Severe Storm Outlook Narrative (AC)
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000
ACUS03 KWNS 030731
SWODY3
SPC AC 030730

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT FRI JUL 03 2015

VALID 051200Z - 061200Z

...THERE IS A SLGT RISK OF SVR TSTMS LATE SUNDAY AFTERNOON AND
EVENING ACROSS MUCH OF CENTRAL AND NORTHERN NEBRASKA...SOUTHERN AND
EASTERN SOUTH DAKOTA AND ADJACENT WEST CENTRAL/SOUTHWEST
MINNESOTA...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS SURROUNDING AREAS OF THE
NORTH CENTRAL PLAINS INTO UPPER MISSISSIPPI VALLEY...

...SUMMARY...
THUNDERSTORMS CAPABLE OF PRODUCING SEVERE WIND AND HAIL ARE EXPECTED
SUNDAY ACROSS PARTS OF NEBRASKA...SOUTH DAKOTA AND ADJACENT PORTIONS
OF SOUTHWESTERN MINNESOTA.

...SYNOPSIS...
LITTLE CHANGE TO THE GENERAL UPPER FLOW PATTERN APPEARS LIKELY FROM
SATURDAY INTO SUNDAY.  SUBTROPICAL RIDGING APPEARS LIKELY TO REMAIN
SOMEWHAT SUPPRESSED...BUT THE STRONGER MID-LATITUDE WESTERLIES ARE
EXPECTED TO REMAIN CONFINED TO THE NORTHERN TIER OF THE
U.S...NORTHWARD.  WITHIN THIS REGIME A POSITIVELY TILTED TROUGH IS
FORECAST TO CONTINUE PROGRESSING EASTWARD ACROSS THE CENTRAL
CANADIAN PROVINCES.  ON ITS TRAILING SOUTHWESTERN FLANK...A SMALLER
SCALE PERTURBATION MAY DIG ACROSS THE INTERNATIONAL BORDER INTO THE
NORTHERN PLAINS BY THE END OF THE PERIOD.  AN ASSOCIATED COLD FRONT
LIKELY WILL ADVANCE SOUTHWARD TO THE LEE OF THE NORTHERN AND CENTRAL
ROCKIES...AND EASTWARD ACROSS THE NORTHERN PLAINS...INTO PORTIONS OF
THE UPPER MISSISSIPPI VALLEY AND MID MISSOURI VALLEY BY 12Z MONDAY.
A CORRIDOR OF STRONG DESTABILIZATION AHEAD OF THIS FRONT IS EXPECTED
TO PROVIDE THE FOCUS FOR THE PRIMARY CONVECTIVE POTENTIAL SUNDAY
AFTERNOON INTO SUNDAY EVENING.  THIS INCLUDES THE RISK FOR SEVERE
STORMS CAPABLE OF PRODUCING LARGE HAIL AND POTENTIALLY DAMAGING WIND
GUSTS.

...NORTH CENTRAL PLAINS INTO UPPER MISSISSIPPI VALLEY...
DUE TO THE ORIENTATION OF THE UPPER TROUGH...MODELS ARE SUGGESTIVE
THAT PRE-FRONTAL MID/UPPER FLOW AND DEEP LAYER SHEAR MAY NOT BECOME
PARTICULARLY STRONG.  HOWEVER...STEEPENING MID-LEVEL LAPSE RATES
ASSOCIATED WITH THE NORTHEASTWARD ADVECTION OF VERY WARM ELEVATED
MIXED LAYER AIR...COUPLED WITH PRE-FRONTAL BOUNDARY LAYER
MOISTENING...ARE EXPECTED TO CONTRIBUTE TO STRONG DESTABILIZATION
WITH DAYTIME HEATING.  BY LATE AFTERNOON...MIXED LAYER CAPE OF
2000-3000+ J/KG APPEARS LIKELY...PARTICULARLY ACROSS CENTRAL AND
NORTHERN NEBRASKA...AND SOUTHERN/EASTERN SOUTH DAKOTA INTO ADJACENT
AREAS OF MINNESOTA.  WITH THE ONSET OF MID-LEVEL HEIGHT FALLS AND
COOLING...INHIBITION IS EXPECTED TO WEAKEN SUFFICIENTLY TO SUPPORT
THE INITIATION OF VIGOROUS STORM DEVELOPMENT ACROSS PARTS OF THE
NORTHERN NEBRASKA PANHANDLE INTO SOUTHWEST AND CENTRAL SOUTH DAKOTA.
 THERMODYNAMIC PROFILES ARE EXPECTED TO BE CONDUCIVE TO SEVERE WIND
GUSTS AND HAIL IN STRONGER ACTIVITY AS IT SPREADS EASTWARD.

STORMS MAY ALSO DEVELOP NORTHEASTWARD ALONG/AHEAD OF THE FRONT INTO
WEST CENTRAL...PERHAPS NORTHERN...MINNESOTA...BY EARLY EVENING.
HOWEVER...STRONGER LOW-LEVEL WARM ADVECTION MAY SUPPORT MORE
PROMINENT CONVECTIVE DEVELOPMENT ACROSS THE REMAINDER OF SOUTHERN
SOUTH DAKOTA AND NORTHERN NEBRASKA...WHERE A
CONSOLIDATING/STRENGTHENING SURFACE COLD POOL MAY EMERGE WITH AN
EVOLVING CLUSTER OF STORMS.

..KERR.. 07/03/2015




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