Severe Thunderstorm Warning 13, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
326 PM CDT FRI APR 23 2010

.DISCUSSION...

SHORT TERM...TONIGHT. WARM FRONT OVER MIDLANDS WAS BECOMING A
LITTLE BETTER DEFINED AT 20Z WITH IT NEAR A OLU-OMA LINE. HOWEVER...
WINDS WERE A BIT MORE SOUTHERLY WITH MORE BREAKS IN THE OVC NOTED
ON AFTN STLT/SFC OBS SW OF BIE/FNB. CONVECTION AT 1930Z WAS MOSTLY
CONFINED TO WRN EDGE OF LEADING WARM FRONT ON NOSE OF MID/UPPER
LEVEL THERMAL TROUGH WELL OFF TO THE WEST OF THE CWA. RUC MESO
ANALYSIS PAGE INDICATED BEST DESTABILIZATION WAS OCCURRING FM
CONVECTION OVER SANDHILLS SEWD INTO SERN NEBR AND 17Z HIGH
RESOLUTION RAPID REFRESH MODEL SHOWED POSSIBLE DEVELOPMENT SE INTO
THIS AXIS OF MORE UNSTABLE AIR IN 22Z-01Z TIME FRAME. 4KM WRF ALSO
DVLPD ACTIVITY FARTHER SE BUT DELAYED IT A BIT TILL 01Z BEFORE
RAPIDLY FILLING IN A LINE ARCING FM NCNTRL NEBR INTO SWRN IA BY
MID EVENING...SORT OF WHERE LEADING EDGE WHERE BREAKS WERE
OCCURRING ON 1930Z VSBL STLT PICS. THE WARMING NEAR 700 MB NOTED
ON AFTN TOP SOUNDING WAS ERODED BY GFS/NAM BY 00Z THUS WOULD
EXPECT AN INCREASE IN DEVELOPMENT ESE FM NCNTRL NEBR RAPIDLY THIS
EVENING AND CATEGORICAL POPS WERE MENTIONED ACROSS NRN/ERN ZONES
ALONG WITH SVR THREAT THROUGH 04Z MOST AREAS...ALTHOUGH THREAT
MAINLY JUST HAIL N OF BNDRY AND NOT EXACTLY SURE HOW THINGS WILL
PLAY OUT SOUTH OF NEBR WARM FRONT IN SEEMINGLY LESSER PCPN CHC
AREA. DRIER AIR STILL FORECAST TO WRAP INTO SWRN ZONES LATE BHND
OCCLUDED FRONT...AND KEPT OVERNIGHT LOWS COOLER THAT AREA.

CHERMOK

MID TERM...SATURDAY THROUGH MONDAY. SURFACE LOW LOCATED ACROSS
SCNTRL NEBRASKA SATURDAY MORNING WILL MOVE TO THE SOUTHERN GREAT
LAKES BY DAYBREAK SUNDAY. PRECIPITATION THREAT SATURDAY WILL HAVE
TWO COMPONENTS...THE WRAPAROUND PRECIP THAT WILL BE AFFECTING
NORTHEAST NEBRASKA...IN THE FORM OF RAIN...AND SHOWERS THAT COULD
DEVELOP ACROSS SOUTHWEST IOWA AND SOUTHEAST NEBRASKA...IN RESPONSE
TO STEEP LAPSE RATES DUE TO COLD TEMPERATURES ALOFT. THIS AREA OF
SHOWERS COULD EVENTUALLY DEVELOP INTO THUNDERSTORMS SATURDAY
AFTERNOON OR EARLY EVENING. SCATTERED TO NUMEROUS MAY BE POSSIBLE
IN THE WRAPAROUND SATURDAY NIGHT...BUT DIMINISHING THROUGH TIME
INTO SUNDAY AS THE LOW FOCUSES WELL EAST OF THE REGION. SUNDAY
NIGHT SHOULD BE DRY WITH WEAK RIDGING ACROSS THE REGION...IN
ADVANCE OF THE NEXT TROUGH THAT MOVES DOWN FROM THE NORTHERN
PLAINS...WHICH COULD TRIGGER A FEW SPOTTY SHOWERS MONDAY INTO
MONDAY NIGHT.

TEMPS SATURDAY SHOULD BE SOMEWHAT TRICKY...RANGING ONLY IN THE UPPER
50S IN OUR NORTHWESTERN CWFA...BUT IN THE LOWER 70S IN THE
SOUTHEAST...SO TIGHT GRADIENTS COULD EXIST RESULTING IN BUST
POTENTIAL. SOMEWHAT COOLISH SUNDAY AND MONDAY WITH BELOW NORMAL
TEMPS.

DEWALD

LONG TERM...TUESDAY THROUGH FRIDAY. BEGINNING OF PERIOD WILL STILL
SEE AN UPPER LEVEL TROUGH MOVING THROUGH THE REGION...WHICH COULD
STILL TRIGGER SPOTTY SHOWERS MONDAY NIGHT AND TUESDAY. THE GFS IS
JUST A TAD QUICKER IN MOVING THE PRECIP THREAT EAST OF THE
REGION...BUT THE PREFERRED ECMWF HAS A SLIGHT SECONDARY TROUGH THAT
MAY STILL BE MOVING THROUGH. TUESDAY STILL LOOKS COOLISH WITH
SLIGHTLY BELOW NORMAL TEMPS IN THE LOW/MID 60S.

