242
FXUS63 KDVN 091051
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
551 AM CDT SAT AUG 9 2025
KEY MESSAGES
- ACTIVE WEATHER IS EXPECTED THROUGH THE BEGINNING OF NEXT WEEK
WITH PERIODS OF SHOWERS AND THUNDERSTORMS LIKELY.
- FLASH FLOODING IS THE MAIN CONCERN THROUGH THE NEXT SEVERAL
DAYS WITH A MODERATE RISK (LEVEL 3 OF 4) FOR EXCESSIVE
RAINFALL. THE STRONGEST STORMS COULD PRODUCE TORRENTIAL
RAINFALL RATES BETWEEN 1-3" PER HOUR AND LOCALLY DAMAGING
WINDS.
- WIDESPREAD 2 TO 4 INCHES OF RAIN ARE POSSIBLE THROUGH MONDAY
WITH SOME AREAS RECEIVING HIGHER AMOUNTS.
SHORT TERM /THROUGH SUNDAY NIGHT/
ISSUED AT 315 AM CDT SAT AUG 9 2025
TODAY
ANOTHER HOT AND HUMID DAY IS EXPECTED FOR PARTS OF THE AREA
WITH HEAT INDICES REACHING THE UPPER 90S TO AROUND 100 MAINLY
NEAR AND SOUTHEAST OF THE QUAD CITIES. TO THE NORTHWEST, PEAK
HEAT INDICES MAY ONLY REACH INTO THE 80S. A SOUTHEASTWARD
PROGRESSING OUTFLOW BOUNDARY MAY REACH NW COUNTIES BY THE MID TO
LATE MORNING HOURS AND CONTINUE TO SLIDE TO THE EAST-SOUTHEAST
INTO THIS AFTERNOON BEFORE STALLING OUT NEAR THE MISSISSIPPI
RIVER. WITH DECAYING CONVECTIVE CLOUD DEBRIS SPREADING OVER THE
AREA AND A SLIGHTLY COOLER AIR MASS BEHIND THE BOUNDARY, A LARGE
PORTION OF THE AREA MAY REMAIN BELOW HEAT ADVISORY CRITERIA
TODAY. LOCATIONS NEAR THE QUAD CITIES AND TO THE SOUTH AND EAST
COULD REACH 100 DEGREE HEAT INDICES FOR SEVERAL HOURS DURING THE
EARLY/MID AFTERNOON. SINCE IT IS A MARGINAL HEAT EVENT, WILL
HOLD OFF ON A HEADLINE AND MESSAGE IMPACTS IN THE HWO AND IN
GRAPHICS. HAVE ALSO CONTINUED TO CAP THE DEWPOINTS TO THE
LOW/MID 70S WITH THE NBM'S UPPER 70S UNLIKELY TO VERIFY.
FLASH FLOODING POTENTIAL: A SURFACE LOW TRACKING THROUGH SOUTH-
CENTRAL CANADA WILL DRAG A WEAK SURFACE FRONT INTO THE MID TO
UPPER MISSISSIPPI VALLEY REGION TODAY. THE FRONT WILL
EFFECTIVELY STALL OUT ACROSS EASTERN IOWA AND NORTHWEST ILLINOIS
FOR THE NEXT FEW DAYS AS SOUTHWESTERLY FLOW ALOFT REMAINS
PARALLEL TO THE BOUNDARY. THIS SYNOPTIC SETUP WILL LIKELY
RESULT IN AREAS OF VERY HEAVY RAINFALL DUE TO SLOW MOVING AND
TRAINING CONVECTION (REPEATED ROUNDS OF STORMS). THE POTENTIAL
FOR HEAVY RAINFALL IS SUPPORTED BY VERY HIGH PWATS UPWARDS OF 2
TO 2.3" (~99 PERCENTILE PER ECMWF ENSEMBLE CLIMATOLOGY) AND
HIGH FREEZING LEVELS UP TO 16 KFT LEADING TO EFFICIENT WARM-RAIN
PROCESS. ADDITIONALLY, THE FORECAST MEAN 850-300MB FLOW IS
PARALLEL TO THE AFOREMENTIONED BOUNDARY, WHICH IS A FAVORABLE
SETUP FOR REPEATED ROUNDS OF STORMS AND EXCESSIVE RAINFALL FOR
SOME AREAS. A FLOOD WATCH REMAINS IN EFFECT FOR MOST OF THE AREA
EXCEPT THE FAR EAST/SOUTHEAST THROUGH MONDAY AM WITH POTENTIAL
FOR PEAK HOURLY RAIN RATES BETWEEN 1-3" FROM THE STRONGEST
STORMS.
