Flash Flood Warning 22, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
216 PM CDT WED JUL 14 2010

.DISCUSSION...

SYNOPSIS...00Z UPPR AIR ANLYS INDCD POTENT...NEARLY VERTICALLY
STACKED...UPPR LVL LO OVR SASK. THE SYSTEM WAS ASSOCIATED WITH A
120 KT H3 JET OVR ND AND SOME 3 M H5 HEIGHT FALLS. STOUT EML
EXTNDD FM THE HIGH PLAINS THRU NEB/ERN SD AT H7 WITH A +18 C TMP
NOTED AT LBF. THE STOUT EML WAS CAPPING A VERY WARM AND MOIST WARM
SECTOR WITH WIDESPREAD H85 DEWPOINTS OF +20 C FM SW TX INTO SRM
MN. 18Z SFC ANLYS INDCD LO PRES OVR CNTRL MN WITH A CDFNT SWWD
THRU NRN NEB AND INTO WRN KS.

FORECAST...SHORT TERM CONCERNS CONT TO CENTER AROUND HEAT AND
SEVERE WEATHER. AHEAD OF THE FNT TODAY...TEMPERATURES HAVE CLIMBED
INTO THE MID 90S+ AND THIS COUPLED WITH DEW POINTS AROUND 80 IS
LEADING TO PRETTY DANGEROUS HEAT CONDS THIS AFTN. WL NOT UPGRADE
TO EXCESSIVE HEAT WARNG AT THIS TIME DUE TO THE SHORT DURATION OF
THE EVNT...BUT WL CERTAINLY CONT WITH THE CURRENT ADVISORY THRU 8
PM. THE PREVIOUSLY MENTIONED STOUT EML WAS LEADING TO STG LAPSE
RATES TODAY ACRS THE WRM SECTOR AHEAD OF THE CDFNT WITH A 12Z H5
TO H7 DELTA-T OF 25 C NOTED AT LBF. THIS WAS LEADING TO EXTREME
POTENTIAL INSTABILITY ACRS THE CNTRL AND SRN CWA THIS AFTN WITH
MLCAPE OF 4000-5000 J/KG...BUT HAS BEEN...AND WL CONT TO CAP THE
ATMOSPHERE TO SURFACED BASED CONVECTION FOR A FEW MORE HOURS.
ALTHOUGH HEIGHT FALLS REMAIN FAIRLY WEAK TO NILL TODAY WITH THE
MAIN ENERGY HEADING THRU THE NRN PLAINS...THE COMBINATION OF
MESOSCALE FORCING WITH THE CDFNT...HOT TEMPERATURES AND WEAK MID LVL
COOLING WL LEAD TO CONVECTIVE DEVELOPMENT BY LATE AFTN. ATTM THIS
FIRST LOOKS TO OCCUR OVR S-CNTRL NEB OR N-CNTRL KS WHERE DEEP
BOUNDARY LAYER MIXING WL ALLOW FOR PARCELS TO REACH THE LFC FIRST.
STORMS THEN SHOULD DEVELOP NE ALONG THE FNT AS THEY MOV E THRU THE
EVNG. WL HAVE THE HIGHEST POPS OVR THE CNTRL AND SRN CWA...BUT
ESPECIALLY THIS EVNG IN THE SW CWA. EFFECTIVE SHEAR IS ACTUALLY
REALLY MARGINAL ALNG AND S OF THE FNT AND THUS ALTHOUGH SOME
ORGANIZATION TO THE CELLS ARE LIKELY...A MULTI-CELLED MODE PULSE
SVR WL BE THE MAIN CONVECTIVE MODE. NEVERTHELESS...WITH EXTREME
INSTABILITY AND STEEP MID-LVL LAPSE RATES...ISO SVR THREAT STILL
THERE FOR WIND AND HAIL. TORNADO THREAT IS NEAR ZERO GIVEN THIS
TYPE OF SET-UP. STORMS WILL SHIFT SWD BY LATE EVNG AND MOST OF THE
FA SHOULD BE CLR OF ACTIVITY BY 4 AM.

