Hail and Damaging Winds in Iowa, June 23, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
305 PM CDT TUE JUN 23 2009

.SHORT TERM...TONIGHT THROUGH FRIDAY

MAIN ISSUE IN THE SHORT TERM IS COLD FRONT POSITION TONIGHT AND
WEDNESDAY...AND RELATED PRECIP CHANCES AND TEMPERATURES. A WEAK
FRONTAL BOUNDARY WILL SETTLE NEAR THE MN/IA BORDER OVERNIGHT
TONIGHT...AND THEN WILL EJECT SOUTHWARD DURING THE DAY WEDNESDAY AS A
MID LEVEL WAVE MOVES THROUGH THE AREA. BEST CHANCES FOR TSTM
FORMATION WILL BE OVERNIGHT TONIGHT IN THE WAKE OF AN OUTFLOW
BOUNDARY...AND AGAIN LATE TOMORROW AFTERNOON AFTER RAPID
DESTABILIZATION THROUGH DIURNAL HEATING. ANY PRECIP THAT FORMS ALONG
THE BOUNDARY WEDNESDAY AFTERNOON AND EVENING WILL BE ABLE TO PERSIST
IN A FAVORABLE PREFRONTAL ENVIRONMENT...SO HAVE EXTENDED POPS THROUGH
THE OVERNIGHT HOURS.

TEMPERATURES SOUTH OF THE BOUNDARY WILL WARM ONCE AGAIN TO NEAR 100
DEGREES...DEWPOINTS WILL REMAIN IN THE MID TO UPPER 70S IN THIS
AIRMASS...AND ANY PRECIPITATION THAT FORMS THIS AFTERNOON AND TONIGHT
WILL ENHANCE LOCAL MOISTURE. EXTENDED THE HEAT ADVISORY FOR COUNTIES
THAT WILL REMAIN IN THE WARM SECTOR TOMORROW...AND HAVE UPGRADED TO
AN EXCESSIVE HEAT WARNING WHERE HEAT INDICES WILL REACH 110 FOR THE
THIRD DAY IN A ROW.

FRONTAL BOUNDARY SHOULD BE OUT OF THE AREA BY THURSDAY MORNING AND
HIGH PRESSURE WILL BUILD INTO THE AREA...SO REST OF THE SHORT TERM
LOOKS RELATIVELY QUIET. TEMPERATURES IN THE SLIGHTLY COOLER AIRMASS
SHOULD REMAIN OUT OF ADVISORY CRITERIA AFTER WEDNESDAY.

.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY

LATEST GFS AND ECM STILL SHOWING SIGNIFICANT DIFFERENCES WRT LARGE
SCALE FLOW AS WELL AS SFC FEATURES. HOWEVER...BOTH FOCUS CONVECTIVE
DEVELOPMENT AROUND A SFC COLD FRONT DROPPING INTO THE CNTRL PLAINS
FRIDAY NIGHT/SATURDAY TIME-FRAME. AS WITH THE LAST SEVERAL RUNS...
DIFFICULT PINNING DOWN SFC BNDRY POSITION DURING THIS TIME GIVEN
VARIOUS TIMING SOLUTIONS TO SHORTWAVE TROFS PUSHING ACROSS SRN
CANADA ALONG WITH AMPLIFYING UPPER RIDGES OVER THE NRN/CNTRL
PLAINS. FOR THE MOST PART THOUGH...BOTH GFS/ECM DO SUGGEST THE SFC
COLD FRONT WILL EVENTUALLY DROP SOUTH OF THE CWA BY LATE SAT AFTN
AND KEEP IT SOUTH THRU THE PD. ON TUESDAY...BOTH PROG ANOTHER COLD
AIRMASS APPROACHING THE CWA FROM THE NORTH. THEREFOR...WILL DESIGN
POPS AROUND ANTICIPATED FROPA DAY 4...THEN TOKEN LOW POPS
THEREAFTER TO SATISFY UNCERTAINTIES.

&&

.AVIATION...
FOR TAF SITES KOFK/KOMA/KLNK VALID THROUGH 24/18Z.