THE 00Z/8.9 HREF PMM 48 HR QPF THROUGH 7 PM SUNDAY HAS A LARGE
AREA OF 1-3 INCHES ACROSS MUCH OF EASTERN IOWA INTO NORTHWEST
ILLINOIS WITH SCATTERED POCKETS OF 4"+. WPC HAS MAINTAINED THE
MODERATE RISKS (LEVEL 3 OF 4) FOR EXCESSIVE RAINFALL, FOR BOTH
TODAY/TONIGHT AND SUNDAY/SUNDAY NIGHT. TOTAL QPF FROM WPC IS
STILL IN THE 2 - 4" RANGE FOR MUCH OF THE AREA WITH POCKETS NEAR
5"+ POSSIBLE ACROSS THE NORTH AND WEST.
RISK FOR SEVERE STORMS: THE FIRST THREAT FOR ORGANIZED
CONVECTION IS FROM THE MID/LATE MORNING INTO THIS AFTERNOON FOR
AREAS MAINLY NORTH OF HIGHWAY 30. A MODERATELY UNSTABLE AIR
MASS WITH MLCAPE BETWEEN 1500-2500 J/KG AND MODEST SHEAR COULD
PROVIDE ENOUGH BALANCE TO MAINTAIN A STRONG WIND GUST THREAT
ACROSS THE NORTHERN OUTLOOK AREA THROUGH EARLY/MID AFTERNOON.
ATTENTION THEN TURNS TO THE POTENTIAL FOR REDEVELOPMENT OF
SCATTERED STORMS DURING PEAK HEATING THIS AFTERNOON AND EARLY
EVENING ALONG THE RESIDUAL OUTFLOW BOUNDARY. CONFIDENCE IS LOW
ON EXACT PLACEMENT OF NEW STORM DEVELOPMENT. LATEST RUNS OF THE
HRRR PUT THE BOUNDARY ALONG THE MISSISSIPPI RIVER COUNTIES THIS
AFTERNOON WITH SOME POTENTIAL FOR CI NEAR THE QUAD CITIES AND TO
THE SOUTH/SOUTHEAST. IF STORMS FORM DURING THIS TIME, HIGH
INSTABILITY (MLCAPE 3000+ J/KG) WOULD BE SUPPORTIVE OF LOCALIZED
DAMAGING WINDS AS THE PRIMARY THREAT, AND WITH THE HIGH
HUMIDITY TORRENTIAL RAINFALL IS ALSO A CONCERN.
LATE TONIGHT THROUGH SUNDAY NIGHT:
ANOTHER ROUND OF CONVECTION IS EXPECTED TO DEVELOP TO OUR WEST
ACROSS PORTIONS OF WESTERN AND CENTRAL IOWA LATE TONIGHT ON THE
NOSE OF AN 850MB JET ACCOMPANIED BY STRONG WV TRANSPORT. THIS
ACTIVITY IS EXPECTED TO GROW UPSCALE AND SLOWLY TRACK TO THE
EAST INTO OUR WESTERN COUNTIES MAINLY AFTER MIDNIGHT AND COULD
POSE AN ISOLATED FLASH FLOOD THREAT THROUGH THE NIGHT INTO
EARLY SUNDAY AM. AT THIS TIME, THE HEAVIEST RAINFALL IS
ANTICIPATED WEST OF THE MISSISSIPPI RIVER FOR THIS PERIOD. THIS
PATTERN LOOKS TO REPEAT ITSELF AGAIN LATER SUNDAY/SUNDAY NIGHT
WITH ADDITIONAL ROUNDS OF CONVECTION FIRING TO OUR WEST ACROSS
CENTRAL IOWA AND THEN TRACKING TOWARD THE EAST INTO OUR
FORECAST AREA. BY THIS TIME, PARTS OF THE AREA WILL LIKELY BE
SATURATED FROM THE SEVERAL INCHES OF RAIN THAT MAY HAVE ALREADY
FALLEN, SO IT WON'T TAKE MUCH TO REACH FLASH FLOOD GUIDANCE WITH
MOST OF WHAT FALLS BEING IMMEDIATELY CONVERTED TO RUNOFF.
