Flash Flood Warning 57, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
335 AM CDT FRI AUG 24 2007

.DISCUSSION...
00Z UA ANALYSIS SHOWED A MOISTURE RICH SWLY H8 FLOW FROM THE SRN
PLAINS THROUGH THE MID MS VALLEY...JUST SOUTH OF A WK H8 FRONT OVER
NW IA.  AT H5 THE MAIN MID LEVEL TROF WAS OVER THE ROCKIES WITH A
COUPLE OF WEAK IMPULSES AHEAD OF THE MAIN TROF OVER THE CENTRAL AND
NORTHERN PLAINS.  AN E-W LINE OF TSRA HAS BEEN SLOWLY SAGGING SOUTH
THROUGH SRN IA SINCE THURSDAY EVENING.  THE CONVECTION APPEARS TO BE
TIED TO LOW LEVEL MOISTURE CONVERGENCE AND ENTRANCE REGION OF H3 JET
STREAK FROM NERN NE INTO SRN MN.

TSRA/HVY RAIN TRENDS FOR TODAY WILL BE THE MAIN CONCERN BECAUSE OF
THE SIGNIFICANT FLASH FLOOD THREAT OVER THE AREA .  CURRENT
THINKING IS THAT THE SRN 1/3 OF THE CWA WILL HAVE THE GREATEST
THREAT OF ADDITIONAL HEAVY RAINS TODAY AS TSRA CONTINUE TO DEVELOP
AND MOVE E OR NE ALONG AND AHEAD OF THE SURFACE FRONT SAGGING SOUTH
THROUGH SERN IA.  SURFACE WAVE OVER NERN KS IS PROGGED TO LIFT NE
ALONG THE BOUNDARY THIS MORNING.  THIS WILL ENHANCE THE TSRA/HVY
RAIN OVER NRN MO...SRN IA AND CENTRAL IL THROUGH 18Z.  THUS THE
GREATEST RISK FOR SIGNIFICANT FLASH FLOODING.  THIS AFTERNOON
BECOMES A LITTLE MORE UNCERTAIN AS THE UPPER TROF MOVES OUT OF THE
ROCKIES AND APPROACHES TO MID MS VALLEY BY THIS EVENING.  THE
CONVECTIVE FEEDBACK ON THE GFS WAS PRODUCING SIGNIFICANT QPF OVER
THE NORTHEN CWA THIS AFTERNOON/EVENING WHILE THE NAM WAS KEEPING IT
FURTHER SOUTH...TIED TO THE MAIN SURFACE FRONT.  HOWEVER...WITH
STRONG TSRA CURRENTLY ALONG THE IA/MO BORDER AND AN AREA OF STRONG
TSRA MOVING EAST OUT OF NERN KS AHEAD OF THE SURFACE WAVE...THE
BETTER SURFACE INSTABILITY AND CONVERGENCE MAY BE SHIFTED FURTHER
SOUTH THIS AFTERNOON...FOCUSING TSRA DEVELOPMENT OVER MO RATHER THAN
SRN IA.   WITH THE UNCERTAINTY ABOUT THIS AFTERNOON AND EVENING HAVE
ELECTED TO KEEP CURRENT FLASH FLOOD WATCH IN PLACE FOR THE ENTIRE
CWA...ESPECIALLY SINCE MOST AREAS CAN NOT TAKE ANY ADDITIONAL HEAVY
RAINS.  THIS SHOULD GIVE THE NEXT SHIFT TIME TO ASSESS THE TRENDS
AND MAKE THE NECESSARY ADJUSTMENTS TO THE AREA AND/OR TIMING OF THE
WATCH.

AFTER THE MID LEVEL TROF MOVES THROUGH TONIGHT...THE SURFACE FRONT
WILL ACCELERATE SOUTHEAST BRINGING A MUCH NEEDED BREAK FROM THE RAIN
BY SATURDAY.  WE SHOULD BE IN FOR A STRETCH OF DRY WEATHER UNTIL MID
WEEK WHEN MODELS SHOW ANOTHER FRONT MOVING INTO THE AREA.  HIGH
PRESSURE BUILDING INTO THE CWA WILL ALSO BRING IN MORE COMFORTABLE
AIR AS DEWPOINTS DROP BACK INTO THE UPPER 50S TO MID 60S BY SUNDAY
AND TEMPS SETTLE BACK INTO THE UPPER 70S TO LOW 80S.  WARM AND HUMID
CONIDITIONS WILL RETURN AGAIN EARLY NEXT WEEK AS SOUTHERLY FLOW SETS
UP AHEAD OF THE NEXT FRONT.  ..DLF...

