORNING AND EXTEND
FROM CENTRAL WI SOUTHWESTWARD THROUGH NORTHERN MO AND INTO SOUTHERN
KS BY WEDNESDAY MORNING. THIS WILL SERVE AS A FOCUS FOR STRONG TO
SEVERE THUNDERSTORM DEVELOPMENT FROM THE MID/UPPER MS VALLEY INTO
PARTS OF THE CENTRAL PLAINS.

FURTHER EAST...A SERIES OF SHORTWAVE IMPULSES WILL MIGRATE
EAST/SOUTHEAST ACROSS NEW ENGLAND AS AN UPPER TROUGH OVER NORTHERN
QUEBEC SHIFTS SOUTHEAST TOWARD NEW BRUNSWICK. SCATTERED
THUNDERSTORMS...SOME STRONG...WILL BE POSSIBLE DURING THE AFTERNOON.

...UPPER MIDWEST/MO VALLEY TO THE CENTRAL PLAINS...

CONVECTION WILL LIKELY BE ONGOING ACROSS PARTS OF MN/WI AND PERHAPS
AS FAR SOUTH AS IA TUESDAY MORNING. THIS EARLY-DAY CONVECTION MAY
PRODUCE SOME MARGINALLY SEVERE WIND/HAIL. THIS EARLY CONVECTION ALSO
WILL COMPLICATE THE SCENARIO FOR AFTERNOON DESTABILIZATION ACROSS
THE REGION DUE TO CLOUD DEBRIS AND OUTFLOWS TRAVERSING THE AREA.
FORECAST GUIDANCE CONTINUES TO INDICATE THE BEST AREA FOR AIRMASS
RECOVERY/DESTABILIZATION WILL BE NEAR THE SOUTHERN EDGE OF MORNING
CONVECTION AND RESIDUAL CLOUD SHIELD FROM FAR SOUTHERN MN/SOUTHWEST
WI INTO IA AND PERHAPS AS FAR SOUTH AS NORTHERN MO. HERE...A NARROW
WARM SECTOR AHEAD OF THE SURFACE COLD FRONT WILL EXIST WITH
DEWPOINTS IN THE UPPER 60S TO LOW 70S...RESULTING IN POCKETS OF
MODERATE INSTABILITY DURING PEAK HEATING. STRONGER FORCING AND
EFFECTIVE SHEAR WILL RESIDE JUST NORTH OF THE BEST THERMODYNAMICS
BUT SHOULD STILL BE SUFFICIENT FOR ORGANIZED BOWS/LINE
SEGMENTS...AND PERHAPS AN ISOLATED SUPERCELL OR TWO...CAPABLE OF
HAIL AND STRONG WINDS.

TO THE SOUTHWEST INTO FAR SE NEB AND SOUTHERN/CENTRAL KS...MORE
ISOLATED...HIGH-BASED CONVECTION IS EXPECTED TO DEVELOP ALONG THE
COLD FRONT. STEEP LAPSE RATES AND A DEEPLY MIXED BOUNDARY LAYER WILL
BRING A RISK FOR STRONG DOWNBURST WINDS WITH ANY STORMS THAT FORM IN
THIS AREA.

...NEW ENGLAND...

THE AIRMASS ACROSS THE REGION WILL BECOME WEAKLY TO MODERATELY
UNSTABLE DURING PEAK HEATING. WIDELY SCATTERED THUNDERSTORMS ARE
EXPECTED TO DEVELOP AND WILL INTENSIFY AS DEEP LAYER SHEAR INCREASES
WITH THE APPROACHING SHORTWAVE IMPULSES. LOW LEVEL WINDS WILL BE
RATHER WEAK...BUT STRENGTHENING NORTHWESTERLIES ABOVE ABOUT 700 MB
WILL BE SUFFICIENT FOR SOME ORGANIZED SOUTHEASTWARD PROPAGATING
CLUSTERS AND PERHAPS A FEW MARGINAL SUPERCELLS. LAPSE RATES WILL BE
RATHER POOR...AND ONLY MARGINAL HAIL IS EXPECTED. BUT FAST STORM
MOTION AND A DEEPLY MIXED BOUNDARY LAYER WILL SUPPORT
GUSTY...LOCALLY DAMAGING WINDS.

..LEITMAN.. 07/27/2015




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