725
FXUS63 KDVN 200553
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1253 AM CDT SUN SEP 20 2026
..06Z AVIATION UPDATE
KEY MESSAGES
- AN INCREASINGLY SYNOPTIC SUPPORTED HEAVY RAIN SET UP CONTINUES
TO EVOLVE TODAY, JUST HOURS FOLLOWING THIS DISSIPATION OF
LAST NIGHT'S HEAVY RAIN MCS.
- HEAVY RAINS WILL AGAIN BREAK OUT TONIGHT, ESPECIALLY ALONG AND NORTH
OF I-80 AND NEAR AND SOUTH OF HIGHWAY 20. THIS AREA IS
ALREADY SATURATED, AND IS BROADLY INCLUDED IN A FLOOD WATCH
UNTIL 7 AM SUNDAY.
- THE MARGINAL RISK FOR ISOLATED SEVERE STORMS WAS ADDED BACK TO
THE AREA BY SPC, BUT THIS RISK REMAINS CONDITIONAL AND LOW IN
OUR AREA.
UPDATE
ISSUED AT 805 PM CDT SAT SEP 19 2026
THE FLOOD WATCH HAS BEEN EXPANDED TO INCLUDE THE FOLLOWING
COUNTIES: IN IOWA...KEOKUK; IN ILLINOIS...HENRY, BUREAU AND
PUTNAM.
THE OVERALL LARGE SCALE SYNOPTIC PICTURE IS VERY FAVORABLE FOR
HEAVY RAIN TONIGHT. THE LLJ SHOULD BEGIN STRENGTHENING IN THE
NEXT FEW HOURS WHICH WILL RESULT IN RAPID DEVELOPMENT OF
CONVECTION ACROSS EASTERN IOWA BETWEEN 10 PM AND 1 AM.
RECENT RUNS FROM THE CAMS GENERALLY POINT TO A WIDESPREAD 1-2
INCHES OCCURRING ACROSS MUCH OF THE AREA WITH NUMEROUS NARROW
BANDS OF 3-5+ INCHES OF RAIN. ADDITIONALLY THERE ARE SUGGESTIONS
FROM THE CAMS THAT LOCALLY HEAVY RAIN MAY ENCROACH INTO THE
NORTHERN PARTS OF KEOKUK, HENRY AND BUREAU COUNTIES.
RECENT RADAR TRENDS ARE SHOWING A DEVELOPING BAND OF CONVECTION
ALONG AND JUST SOUTH OF I-80 IN ILLINOIS WITH A SLOW WESTWARD
EXPANSION INTO EASTERN IOWA. THE CAMS HAVE BEEN SUGGESTING THE
AREA BETWEEN I-80 AND HIGHWAY 20 AS THE PRIMARY FOCUS FOR THE
BANDS OF HEAVY RAIN TONIGHT. HOWEVER, IF THE RADAR TRENDS ARE
ARE CORRECT THEN THE HEAVIEST RAIN MAY BE JUST SOUTH OF I-80 TO
JUST NORTH OF HIGHWAY 30. THUS THE NECESSITY OF EXPANDING THE
AREAL COVERAGE OF THE WATCH.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 105 PM CDT SAT SEP 19 2026
THE OVERNIGHT MCS IMPACTED NEARLY ALL LOCATIONS ALONG AND NORTH
OF I- 80 EARLY TODAY, RESULTING IN WIDESPREAD 1 TO 4 INCH
RAINS, THAT WERE HIGHEST IN OUR HIGHWAY 20 CORRIDOR. SINCE 10
AM, THE INTENSITY HAS DECREASED, ALONG WITH COVERAGE OF HEAVY
RAINS. IN THE MEAN TIME, CLOUDS AND SCATTERED SHOWERS CONTINUE
TO MOVE EAST OVER THE AREA, AS WARM ADVECTION CONTINUES TO FORCE
SHOWERS IN A HIGH PWAT ATMOSPHERE. OUR FREEZING LEVEL ON OUR
18Z SOUNDING (JUST LAUNCHED) IS 13,900 FT! FOR SEPTEMBER, THAT
IS REMARKABLY HIGH, AND SHOWS HOW ANOMALOUS THIS ATMOSPHERE IS.
SPC MESOSCALE ANALYSIS CONTINUES TO SHOW MOISTURE TRANSPORT
AIMED INTO IOWA AND ILLINOIS, WITH STRONG HEATING ONGOING TO OUR
SOUTHWEST IN MISSOURI AND KANSAS. THUS, THERE WILL BE AMPLE
MUCAPE AND MOISTURE TO SUPPORT ANOTHER ROUND OF STORMS OVER OUR
AREA.