&&

.AVIATION...
SEVERAL LARGE THUNDERSTORM COMPLEXES WILL CONTINUE TO MOVE ALONG A
STATIONARY FRONT DRAPED ACROSS NORTHWEST MISSOURI THROUGH EASTERN
IOWA INTO NORTHWEST ILLINOIS TODAY. THESE WILL RESULT IN IFR CIGS
AND VISIBILITIES WITH INTENSE RAINFALL RATES...WITH BRL AND MLI
TERMINALS IMPACTED THE MOST. OUTSIDE OF THUNDERSTORMS...POOLING LOW
LEVEL MOISTURE WILL RESULT IN WIDESPREAD MVFR CIGS AND VISIBILITIES
AND AREAS DIPPING INTO IFR CRITERIA THIS MORNING. THUNDERSTORMS WILL
FINALLY EXIT THE AREA LATE TONIGHT INTO SATURDAY MORNING AS THE
FRONT PUSHES SOUTHEAST. HOWEVER...LINGERING MOISTURE WILL SUPPORT
AREAS OF IFR STRATUS AND FOG THROUGH MID MORNING. ..SHEETS..

&&

.HYDROLOGY...
FLOODING IS OCCURRING OR WILL OCCUR SOON AT NUMEROUS FORECAST POINTS
IN THE HSA.  FORECASTS FOR PARTS OF THE CEDAR AND WAPSIPINICON
RIVERS IN THE NORTHERN PART OF THE HSA WERE LOWERED DUE TO THE
HEAVIER PCPN SETTING UP FURTHER SOUTH THURSDAY AND THURSDAY NIGHT.
HOWEVER...FORECASTS FOR THE ROCK RIVER IN NORTHERN ILLINOIS HAVE
BEEN BUMPED INTO THE MAJOR FLOOD CATEGORY...FOR COMO...JOSLIN AND
MOLINE. HYDROLOGIC MODEL RUNS FROM THURSDAY AFTERNOON AND EVENING
HAVE BEEN CONSISTENT IN RAISING THESE POINTS INTO THE MAJOR FLOOD
CATEGORY. 24 HOUR RAINFALL ESTIMATES OF 1 TO 3 INCHES OVER THE LOWER
PORTIONS OF THE ROCK RIVER...ENDING THURSDAY NIGHT...ALSO LEND
CREDIBILITY TO THE HIGHER FORECAST.  MINOR TO MODERATE FLOODING IS
FORECAST TO OCCUR AT MOST LOCATIONS NEAR OR SOUTH OF INTERSTATE 80
IN SERN IA...ON THE WAPSIPINICON...CEDAR...IOWA...DES MOINES AND
MISSISSIPPI RIVERS DURING THE NEXT SEVERAL DAYS. AT THIS
POINT...THESE FORECASTS WERE BASED ON THE THE HEAVIER RAINS STAYING
SOUTH OF INTERSTATE 80 THROUGH FRIDAY EVENING.  CURRENT CONVECTIVE
TRENDS ARE SUPPORTING THIS QPF FORECAST.  ALTHOUGH SOME FORECAST
MODELS ARE TRYING TO BRING THE HEAVIER RAIN FUTHER NORTH.  IF THIS
WERE TO OCCUR THEN THE ADDITIONAL RUNOFF COULD PUSH THE RIVERS IN
SOUTH EAST AND EAST CENTRAL IOWA AND NORTHWEST ILLINOIS HIGHER THAN
CURRENTLY FORECAST. ...DLF...

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...FLASH FLOOD WATCH THROUGH THIS EVENING.

IL...FLASH FLOOD WATCH THROUGH THIS EVENING.

