Hail in Iowa, May 23, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1038 AM CDT WED MAY 23 2007

.UPDATE...
DIFFICULT FORECAST FOR THIS AFTERNOON. ATMOSPHERE WILL DESTABILIZE
SOME THIS AFTERNOON...BUT MAIN LIFT DOES NOT MOVE OVER THE AREA
UNTIL AFTER 00Z. LATEST WATER VAPOR IMAGERY SHOWED A VERY STRONG
DISTURBANCE OVER SERN UT AND WRN CO. A CLOSED LOW WAS NEAR THE
ND/SD/MT BORDER. 850 MB MOIST AXIS STRETCHED FROM TX ACROSS OK...
ERN KS AND IA INTO MN. AT THE SURFACE...A SLOW MOVING COLD FRONT
STRETCHED FROM WRN MN INTO ERN NE...ACROSS KS AND INTO THE PNHDL
OF TX. DEWPOINTS WERE IN THE 60S AHEAD OF THE FNT. BEST CHANCES
FOR SEVERE WEATHER AND HEAVY RAIN ARE OVER ABOUT THE SOUTHEAST 2/3
OF THE AREA. HEAVIEST RAIN WILL BE OVERNIGHT AND WILL NEED TO
CONSIDER A FLASH FLOOD WATCH FOR PARTS OF THE AREA.

WILL PROBABLY UPDATE TEXT PRODUCTS AGAIN EARLY AFTERNOON.

&&

.AVIATION...
MARGINAL VFR CEILINGS OVER THE AREA AT MID/LATE MORNING WILL BE
LIFTING A LITTLE THIS AFTN...BUT STILL EXPECT SOME AREAS OF
MARGINAL VFR. VISIBILITIES COULD BE IFR WITH TSTM ACTIVITY THIS
EVENING AND OVERNIGHT...AND WILL ALSO PROBABLY SEE SOME IFR
CEILINGS AFTER MIDNIGHT.

&&

.PREV DISCUSSION... /ISSUED 300 AM CDT WED MAY 23 2007/

DISCUSSION...
TIMING AND POSITION OF FRONTAL BOUNDARIES WILL REMAIN MAIN FORECAST
CHALLENGE IN THE SHORT TERM.

FRONTAL BOUNDARY EXTENDED FROM EASTERN SOUTH DAKOTA THROUGH EASTERN
NEBRASKA AND WESTERN KANSAS AT 07Z. CONVECTION WHICH HAD DEVELOPED
OVER CENTRAL NEBRASKA LATE YESTERDAY AFTERNOON ALONG THE FRONT WAS
NOW OVER NORTHEAST NEBRASKA INTO CENTRAL KANSAS. NEBRASKA CONVECTION
HAS GENERALLY BEEN WEAKENING WITH TREND EXPECTED TO CONTINUE AS
COMPLEX MOVES EAST ACROSS THE AREA THIS MORNING. LATEST MODELS
CONTINUE TO INDICATE BOUNDARY STALLING OUT ACROSS THE AREA TODAY AS
SECONDARY FRONT APPROACHES FROM THE NORTHERN PLAINS. WILL CARRY
SCATTERED RW-/TRW- FOR EASTERN PORTIONS OF THE AREA EARLY THIS
MORNING WITH SOME BREAK EXPECTED BEFORE REDEVELOPMENT LATE THIS
AFTERNOON. LOCATION UNCERTAIN AT THIS TIME DEPENDING ON HOW SURFACE
FRONTS INTERACT AND TIMING OF SHORTWAVE ENERGY...BUT LATEST
INDICATIONS PLACE IT SOMEWHERE NEAR WESTERN BORDER OF THE CWA.

CHANCE OF SEVERE STORMS LATE AFTERNOON INTO THE EVENING AS WELL AS
HEAVY RAIN TONIGHT. DAY SHIFT WILL HAVE HONOR OF DELINEATING
SPECIFIC AREA FOR ANY FLOOD WATCH BUT LATEST HPC GUIDANCE POINTS TO
SOUTHEAST NEBRASKA INTO WEST CENTRAL IOWA. HAVE CONTINUED TO CARRY
HIGHEST POPS FOR WEDNESDAY NIGHT PERIOD WITH NAM LINGERING POPS
ACROSS MUCH OF THE AREA THROUGH THURSDAY MORNING. GFS A BIT FASTER
IN MOVING THE PRECIP OUT ON THURSDAY...OPPOSITE OF SOLUTIONS FROM
PREVIOUS 00Z RUN. TEMPERATURES TRENDED TOWARD BLEND OF 00Z MODELS
WITH ONLY MINOR CHANGES FROM PREVIOUS FORECAST.

