Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS02 KWNS 051733
SWODY2
SPC AC 051732

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1232 PM CDT SUN JUL 05 2015

VALID 061200Z - 071200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE UPPER MS
VALLEY SOUTHWEST TO THE SOUTHERN PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS FROM THE UPPER MS VALLEY TO THE
TEXAS PANHANDLE...

...SUMMARY...
AN EXTENSIVE BUT BROKEN LINE OF STRONG TO SEVERE THUNDERSTORMS CAN
BE EXPECTED MONDAY AFTERNOON AND EVENING ALONG A CORRIDOR FROM
SOUTHERN WISCONSIN AND NORTHERN ILLINOIS SOUTHWESTWARD INTO
IOWA...NORTHERN MISSOURI...EASTERN KANSAS...AND NORTHERN OKLAHOMA.
OTHER SCATTERED AFTERNOON STORMS WILL OCCUR FROM FLORIDA NORTHWARD
TO THE MID-ATLANTIC...AND ACROSS THE CENTRAL AND SOUTHERN ROCKIES.

...OVERVIEW...
A SERIES OF STRONG/PROGRESSIVE SHORTWAVE TROUGHS ORBITING A LARGER
COMPLEX OF UPPER LOWS ACROSS NORTHERN CANADA WILL ACT TO
SUBSTANTIALLY DAMPEN THE BROAD SUBTROPICAL RIDGE ACROSS THE INTERIOR
WEST AND CENTRAL CONUS THIS PERIOD. THE SYNOPTIC COLD FRONT
ACCOMPANYING THE LEADING IMPULSE WILL TRANSLATE EAST ACROSS THE
UPPER MS VALLEY AND WRN/UPPER GREAT LAKES THROUGH MONDAY AFTERNOON
AND EVENING AS STRONGER UPPER FLOW AND FORCING SPREAD EAST ALONG AND
NORTH OF THE INTERNATIONAL BORDER. MODEST POST-FRONTAL SURFACE
PRESSURE RISES FROM THE CANADIAN PRAIRIES TO THE NORTHERN PLAINS
WILL PROMOTE A SOUTH/SOUTHEASTWARD ADVANCE OF THE COLD FRONT FROM
THE CORN BELT TO THE CENTRAL/SOUTHERN PLAINS. BY LATE MONDAY
AFTERNOON THE FRONT WILL BE SITUATED FROM WI/IA SOUTHWESTWARD TO THE
SOUTHERN HIGH PLAINS...COINCIDENT WITH A CORRIDOR OF STRONG TO
LOCALLY EXTREME INSTABILITY.

ELSEWHERE....A COMPACT AND PERSISTENT MIDLEVEL LOW...CURRENTLY OVER
THE SOUTHERN APPALACHIANS...WILL DEAMPLIFY AND EJECT NORTHEASTWARD
TOWARD THE MID-ATLANTIC...AHEAD OF THE STRONGER HEIGHT FALLS
OCCURRING OVER THE GREAT LAKES REGION.

...GREAT LAKES TO CENTRAL/SOUTHERN PLAINS...
AFOREMENTIONED SHORTWAVE TROUGH WILL MAKE QUICK PROGRESS ALONG THE
INTERNATIONAL BORDER WITH 500MB HEIGHT FALLS AROUND 30-60M PER 12H
FORECAST TO SPREAD FROM MN ACROSS NORTHERN WI DURING THE DAY. MODEST
TO STRONG SURFACE-BASED DESTABILIZATION APPEARS POSSIBLE AHEAD OF
THE FRONT AND WEAK SURFACE WAVE OVER WI WHERE EFFECTIVE SHEAR
ACCOMPANYING THE LARGE SCALE FORCING FOR ASCENT WILL LIKELY BE
SUFFICIENT FOR STORM PERSISTENCE/ORGANIZATION. PRIMARY UNCERTAINTY
WITH NORTHWARD EXTENT IS THE DEGREE TO WHICH AIRMASS CAN SUPPORT
SURFACE BASED CONVECTION GIVEN POTENTIAL FOR EARLY-DAY
CLOUDS/CONVECTIVE DEBRIS FROM OVERNIGHT ACTIVITY. PRESENT
INDICATIONS SUGGEST BEST PROSPECTS FOR SEVERE STORMS...POSSIBLY IN
THE FORM OF LINE SEGMENTS WITH EMBEDDED SUPERCELLS...WILL EVOLVE
ACROSS CENTRAL AND SRN WI DURING THE LATE AFTERNOON/EARLY EVENING.
THE CHANCE FOR WIND DAMAGE AND PERHAPS A TORNADO WILL PEAK IN THE
21-00 UTC TIME FRAME.

SHEAR AND LARGE SCALE SUPPORT FOR ASCENT DECREASE MARKEDLY ALONG THE
TRAILING COLD FRONT FROM IA SOUTHWESTWARD TO KS/NORTHERN OK.
HOWEVER...LIFT ALONG THE TRAILING BOUNDARY WILL COINCIDE WITH THE
DIURNAL MAXIMUM IN DESTABILIZATION ALONG THIS CORRIDOR WHERE SBCAPE
IS FORECAST TO RANGE FROM 2000-4000 J/KG BY LATE AFTERNOON. GIVEN
MAGNITUDE OF INSTABILITY AND BULK SHEAR VALUES IN THE RANGE OF
15-30KT...IT SEEMS REASONABLE TO EXPECT A FEW SEVERE STORMS WITH
DAMAGING WINDS AND PERHAPS MARGINALLY SEVERE HAIL. WHILE WEAKEST
SHEAR ALONG THE BOUNDARY WILL EXIST FROM NORTHERN MO TO
KS/OK...DCAPE VALUES IN THE HOT AND DEEPLY MIXED PRE-FRONTAL AIRMASS
ARE FORECAST TO EXCEED 1000 J/KG BY 21 UTC. SCATTERED DAMAGING WIND
POTENTIAL SHOULD ACCOMPANY THE BROKEN CONVECTIVE LINE AS IT
TRAVERSES THIS INSTABILITY AXIS BETWEEN 21-03 UTC.

..CARBIN.. 07/05/2015



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