MO...FLASH FLOOD WATCH THROUGH THIS EVENING.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
525 AM CDT FRI AUG 24 2007

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-251030-
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-
525 AM CDT FRI AUG 24 2007

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

THERE IS A THREAT OF FLASH FLOODING OVER MUCH OF THE AREA
TODAY. THE GROUND IS NEARLY SATURATED FROM THE HEAVY RAINS THAT
HAVE FALLEN DURING THE LATE SEVERAL DAYS. THE ADDITIONAL RAIN THAT
IS EXPECTED TODAY MAY RESULT IN FLASH FLOODS. THE GREATEST RISK OF
FLASH FLOODING WILL BE SOUTHEAST OF A LINE FROM NEAR OTTUMWA
THROUGH THE QUAD CITIES...WHERE PERIODS OF THUNDERSTORMS THROUGH
THIS AFTERNOON COULD PRODUCE ANOTHER 1 TO 3 INCHES OF RAIN.

THERE IS ALSO A THREAT OF SEVERE THUNDERSTORMS THIS AFTERNOON AND
THIS EVENING...SOUTHEAST OF A LINE RUNNING THROUGH
KEOSAUQUA...WAPELLO AND GENESEO.  DAMAGING STRAIGHT LINE WINDS
WILL BE THE GREATEST SEVERE THREAT.

MANY RIVERS IN THE AREA ARE OUT OF THEIR BANKS OR ARE EXPECTED TO
RISE OUT OF THEIR BANKS DURING THE NEXT SEVERAL DAYS. MINOR TO
MODERATE FLOODING IS EXPECTED ON PARTS OF THE
CEDAR...IOWA...WAPSIPINICON...ENGLISH...SKUNK AND DES MOINES
RIVERS. MODERATE FLOODING IS EXPECTED ON PARTS OF THE PECATONICA
RIVER...WITH MAJOR FLOODING FORECAST ON PARTS OF THE ROCK RIVER.
THE MISSISSIPPI WILL EXPERIENCE MINOR TO MODERATE FLOODING FROM
THE QUAD CITIES SOUTH THROUGH GREGORY LANDING.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THUNDERSTORMS ARE EXPECTED TO MOVE BACK OVER THE AREA TUESDAY AND
WEDNESDAY. AT THIS TIME IT IS TO SOON TO DETERMINE IF THEY WILL POSE A
SEVERE WEATHER THREAT.

THE WIDESPREAD RIVER FLOODING WILL CONTINUE THROUGH THE MIDDLE OF
NEXT WEEK.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND THIS EVENING
IN SOUTHEAST IOWA...WEST CENTRAL ILLINOIS AND NORTHEAST MISSOURI.

DLF

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
610 AM CDT FRI AUG 24 2007

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0605 AM     HEAVY RAIN       N KAHOKA                40.42N 91.72W
08/24/2007  M2.20 INCH       CLARK              MO   TRAINED SPOTTER

            RAINFALL SINCE 930 PM

&&

SHEETS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
658 AM CDT FRI AUG 24 2007

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0656 AM     HEAVY RAIN       DALLAS CITY             40.63N 91.16W
08/24/2007  M2.07 INCH       HANCOCK            IL   TRAINED SPOTTER

            24 HOUR TOTAL.

&&

ELLIOTT

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
700 AM CDT FRI AUG 24 2007

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0656 AM     HEAVY RAIN       BIBLE GROVE             40.35N 92.30W
08/24/2007  M6.40 INCH       SCOTLAND           MO   TRAINED SPOTTER

            1.10 FROM 1130 AM ON 23 AUG TO 10 PM. THEN 5.30 INCHES
            SINCE 10 PM LAST NIGHT.

&&

ELLIOTT

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
727 AM CDT FRI AUG 24 2007

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0725 AM     HEAVY RAIN       CANTRIL                 40.64N 92.07W
08/24/2007  M5.00 INCH       VAN BUREN          IA   TRAINED SPOTTER

            SINCE 9 PM ON 23 AUG.

&&

ELLIOTT

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
750 AM CDT FRI AUG 24 2007

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0749 AM     HEAVY RAIN       3 S STOCKPORT           40.81N 91.83W
08/24/2007  M4.70 INCH       VAN BUREN          IA   TRAINED SPOTTER

            12 HOUR TOTAL.

&&

ELLIOTT

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
759 AM CDT FRI AUG 24 2007

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0759 AM     HEAVY RAIN       WEVER                   40.72N 91.23W
08/24/2007  M4.00 INCH       LEE                IA   TRAINED SPOTTER

            TOTAL SINCE 4 PM ON 23 AUG.

&&

ELLIOTT