VFR CONDS ARE GENERALLY EXPECTED THRU THE PERIOD. TSRA ARE LIKELY TO
DVLP ALNG AN OUTFLOW BOUNDARY THIS EVNG BETWEEN THE OMA AND OFK
TERMINALS. SOME OF THIS ACTIVITY WL LIKELY SINK TO THE SOUTH AND MAY
AFFECT THE OMA TAF. TIMING UNCERTAINTIES PRECLUDE MENTION AT THIS
TIME DUE TO THE MESOSCALE NATURE OF THE CONVECTION...BUT WL CONT TO
MONITOR. OTHERWISE...CONVECTION POSSIBLE OVERNIGHT OFK...BUT AGAIN
UNCERTAINTIES AS TO WHEN HI PLAINS CONVECTION WL WORK EWD PRECLUDES
MENTION ATTM. WHEN CONVECTION DOES AFFECT A TERMINAL...MVFR CONDS
ARE LIKELY.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...HEAT ADVISORY UNTIL 9 PM CDT WEDNESDAY FOR NEZ034-042>045-050-
     051-065-066-078-088-089.

     EXCESSIVE HEAT WARNING UNTIL 9 PM CDT WEDNESDAY FOR NEZ052-053-
     067-068-090>093.

IA...HEAT ADVISORY UNTIL 9 PM CDT WEDNESDAY FOR IAZ043-055-056.

     EXCESSIVE HEAT WARNING UNTIL 9 PM CDT WEDNESDAY FOR IAZ069-079-
     080-090-091.

&&

LAFLIN/DEE/JB

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1207 PM CDT TUE JUN 23 2009

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-240715-
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-
1207 PM CDT TUE JUN 23 2009

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

THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORMS TO THE NORTH OF A
COLUMBUS TO OMAHA TO ATLANTIC IOWA LINE. THEM MOST LIKELY TIME FOR
SEVERE THUNDERSTORMS WILL BE AFTER 2 PM WITH THE MAIN THREAT BEING
DAMAGING WINDS AND LARGE HAIL.

SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS AFTERNOON
OVER NORTH CENTRAL AND NORTHEAST NEBRASKA NEAR A COLD FRONT.
ALTHOUGH SHEAR IS GENERALLY WEAK...STRONG INSTABILITY NEAR THE
FRONT WILL ALLOW A FEW STORMS TO BECOME SEVERE. THE MAIN THREAT
WITH THESE STORMS WILL BE DAMAGING WINDS AS THEY MOVE ACROSS THE
AREA THROUGH THE EVENING AND OVERNIGHT...BUT MARGINALLY SEVERE
HAIL IS ALSO POSSIBLE.

HOT AND HUMID CONDITIONS WILL CONTINUE THROUGH EARLY THIS EVENING.
HIGH TEMPERATURES ON TUESDAY WILL REACH THE MID TO UPPER
90S...AND WHEN COMBINED WITH THE HUMIDITY...THE HEAT INDEX WILL
CLIMB TO 105 TO 112.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THUNDERSTORMS ARE POSSIBLE FROM TUESDAY NIGHT THROUGH THURSDAY AS
A WEAK COLD FRONT DROPS INTO THE PLAINS. A FEW SEVERE STORMS ARE
POSSIBLE...WITH DAMAGING WINDS AND LARGE HAIL THE PRIMARY THREATS.
LOCALLY HEAVY RAIN MAY ALSO OCCUR WITH ANY STORMS THAT DEVELOP.

THE NEXT CHANCE FOR STORMS WILL COME FRIDAY NIGHT THROUGH
SATURDAY...BUT DEPENDING HOW FAR SOUTH THE FRONT PUSHES AND MOVES
BACK NORTH...THUNDERSTORM CHANCES COULD LAST INTO MONDAY.

HOT TEMPERATURES IN THE UPPER 80S TO UPPER 90S ARE EXPECTED FOR
WEDNESDAY. THE AFTERNOON HEAT INDEX VALUES SHOULD RANGE FROM 90IN
THE NORTH TO 108 IN THE SOUTH.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY NOT BE NEEDED THIS AFTERNOON OR
TONIGHT...BUT SPOTTERS ARE ENCOURAGED TO REPORT ANY STRONG WINDS OR
HAIL.

BOUSTEAD