Severe Thunderstorm Warning 111, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
307 PM CDT SUN AUG 9 2009

.SYNOPSIS...
H5 RIDGE HAS MOVED TO THE SOUTHEAST CONUS RESULTING IN SOUTHWEST
FLOW ALOFT ACROSS THE PLAINS AND MIDWEST. NUMEROUS SHORTWAVES AND
VORT MAXES WERE EMBEDDED IN THE FLOW WITH ONE NEAR THE MISSOURI
RIVER AND SEVERAL OTHERS IMMEDIATELY BEHIND IT. SATELLITE/RADAR
TRENDS INDICATE CONVECTION RUNNING FROM SOUTHEAST NEBRASKA
NORTHEAST INTO WISCONSIN. ABBREVIATED 18Z SFC ANALYSIS HAS A LOW
IN NORTH CENTRAL KANSAS WITH THE FRONT EXTENDING INTO SOUTHERN
IOWA. THE FRONT IS NOT DEFINED ACROSS IOWA DUE TO THE NUMEROUS
MESOSCALE OUTFLOW BOUNDARIES. A WAKE LOW WAS OVER KALO WITH A MESO
HIGH JUST NORTH OF THE DES MOINES METRO AREA. SFC DEW POINTS WERE
IN THE LOW TO MID 70S ACROSS THE AREA WHILE PRECIPITABLE WATERS
WERE APPROACHING 2 INCHES FROM SOUTHERN LAKE MICHIGAN INTO
NORTHEAST KANSAS.

&&

.DISCUSSION...
CURRENTLY RUNNING WELL BEHIND AND THERE IS MUCH TO TALK ABOUT. I
WILL TRY TO GET THE AFTERNOON PACKAGE OUT AS CLOSE TO ON TIME AS
POSSIBLE BUT SOME DELAY IS EXPECTED.

CURRENT AREAL COVERAGE FOR HEAT LOOKS GOOD AND WILL LET IT
CONTINUE TO EXPIRATION. MESOSCALE SITUATION IS SETTING UP FOR A
NEAR CLASSIC HEAVY RAIN/FLASH FLOOD EVENT FOR TONIGHT. AS A
RESULT...HEADLINES FOR WATER WILL BE ISSUED WITH THE AFTERNOON
PACKAGE. DUE TO UNCERTAINTY...ADDED A BUFFER OF COUNTIES TO THE
WATCH AREA AND ALSO EXTENDED THE WATCH UNTIL MID MONDAY MORNING TO
COVER THE MORNING COMMUTE.

CONVECTION SHOULD RE-FIRE THIS EVENING AND EVOLVE INTO A CLASSIC
HEAVY RAIN MCS ON THE COLD SIDE OF THE BOUNDARIES. THE ACTUAL COLD
FRONT WILL CONTINUE TO SLOWLY SAG SOUTH AND EAST AND PROVIDE AN
EFFECTIVE BOUNDARY FOR HEAVY RAIN. THE LOW IN NORTHEAST KANSAS IS
PROGGED TO MOVE ALONG THE FRONT AND ENHANCE THE LIFT.

CONVECTION WILL STILL BE ONGOING MONDAY MORNING AND RESIDUAL
BOUNDARIES WILL PROLONG PRECIP THROUGH AT LEAST THE MORNING HOURS.
ANY DIURNAL HEATING ALONG WITH THE BOUNDARIES MAY ALLOW ADDITIONAL
CONVECTION TO FIRE IN THE AFTERNOON.

MONDAY NIGHT/TUESDAY...ANOTHER WAVE MOVES ALONG THE FRONT WHICH
MAY ALLOW SOME ADDITIONAL CONVECTION TO AFFECT THE SOUTHERN THIRD
OF THE CWFA. THIS DEVELOPMENT WILL BE HIGHLY DEPENDENT ON WHAT
HAPPENS DURING THE DAY ON MONDAY. IT IS CONCEIVABLE THAT LITTLE OR
NO PRECIP MAY OCCUR ACROSS THE SOUTH MONDAY NIGHT/TUESDAY.

TUESDAY NIGHT ON...GENERALLY QUIET WX WILL BE SEEN WITH TEMPERATURES
AROUND OR SLIGHTLY ABOVE NORMAL. HOWEVER...THERE IS AN IMPORTANT
CAVEAT. FEATURES THAT HELP GENERATE CONVECTION DURING THE SUMMER ARE
INHERENTLY WEAK AND ARE LIKELY BEING SMOOTHED OUT IN THE MODEL
SOLUTIONS. THEREFORE...WHILE MUCH OF THE TIME PERIOD WILL LIKELY BE
DRY...ONE CANNOT RULE OUT DIURNAL CONVECTION DEVELOPING LATER IN THE
WEEK AS BETTER MOISTURE BEGINS FLOWING NORTH AGAIN.
...08...

