Severe Thunderstorm Warning 180, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
627 PM CDT TUE AUG 6 2013

.AVIATION...00Z TAFS FOR KOFK...KLNK AND KOMA.

THUNDERSTORMS DEVELOPING ALONG A COLD FRONT WILL AFFECT KOFK FOR
THE FIRST COUPLE HOURS OF TAF CYCLE BEFORE MOVING OFF TO THE
SOUTHEAST. THEN KOMA AND KLNK WILL SEE THUNDERSTORMS IN THE 02Z
THROUGH 07Z WINDOW. THUNDERSTORM COVERAGE IS EXPECTED TO INCREASE
ALONG THIS FRONT STRETCHING FROM WEST TO EAST ACROSS EASTERN
NEBRASKA. ASSOCIATED IFR CONDITIONS CAN BE EXPECTED WITH
THUNDERSTORMS...AND LARGE HAIL WITH WIND GUSTS TO 50KT ARE
POSSIBLE IN ISOLATED STORMS.

AFTER FRONT MOVES SOUTH OF TAF SITES AFTER 07Z...VFR CONDITIONS
ARE EXPECTED THROUGH WEDNESDAY AFTERNOON WITH NORTH TO NORTHEAST
WINDS AVERAGING 10 TO 15KT AND SCATTERED CLOUDS NEAR FL040.

DERGAN

&&

.PREV DISCUSSION... /ISSUED 234 PM CDT TUE AUG 6 2013/

DISCUSSION...

MODELS IN PRETTY GOOD AGREEMENT LARGE SCALE WILL BEGIN TO
TRANSITION LATER THIS WEEK WHEN DOME OF HIGH PRESSURE BUILDS OVER
THE CONUS AND BREAKS DOWN STAGNANT UPPER TROFS OFF THE WEST COAST
AND ERN CANADA. ECM AND CMC ENSEMBLES SUPPORT THIS AS WELL.
HOWEVER...DESPITE THE HIGH BUILDING IN...NOT MUCH TEMP RECOVERY
PROGGED THRU THIS WEEKEND AS MAX TEMPS OVERALL WILL REMAIN
SLIGHTLY BELOW NORM OVER MOST OF THE CNTRL PLAINS...DAKOTAS...AND
UPPER MIDWEST.

THIS AFT AND TONIGHT...MOST OF THE REGION IS UNDER A SLGT RISK FOR
SVR STORM DEVELOPMENT. ALL THIS IN PART TO A SHORT WAVE TROF
DROPPING DOWN THE DAKOTA DRAGGING A COLD FRONT INTO THE CNTRL
PLAINS. HAVE NOTICED THOUGH LATEST MODELS HAVE SLOWED THE BNDRY DOWN
QUITE A BIT COMPARED TO YESTERDAYS RUN AND NOW ADVERTISE THE FRONT NOT
MAKING IT TO THE NRN CWA UNTIL LATE AFTN. THE ENVIRONMENT LEADING
UP TO FROPA WILL BE QUITE MOIST...PRECIP WATER 1.5-2" WITH KI OVER
50. INSTABILITY PARAMETERS ALSO QUITE STOUT...MU CAPE 5000
J/KG...LI -12...TT NEAR 60. WIND SHEAR ALSO QUITE STRONG WITH EFF
SHEAR VALUES AROUND 60KT. PARAMETERS ARE PRIME FOR SC STORMS TO
DEVELOP WITH HAIL THE INITIAL PRIMARY THREAT. LATER ON THEN STORMS
SHOULD EVOLVE TO AN ORGANIZED COMPLEX WITH DAMAGING WINDS BECOMING
THE MAIN THREAT. ALSO PER EFF SRH PROGS...CANNOT TOTALLY DISCOUNT
A FEW TORNADIC STORMS EARLY ON.

AS THE FRONT SINKS DEEPER INTO THE CNTRL PLAINS...THEN STALLS SOUTH
OF THE CWA THRU THRU THIS WEEKEND. MEANWHILE MODELS SHOW A SECONDARY
SURGE OF COOL AIR DROPPING DOWN THRU THE NRN PLAINS/UPPER MIDWEST ON
THURSDAY  EARLY NEXT WEEK THEN...SFC BNDRY BEGINS TO SLOWLY SHIFT
EAST IN RESPONSE TO AFOREMENTIONED ALTERING LARGE SCALE FLOW.

