179
FXUS63 KDVN 311732
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1232 PM CDT FRI JUL 31 2026
KEY MESSAGES
- WIDESPREAD SOAKING RAINFALL IS EXPECTED TODAY THROUGH SATURDAY
WITH AN 80-100% CHANCE OF RAINFALL AMOUNTS OVER 1 INCH AND A
40-70% CHANCE OF RAINFALL AMOUNTS OVER 2 INCHES. A SLIGHT RISK
(LEVEL 2 OF 4) FOR LOCALIZED FLASH FLOODING IS IN EFFECT
AREA-WIDE.
- A CONDITIONAL RISK (LEVEL 1 OF 5) FOR SEVERE THUNDERSTORMS IS
IN EFFECT THIS AFTERNOON INTO THE EVENING FOR AREAS SOUTH OF
HIGHWAY 20. THE PRIMARY THREAT WITH ANY STORMS WILL BE
ISOLATED DAMAGING WINDS. ISOLATED TORNADOES ARE POSSIBLE IN
SOUTHEAST IOWA AND NORTHEAST MISSOURI.
SHORT TERM /THROUGH SATURDAY NIGHT/
ISSUED AT 259 AM CDT FRI JUL 31 2026
A DAY OF ON-AND-OFF RAIN IS IN STORE FOR THE AREA TODAY AS A
SEASONABLY STRONG SHORTWAVE TROUGH INTENSIFIES AND MOVES THROUGH THE
AREA. EARLY THIS MORNING, CYCLOGENESIS HAS SUPPORTED THE DEVELOPMENT
OF A SURFACE LOW ALONG THE NE-SD-IA BORDER. IN THE WARM SECTOR,
ADVECTION ALONG THE WARM CONVEYOR BELT HAS SUPPORTED MOISTURE
TRANSPORT INTO MISSOURI AND IOWA WITH PWATS OF 2.0+ INCHES. WHILE
THIS IS RATHER ANOMALOUS AT WELL ABOVE 1.7 INCHES, THE 90TH
PERCENTILE, IT IS NOT OUT OF THE QUESTION GIVEN UPSTREAM PWATS OF
2.39 INCHES SAMPLED IN KOAX'S 31/00Z SOUNDING. WITH THIS INCREASING
MOISTURE AND SYNOPTIC UPLIFT ALONG THE EASTERN SIDE OF THIS
INTENSIFYING CYCLONE, A WIDESPREAD RAIN EVENT IS EXPECTED TODAY
THROUGH SATURDAY.
WHILE RAIN IS EXPECTED THROUGHOUT MUCH OF THE DAY, DRY PERIODS ARE
EXPECTED BETWEEN MULTIPLE ROUNDS OF SHOWERS AND STORMS. WHILE SOME
SHOWERS ARE MOVING THROUGH THE AREA NOW, THE MAIN LINE, WHICH IS
CURRENTLY A WEAKENING MCS STRETCHING FROM NORTHEAST KANSAS INTO
CENTRAL IOWA, WILL REACH EASTERN IOWA AROUND DAYBREAK. SHOWERS ARE
EXPECTED AREA-WIDE AS IT MOVES EASTWARD, AND PARTS OF SOUTHEAST IOWA
AND NORTHEAST MISSOURI MAY SEE EMBEDDED THUNDERSTORMS DUE TO MLCAPE
UP TO 500 J/KG. BY EARLY AFTERNOON, THIS LINE OF SHOWERS AND STORMS
WILL PUSH THROUGH WESTERN ILLINOIS, ALLOWING FOR DRY PERIODS AND
POTENTIALLY SOME CLEARING ACROSS EASTERN IOWA AND NORTHEAST
MISSOURI.
