Severe Thunderstorm Warning 6, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
210 AM CDT TUE APR 29 2003

FORECAST CHALLENGES...MCS/SEVERE POTENTIAL TONIGHT AND SIGNIFICANT
SEVERE POTENTIAL FOR WEDNESDAY.

SYNOPSIS-
SOMEWHAT COMPLICATED PATTERN EXISTS THIS EVENING AS THE
PLAINS BECOME INCREASINGLY INFLUENCED BY THE MAIN WESTERN TROF. AS
OF EARLY THIS MORNING...CONVECTION APPEARS TO BE FOCUSED ALONG THE
850MB FRONT STRETCHING FROM NORTHEAST CO THROUGH EAST CENTRAL KS.
THIS ACTIVITY IS SUPPORTED WELL BY UPPER LEVEL DIFFLUENCE ON THE
NOSE OF 100KT JET STREAK UP AT 300MB.

FORECAST-
WITH THE 850MB FRONT LIFTING TO SOUTHERN NEBRASKA THIS
MORNING...AND OVERRUNNING WAA INCREASING THROUGH THE MORNING
HOURS...THERE IS GOOD MODEL AGREEMENT IN DEVELOPING PCPN THIS
MORNING ACROSS MUCH OF EASTERN NEBRASKA AND WESTERN IOWA. THIS PCPN
WILL AID IN HOLDING THE MAIN WARM FRONT NEAR OR JUST SOUTH OF THE
CWA THIS AFTERNOON.  THE PLACEMENT OF THIS FRONT WILL BE CRITICAL TO
THE SEVERE WEATHER POTENTIAL DURING THE NEXT 48 HOURS.

THOUGH BOTH THE ETA AND GFS SEEM REASONABLE WITH THEIR
INITIALIZATION AND AGREEMENT ON THE EAST WEST WARM FRONTAL
POSITION THROUGH 36 HOURS...THEY DIVERGE COMPLETELY AS TO HOW THE
UPPER LEVEL LOW EJECTS INTO THE PLAINS WEDNESDAY.  THE ETA HAS HELD
TO BRINGING IN A POWERFUL WAVE WEDNESDAY NIGHT...CLOSING OFF AN UPPER
LOW BY THURSDAY MORNING OVER KFSD. THE GFS NO LONGER BRINGS OUT THE
MAIN LOW...BUT A CONTINUATION OF LESS ENERGETIC SOUTHWEST FLOW
THROUGH FRIDAY...WITH A MODEST WAVE COMING OUT WEDNESDAY NIGHT. AS
DISCUSSED BY HPC...THE GFS APPEARS TO BE THE ODD MODEL OUT...AN HAS
LITTLE CONSISTENCY FROM ANY PREVIOUS GFS SOLUTION.  THUS...WE ARE
FAVORING THE ETA SOLUTION FOR THIS FORECAST...AS IS MESHES WELL WITH
PAST RUNS AND LATEST CANADIAN.

TO SAY THE LEAST...WITH THE MAIN SYNOPTIC WARM FRONT SETTING UP OVER
THE CENTRAL OR SOUTHERN CWA THROUGH WEDNESDAY...POPS WILL BE NEEDED
IN EVERY PERIOD THROUGH WEDNESDAY NIGHT.  AM LESS CONFIDENT ON
CHANCES FOR PCPN THURSDAY...THROUGH GOING FORECAST ACCOUNTS FOR
SLOWER PROGRESSION OF THE ETA/S UPPER LOW SOLUTION.  WILL KEEP THESE
POPS GOING.  TONIGHT...WITH A STRONG LLJ AIMED RIGHT AT EASTERN
NEBRASKA FROM 06-12Z...FEEL CATEGORICAL POPS ARE NEEDED ALONG WITH
RISK OF SEVERE IN THE SOUTH.  PCPN MAY LINGER WEDNESDAY
MORNING...BEFORE DRYING OUT AND RELOADING FOR WEDNESDAY
AFTERNOON/EVENING.  AS THE MAIN WAVE ROLLS OUT INTO NEBRASKA
WEDNESDAY AFTERNOON...AND THE SFC LOW MOVES ACROSS THE CWA...THE
POSSIBILITY FOR SEVERE WEATHER MAY BE SIGNIFICANT. WITH STRONG DEEP
LAYER SHEAR...ESPECIALLY NEAR THE PATH OF THE SFC LOW...AND CAPE
VALUES 2000-3500J/KG SUPERCELLS SEEM LIKE A GOOD BET. IF THIS
SCENARIO MATERIALIZES CLOSE TO THE 00Z ETA THERE WILL BE A RISK OF
TORNADIC STORMS. WILL HIGHLIGHT RISK OF SVR STORMS IN HWO AND ZFP.