MODELS ARE IN GOOD AGREEMENT SHOWING A SHORT WAVE OVER KANSAS (SEEN
ON WV THIS MORNING), MOVING UP OVER OUR REGION TONIGHT. THIS WILL
TRIGGER STORMS TO FORM, ESPECIALLY WHERE THE WARM FRONT TO OUR WEST
MEET THE OUTFLOW BOUNDARY. THAT POINT AT 1230 PM THIS AFTERNOON IS
LOCATED JUST SOUTHWEST OF DES MOINES. UNFORTUNATELY, THE TRAJECTORY
OF STORMS THAT FORM NEAR THAT POINT WILL SPREAD OVER THE CWA, AND
MUCH LIKE LAST NIGHT, TRAINING STORMS ARE EXPECTED. OUR ONGOING
FORECAST ALREADY HAD A GOOD HANDLE ON THAT, THOUGH WITH WPC
EXPANDING THE MODERATE (LEVEL 3 OUT OF 4) WESTWARD ALONG I-80 TO OUR
WESTERN COUNTIES I HAVE EXPANDED THE FLOOD WATCH INTO THAT AREA.
TONIGHT'S STORMS COULD BE CAPABLE OF A BRIEF WINDOW OF STRONG TO
SEVERE WIND GUSTS, IF THE ATMOSPHERE OVER EASTERN IOWA CAN SEE SOME
PM HEATING. THAT REMAINS QUESTIONABLE WITH CLOUDS AND RAIN SHOWERS
CONTINUING TO MOVE OVER THE AREA. IN ANY CASE, BY THE TIME A
MULTICELL LINE IS FORMED, AN WEST TO EAST BAND OF THUNDERSTORMS WITH
TORRENTIAL RAINFALL OF 1-2 PER HOUR EXPECTED. THUS, MUCH LIKE LAST
NIGHT, A BROAD AXIS OF 1-3 INCHES IS EXPECTED, WITH A MAXIMUM OF 3-
5" POSSIBLE WITHIN IT. THERE IS SOME THREAT THAT THIS COULD OVERLAY
LAST NIGHT'S HEAVY AXIS IN THE NORTH, AND IF SO, HIGHER LEVEL
IMPACTS WOULD BE EXPECTED. THIS MORNING, CREEKS ALONG HIGHWAY 20
WERE REPORTED TO BE HIGH TO JUST OUT OF THEIR BANKS, PER EMA
REPORTS. DUBUQUE COUNTY DID SEE SOME CREEK FLOODING ALONG CATFISH
CREEK AND THE LITTLE MAQUOKETA RIVER. TONIGHT, WE MAY SEE SOME
FLASH FLOOD WARNING CONTAINING "CONSIDERABLE" WORDING, VS BASELINE
WARNINGS, AS THIS SITUATION IS JUST HOURS REMOVED FROM THE RAIN THIS
MORNING. URBAN AREAS, INCLUDING CEDAR RAPIDS, IOWA CITY, MUSCATINE,
AND QUAD CITIES ARE INCLUDED FOR METRO AREAS FOR URBAN FLOODING
POTENTIAL.
LONG TERM /MONDAY THROUGH SATURDAY/
ISSUED AT 105 PM CDT SAT SEP 19 2026
SUNDAY...A COOLER CLOUDY AND POST-FRONTAL DAY WITH ONGOING LIFT UP
AND OVER THE LLVL BAROCLINICITY WHICH SHOULD BE SETTLING OFF TO THE
SOUTH OF THE DVN CWA. INCREASING NORTH TO NORTHEASTERLY BOUNDARY
LAYER(BL) WINDS WITH SOME SPOTTY RAIN WILL MAKE FOR NOT A VERY NICE
DAY WITH A LOT OF THE AREA HELD DOWN IN THE 60S TO LOW 70S. WITH THE
UPPER WAVE STILL MOVING ACRS THE AREA, SUPPOSE SOME ISOLATED
THUNDERSTORMS POSSIBLE AS WELL AS NUISANCE FUNNELS.