ADDITIONAL SHOWERS AND STORMS, INCLUDING SOME STRONG TO SEVERE, ARE
POSSIBLE THIS AFTERNOON THROUGH THE EVENING. ANY CLEARING THAT
OCCURS, COUPLED WITH CONTINUED WAA IN THE WARM SECTOR, WILL LEAD TO
INCREASED INSTABILITY THROUGH THE LOW LEVELS, WITH MUCH OF THE
GUIDANCE SHOWING MLCAPE OF 1000-1500 J/KG. DEEP LAYER SHEAR IS MORE
SUPPORTIVE OF A SEVERE RISK, WITH 25-35 KTS THROUGH MUCH OF THE
AREA. THE PRIMARY THREATS WITH ANY STRONG TO SEVERE STORMS WILL BE
ISOLATED DAMAGING WINDS DUE TO STRONG WINDS ALOFT. A SECONDARY
THREAT IN THE VICINITY OF THE LOW ACROSS SOUTHEAST IOWA AND
NORTHEAST MISSOURI IS AN ISOLATED TORNADO OR LANDSPOUT, AS STRONGER
LOW-LEVEL SHEAR (0-3 KM SRH OF 200-300) AND VEERING PROFILES IN THE
VICINITY OF THE LOW AND COLD FRONT WILL BE SUPPORTIVE OF LOW-TOPPED
SUPERCELLS. GIVEN THESE THREATS, SPC HAS ISSUED A CONDITIONAL
MARGINAL (LEVEL 1 OF 5) RISK FOR AREAS SOUTH OF HIGHWAY 20 AND A
SLIGHT (LEVEL 2 OF 5) FOR THE FAR SOUTHERN REACHES OF THE AREA INTO
EASTERN MISSOURI AND WESTERN ILLINOIS.
SCATTERED SHOWERS WILL CONTINUE OVERNIGHT THROUGH SATURDAY AFTERNOON
AS THE LOW SLOWLY WORKS ITS WAY SOUTHEASTWARD. TOTAL RAINFALL
ACCUMULATIONS THROUGH SATURDAY OF 1-3 INCHES ARE EXPECTED, WITH THE
NBM HAVING AN 80-100% CHANCE OF EXCEEDING 1 INCH AREA-WIDE. SOME
AREAS, PARTICULARLY THOSE IN SOUTHEAST IOWA AND NORTHEAST MISSOURI,
HAVE LOWER CHANCES OF EXCEEDING 2 INCHES, LEADING TO A 40-70%
SOUTHWEST-TO-NORTHEAST GRADIENT OF 2 INCH EXCEEDANCE PROBABILITIES.
SOME GUIDANCE SUGGESTS THAT LOCALLY HIGHER AMOUNTS OF 3-5 INCHES MAY
ALSO BE POSSIBLE. THIS WILL BE QUITE WELCOME DUE TO RECENT DRYNESS,
WHICH IN TURN WILL HELP REDUCE FLOODING RISKS. THE GREATEST CHANCE
FOR ANY FLOODING WILL BE IF SLOW-MOVING HEAVY RAINFALL REPEATEDLY
MOVES OVER URBAN AREAS OR AREAS WITH POOR DRAINAGE. DUE TO THIS, WPC
HAS ISSUED A SLIGHT (LEVEL 2 OF 4) RISK FOR FLASH FLOODING AREA-WIDE
TODAY.
AS SHOWERS END ON SATURDAY AFTERNOON, A STRONG PRESSURE GRADIENT ON
THE BACKSIDE OF THE LOW WILL INDUCE GUSTY NORTHERLY WINDS UP TO 30
MPH THAT LAST THROUGH LATE EVENING.
LONG TERM /SUNDAY THROUGH THURSDAY/
ISSUED AT 259 AM CDT FRI JUL 31 2026
THE UPPER-LEVEL TROUGH THAT WILL HELP BRING PRECIPITATION ACROSS THE
AREA TODAY AND SATURDAY WILL FINALLY DEPART THE REGION TO THE EAST
SUNDAY, LEADING TO A PERIOD OF DRY CONDITIONS. SURFACE HIGH PRESSURE
BUILDING ACROSS THE AREA, ALONG WITH UPPER-LEVEL RIDGING OVER THE
INTERMOUNTAIN WEST REGION PROTRUDING FROM A LARGE UPPER-LEVEL HIGH
OVER THE SOUTHWESTERN CONUS, WILL SUPPORT MORE QUIESCENT CONDITIONS
THROUGH TUESDAY, WITH SEASONAL TEMPERATURES (HIGHS IN THE LOWER 80S)
FOR SUNDAY THROUGH TUESDAY.