NO SIGNIFICANT CHANGES MADE TO THE EXTENDED.  DRY WEATHER EXPECTED
FRIDAY AND SATURDAY...FOLLOWED BY ANOTHER PERIOD OF MOIST UNSETTLED
SOUTHWEST FLOW SATURDAY NIGHT THROUGH MONDAY.

THANKS FOR COORDINATION SURROUNDING OFFICES AND SPC.

.OMA...NONE.

ERVIN

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-291100-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
550 PM CDT MON APR 28 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PARTS OF EASTERN NEBRASKA
AND SOUTHWEST IOWA.

.DAY ONE...TONIGHT AND TUESDAY AFTERNOON

THUNDERSTORMS ARE POSSIBLE LATE TONIGHT ACROSS MUCH OF EASTERN
NEBRASKA AND SOUTHWEST IOWA.  A FEW OF THESE STORMS COULD BE
STRONG...ESPECIALLY SOUTHWEST OF A LINE FROM DAVID CITY TO
BEATRICE. THE MAJORITY OF ANY SEVERE WEATHER...HOWEVER...SHOULD
BE SOUTH OR WEST OF THE AREA. THE THUNDERSTORMS ARE EXPECTED TO
DEVELOP ACROSS A COUPLE OF AREAS AREAS. A NEARLY STATIONARY FRONT
ACROSS CENTRAL KANSAS COULD PROVIDE ONE FOCUS LATER TONIGHT WITH
THUNDERSTORMS DEVELOPING NORTH OF THIS BOUNDARY AS WARM AND MOIST
AIR SPREADS NORTH ACROSS IT.  OTHER THUNDERSTORMS SHOULD DEVELOP
THIS EVENING OVER THE WESTERN HIGH PLAINS. THIS ACTIVITY IS
FORECAST TO SPREAD EAST AND SOUTHEAST TOWARD THE REGION LATE
TONIGHT AND INTO TUESDAY MORNING.

THUNDERSTORMS ARE FORECAST TO WEAKEN AND CONTINUE TO MOVE EAST
ACROSS THE AREA LATE TUESDAY MORNING.  INSTABILITY WILL INCREASE
THROUGH THE AFTERNOON HOWEVER AND STRONG THUNDERSTORMS MAY
REDEVELOP IN THE LATE AFTERNOON.

.DAYS TWO THROUGH SEVEN...TUESDAY NIGHT THROUGH MONDAY

THERE IS A SLIGHT RISK OF SEVERE STORMS TUESDAY NIGHT AND EARLY
WEDNESDAY AS
THE FRONT BEGINS TO LIFT NORTH OVER THE AREA.  STORMS MAY
CONTINUE INTO EARLY THURSDAY MORNING A STRONG UPPER LEVEL SYSTEM
PUSHES ACROSS THE AREA.

THERE IS A CHANCE FOR THUNDERSTORMS LATE THIS WEEKEND AS
WELL...MAINLY FROM LATE SATURDAY INTO MONDAY.

.SPOTTER INFORMATION STATEMENT...

STORM SPOTTER ACTIVATION IS NOT LIKELY TONIGHT...BUT MAY BE
REQUIRED TUESDAY AND WEDNESDAY.

GRIFFIS