LONG TERM /MONDAY THROUGH FRIDAY/
ISSUED AT 315 AM CDT SAT AUG 9 2025
ACTIVE WEATHER IS EXPECTED EARLY IN THE WEEK WITH A SURFACE
BOUNDARY DRAPED ACROSS EASTERN IOWA AND NORTHWEST ILLINOIS, AND
SOUTHWESTERLY FLOW ALOFT GUIDING OCCASIONAL COMPLEXES OF
SHOWERS AND THUNDERSTORMS THROUGH THE REGION. THIS COULD RESULT
IN ADDITIONAL AREAS OF HEAVY RAINFALL, MAINLY ON MONDAY AND
MONDAY NIGHT. A SHORTWAVE TROUGH IS FORECAST TO SWING THROUGH
THE GREAT LAKES ON TUESDAY, WHICH SHOULD HELP TO PUSH THE FRONT
TO THE SOUTHEAST OF THE AREA AND GIVE US A REPRIEVE FROM THE
HEAVY RAIN. SEASONABLE TEMPERATURES IN THE 80S AND HUMID
CONDITIONS LOOK TO CONTINUE THROUGH THE WEEK.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 537 AM CDT SAT AUG 9 2025
MAIN CONCERNS THROUGH THE PERIOD WILL BE OCCASIONAL CHANCES FOR
SCATTERED SHOWERS AND THUNDERSTORMS AS A SURFACE BOUNDARY STALLS
OUT ACROSS EASTERN IOWA AND NORTHWEST ILLINOIS. CONFIDENCE REMAINS
LOW REGARDING THE MOST LIKELY TIMING AND PLACEMENT OF SHOWERS/STORMS
DUE TO THE EXPECTATION FOR SCATTERED COVERAGE. USED PROB30S TO
MESSAGE THUNDER POTENTIAL AT CID AND DBQ FOR THE LATE MORNING
INTO AFTERNOON PERIOD, AND ONLY SHOWERS FOR NOW AT MLI/BRL.
ADDITIONAL SCATTERED DEVELOPMENT IS POSSIBLE LATE THIS AFTERNOON
AND EVENING, AND AGAIN LATE TONIGHT (AFTER 06Z/SUNDAY). ANTICIPATE
PREVAILING VFR THROUGH THE PERIOD WITH ONLY BRIEF MVFR/IFR
POSSIBLE IN THE VICINITY OF ANY SHOWERS/STORMS.
HYDROLOGY
ISSUED AT 313 PM CDT FRI AUG 8 2025
RISES ON AREA RIVERS ARE EXPECTED THROUGH THE WEEKEND AND INTO NEXT
WEEK. NCRFC IS USING 24 HOURS OF QPF IN THEIR FORECASTS. WHILE
THIS MAY NOT CAPTURE THE MAJORITY OF THE RAINFALL WE EXPECT TO
SEE, LOW CONFIDENCE ON QPF PAST 24 HOURS MAKES FORECASTS LONGER
THAN THAT SUBJECT TO WILD SWINGS. THAT SAID, WE EXPECT SOME
RIVERS IN FLOOD TO START RISING AGAIN AND POSSIBLY TO HIGHER
CRESTS. ADDITIONAL RIVERS MAY ENTER FLOOD STAGE AS WELL. WITH
THE CORN TASSELED OUT, WE EXPECT TO SEE MAYBE MORE RUNOFF THAN
WE HAVE IN THE LAST FEW WEEKS AS THE CROPS ARE STORING LESS
WATER NOW. STAY TUNED TO ADDITIONAL FORECASTS INTO THE WEEKEND.
DVN WATCHES/WARNINGS/ADVISORIES
IA...FLOOD WATCH FROM 1 PM CDT THIS AFTERNOON THROUGH MONDAY
AFTERNOON FOR IAZ040>042-051>054-063>068-076>078-087>089-
098-099.
IL...FLOOD WATCH FROM 1 PM CDT THIS AFTERNOON THROUGH MONDAY
AFTERNOON FOR ILZ001-002-007-009-015-016-024>026-034.
MO...FLOOD WATCH FROM 1 PM CDT THIS AFTERNOON THROUGH MONDAY
AFTERNOON FOR MOZ009-010.
SHORT TERM...UTTECH
LONG TERM...UTTECH
AVIATION...UTTECH
HYDROLOGY...GIBBS
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