TIMING PROBLEMS REMAIN AN ISSUE IN THE EXTENDED PERIOD WITH 00Z
MODELS SLOWING RETURN OF POPS TO SATURDAY NOE INSTEAD OF FRIDAY. NO
CHANGES TO THIS PORTION OF THE FORECAST.

AVIATION...
OUTFLOW-DRIVEN CONVECTION WILL CONTINUE TO SWEEP THROUGH EASTERN
NEBRASKA CAUSING MVFR/IFR CIGS/VSBYS WITHIN THE RAIN AREAS. OVERALL
LOW LEVEL MOISTURE AND SOUTH WINDS HAVE DELIVERED MVFR CIGS ACROSS
THE AREA...AND EXPECT THOSE CIGS TO GRADUALLY LIFT TO VFR DURING THE
15Z TO 18Z TIME FRAME. COLD FRONT DRIFTING FROM CENTRAL INTO EASTERN
NEBRASKA WILL PROVIDE FOCUS FOR CONVECTION DURING THE AFTERNOON AND
OVERNIGHT. WHERE EXACTLY FRONT WILL STALL AND CONVECTION WILL FIRE
IS STILL IN QUESTION...ESPECIALLY GIVEN THIS MORNINGS
CONVECTION...BUT STRONG THUNDERSTORMS ARE LIKELY NEAR THE FRONT
AFTER 00Z.

&&

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

48

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
141 PM CDT WED MAY 23 2007

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-240000-
ANTELOPE-BOONE-BURT-BUTLER-CASS-CEDAR-COLFAX-CUMING-DODGE-DOUGLAS-
FREMONT IA-GAGE-HARRISON IA-JEFFERSON-JOHNSON-KNOX-LANCASTER-MADISON-
MILLS IA-MONONA IA-MONTGOMERY IA-NEMAHA-OTOE-PAGE IA-PAWNEE-PIERCE-
PLATTE-POTTAWATTAMIE IA-RICHARDSON-SALINE-SARPY-SAUNDERS-SEWARD-
SHELBY IA-STANTON-THURSTON-WASHINGTON-WAYNE-
141 PM CDT WED MAY 23 2007

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

THE ATMOSPHERE DESTABILIZED EARLY THIS AFTERNOON AND THUNDERSTORMS
DEVELOPED ALONG AND AHEAD OF A FRONTAL SYSTEM THAT IS OVER THE
AREA. A SEVERE THUNDERSTORM WATCH IS IN EFFECT FOR PORTIONS OF
SOUTHEAST NEBRASKA AND SOUTHWEST IOWA INTO THIS EVENING. SOME
STORMS COULD PRODUCE HAIL AND GUSTY WINDS...MAINLY SOUTHEAST OF
A LINE FROM BEATRICE TO HARLAN IOWA.

THE CHANCE FOR THUNDERSTORMS SHOULD INCREASE DRAMATICALLY THIS
EVENING AND TONIGHT...AS A STRONG UPPER LEVEL DISTURBANCE MOVES
THROUGH THE REGION.

A SLOW MOVING FRONTAL BOUNDARY WILL BE THE FOCUS FOR THUNDERSTORMS
THIS EVENING AND TONIGHT. SOME SEVERE STORMS ARE POSSIBLE. LARGE
HAIL AND DAMAGING WINDS WOULD BE THE MAIN HAZARDS. AS THE NIGHT
PROGRESSES...THE THREAT FOR HEAVY RAIN AND FLOODING WILL INCREASE.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THUNDERSTORMS MAY LINGER INTO THURSDAY MORNING OVER EASTERN PARTS
OF THE AREA BEFORE MOVING OUT DURING THE AFTERNOON.

THE WEATHER PATTERN THROUGH THE MEMORIAL DAY WEEKEND LOOKS SOMEWHAT
UNSETTLED WITH VARYING THUNDERSTORM CHANCES. AT THIS TIME...FRIDAY
NIGHT AND SATURDAY SEEM TO HAVE THE HIGHEST THUNDERSTORM CHANCES...
ALTHOUGH STORMS CAN NOT BE RULED OUT LATE SUNDAY OR ON MEMORIAL
DAY.

.SPOTTER INFORMATION STATEMENT...

STORM SPOTTER ACTIVATION MAY BE REQUIRED LATE THIS AFTERNOON OR THIS
EVENING.

MILLER