IN TERMS OF ACTIVE WEATHER, IT APPEARS MAINLY WEDNESDAY/THURSDAY
WILL BE THE TIME TO WATCH AS THE UPPER-LEVEL RIDGING BREAKS DOWN,
ALLOWING A MID-LEVEL TROUGH TO APPROACH THE REGION. AN ATTENDANT
SURFACE COLD FRONT IS ALSO PROGGED TO ACCOMPANY THE TROUGH, ALTHOUGH
THERE ARE SIGNIFICANT TIMING DIFFERENCES AMONG THE GLOBAL MODELS OF
THE FRONT, AND THUS, TIMING OF PRECIPITATION WITH THAT BOUNDARY.
SEVERE WEATHER POTENTIAL WITH THIS FRONT APPEARS TO BE PRETTY LOW AT
THIS TIME, GIVEN MODEST VALUES OF INSTABILITY AND SHEAR (25-35 KNOTS
FOR 0-6 KM SHEAR MAGNITUDES). THE VARIOUS MACHINE LEARNING SEVERE
WEATHER PROBABILITY GUIDANCE SUPPORTS THE MORE LIMITED SEVERE
WEATHER SIGNAL.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 1212 PM CDT FRI JUL 31 2026
A MESSY AVIATION FORECAST IS AHEAD OF US, AS WE HAVE A SLOW-
MOVING STORM SYSTEM PASS THROUGH THE AREA OVER THE NEXT 24
HOURS. WE CURRENTLY ARE WATCHING THE SHIELD OF WIDESPREAD
RAINFALL MOVE OUT OF THE AREA, WHICH HAS BROUGHT IFR VIS/CIGS TO
MUCH OF THE AREA THIS MORNING. FOR THE REMAINDER OF THE
AFTERNOON, A BROKEN-OVERCAST DECK WILL REMAIN, WITH CIGS AROUND
1000-2000 FT. ISOLATED-SCATTERED SHOWERS WILL PASS THROUGH THE
AREA BETWEEN 18-21Z, WITH INCREASING CHANCES AND COVERAGE OF
THUNDERSTORMS AFTER 21Z. WITH ANY SHOWER/STORM, LOWER CIGS AND
VIS CAN BE EXPECTED. WE CAN SEE CIGS DROP TO AS LOW AS 500 FT OR
LOWER, ESPECIALLY AT CID/DBQ AFTER 00Z THIS EVENING, WITH VIS
BETWEEN 2-5 SM. AT MLI/BRL, CIGS MAY DROP AS LOW AS 500-1000 FT
IN THUNDERSTORMS WITH VIS OF 3-5 SM. THESE CONDITIONS WILL
CONTINUE WELL INTO THE NIGHT AND THROUGH SATURDAY MORNING, WITH
FLIGHT CONDITIONS NOT IMPROVING FOR MANY UNTIL AT LEAST 18Z
SATURDAY. FREQUENT LIGHTNING AND GUSTY WINDS CAN BE EXPECTED AT
TERMINALS WITH ANY THUNDERSTORM, WITH HEAVY RAINFALL POSSIBLY
DROPPING VIS LOWER THAN CURRENTLY ADVERTISED.
WITH THE SURFACE LOW TRACKING OVERHEAD THROUGH THE TAF PERIOD,
WINDS WILL BE QUITE VARIABLE, ESPECIALLY BETWEEN 00-12Z. AHEAD
OF THE SURFACE LOW, WINDS WILL LARGELY BE OUT OF THE
SOUTH/SOUTHEAST, BECOMING NORTHEASTERLY ON THE BACKSIDE AROUND
08Z AND BEYOND. WIND SPEEDS WILL INCREASE QUITE A BIT ON THE
BACKSIDE OF THE SYSTEM, WITH GUSTS UPWARDS TO 25-30 KTS OUT OF
THE NORTHEAST BY 12Z SATURDAY FOR MOST OF THE AREA. LARGELY
LIGHT (5-10 KTS) AND VARIABLE WINDS CAN BE EXPECTED UNDER THE
SURFACE LOW.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
SHORT TERM...ELLINGWORTH
LONG TERM...SCHULTZ
AVIATION...GUNKEL
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