&&

.AVIATION...
A COLD FRONT WILL SLOWLY CROSS EASTERN IOWA TONIGHT.  THUNDERSTORMS
ARE EXPECTED TO CONTINUE TO DEVELOP ALONG THE FRONT MOVING NORTHEAST
AND AFFECTING AREA TAF SITES INTERMITTENTLY THROUGH 18Z.  OUTSIDE OF
THUNDERSTORMS...VFR CIGS ARE EXPECT AT KBRL AND AND MVFR CIGS AT
KCID/KDBQ/KMLI.
...33...

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...FLASH FLOOD WATCH THROUGH MONDAY MORNING FOR BENTON-BUCHANAN-
     CEDAR-CLINTON-DELAWARE-DUBUQUE-IOWA-JACKSON-JOHNSON-JONES-
     LINN.

     HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR DES MOINES-HENRY
     IA-JEFFERSON-KEOKUK-LEE-LOUISA-MUSCATINE-SCOTT-VAN BUREN-
     WASHINGTON.

IL...FLASH FLOOD WATCH THROUGH MONDAY MORNING FOR CARROLL-JO DAVIESS-
     STEPHENSON.

     HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR BUREAU-HANCOCK-
     HENDERSON-HENRY IL-MCDONOUGH-MERCER-PUTNAM-ROCK ISLAND-
     WARREN.

MO...HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR CLARK-SCOTLAND.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
459 AM CDT SUN AUG 9 2009

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-101000-
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-
459 AM CDT SUN AUG 9 2009

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...TODAY AND TONIGHT

DANGEROUS HEAT AND HUMIDITY WILL CONTINUE OVER MUCH OF THE AREA
TODAY. HEAT INDEX VALUES WILL AGAIN REACH 100 TO 105 DEGREES AND
LAST THROUGH EARLY EVENING. A HEAT ADVISORY REMAINS IN EFFECT THROUGH
THIS EVENING FOR AREAS GENERALLY SOUTH OF HIGHWAY 20. A COOL FRONT
PUSHING TOWARD THE AREA MAY PRODUCE AREAS OF CLOUDS AND SCATTERED
THUNDERSTORMS...WHICH WOULD BRING SOME RELIEF FROM THE HEAT BY MID
AFTERNOON IN AREAS WEST OF A LINE FROM WASHINGTON IOWA...UP TOWARD
DUBUQUE.

THE COLD FRONT WILL BRING A ROUND OF STRONG TO SEVERE THUNDERSTORMS
TO PORTIONS OF THE OUTLOOK AREA THIS EVENING AND OVERNIGHT. THE
PRIMARY THREAT IS EXPECTED TO BE DAMAGING WINDS UP TO 65 MPH AS THESE
STORMS DEVELOP IN WESTERN AND CENTRAL IOWA AND THEN MOVE ACROSS THE
LOCAL AREA. A SECONDARY THREAT WOULD BE LARGE HAIL IF A FEW STORMS
WHERE ABLE TO DEVELOP THIS AFTERNOON RIGHT OVER THE OUTLOOK AREA.
THESE STORMS WILL HAVE LARGE AMOUNTS OF MOISTURE TO WORK WITH AND
HEAVY RAINFALL WILL ALSO BE A THREAT. AREAS THAT RECEIVE REPEATED
THUNDERSTORM ACTIVITY THIS AFTERNOON AND ESPECIALLY TONIGHT WILL
HAVE THE POTENTIAL OF ACCUMULATING 1 TO 3 INCHES OF RAINFALL WITH
LOCALLY HIGHER AMOUNTS BY MONDAY MORNING. THIS TYPE OF RAINFALL
FALLING ON AREAS THAT HAVE ALREADY RECEIVED HEAVY RAINFALL OVER THE
PAST FEW DAYS WOULD PRODUCE A FLASH FLOOD THREAT...AS WELL AS
SIGNIFICANT RISES ON AREA RIVERS AND STREAMS.

THE STORM PREDICTION CENTER HAS PLACED AREAS ALONG AND NORTH OF A
LINE FROM MEMPHIS MISSOURI...TO MONMOUTH AND PRINCETON ILLINOIS IN A
SLIGHT RISK FOR SEVERE STORMS FOR LATE TODAY AND TONIGHT.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

MONDAY WILL CONTINUE TO SEE THE THREAT FOR THUNDERSTORMS...WITH SOME
HEAVY RAIN AND ISOLATED SEVERE STORMS POSSIBLE. THE STORM PREDICTION
CENTER IS FORECASTING A SLIGHT RISK FOR SEVERE STORMS OVER THE ENTIRE
OUTLOOK AREA. THE THREAT FOR SEVERE STORMS WILL END FROM WEST TO EAST
DURING THE DAY AS A COLD FRONT MOVES OUT AWAY FROM THE AREA. THE
PRIMARY THREATS FROM STRONG STORMS WILL BE GUSTY WINDS AND HEAVY RAIN
AMOUNTS.

A LOW CHANCE FOR NON SEVERE THUNDERSTORMS WILL CONTINUE THROUGH
TUESDAY SOUTH OF HIGHWAY 34.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TODAY AND TONIGHT.

12/ERVIN

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