REMOVED POPS FOR THUR/THUR NIGHT FROM THE CWA. LOOKS LIKE THE
EFFECTIVE FNT WL SAG FAR ENOUGH S THAT OUR CWA SHLD BE CLEAR OF
PRECIP WITH MOSTLY SUNNY SKIES. COOLER AIR SHLD MOV INTO THE FA ON
THUR...BUT MAIN DIFFERENCE WL BE THE MUCH COOLER DEWPOINTS
CURRENTLY OVR WRN DAKOTAS. RETURN FLOW STARTS ON FRI IN THE NW
CWA...AND ALTHOUGH CHANCES ARE SLIGHT...CLD SEE AN ISO WEAK STORM
MOV INTO THE NW CWA BY LATE AFTN AND CONT INTO THE EVNG. NEXT
SYSTEM WL START TO AFFECT THE AREA ON SAT AS A LOW-AMPLITUDE
SHRTWV TROF QUICKLY MOVS THRU THE NRN PLAINS. THIS WL ALLOW FOR A
SFC LO AND WEAK CDFNT TO MOV INTO THE REGION BY AFTN. INCREASED
HIGHS AHEAD OF THE FNT WITH GOOD MIXING AND WARM H85 AIR. CHC FOR
STORMS WL MOV IN ON SAT NIGHT AS CONVECTION FM THE W MAY MOV INTO
THE AREA. THIS BOUNDARY THEN LOOKS LIKE IT MAY LINGER FOR A BIT
OVR THE ARE INTO MON BEFORE RETREATING NWD. HAVE KEPT SOME SCHC
POPS IN DURING THIS TIME NEAR THE FRONTAL BOUNDARY. TMPS REALLY
START TO WARM AGAIN TOWARD TUE/WED AS UPPR LVL RIDGE BUILDS IN AND
WENT WARMER THAN HPC OR MEX GIVEN THE ENSEMBLE SUPPORT.

BOUSTEAD

&&

.AVIATION...

TAF SITES KOFK/KOMA/KLNK

18Z TAFS

COLD FRONT EXPECTED TO MOVE THROUGH KOFK AROUND 21Z THEN KOMA AND
KLNK 00Z-02Z. OTHER THAN PERIOD OF MVFR IN THUNDERSTORMS ASSOCIATED
WITH THE FRONT EXPECT VFR CONDITIONS FOR MUCH OF THE PERIOD AS DRIER
AND COOLER AIR MOVES INTO THE AREA BEHIND THE FRONT TONIGHT.

FOBERT

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR NEZ034-044-045-
     050>053-065>068-078-088>093.

IA...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR IAZ043-055-056-069-
     079-080-090-091.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
448 PM CDT WED JUL 14 2010

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-151200-
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-
448 PM CDT WED JUL 14 2010

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 THURSDAY

SEVERE STORMS ARE POSSIBLE THIS EVENING ACROSS MUCH OF NORTHEAST AND
EAST CENTRAL NEBRASKA AND WEST CENTRAL IOWA. LARGE HAIL AND
DAMAGING WINDS ARE THE PRIMARY HAZARDS ALONG WITH LOCALLY HEAVY RAIN.

A COLD FRONT WILL CONTINUE TO MOVE SOUTH INTO THE REGION AND IS
EXPECTED TO REACH THE KANSAS NEBRASKA BORDER TOWARD MIDNIGHT. THIS
FRONT WILL BE THE MAIN FOCUS FOR THE THUNDERSTORMS.

IN ADDITION...HOT TEMPERATURES IN THE MID TO UPPER 90S AND A VERY
HUMID AIR MASS WILL COMBINE TO CREATE HEAT INDEX VALUES FROM 105 TO
115 THROUGH 8 PM. A HEAT ADVISORY IS IN EFFECT SOUTH OF A LINE
FROM DAVID CITY TO DODGE TO ONAWA IOWA UNTIL 8PM.

FLOODING WILL ALSO CONTINUE ALONG THE MISSOURI RIVER IN FAR
SOUTHEAST NEBRASKA AROUND BROWNVILLE AND RULO.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THUNDERSTORMS ARE AGAIN POSSIBLE FRIDAY NIGHT...SATURDAY NIGHT INTO
SUNDAY NIGHT AND AGAIN ON MONDAY NIGHT.

FLOODING IS EXPECTED TO CONTINUE ALONG THE MISSOURI RIVER
FROM BROWNVILLE DOWNSTREAM THROUGH RULO INTO THE WEEKEND.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY BE NEEDED THIS EVENING.

KERN

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