633
FXUS63 KDVN 241651
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1151 AM CDT THU SEP 24 2026
KEY MESSAGES
- MOSTLY CLOUDY SKIES WILL CONTINUE THROUGH THE UPCOMING
WEEKEND, WITH CHANCES OF SPOTTY LIGHT RAIN SHOWERS.
PRECIPITATION CHANCES INCREASE FURTHER TOWARDS MID-WEEK NEXT
WEEK WHEN A LARGER AND WETTER SYSTEM MOVES IN.
- TEMPERATURES WILL CONTINUE TO BE COOLER THAN AVERAGE INTO THE
WEEKEND, MODERATING BACK TO SEASONABLE OR EVEN SLIGHTLY ABOVE
NORMAL LEVELS NEXT WEEK.
SHORT TERM /THROUGH FRIDAY NIGHT/
ISSUED AT 1150 AM CDT THU SEP 24 2026
THE GENERALLY CLOUDY WEATHER PATTERN LOOKS TO CONTINUE TODAY THROUGH
AT LEAST SATURDAY. PARTLY TO MOSTLY CLOUDY SKIES TODAY WERE SEEN
THANKS LARGELY TO A STOUT LOW-LEVEL THERMAL INVERSION IN THE 850-700
MB LAYER, WHICH CAN BE SEEN ON THE 24.12Z ILX RAOB SOUNDING. AN
EXTENSION OF A LARGE HIGH PRESSURE SYSTEM ANCHORED OVER SOUTHERN
QUEBEC CANADA WILL BREAK DOWN OVERNIGHT TONIGHT, ALLOWING A WEAK MID-
LEVEL SHORTWAVE TO RIDE MID-LEVEL RIDGING AND MOVE INTO OUR AREA.
THE LATEST SUITE OF HIGH-RES MODEL SOUNDINGS SUGGEST A LAYER OF DRY
AIR NEAR THE 800 MB LEVEL SHOULD HELP INHIBIT RAINFALL ACCUMULATIONS
TONIGHT, BUT THIS LAYER SHOULD ERODE IN TIME FRIDAY MORNING AS
HIGHER PWAT VALUES OF AROUND 1.4 TO 1.7 INCHES BUILDS IN AFTER
SUNRISE FRIDAY. CHANCES OF RAINFALL WILL PEAK AROUND 30-60% FOR ANY
GIVEN HOUR FROM MIDNIGHT TONIGHT THROUGH FRIDAY AFTERNOON. A LACK OF
INSTABILITY AND ROBUST NOCTURNAL LOW-LEVEL JET WILL HELP KEEP ANY
THUNDERSTORMS AT BAY. AS FAR AS RAINFALL TOTALS ARE CONCERNED
TONIGHT THROUGH FRIDAY AFTERNOON, AMOUNTS ARE GENERALLY EXPECTED TO
BE A TENTH OF AN INCH OR LESS, WITH EXCEEDANCE PROBABILITIES OF A
TENTH AROUND 30-60% (HIGHEST OVER SOUTHEAST IOWA INTO NORTHEAST
MISSOURI). DUE TO PERSISTENT CLOUD COVER, LOW TEMPERATURES WILL
GENERALLY HOVER NEAR 60 TONIGHT, AND HIGHS FRIDAY IN THE MIDDLE 60S.
FRIDAY NIGHT SHOULD SEE A BRIEF LULL PRECIPITATION CHANCES BEFORE
INCREASING DURING THE DAYLIGHT HOURS SATURDAY (MORE ON THAT IN THE
LONG TERM SECTION). FRIDAY NIGHT LOWS SHOULD BE SIMILAR TO WHAT
THEY'RE EXPECTED TO BE FOR TONIGHT, ALTHOUGH SOME UPPER 40S TO LOWER
50S ARE POSSIBLE OVER NORTHWEST ILLINOIS WHERE CLEARER SKIES ARE
EXPECTED.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
ISSUED AT 1150 AM CDT THU SEP 24 2026
AN ACTIVE WEATHER PATTERN CONTINUES FOR THIS WEEKEND INTO MID-WEEK
NEXT WEEK. FIRST, ANOTHER MID-LEVEL SHORTWAVE WILL ATTEMPT TO BUILD
IN FROM THE WEST SATURDAY INTO SATURDAY NIGHT. AN INTERESTING SIGNAL
IN THE GLOBAL DETERMINISTIC MODELS IS FOR THE QPF TO BUILD IN TO OUR
FAR WESTERN FORECAST AREA BUT STRUGGLE TO PROGRESS EASTWARD. THE
SUSPICION IS THAT DRY EASTERLY FLOW, WITH A LINGERING HIGH PRESSURE
RIDGE AXIS NEAR LAKE MICHIGAN, WILL HELP INHIBIT PRECIPITATION
EXPANSION EASTWARD. THIS WOULD SUGGEST THAT THE FOOTPRINT FOR A
WETTING RAINFALL IN OUR AREA WOULD BE SMALLER, AND THIS IS BACKED UP
BY THE LATEST NBM EXCEEDANCE PROBABILITIES OF A QUARTER INCH OR MORE
OF RAIN, HIGHLIGHTING 50-80% CHANCES ALONG AND WEST OF US HIGHWAY
218. THE SIGNAL IS FOR THE PRECIPITATION TO WANE SUNDAY MORNING AS
MID-LEVEL RIDGING REINVIGORATES AND WEAKENS THE SHORTWAVE FORCING.
