Severe Thunderstorm Warning 197, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1154 PM CDT FRI AUG 3 2012

.AVIATION...
06Z TAFS FOR KOFK...KLNK AND KOMA.

COLD FRONT APPROACHING KOFK AT 06Z WILL SWEEP THROUGH EASTERN
NEBRASKA BY 12Z. INITIALLY A WIND SHIFT TO THE NORTHWEST AT 15KTS
WILL ACCOMPANY THE FRONT. THEN SCATTERED SHOWERS AND THUNDERSTORMS
BEHIND THE FRONT WILL MOVE INTO KOFK BY 13Z...THE KOMA AND KLNK BY
18Z. GENERALLY VFR CIGS BETWEEN FL050 AND FL100 CAN BE
EXPECTED...HOWEVER BRIEF MVFR CIGS/VSBYS ARE LIKELY WITH ANY
THUNDERSTORMS. PRECIPITATION SHOULD END AT KOFK BY 18Z...THEN
BEFORE 00Z AT KOMA AND KLNK. CLEAR SKIES WILL FOLLOW.

DERGAN

&&

.PREV DISCUSSION... /ISSUED 318 PM CDT FRI AUG 3 2012/

DISCUSSION...

SYNOPSIS...12Z UPPER AIR ANLS INDCD 80 KT H3 JET DIVING INTO THE
NORTHERN ROCKIES ACRS MT. THIS JET WAS ASSOCIATED WITH A CLOSED
MID LEVEL CIRCULATION AND A 90 M H5 HEIGHT FALL. STG MID LEVEL
LAPSE RATES ASSOCIATED WITH AN EML EXTNDG ACRS THE CNTRL AND WRN
HI PLAINS WITH H7 TO H5 DELTA-T GREATER THAN 20 C. THIS EML WAS
CAPPING OFF A SEASONABLY MOIST LOWER LEVEL ATMOSPHERE WITH +15 C
H85 DEWPOINTS FM WRN KS INTO WRN NEB. 19Z SFC ANLYS INDCD A STG
CDFNT FM NRN SD INTO NW NEB WITH LOW PRES AROUND KPIR.

FORECAST...SIGNIFICANT CHANGES ARE IN STORE FOR THE FA AS THE
PREVIOUSLY MENTIONED UPPER LEVEL SYSTEM ROTATES THROUGH THE CNTRL
AND NRN PLAINS OVER THE NEXT 36 HOURS. SFC CDFNT WILL DROP TOWARD
OUR NW FA BY THIS EVNG WITH 2-3 MB 3-HR PRES RISES BEHIND THE FNT.
THE ATMOSPHERE ALONG AND AHEAD OF THE FNT IS BECOMING MODERATELY
UNSTABLE WITH OBJECTIVE ANALYSIS INDCG 2-3 K J/KG OF MLCAPE WHICH
IS ALSO SUPPORTED FM 12Z ROABS. THOUGH MID AFTN VISIBLE SAT
IMAGERY INCS THAT THE ATMOSPHERE REMAINS CAPPED OVER NEB ALNG THE
CDFNT. THIS CAP IS EXPECTED TO ERODE OVER THE NEXT 2-3 HRS AS THE
TEMPERATURES AHEAD OF THE FNT SOAR TO 100 AND UPPER LEVEL SUPPORT
INCREASES. THIS SHOULD LEAD TO CI BY 22-23Z ALNG THE CDFNT INTO
NRN NEB. THE COMBINATION OF THE THE INSTABILITY AND EFFECTIVE
SHEAR OF 30-35 KT WILL ALLOW FOR SOME ORGANIZATION TO THE
CONVECTION OVER THE FAR NRN CWA WITH A FEW SVR STORMS POSSIBLE.
THE MAIN THREAT WOULD BE WIND AND HAIL. STRONGER DEEP-LAYER SHEAR
ACRS THE SD/MN WILL LIKELY LEAD TO A FASTER PROPAGATION OF THE
CONVECTION TO OUR N...ALLOWING FOR THE TSRA IN OUR FA TO BECOME
INCREASINGLY ALIGNED WEST TO EAST WITH A SLOW SWD PROPAGATION
EXPECTED. THUS WILL CONFINE POPS /IN THE LIKELY CAT/ TO THE NRN
CWA THIS EVNG. AFTER MIDNIGHT THE CONVECTION WILL GENERALLY WEAKEN
WHILE TRYING TO SHIFT SWD WITH ONLY SCHC POPS WARRANTED ALNG AND S
OF I-80. WE WILL LIKELY SEE AN INCREASE IN SHOWERS BEHIND THE FNT
OVER NE NEB LATE TONIGHT AND INTO SAT MRNG AS STG UPPER LEVEL
SUPPORT BECOMES JUXTAPOSED WITH THE MID LEVEL FRONTOGENESIS AND
WEAK STABILITY. THIS ACTIVITY SHOULD GENERALLY PUSH E OF THE FA BY
MID DAY ON SAT AS THE SFC FNT SHIFT S OF THE FA. THERE IS A SMALL
CHANCE OF A FEW EARLY AFTN STORMS NEAR THE KS/NEB AND IA/MO
BORDER BEFORE THE INSTABILITY AND FNT SHIFT EWD.

TEMPERATURES WILL BE SOME 15 TO 20 DEGREES COOLER ON SAT OVER
MOST OF THE AREA WITH A GOOD DEAL OF MORNING CLOUDS AND A NW WIND.
SFC HIGH PRESSURE WILL OVERSPREAD THE FA ON SAT NIGHT LEADING TO A
VERY NICE NIGHT WITH CLEAR SKIES...LIGHT WINDS AND COOL
TEMPERATURES. DRY WEATHER WILL CONT FOR SUN AND A GOOD DEAL OF MON
WITH TEMPERATURES NEAR OR SLIGHTLY BELOW NORMAL.

BOUSTEAD

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
447 PM CDT FRI AUG 3 2012

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-041200-
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-
447 PM CDT FRI AUG 3 2012

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 SATURDAY

SEVERE THUNDERSTORMS WITH LARGE HAIL AND DAMAGING WINDS ARE
POSSIBLE DURING THE EVENING ACROSS NORTHEAST NEBRASKA...MAINLY
NORTHWEST OF A LINE FROM THURSTON TO WISNER AND PLATTE CENTER.
A COLD FRONT DRIFTING INTO THE AREA WILL TAP HIGH INSTABILITY
ACROSS THE REGION TO PRODUCE THE POTENTIALLY SEVERE STORMS. HIGHER
SHEAR NEAR AND NORTH OF THE SOUTH DAKOTA BORDER WILL FOCUS MOST OF
THE SEVERE STORMS THERE.

AFTER MIDNIGHT...THUNDERSTORMS ARE POSSIBLE ACROSS ALL OF THE
OUTLOOK AREA AS THE COLD FRONT SLOWLY SINKS SOUTHEAST...WITH THE
CHANCE FOR STORMS PERSISTING THROUGH MUCH OF SATURDAY. SEVERE
STORMS ARE NOT EXPECTED WITH THE ACTIVITY AFTER MIDNIGHT AND
THROUGH SATURDAY.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THERE IS A SLIGHT CHANCE OF THUNDERSTORMS MONDAY NIGHT...AND
TUESDAY NIGHT INTO WEDNESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED TONIGHT OR SATURDAY.