Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS02 KWNS 181731
SWODY2
SPC AC 181730

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT THU SEP 18 2014

VALID 191200Z - 201200Z

...NO SVR TSTM AREAS FORECAST...

...SUMMARY...
THERE IS A LOW PROBABILITY OF ISOLATED HAIL ACROSS PORTIONS OF THE
UPPER MISSISSIPPI VALLEY FRIDAY EVENING.

...SYNOPSIS...
A LOW-AMPLITUDE SHORTWAVE TROUGH WILL AFFECT THE NRN PLAINS AND INTO
THE UPPER GREAT LAKES THROUGH THE PERIOD...WITH A LEADING
DISTURBANCE MOVING QUICKLY FROM THE ERN DAKOTAS TOWARD LAKE SUPERIOR
DURING THE DAY...THEN MORE SUBSTANTIAL HEIGHT FALLS OVERNIGHT ACROSS
THE UPPER MS VALLEY.

A SURFACE TROUGH WILL MOVE FROM THE ERN DAKOTAS AROUND 00Z INTO THE
UPPER MS VALLEY BY 12Z SAT AS A NARROW PLUME OF 60S DEWPOINTS
STREAMS NWD INTO SRN MN FRIDAY EVENING RESULTING IN SUFFICIENT
INSTABILITY FOR A FEW STRONG TO SEVERE STORMS MAINLY FROM SRN MN
INTO WI.

ELSEWHERE...RESIDUAL COOL AIR ALOFT ACROSS THE SERN STATES AND
DAYTIME HEATING MAY RESULT IN SCATTERED NON-SEVERE STORMS.

...UPPER MS VALLEY LATE...
A LEADING SHORTWAVE DISTURBANCE WILL BE RESPONSIBLE FOR EARLY RAIN
AND STORMS ACROSS NRN MN INTO NRN WI AND UPPER MI...AIDED BY A 50 KT
SWLY LOW-LEVEL JET. ONLY VERY SMALL HAIL IS EXPECTED FROM THIS
ACTIVITY AS IT WILL BE ELEVATED WITH WEAK INSTABILITY. 850 MB FLOW
WILL VEER BEHIND THIS INITIAL WAVE...WITH NEUTRAL HEIGHT TENDENCIES
AROUND 00Z. IN ADDITION...A SUBSTANTIAL CAPPING INVERSION WILL BE IN
PLACE ACROSS THE WARM SECTOR...WITH NO STORMS EXPECTED DURING THE
DAY.

DURING THE EVENING...COOLING ALOFT WILL EVENTUALLY DECREASE THE
CAPPING INVERSION. HOWEVER...LOW-LEVEL FLOW WILL CONTINUE TO VEER AS
THE PRIMARY COLD FRONT ARRIVES. ELEVATED CONVECTION IS EXPECTED TO
MATERIALIZE FROM NEBRASKA ACROSS ERN SD...SRN MN AND WI BY 03-06Z.
THE NEB-SD PORTION WILL BE DRIVEN MAINLY BY FRONTOGENESIS...WHILE
THE MORE SUBSTANTIAL WARM ADVECTION AHEAD OF THE UPPER TROUGH WILL
BE LOCATED OVER WI. THEREFORE...HAVE MOVED THE 5% HAIL PROBABILITIES
EWD INTO WI. HERE...ELEVATED INSTABILITY WITH COOL UPPER-LEVEL
PROFILES AND SUBSTANTIAL DEEP LAYER SHEAR ABOVE CLOUD BASE MAY YIELD
SEVERE HAIL.

..JEWELL.. 09/18/2014



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