OTHERWISE HEADING INTO AND THRU THIS WEEKEND...PCPN CHANCES STILL
REVOLVING AROUND MIGRATING SFC BNDRY AS WELL AS A SERIES OF VORT
MAXES. MODELS ADVERTISE THE SFC FRONT SLOWING DOWN...THEN MEANDERING
INVOF THE WRN/SRN CWA THE REST OF THE FCST PD.  THUS EXPECT THAT IS
WHERE BEST CHANCES FOR RAIN WILL GENERALLY BE FOUND.

DEE

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&

99/99

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
500 PM CDT TUE AUG 6 2013

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-071200-
MONONA-HARRISON-SHELBY-POTTAWATTAMIE-MILLS-MONTGOMERY-FREMONT-
PAGE-KNOX-CEDAR-THURSTON-ANTELOPE-PIERCE-WAYNE-BOONE-MADISON-
STANTON-CUMING-BURT-PLATTE-COLFAX-DODGE-WASHINGTON-BUTLER-
SAUNDERS-DOUGLAS-SARPY-SEWARD-LANCASTER-CASS-OTOE-SALINE-
JEFFERSON-GAGE-JOHNSON-NEMAHA-PAWNEE-RICHARDSON-
500 PM CDT TUE AUG 6 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
IOWA...WEST CENTRAL IOWA...EAST CENTRAL NEBRASKA...NORTHEAST
NEBRASKA AND SOUTHEAST NEBRASKA.

.DAY ONE...TONIGHT AND WEDNESDAY

THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORMS ACROSS ALL OF THE
OUTLOOK AREA THIS EVENING AND OVERNIGHT. LARGE HAIL AND DAMAGING
WINDS WILL BE THE PRIMARY HAZARDS.

A COUPLE OF AREAS OF POTENTIAL THUNDERSTORM DEVELOPMENT WILL HAVE
TO BE WATCHED THIS EVENING. ONE AREA OF CONCERN IS OVER NORTHEAST
NEBRASKA AND WEST CENTRAL IOWA...AHEAD OF A WEAK COLD FRONT.
MODEST INSTABILITY IS AVAILABLE HERE...WITH STRONG SHEAR NEAR A
MID LEVEL JET STREAM. THUNDERSTORMS WILL LIKELY DEVELOP ALONG THE
COLD FRONT FROM NEAR NELIGH TO WAYNE LATE THIS AFTERNOON...THEN
SPREAD EAST AND SOUTHEAST DURING THE EVENING.

THE OTHER AREA OF CONCERN IS OVER EAST CENTRAL AND SOUTHEAST
NEBRASKA...AS WELL AS SOUTHWEST IOWA. IN THIS AREA...INSTABILITY
IS HIGH WITH MODERATE SHEAR. HOWEVER LOW LEVEL CONVERGENCE IS
WEAK...WITH NO DEFINED FRONTAL BOUNDARIES TO KICK THINGS OFF. BUT
GIVEN THE HIGH INSTABILITY...SOME STORMS COULD BUBBLE UP DURING
THE LATE AFTERNOON AND EARLY EVENING. THE MORE LIKELY SCENARIO IS
FOR STORMS TO FIRE AS THIS COLD FRONT MOVES INTO THIS AREA LATER
IN THE EVENING.

ANY STORMS THAT DO FIRE OVER THE OUTLOOK AREA THROUGH THIS EVENING
HAVE THE POTENTIAL TO BECOME SEVERE. THE FOCUS WILL SHIFT TO
SOUTHEAST NEBRASKA AND SOUTHWEST IOWA AFTER MIDNIGHT AS THE COLD
FRONT PUSHES SOUTH...WITH MOST POTENTIAL SEVERE WEATHER WANING
TOWARD MORNING. A FEW STORMS COULD LINGER IN SOUTHEAST NEBRASKA
AND SOUTHWEST IOWA ON WEDNESDAY...BUT SEVERE STORMS ARE NOT
EXPECTED THEN.

.DAYS TWO THROUGH SEVEN...WEDNESDAY NIGHT THROUGH TUESDAY

THERE IS A CHANCE FOR THUNDERSTORMS WEDNESDAY NIGHT THROUGH FRIDAY
NIGHT AS THE COLD FRONT THAT WILL MOVE SOUTH OF US ON WEDNESDAY
LIFTS BACK NORTH. THEN MORE THUNDERSTORMS ARE POSSIBLE SUNDAY
THROUGH TUESDAY.

.SPOTTER INFORMATION STATEMENT...

STORM SPOTTER ACTIVATION MAY BE REQUIRED THIS EVENING OVER ALL OF
THE OUTLOOK AREA...THEN ONLY IN SOUTHEAST NEBRASKA AND SOUTHWEST
IOWA AFTER MIDNIGHT.

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