Damaging Winds and Heavy Rain in Iowa, June 10, 2004

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
415 PM CDT THU JUN 10 2004

.SYNOPSIS...STATIONARY FRONT ACROSS IOWA INTO NORTHERN ILLINOIS TO
REMAIN THERE OVERNIGHT. THUNDERSTORM COMPLEX TO DEVELOP IN THE
PLAINS TONIGHT TO ARRIVE LATE TONIGHT BRINGING ANOTHER ROUND OF
RAIN. THUNDERSTORMS TO REDEVELOP IN THE AFTERNOON FRIDAY WITH
DAYTIME HEATING. POTENTIAL DOES EXIST LATE FRIDAY AFTERNOON AND
EVENING FOR SEVERE STORMS TO DEVELOP.

&&

.SHORT TERM...(TONIGHT AND FRIDAY)...
STATIONARY FRONT ACROSS THE EXTREME NORTH PART OF THE CWFA TO REMAIN
THERE OVERNIGHT. MODELS INDICATE AN MCS TO FIRE TONIGHT BUT THE
QUESTION IS WHERE. LIKELY AREA TO BE IN NEBRASKA WHERE THE LLJ IS
THE STRONGEST AND THEN MOVE ROUGHLY ALONG THE FRONT BRUSHING THE
NORTHERN CWFA LATE TONIGHT AND FRIDAY MORNING.

MODELS HAVE MANY SUBTLE DIFFERENCES BETWEEN THEM ON FRIDAY. HOWEVER
ALL AGREE ON THE ATMOSPHERE DRYING OUT DURING THE DAY. IF PLENTY OF
DIURNAL HEATING CAN TAKE PLACE...THUNDERSTORMS TO FIRE AGAIN DURING
THE AFTERNOON. FAVORABLE SHEAR PROFILES INDICATE STORMS WILL BE
ROTATING. KEY FACTOR IS WILL THERE BE AN OUTFLOW BOUNDARY OVER THE
AREA. IF THERE IS ONE...POTENTIAL THEN EXISTS FOR SIGNIFICANT SEVERE
STORMS TO DEVELOP DURING THE LATE AFTERNOON HOURS. IN HOUSE
CALCULATIONS SUGGEST POTENTIAL OF STRAIGHT LINE WINDS OVER 80 MPH
WITH BASEBALL SIZED HAIL IF TEMPS CAN GET INTO THE UPPER 80S WITH
DEW POINTS AROUND 73. TORNADO COULD ALSO OCCUR WITH POTENTIAL
RANGING FROM F1 TO F3. HOWEVER...ONCE AGAIN...THIS IS ALL DEPENDENT
ON AN OUTFLOW BOUNDARY BEING OVER THE AREA AND HOW MUCH HEATING CAN
TAKE PLACE DURING THE DAY. IF NO OUTFLOW BOUNDARY IS PRESENT AND IF
HEATING ONLY GETS US INTO THE LOWER 80S...SEVERE POTENTIAL TO BE
GREATLY REDUCED IF NOT ELIMINATED.     ...08...

.LONG TERM...
(SATURDAY THROUGH MONDAY)...
MODELS ARE IN GOOD AGREEMENT THAT H5 S/W AND WEAK SURFACE WAVE WILL
MOVE THROUGH CWA FRIDAY NIGHT. ETA FCST SOUNDINGS ARE SHOWING VERY
UNSTABLE AIR AHEAD OF THE SYSTEM WITH CAPES OVER 3K J/KG AT KBRL
BY LATE AFTERNOON.  WITH AMOUNT OF INSTABILITY AND GOOD MID LEVEL
FORCING...EXPECT A SEVERE WEATHER EVENT FOR THE CWA FRIDAY EVENING.
CURRENT THINKING HERE IS THAT LINEAR WIND PROFILES DURING THE
EVENING SUGGEST A DAMAGING WIND EVENT AS A SQUALL LINE SWEEPS ACROSS
THE CWA. LARGE HAIL WILL ALSO BE A THREAT AS MID LEVELS DRY
SIGNIFICANTLY THE NEXT 24 HOURS.  SYSTEM SHOULD MOVE TO OUR EAST BY
SATURDAY MORNING AND WILL HOLD ON LINGERING SHRA WORDING IN THE NERN
SECTIONS.  MORE S/W ENERGY MOVES OUT OF THE MEAN MID LEVEL WRN U.S.
TROF SATURDAY EVENING.  BOTH THE ETA AND THE GFS SHOW A SURFACE LOW
DEVELOPING OVER CNTRL KS AHEAD OF THE S/W BY SATURDAY EVENING.  FLOW
AHEAD OF THE DEVELOPING LOW WILL FOCUS LOW LEVEL MOISTURE
CONVERGENCE OVER NERN KS/SERN NE CREATING THE POTENTIAL FOR MCS
DEVELOPMENT SATURDAY NIGHT. MODELS ARE IN GOOD AGREEMENT SHIFTING
MEAN H5 TROF  EAST INTO THE PLAINS BY SUNDAY...BUT ARE HAVING
TROUBLE RESOLVING SMALL SCALE FEATURES MOVING THROUGH THE BASE OF
THE TROUGH. FOR NOW WILL GO WITH A BROAD BRUSH 30 POPS FOR SUNDAY
NIGHT INTO MONDAY.

