Severe Thunderstorm Warning 280, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
153 PM CDT SAT JUN 21 2008

.DISCUSSION...

CONVECTION HAD BEGUN TO DVLP JUST NW OF THE CWA AT 1730Z IN LOW
LVL CONVERGENT AREA WHERE H85 MOISTURE HAD BEGUN TO RETURN IN WAKE
OF A POCKET OF DRIER AIR THAT HAD SPREAD SWD ALONG MO RIVER THIS
AFTN. THIS DRIER AIR HAD KNOCKED SFC DWPTS DOWN SOME 5-10 DEG F
LOWER OVR MUCH OF THE CWA COMPARED TO YDA ATTM. HOWEVER...THRU
EARLY EVENING SOME LOW LVL MOISTURE SHOULD RETURN TO MUCH OF THE
REGION WHICH SHOULD ALLOW FOR CONVECTION TO SPREAD E AND SE ACROSS
THE CWA. IN ADDITION...JET SEGMENT MORNING UA AND LATEST RUC ANLYS
SHOWED PUNCHING TWD SERN SD COULD AID IN LIFT ACROSS THE CWA INTO
THIS EVENING. ZERO-6KM SHEAR WAS INDICATED TO BE STRONGER THAN YDA
AND 1000-850 MB LAPSE RATES SIMILAR...SPCLY NRN ZONES. WOULD
EXPECTED SVR STORMS NRN SECTIONS WHERE MLCAPES WERE A BIT HIGHER
WITH STRENGTH FTHR SWD A LTL MORE INDETERMINATE BASED ON HOW MUCH
LOW LVL MOISTURE/CAPE CAN RETURN. BASED ON CURRENT DWPTS UPSTREAM
AND SAT AM LOWS...TRIMMED BACK LOWS A BIT CNTRL/N.

AS AN EMBEDDED WAVE WRAPS AROUND SRN CANADA UPPER TROUGH/LOW TNGT...
AN H5 THERMAL TROUGH WILL SWING DOWN ALONG AND E OF THE MO RIVER
ON SUNDAY. THIS COULD AID IN AFTN TSTM DVLPMENT AGAIN WHERE LOWER
LVL MOISTURE PERSISTS. ATTM INCLUDED SMALL POPS SRN SECTIONS AS
WIND FIELDS FM SFC-H85 WERE FCST TO REMAIN FAIRLY WEAK MUCH OF
THE DAY WITH DRYING POSSIBLY MINIMAL. MOST AREAS COULD POSSIBLY BE
A DEG OR TWO COOLER THAN TDA BASED ON SLIGHTLY COOLER H85 TEMPS.
WITH SFC HIGH CONTG TO FEED SWD SUN NGT...WOULD EXPECT MON AM TO
BE EVEN COOLER THAN SUN WITH A LARGE FETCH OF SFC DWPTS IN THE 40S
CURRENTLY OBSERVED N THRU ND INTO CANADA. LOOKS SOMEWHAT DOUBTFUL
WITH ESERLY FLOW AND SIMILAR H85 TEMPS THAT MONDAY MAX TEMPS
WOULD BE MUCH WARMER...IF ANY...THAN SUNDAY.

NEXT SIGNIFICANT CHC OF TSTMS APPEARS IT WILL ARRIVE IN MON NGT/TUE
PD AS A STRONGER TROUGH WILL RIDE OVR UPPER RIDGE
COINCIDENT WITH OR AIDING IN LOW LVL MOISTURE RETURN. PREV FCST
APPEARS TO HANDLE THIS WELL.  BEYOND THAT PD KEPT SMALL POPS IN
REMAINDER OF FCST. UPPER HGTS DO ATTEMPT TO BUILD WHICH COULD TEND
TO LIMIT ANY CONVECTIVE COVERAGE OVER THE CWA ALONG WITH
INCREASING TEMPS.

&&

.AVIATION...
FOR TAF SITES KOMA...KLNK AND KOFK...THROUGH 22/18Z.

VFR CONDITIONS EXPECTED THROUGH THE ENTIRE FCST PD.  THERE IS A
POSSIBILITY OF MVFR CONDITIONS DEVELOPING WITH RESPECT TO
VISIBILITIES ACROSS ALL THREE TAF SITES BY 21Z THRU 22/01Z...DUE TO
POTENTIAL FOR THUNDERSTORM ACTIVITY.  SFC WINDS WL REMAIN LIGHT
THROUGH THE PERIOD. SCATTERED CU WITH BASES NEAR 7K FT ARE STARTING
TO FORM ACROSS PORTIONS OF THE FCST AREA. BY MID AFTERNOON...CU WILL
LIKELY BECOME MORE WIDESPREAD WITH CHANCES FOR THUNDERSTORMS
INCREASING AS WELL.

&&

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

CHERMOK/REESE

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1128 AM CDT SAT JUN 21 2008

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-220630-
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-
1128 AM CDT SAT JUN 21 2008

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

A REPEAT OF THE LAST COUPLE OF DAYS WITH STRONG TO SEVERE
THUNDERSTORMS EXPECTED TO DEVELOP OVER EASTERN NEBRASKA AND
SOUTHWEST IOWA THIS AFTERNOON. AS THE DAY CONTINUES TO HEAT UP...
INSTABILITY WILL INCREASE ACROSS THE AREA. NORTHWEST WINDS ALOFT
WILL PROVIDE WIND SHEAR NECESSARY FOR SEVERE WEATHER. LARGE HAIL
AND DAMAGING WINDS WILL BE THE PRIMARY HAZARDS...BUT AN ISOLATED
TORNADO CANNOT BE RULED OUT. THE THUNDERSTORM ACTIVITY SHOULD
DECREASE WITH LOSS OF HEATING LATER THIS EVENING.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THUNDERSTORMS ARE ALSO POSSIBLE MUCH OF NEXT WEEK...WITH STRONG OR
SEVERE STORM CHANCES HIGHEST MONDAY NIGHT INTO TUESDAY AND ALSO
THURSDAY NIGHT. A RELATIVELY UNSETTLED WEATHER PATTERN WILL
PERSIST NEXT WEEK...AS THE REGION REMAINS ON THE EDGE OF THE UPPER
LEVEL RIDGE ASSOCIATED WITH THE JET STREAM...THAT HAS PERSISTED
OVER THE SOUTHWESTERN AND SOUTHERN UNITED STATES.

.SPOTTER INFORMATION STATEMENT...

STORM SPOTTERS WILL LIKELY BE NEEDED THIS AFTERNOON AND EVENING...MAINLY
FROM 3 PM TO 10 PM.

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