Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS01 KWNS 290550
SWODY1
SPC AC 290549

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1249 AM CDT FRI AUG 29 2014

VALID 291200Z - 301200Z

...NO SVR TSTM AREAS FORECAST...

...SUMMARY...
SCATTERED THUNDERSTORMS ARE LIKELY TODAY ACROSS MUCH OF THE LOWER
CENTRAL PLAINS INTO THE OZARKS...NORTHWARD THROUGH THE UPPER
MISSISSIPPI VALLEY AND UPPER GREAT LAKES REGION.  SOME OF THIS
ACTIVITY COULD BE LOCALLY STRONG.  SCATTERED STRONG THUNDERSTORM
DEVELOPMENT ALSO APPEARS POSSIBLE LATE THIS AFTERNOON ACROSS PARTS
OF THE EASTERN DAKOTAS.

...SYNOPSIS...
STRONGER MID-LEVEL WESTERLIES GENERALLY REMAIN CONFINED TO CANADA
AND THE FAR NORTHERN TIER OF THE U.S...WITH A NUMBER OF PROGRESSIVE
EMBEDDED SHORT WAVE PERTURBATIONS.  ONE SIGNIFICANT IMPULSE IS NOW
APPROACHING THE BRITISH COLUMBIA AND PACIFIC NORTHWEST COAST...AND
IS FORECAST TO CONTINUE GRADUALLY INLAND ACROSS THE CANADIAN
ROCKIES...THE CASCADES AND PORTIONS OF THE NORTHERN U.S.
INTERMOUNTAIN REGION DURING THIS PERIOD.  AS THIS OCCURS...THE
INCREASINGLY DEFORMED REMNANTS OF A DOWNSTREAM CLOSED LOW...WITHIN
THE SOUTHERN BRANCH OF SPLIT MID/UPPER LEVEL WESTERLIES...APPEARS
LIKELY TO ACCELERATE NORTHEASTWARD OUT OF THE CENTRAL PLAINS.  AT
THE SAME TIME...MODELS SUGGEST THAT SUBTROPICAL RIDGING WILL BUILD
NORTHWARD FROM A STRENGTHENING HIGH NEAR SOUTH ATLANTIC COASTAL
AREAS THROUGH THE MIDDLE AND NORTHERN ATLANTIC SEABOARD.  WHILE A
SIGNIFICANT NORTHWARD SURGE OF TROPICAL MOISTURE ALREADY APPEARS
UNDERWAY...FROM THE WESTERN GULF OF MEXICO TOWARD THE LOWER
MISSISSIPPI VALLEY...THE IMPACT OF THIS MOISTURE RETURN IS EXPECTED
TO REMAIN RELATIVELY LIMITED TODAY...INLAND OF WESTERN AND CENTRAL
GULF COASTAL AREAS.

...SOUTH CENTRAL PLAINS INTO UPPER MIDWEST...
AS THE CENTRAL PLAINS IMPULSE APPROACHES THE UPPER MIDWEST LATER
TODAY...MODEST STRENGTHENING OF SOUTHWESTERLY LOWER/MID TROPOSPHERIC
FLOW /20-40 KT/ APPEARS POSSIBLE AHEAD OF IT...ON THE NORTHWESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE.  WHILE ASSOCIATED MOMENTUM AND
VERTICAL SHEAR MAY BE ENOUGH TO ENHANCE LATE AFTERNOON AND EARLY
EVENING CONVECTIVE DEVELOPMENT...THE FORECAST ENVIRONMENT...IN
GENERAL...SEEMS AT BEST ONLY MARGINALLY CONDUCIVE TO SEVERE STORM
DEVELOPMENT.  LAPSE RATES ARE NOT EXPECTED TO BECOME PARTICULARLY
STEEP...AND REMNANT CLOUD COVER/PRECIPITATION ASSOCIATED WITH EARLY
DAY CONVECTION AHEAD OF THE UPPER IMPULSE WILL COMPLICATE BOUNDARY
LAYER DESTABILIZATION.  HOWEVER...WHERE INSOLATION BECOMES
SUFFICIENT TO SUPPORT THE DEVELOPMENT OF MODERATELY LARGE
CAPE...THUNDERSTORM ACTIVITY CAPABLE OF PRODUCING AT LEAST LOCALIZED
STRONG WIND GUSTS DOES APPEAR POSSIBLE.  IT DOES NOT APPEAR OUT OF
THE QUESTION THAT HODOGRAPHS ALONG AN EFFECTIVE WARM FRONTAL ZONE
ACROSS PARTS OF NORTHERN WISCONSIN INTO WESTERN UPPER MICHIGAN COULD
SUPPORT AN ISOLATED BRIEF TORNADO.

...EASTERN DAKOTAS...
IN THE WAKE OF THE IMPULSE ACCELERATING TOWARD THE UPPER
MIDWEST...MODELS SUGGEST THAT A NARROW CORRIDOR OF MODERATELY LARGE
CAPE /ON THE ORDER OF 2000 J PER KG/ MAY DEVELOP WITHIN AN AXIS OF
STRONGER DAYTIME HEATING...AHEAD OF A SOUTHEASTWARD ADVANCING COLD
FRONT.  AIDED BY FORCING ASSOCIATED WITH A SHORT WAVE IMPULSE
/CURRENTLY TURNING EAST SOUTHEAST OF THE MONTANA
ROCKIES/...DESTABILIZATION SHOULD BE SUFFICIENT TO SUPPORT SCATTERED
THUNDERSTORM DEVELOPMENT.  ALTHOUGH VERTICAL SHEAR LIKELY WILL BE
WEAK...THERMODYNAMIC PROFILES APPEAR SUPPORTIVE OF LOCALLY STRONG
WIND GUSTS AND HAIL WHICH COULD APPROACH OR BRIEFLY EXCEED SEVERE
LIMITS BEFORE STORMS DIMINISH THIS EVENING.

..KERR/LEITMAN.. 08/29/2014



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