WITH THE CLOUD COVER AND RAIN IN PLACE, TEMPERATURES WILL FEEL
COOLER THAN AVERAGE, WITH HIGHS IN THE LOWER TO MIDDLE 60S FOR MOST
SATURDAY AND SUNDAY.
SUNDAY NIGHT THROUGH MONDAY APPEARS LIKELY TO BE A DRY PERIOD THANKS
TO HIGH PRESSURE DOMINATING OVER THE REGION. PARTLY TO MOSTLY SUNNY
SKIES AND SOUTHEASTERLY FLOW MONDAY SHOULD RESULT IN THE RETURN OF
UPPER 60S TO LOWER 70S FOR HIGH TEMPERATURES.
THIS PERIOD OF DRYNESS WILL COME TO AN END MID-WEEK AS A LARGER
SYSTEM BUILDS IN SOMETIME AROUND LATE TUESDAY/WEDNESDAY. A LONGER
WAVE TROUGH, WITH MODELS SHOWING A STRONG TROPICAL CONNECTION TO THE
SYSTEMS IN THE EASTERN PACIFIC, SHOULD TRANSLATE THROUGH THE AREA,
ALTHOUGH THE EXACT TIMING OF ASSOCIATED PRECIPITATION REMAINS
UNCERTAIN. HOWEVER, THERE IS A STRONG SIGNAL FOR ABUNDANT MOISTURE
WITH THIS SYSTEM, WITH PWAT VALUES OF AROUND 1.5 TO 2 INCHES.
EXCEEDANCE PROBABILITIES OF 1.6 INCH PWATS ARE AROUND 50-70% PER THE
LATEST LREF ENSEMBLE, SUPPORTING A PERIOD OF HEAVY RAINFALL
POTENTIAL. NOW, IT REMAINS UNCLEAR HOW LONG THIS PERIOD OF RAINFALL
WILL LAST INTO WEDNESDAY, GIVEN DIFFERING END TIMES OF PRECIP PER
THE GFS/ECMWF/CMC GLOBAL MODEL SOLUTIONS AS SOME GUIDANCE SHOWS A
LARGE PROGRESSIVE LONGER WAVE TROUGH SWEEPING ACROSS THE MID-CONUS
VERSUS A SLOWER CUT-OFF LOW WITH MULTIPLE ROUNDS OF RAINS MID TO
LATE WEEK. THE LATTER SCENARIO WOULD BE MORE CONCERNING FOR HEAVY
RAINFALL/FLASH FLOODING, GIVEN WET ANTECEDENT CONDITIONS, SO THIS
MID-WEEK SYSTEM DOES BEAR WATCHING.
AVIATION /12Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 555 AM CDT THU SEP 24 2026
PREDOMINANTLY VFR ALTHOUGH SOME TRANSIENT POCKETS OF MVFR (CEILINGS)
ARE POSSIBLE THIS MORNING AND AGAIN LATER TONIGHT.
ONE AREA OF STRATUS WITH PREDOMINANTLY VFR CEILINGS AROUND 3500FT
EXTENDS ROUGHLY ALONG THE MISS. RIVER MOVING WESTWARD WHILE CLEARING
BRIEFLY TO THE EAST. WE COULD SEE SOME SCATTERING OF CLOUDS AT THE
RIVER TERMINALS BRIEFLY EARLY THIS MORNING. HOWEVER, BETWEEN MORE
STRATUS TO THE EAST AND DIURNAL CU DEVELOPMENT EXPECTING PREDOMINANTLY
BROKEN COVERAGE OF CLOUDS INTO TONIGHT. THERE IS A CHANCE FOR POCKETS
OF BRIEF MVFR CEILINGS WITHIN THE STRATUS THIS MORNING BEFORE FULLY
LIFTING TO VFR THIS AFTERNOON. ANY STRATUS LINGERING DEEPER INTO TONIGHT
COULD LOWER INTO TRANSITORY MVFR POCKETS WITH BL COOLING. A WEAKENING
SYSTEM WILL ALSO BRING A CHANCE FOR LIGHT RAIN OVERNIGHT, WHICH IS HANDLED
WITH PROB30 MENTION. WINDS LOOK TO REMAIN FROM THE E/NE AT 5-12 KT
THROUGHOUT THE PERIOD.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
SHORT TERM...SCHULTZ
LONG TERM...SCHULTZ
AVIATION...MCCLURE
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