Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS02 KWNS 201731
SWODY2
SPC AC 201730

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT WED AUG 20 2014

VALID 211200Z - 221200Z

...NO SVR TSTM AREAS FORECAST...

...SUMMARY...
THUNDERSTORMS...A FEW OF WHICH COULD BE STRONG TO SEVERE...MAY OCCUR
OVER PARTS OF THE GREAT LAKES AND OHIO VALLEY AS WELL AS A PORTION
OF NEBRASKA AND NORTHERN KANSAS. SOME HAIL AND GUSTY WINDS WILL BE
POSSIBLE WITH THE STRONGEST STORMS.

...SYNOPSIS...

BLOCKING SYNOPTIC PATTERN WILL PERSIST THROUGH THURSDAY WITH MEAN
RIDGE OVER THE CNTRL U.S. FLANKED BY UPPER TROUGHS OVER THE ERN AND
WRN STATES. THE ERN U.S. UPPER TROUGH WILL DEAMPLIFY AS A SHORTWAVE
TROUGH WITHIN ITS BASE CONTINUES EWD AND OFF THE ATLANTIC SEABOARD
EARLY THURSDAY. A LOW AMPLITUDE SHORTWAVE TROUGH WILL MOVE FROM THE
UPPER MS VALLEY INTO SWRN ONTARIO THURSDAY MORNING. CUTOFF LOW OVER
SRN CA WILL DRIFT SLOWLY EAST INTO AZ. AT THE SFC A LEE TROUGH WILL
RESIDE ACROSS THE CNTRL PLAINS AND A COLD FRONT WILL ADVANCE SEWD
THROUGH THE NRN PLAINS DURING THE DAY. A WARM FRONT IS EXPECTED TO
LIFT SLOWLY NWD THROUGH NRN PORTIONS OF THE OH VALLEY AND INTO THE
GREAT LAKES.

...UPPER MS VALLEY...OH VALLEY AND GREAT LAKES AREA...

THUNDERSTORMS ARE EXPECTED TO BE ONGOING AND FAIRLY WIDESPREAD FROM
A PORTION OF THE UPPER MS VALLEY SEWD INTO THE GREAT LAKES AND OH
VALLEY WITHIN ZONE OF ISENTROPIC ASCENT NORTH OF WARM FRONT. SOME OF
THIS ACTIVITY WILL LIKELY PERSIST DURING THE DAY. HOWEVER...THE WARM
SECTOR SOUTH OF THESE STORMS SHOULD GRADUALLY DESTABILIZE WITH ONSET
OF DIABATIC WARMING SUPPORTING 2000-3000 J/KG MLCAPE. THERE WILL BE
SOME POTENTIAL FOR ADDITIONAL STORMS TO DEVELOP OR ONGOING STORMS TO
REINTENSIFY NEAR THE CONVECTIVELY REINFORCED WARM FRONT AND WHERE
MOIST AND UNSTABLE INFLOW FROM THE DESTABILIZING WARM SECTOR WILL BE
MAXIMIZED. ACTIVITY WILL BE EMBEDDED WITHIN MODEST NWLY FLOW ALOFT
WITH 30-35 KT EFFECTIVE SHEAR. THERE IS CONCERN THAT AS STORMS
REINTENSIFY/REDEVELOP THEY COULD EVOLVE INTO A SEWD ADVANCING
ORGANIZED CLUSTER...POSING A THREAT FOR DAMAGING WIND.
HOWEVER...UNCERTAINTY REGARDING EVOLUTION OF MORNING STORMS AND WEAK
FORCING ALOFT WITH MODEST HEIGHT RISES LOWERS CONFIDENCE IN A MORE
ORGANIZED SEVERE EVENT. NEVERTHELESS...THIS AREA WILL CONTINUE TO BE
MONITORED FOR A POSSIBLE SLIGHT RISK IN LATER OUTLOOKS.

...NEB AND NRN KS...

A FEW STORMS COULD DEVELOP IN VICINITY OF LEE TROUGH FROM NEB INTO
NRN KS WHERE STEEP LAPSE RATES...MODERATE INSTABILITY AND INVERTED-V
BOUNDARY LAYERS WILL EXIST. ISOLATED DOWNBURST WINDS AND SOME HAIL
WILL BE POSSIBLE WITH THE STRONGER STORMS.

..DIAL.. 08/20/2014



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