Severe Thunderstorm Warning 240, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
257 PM CDT MON JUL 21 2008

.SYNOPSIS...
FRONTAL BOUNDARY ACROSS SOUTHERN IOWA WILL BE THE FOCUS FOR
CONVECTION TONIGHT...WITH FRONT GRADUALLY SHIFTING SOUTHWARD. HIGH
PRESSURE BUILDING INTO THE GREAT LAKES REGION SHOULD BRING MORE
PLEASANT CONDITIONS FOR MID WEEK. FOR THURSDAY AND FRIDAY WARM FRONT
RETURNS TO THE REGION BRINGING BACK THUNDERSTORM CHANCES. ANOTHER
HIGH PRESSURE SYSTEM DROPS SOUTHWARD INTO THE UPPER MIDWEST FOR THIS
UPCOMING WEEKEND...WITH ACTIVE FRONTAL BOUNDARY NEARBY IN MO.

&&

.SHORT TERM...TONIGHT AND TUESDAY...
FRONTAL BOUNDARY LIES ACROSS SOUTHERN IOWA AND WILL BE THE FOCUS FOR
INTENSE THUNDERSTORMS TOWARDS EVENING. STRONG TEMPERATURE CONTRAST
EXISTS WITH TEMPERATURES WELL INTO THE 90S TO NEAR 100 IN KS AND MO
WHILE READINGS ONLY IN THE 70S IN SOUTHERN WI. AIRMASS IS CAPPED
SOUTH OF BOUNDARY BUT SHOULD WEAKEN BY EVENING. 18Z SPECIAL BALLOON
LAUNCH AT KDVN SHOWED 500 MB WIND SPEED OF 60 KNOTS WHICH WILL
SUPPORT DAMAGING WINDS IN THE STRONGER STORMS. WILL NEED TO KEEP AN
EYE OUT FOR BOWING SEGMENTS WHICH WILL ENHANCE WIND DAMAGE. WILL
HAVE MENTION OF SEVERE IN THE GRIDS. BULK OF SEVERE WEATHER SHOULD
BE OVER WITH BY MIDNIGHT WITH FRONT SAGGING FARTHER SOUTHWARD. WILL
KEEP SLIGHT CHANCE OF STORMS FOR TUESDAY IN OUR FAR SOUTHERN CWA
WITH FRONTAL BOUNDARY IN NORTHERN MO. OTHERWISE BULK OF THE CWA WILL
HAVE QUIET WEATHER WITH GRADUALLY LOWERING HUMIDITIES.

..HAASE..

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY...
TUE NIGHT THROUGH WED STILL LOOKS TO BE A QUIET WEATHER PERIOD WITH
AREA IN UPPER LEVEL NW FLOW BETWEEN NORTHERN PLAINS RIDGE AXIS AND
LOW OVER EASTERN GREAT LAKES. AT SURFACE...HIGH PRESSURE OVER
WESTERN GREAT LAKES WILL FEED SEASONABLY COOL AND DRY AIR INTO THE
REGION. THIS WILL MINS LOWS TO DROP INTO THE 50S NORTH OF I-80 WITH
HIGHS IN UPPER 70S TO LOWER 80S.

BEST CHANCE FOR THUNDERSTORMS THROUGHOUT WILL BE LATE WED NIGHT INTO
THU NIGHT AS UPPER LEVEL SHORTWAVE TOPS THE RIDGE AXIS AND PASSES SE
ACROSS THE REGION. THIS ALLOWS DEEPER MOISTURE TO SURGE NORTH INTO
THE CENTRAL PLAINS. WILL KEEP LOW POPS WED NIGHT IN THE ESPECIALLY
THE WESTERN CWFA FOR ELEVATED CONVECTION ON THE DEVELOPING
NOCTURNAL JET. MODELS DEPICT MAIN SHORTWAVE AND STRONGEST FORCING
ACROSS EASTERN IA THU MORNING AND HAVE NARROWED CHANCE POPS TO
MAINLY THIS PERIOD. SLIGHT CHANCES MAINTAINED FOR THU NIGHT INTO FRI
AS MODELS SUGGESTING LOW POTENTIAL FOR ADDITIONAL THUNDERSTORMS WITH
PASSAGE OF WEAK COLD FRONT.

FRI NIGHT THROUGH MON...NW FLOW CONTINUES WITH ECMWF MAINTAINING THE
SYNOPTIC FRONT FURTHER SOUTH THAN THE GFS AND THUS KEEPING ANY
POTENTIAL PRECIPITATION SOUTH OF THE AREA. HAVE MAINTAINED CONTINUITY
WITH THIS SOLUTION WITH HIGHS IN 80S AND LOWS IN 60S THROUGHOUT.
..SHEETS..

&&

.AVIATION...
THUNDERSTORMS SHOULD INCREASE IN COVERAGE AND INTENSITY LATER THIS
AFTERNOON AND INTO EARLY TONIGHT...ESPECIALLY SOUTH OF HIGHWAY 30.
MVFR TO OCNL IFR CONDITIONS IN THUNDERSTORMS. STORMS SHOULD
GRADUALLY SHIFT SOUTH AND EAST OF THE TAF SITES BY MIDNIGHT. VFR
CONDITIONS EXPECTED LATER TONIGHT AND TUESDAY AS HIGH PRESSURE
BUILDS INTO THE GREAT LAKES. LIGHT AND VARIABLE WINDS LATER TONIGHT
WITH NORTHEAST WINDS AROUND 10 KNOTS ON TUESDAY.

..HAASE..

&&

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

&&

HAASE/SHEETS

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
312 PM CDT MON JUL 21 2008

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-221000-
BUCHANAN-DELAWARE-DUBUQUE-BENTON-LINN-JONES-JACKSON-IOWA-JOHNSON-
CEDAR-CLINTON-MUSCATINE-SCOTT-KEOKUK-WASHINGTON-LOUISA-JEFFERSON-
HENRY IA-DES MOINES-VAN BUREN-LEE-JO DAVIESS-STEPHENSON-CARROLL-
WHITESIDE-ROCK ISLAND-HENRY IL-BUREAU-PUTNAM-MERCER-HENDERSON-
WARREN-HANCOCK-MCDONOUGH-SCOTLAND-CLARK-
312 PM CDT MON JUL 21 2008

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

.DAY ONE...THIS AFTERNOON AND TONIGHT
THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON
AND INTO EARLY TONIGHT ALONG AND SOUTH OF HIGHWAY 34. WIDESPREAD
DAMAGING WINDS IN EXCESS OF 70 MPH IS THE MAIN THREAT.

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON
AND INTO EARLY TONIGHT BETWEEN HIGHWAY 30 AND HIGHWAY 34. THE MAIN
THREAT FROM THESE STORMS WILL BE DAMAGING WINDS IN EXCESS OF 60 MPH.
LARGE HAIL AND LOCALLY HEAVY RAIN IS A SECONDARY THREAT.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY
THERE IS A CHANCE OF THUNDERSTORMS ON THURSDAY. IT IS TOO EARLY TO
DETERMINE THE SEVERE WEATHER POTENTIAL.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL BE NEEDED LATE THIS AFTERNOON INTO EARLY
TONIGHT.

HAASE

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