MONDAY THROUGH FRIDAY...QUICK LOOK AT THE LONGER RANGE SUGGESTS THAT
THE LARGE UPPER LOW/WAVE CURRENTLY CENTERED OVER SOUTHERN ID WILL
ROLL EASTWARD ACRS THE NORTHERN PLAINS AND TOWARD THE UPPER MS RVR
VALLEY THROUGH TUESDAY. THIS MAY KEEP CLOUDY, COOLER WEATHER GOING
ACRS THE AREA AS WELL AS SCTRD SHOWERS FOR THE EARLY NEXT WEEK
PERIOD. AS THIS UPPER WAVE FILLS AND PULLS OFF TO THE EAST, THERE
MAY BE A MID WEEK PRECIP LULL UNTIL MEDIUM RANGE ENSEMBLE INDICATED
NEXT PASSING TROF BRINGS THE NEXT PRECIP CHANCES BY THU NIGHT OR
NEXT FRIDAY. COOLER TEMP REGIME STILL LOOKS TO LAST MUCH OF THE
WEEK.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 1245 AM CDT SUN SEP 20 2026
MCS PRODUCING WIDESPREAD SHOWERS AND THUNDERSTORMS WITH
ASSOCIATED LOW MVFR TO IFR CONDITIONS WILL HAMPER AVIATION
GREATLY INTO SUNDAY MORNING EXCEPT FOR MAYBE THE DBQ SITE WHICH
MOST OF THE ACTIVITY WILL LOOK TO PASS SOUTH OF. PASSING SFC LOW
AND TROF WILL MAKE FOR VARIABLE AND RATHER LIGHT SFC WIND REGIME
OVERNIGHT INTO EARLY SUNDAY MORNING, BEFORE THE SFC WAVE PASSES
AND ALLOWS FOR THE WINDS TO GO NORTHEASTERLY AND INCREASE TO
10-15 KTS WITH GUSTS AS THE DAY PROGRESSES. IFR TO LOW MVFR
CLOUD DECKS WILL PERSIST MUCH OF SUNDAY MORNING, BEFORE
TRENDING UP TO HIGHER CRITERIA MVFR SUNDAY AFTERNOON INTO
EVENING. SOME CHANCE FOR VFR CIGS NORTH OF I-80 SUNDAY EVENING.
AFTER THE MORE WIDESPREAD PRECIP MOVES OUT SUNDAY MORNING, THERE
WILL BE A CHANCE FOR SCTRD TO ISOLATED LIGHTER SHOWERS
DEVELOPING IN A HIT AND MISS FASHION THROUGH SUNDAY EVENING.
HYDROLOGY
ISSUED AT 1040 AM CDT SAT SEP 19 2026
THIS MORNINGS MCS BROUGHT WIDESPREAD MODERATE TO HEAVY RAIN TO
PORTIONS OF THE AREA MAINLY ALONG AND NORTH OF THE INTERSTATE 80
CORRIDOR COUNTIES. RAINFALL AMOUNTS IN THIS AREA WERE 2 TO 4
INCHES WITH THE HEAVIEST RAINS FALLING ALONG AND EAST OF OF A
MANCHESTER TO MAQUOKETA LINE. THIS HAS CAUSED MANY AREA CREEKS
TO RISE THIS MORNING AND ADDITIONAL RAINFALL TODAY AND TONIGHT
INCREASES THE THREAT FOR FLASH FLOODING TO OCCUR ESPECIALLY IN
AREAS THAT SAW THE HEAVIEST RAINFALL THE LAST 3 DAYS. A FLOOD
WATCH FOR FLASH FLOODING POTENTIAL REMAINS IN EFFECT FOR
PORTIONS OF EASTERN IOWA AND NORTHWEST ILLINOIS UNTIL 7 AM
SUNDAY.
WIDESPREAD HEAVY RAINS ARE LEADING TO RISES ON AREA RIVERS. THE
HEAVIEST RAINS THE LAST 3 DAYS HAVE FALLEN IN THE MAQUOKETA,
WAPSIPINICON, ROCK, PECATONICA, ENGLISH AND CEDAR RIVER BASINS.
THIS IS LEADING TO FORECAST RISES ABOVE FLOOD STAGE AT MANY
LOCATIONS OVER THE NEXT SEVERAL DAYS. RIVER FLOOD WATCHES HAVE
BEEN ISSUED AT MANY LOCATIONS ON THESE RIVERS. CERTAINTY WILL
INCREASE ON POTENTIAL FLOODING BY TOMORROW MORNING AFTER THE
NEXT ROUND OF STORMS MOVES ACROSS THE AREA TONIGHT INTO SUNDAY
MORNING.
DVN WATCHES/WARNINGS/ADVISORIES
IA...FLOOD WATCH UNTIL 7 AM CDT THIS MORNING FOR IAZ040>042-051>054-
063>068-076>078.
IL...FLOOD WATCH UNTIL 7 AM CDT THIS MORNING FOR ILZ001-002-007-009-
015>018-024.
MO...NONE.
UPDATE...08
SHORT TERM...ERVIN
LONG TERM...12
AVIATION...12
HYDROLOGY...COUSINS
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page