RIDGE THEN BUILDS ACROSS THE REGION ON WEDNESDAY WITH A DECENT
SOUTHERLY FLOW RETURNING TO THE REGION. THIS SHOULD PROVIDE AMPLE
SUNSHINE WHICH SHOULD HELP TO BOOST TEMPS BACK INTO THE UPPER 60S
AND DRY.

DIGGING TROUGH THROUGH THE ROCKIES WEDNESDAY NIGHT COULD SEND A FRONT
INTO THE REGION ON THURSDAY. WILL HAVE SOME POPS IN THERE DURING
THIS TIME WITH A SIGNIFICANT WARMUP IN PLACE AHEAD OF THE FRONT WITH
TEMPS REACHING THE LOWER/MID 70S. WILL MAINTAIN CONTINUITY WITH
PRECIP CHANCES THURSDAY NIGHT AS THE FRONT MOVES THROUGH...BUT FEEL
THAT THE PRECIP THREAT MAY BE /JUST/ SOUTH AND EAST OF THE CWFA BY
FRIDAY. SLIGHTLY COOLER...BUT NEAR NORMAL ON FRIDAY BEHIND THE FRONT.

DEWALD

&&

.AVIATION...
TAF SITES KOFK/KOMA/KLNK

18Z TAFS

PER PREV AVIATION DISCUSSION BREAK IN PCPN HAD OCCURRED AT TAF SITES
TO BEGIN FORECAST PD...WITH NEW CONVECTION AT 20Z CONFINED TO NEBR
SANDHILLS WEST OF KOFK. ACTIVITY EXPECTED TO DEVELOP ESE INTO SERN
NEBR/SWRN IA THROUGH 03Z AND THUS TEMPO GROUPS WERE INCLUDED AT ALL
3 TAF SITES FROM LATE AFTN INTO THIS EVENING.  ALTHOUGH TEMPORARY
MVFR CIGS POSSIBLE AT KOMA...AND AT KLNK AND KOMA WITH ANY TSTM
ACTIVITY...NO CIGS OR CIGS ABOVE MVFR ARE EXPECTED AFTER MID EVENING
AT THOSE 2 SITES.  LOW CIGS/VSBYS THAT PLAGUED KOFK SHOULD IMPROVE
THROUGH EARLY EVENING BUT CIGS COULD GO BACK DOWN AGAIN AS SFC WINDS
TURN MORE EASTERLY LATER TONIGHT.  AREAS OF FOG POSSIBLE IN CLEARING
AREA LATE TNGT...BUT DRIER AIR THAT IS FORECAST TO WRAP INTO SYSTEM
LATE TNGT COULD LIMIT THAT FROM DVLPG AT KLNK/KOMA.

CHERMOK

&&

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

DEWALD/CHERMOK

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
452 PM CDT FRI APR 23 2010

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-241200-
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-
452 PM CDT FRI APR 23 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EASTERN NEBRASKA
AND WESTERN IOWA.

.DAY ONE...TONIGHT AND SATURDAY

SEVERE THUNDERSTORMS MAY STILL DEVELOP THIS EVENING ACROSS
PORTIONS OF EASTERN NEBRASKA AND SOUTHWESTERN IOWA AS A WARM FRONT
CONTINUES TO PUSH NORTHWARD INTO THE REGION. PRESENT INDICATIONS
SUGGEST THAT THUNDERSTORMS COULD DEVELOP IN AN ARC FROM NEAR ALBION
OR NELIGH SOUTHEASTWARD THROUGH WAHOO OR LINCOLN OR FALLS CITY...THEN
SOUTHWARD TOWARD TOPEKA. THE THUNDERSTORMS WOULD THEN MOVE NORTH
AND NORTHEAST FROM THIS AREA THROUGH THE EVENING. LARGE HAIL AND
DAMAGING WINDS WILL BE POSSIBLE IN ANY STORMS THAT DEVELOP THIS
EVENING...BUT ANY STORM THAT DEVELOPS ON OR NEAR THE WARM FRONT
COULD PRODUCE A TORNADO THROUGH MID EVENING AS WELL. OVERNIGHT...
THUNDERSTORMS SHOULD SHIFT INTO NORTHEAST NEBRASKA AND WESTERN
IOWA WITH SOME HAIL STILL POSSIBLE.

ON SATURDAY...AS AN UPPER LEVEL LOW PRESSURE SYSTEM MOVES INTO THE
AREA...THUNDERSTORMS MAY STILL BE POSSIBLE ACROSS PORTIONS OF
EASTERN NEBRASKA AND SOUTHWEST IOWA IN THE AFTERNOON. DUE TO COLD
TEMPERATURES ALOFT...SOME WOULD BE POSSIBLE...GENERALLY EAST OF A
LINE FROM BEATRICE NEBRASKA TO ONAWA IOWA.

.DAYS TWO THROUGH SEVEN...SATURDAY NIGHT THROUGH FRIDAY

ANOTHER WEATHER DISTURBANCE MOVING INTO THE REGION COULD BRING
MORE THUNDERSTORMS TO THE AREA WEDNESDAY NIGHT THROUGH THURSDAY
NIGHT.

.SPOTTER INFORMATION STATEMENT...

STORM SPOTTER ACTIVATION COULD BE NEEDED ACROSS PARTS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
809 PM CDT FRI APR 23 2010

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0805 PM     HAIL             WAVERLY                 40.91N 96.53W
04/23/2010  M1.00 INCH       LANCASTER          NE   TRAINED SPOTTER

&&

VDEWALD

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