LONG TERM...(TUESDAY THROUGH THURSDAY)...
MODELS DIFFERENCES BECOME MORE APPARENT BY MIDWEEK WITH RESPECT TO
VARIOUS SOLUTIONS ON HOW THE MID LEVEL FLOW EVOLVES DURING THE
PERIOD.  WITH LITTLE CONSISTENCY BETWEEN MODELS WILL STAY CLOSE TO
PREVIOUS FORECAST KEEPING DRY WEATHER FOR TUESDAY AND CHANCE POPS
FOR THE REST OF THE WEEK.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.

&&

DLF

HAZARDOUS WEATHER OUTLOOK...CORRECTION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
400 PM CDT THU JUN 10 2004

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-111000-
BENTON IA-BUCHANAN IA-BUREAU IL-CARROLL IL-CEDAR IA-CLARK MO-
CLINTON IA-DELAWARE IA-DES MOINES IA-DUBUQUE IA-HANCOCK IL-
HENDERSON IL-HENRY IA-HENRY IL-IOWA IA-JACKSON IA-JEFFERSON IA-
JO DAVIESS IL-JOHNSON IA-JONES IA-KEOKUK IA-LEE IA-LINN IA-LOUISA IA-
MCDONOUGH IL-MERCER IL-MUSCATINE IA-PUTNAM IL-ROCK ISLAND IL-
SCOTLAND MO-SCOTT IA-STEPHENSON IL-VAN BUREN IA-WARREN IL-
WASHINGTON IA-WHITESIDE IL-
400 PM CDT THU JUN 10 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST IOWA...
EAST CENTRAL IOWA...SOUTHEAST IOWA...NORTHWEST ILLINOIS...NORTH
CENTRAL ILLINOIS...WEST CENTRAL ILLINOIS AND NORTHEAST MISSOURI.

.DAY ONE...TONIGHT

SCATTERED THUNDERSTORMS OVER SOUTHEAST IOWA...WEST CENTRAL ILLINOIS
AND NORTHEAST MISSOURI WILL PRODUCE SOME LOCALLY HEAVY RAIN AND WIND
GUSTS OF 30 TO 40 MPH THIS EVENING.  A WEAK ISOLATED TORNADO WILL
ALSO BE POSSIBLE ALONG AND SOUTH OF HIGHWAY 34 AS THUNDERSTORMS
INTERACT WITH A WEAK SURFACE BOUNDARY OVER SOUTHEAST IOWA INTO WEST
CENTRAL ILLINOIS.  THE THREAT OF ANY TORNADO DEVELOPMENT SHOULD END
BY MID EVENING.

ANOTHER ROUND OF THUNDERSTORMS WILL BE POSSIBLE LATE
TONIGHT...MAINLY ALONG AND NORTH OF INTERSTATE 80.  LOCALLY HEAVY
RAIN WILL BE POSSIBLE AS THE STORMS MOVE EAST ALONG A FRONT STALLED
OVER EAST CENTRAL IOWA AND NORTHERN ILLINOIS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

SEVERE THUNDERSTORMS WILL BE POSSIBLE ACROSS PORTIONS OF EASTERN
IOWA AND NORTHWEST ILLINOIS LATE FRIDAY AFTERNOON AND FRIDAY NIGHT.
STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP IN WESTERN
AND CENTRAL IOWA FRIDAY AFTERNOON...AS AN UPPER LEVEL DISTURBANCE
INTERACTS WITH A STALLED OUT FRONT OVER THE REGION. OTHER ISOLATED
THUNDERSTORMS MAY FORM OVER EASTERN IOWA...ALONG THE STATIONARY
FRONT DURING THE LATE AFTERNOON HOURS. THERE WILL BE ENOUGH
INSTABILITY AND WIND SHEAR...DURING THE AFTERNOON AND EARLY
EVENING HOURS...TO ALLOW SOME STORMS TO BECOME SUPERCELLS.
THESE STORMS WILL BE CAPABLE OF PRODUCING VERY LARGE HAIL...DAMAGING
WINDS...AND TORNADOES. BY EVENING...THUNDERSTORMS ARE EXPECTED TO
FORM INTO A SQUALL LINE AND MOVE THROUGH MUCH OF EASTERN IOWA AND
NORTHWEST ILLINOIS.  DAMAGING WINDS...LARGE HAIL...AND A FEW
TORNADOES MAY OCCUR WITH THESE STORMS THROUGH LATE EVENING.  THE
GREATEST RISK FOR ANY TORNADOES WILL BE ALONG AND JUST NORTH OF THE
STATIONARY FRONT.  AT THIS TIME...THIS FRONT IS EXPECTED TO BE FROM
CEDAR RAPIDS...TO DAVENPORT...TO PRINCETON ILLINOIS FRIDAY
AFTERNOON.  STAY TUNED TO NOAA WEATHER RADIO...OR LOCAL MEDIA FOR
FURTHER UPDATES ON THIS POTENTIAL SEVERE WEATHER EVENT.

MORE THUNDERSTORMS WILL BE POSSIBLE SATURDAY NIGHT AND SUNDAY...AND
AGAIN TUESDAY NIGHT AND WEDNESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS POSSIBLE OVER NORTHWEST ILLINOIS TODAY...AND
MAY BE NEEDED OVER EASTERN IOWA AND NORTHWEST ILLINOIS LATE FRIDAY
AFTERNOON AND FRIDAY NIGHT.

REA/ERVIN/DLF