Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS01 KWNS 302000
SWODY1
SPC AC 301958

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT SAT AUG 30 2014

VALID 302000Z - 311200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN HIGH
PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF LOWER MI...

...SUMMARY...
A FEW SEVERE STORMS ARE POSSIBLE LATE THIS AFTERNOON AND EVENING
ACROSS PARTS OF THE NORTHERN HIGH PLAINS AND OVER PARTS OF LOWER
MICHIGAN.  OTHER STRONG STORMS ARE POSSIBLE TODAY IN A CORRIDOR
ARCING FROM THE CENTRAL GULF COAST INTO THE TENNESSEE VALLEY.

THE ONLY CHANGE TO THE OUTLOOK FOR THIS ISSUANCE IS TO EXPAND THE 5
PERCENT WIND PROBABILITY NWD ACROSS NRN KY INTO SRN IND AND SW OH. A
2 PERCENT TORNADO PROBABILITY HAS ALSO BEEN ADDED IN THIS AREA. THE
WILMINGTON OH WSR-88D VWP SHOWS 0-3 KM STORM RELATIVE HELICITY JUST
ABOVE 150 M2/S2 WITH SOME SPEED SHEAR IN THE LOWEST KM AGL. THIS
COMBINED WITH MODERATE INSTABILITY EVIDENT ON MESOSCALE ANALYSIS MAY
BE ENOUGH FOR MARGINAL TORNADO THREAT THIS AFTERNOON. AN MCD WILL BE
FORTHCOMING ON THIS SCENARIO.

..BROYLES.. 08/30/2014

.PREV DISCUSSION... /ISSUED 1124 AM CDT SAT AUG 30 2014/

...NORTHERN HIGH PLAINS...
A BROAD UPPER TROUGH IS MOVING ACROSS THE NORTHWEST STATES...WITH A
LEAD SHORTWAVE IMPULSE OVER WESTERN/CENTRAL MT.  LARGE SCALE LIFT IN
ADVANCE OF THIS FEATURE WILL AFFECT PARTS OF EASTERN MT/NORTHEAST WY
BY MID AFTERNOON...AND INTO THE WESTERN DAKOTAS THIS EVENING.  LOW
LEVEL MOISTURE AND INSTABILITY ARE RATHER LIMITED ACROSS THIS REGION
THIS MORNING...BUT SOUTHEASTERLY LOW LEVEL WINDS WILL CONTINUE TO
SLOWLY DESTABILIZE THE AREA LEADING TO SCATTERED AFTERNOON
THUNDERSTORM DEVELOPMENT.  IT APPEARS LIKELY THAT HIGH-BASED
THUNDERSTORMS THAT DEVELOP OVER THE BIGHORN MOUNTAINS LATER TODAY
WILL SPREAD EASTWARD ACROSS THE SLIGHT RISK AREA THIS EVENING.
VERTICAL SHEAR PROFILES WILL PROMOTE SUPERCELL/BOW STRUCTURES
CAPABLE OF DAMAGING WINDS AND LARGE HAIL.  STRENGTHENING LOW LEVEL
WINDS AROUND DUSK MAY ALSO RESULT IN AN ISOLATED TORNADO OVER THE
WESTERN DAKOTAS THIS EVENING.

...LOWER MI...
WATER VAPOR IMAGERY SHOWS A PROGRESSIVE SHORTWAVE TROUGH OVER WI.
THIS SYSTEM WILL TRACK NORTHEASTWARD ACROSS PARTS OF LOWER MI THIS
AFTERNOON AND EARLY EVENING.  SIGNIFICANT CLOUD COVER OVER LOWER MI
IS SLOWLY ERODING AND MOVING OUT OF THE AREA...WHICH MAY RESULT IN A
FEW HOURS OF STRONG HEATING THIS AFTERNOON.  DEWPOINTS NEAR 70F WILL
RESULT IN MLCAPE VALUES OF 1000-1500 J/KG.  FORECAST SOUNDINGS ALSO
SHOW FAVORABLE WIND FIELDS FOR ORGANIZED/SEVERE STORMS WITH
EFFECTIVE SHEAR OF 30-40 KNOTS.  IT REMAINS UNCLEAR HOW MANY ROBUST
STORMS WILL AFFECT THIS AREA TODAY.  HOWEVER...THOSE STORMS THAT
FORM WILL BE RELATIVELY FAST-MOVING...AND WILL POSE A RISK OF
LOCALLY DAMAGING WIND GUSTS.



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