349
FXUS63 KDVN 051127
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
627 AM CDT WED AUG 5 2026
KEY MESSAGES
- MULTIPLE ROUNDS OF REPEATING STORMS TODAY POSES A FLASH FLOOD
THREAT, ESPECIALLY ALONG AND SOUTH OF INTERSTATE 80. RAIN
AMOUNTS BETWEEN 0.5-3" LIKELY WITH LOCALIZED 4" TOTALS
POSSIBLE. A FLOOD WATCH HAS BEEN ISSUED FOR MOST AREAS SOUTH
OF I-80.
- THERE IS A MARGINAL (LEVEL 1 OF 5) RISK FOR SEVERE WEATHER
TODAY. THE PRIMARY HAZARD WITH ANY SEVERE STORMS WILL GUSTY
WINDS.
- DRIER CONDITIONS LATE WEEK AND INTO THE WEEKEND WITH A
POSSIBLE RETURN TO ACTIVE WEATHER EARLY NEXT WEEK ALONG WITH
SLIGHTLY ABOVE AVERAGE TEMPERATURES.
SHORT TERM /THROUGH THURSDAY NIGHT/
ISSUED AT 152 AM CDT WED AUG 5 2026
AN ACTIVE WEDNESDAY AHEAD! A SHORTWAVE TROUGH IS EXPECTED TO DIVE
INTO THE BASE OF A LONGWAVE TROUGH OVER THE REGION AND HELP SPAWN
WIDESPREAD SHOWERS AND STORMS (70-90% COVERAGE) ALONG AND NORTH
OF A STATIONARY BOUNDARY DRAPED ACROSS OUR SOUTHERN CWA. THE
INGREDIENTS ARE THERE FOR HEAVY RAINFALL: ENHANCED DIFFLUENT
FLOW ALOFT, PVA AT 500 MB, F-GEN IN THE 850MB-700MB LAYER, AND
1-2 INCH PWATS ORIENTED NORTHWEST TO SOUTHEAST. INTERSTATE 80
WILL BE THE DIVIDING LINE FOR THE HEAVIEST RAINFALL WITH AREAS
SOUTH SEEING 1-3 INCHES ACROSS TWO ROUNDS OF STORMS (ONE IN THE
MORNING AND A SECOND IN THE LATE AFTERNOON/EVENING) WHILE AREAS
NORTH COULD ONLY SEE 0.5-1 INCH MOSTLY IN THE MORNING ROUND. IN
TERMS OF SEVERE WEATHER, THE THREAT APPEARS LIMITED AND
UNCERTAIN AS MORNING CONVECTION AND CLOUD COVER IS EXPECTED TO
DAMPEN DIURNAL HEATING AND CUT INTO THE AVAILABLE ENERGY FOR
STORMS; HOWEVER, AREAS ALONG AND SOUTH OF INTERSTATE 80 THAT SEE
BREAKS IN THE CLOUDS DURING THE EARLY AFTERNOON COULD SEE SOME
MODEST DESTABILIZATION IN THE FORM OF 500-1000 J/KG. THERE IS
GREATER CONFIDENCE THOUGH ON THE 0-6 KM BULK SHEAR WITH A
80-100% CHANCE FOR IT TO EXCEED 35 KNOTS WEDNESDAY AFTERNOON
ALONG AND WEST OF THE MISSISSIPPI RIVER. WITH ALL THESE
FACTORS, THE SPC DOES HAVE A MARGINAL RISK (LEVEL 1 OF 5) FOR
THE AREAS ALONG AND SOUTH OF INTERSTATE 80 IN THE LOW CAPE, HIGH
SHEAR ENVIRONMENT. PRIMARY THREATS WILL BE GUSTY WINDS,
LIGHTNING, AND HEAVY RAINFALL, BUT SMALL HAIL AND AN ISOLATED
TORNADO CANNOT BE RULED OUT.
HEADING INTO TONIGHT, THE SHORTWAVE TROUGH AND CONVECTION
PUSHES THE SURFACE BOUNDARY SOUTHEASTWARD OUT OF OUR CWA AS DRY
AIR ADVECTION IN THE MID-LEVELS BEGINS AND HIGH PRESSURE BUILDS
IN. ISOLATED SHOWERS AND STORMS (20-30% COVERAGE) COULD STILL
CONTINUE INTO THE OVERNIGHT HOURS WEDNESDAY ALONG AND SOUTH OF
HIGHWAY 34, BUT COVERAGE SHOULD DECREASE BY THURSDAY MORNING.
DESPITE THE FRONTAL PASSAGE, LOWS WILL ONLY DROP INTO THE 60S
WITH RESIDUAL SURFACE MOISTURE AND CLOUD COVER CUTTING INTO THE
RADIATIONAL COOLING.
THURSDAY WILL BE MOSTLY DRY AS SURFACE HIGH PRESSURE CAMPS OVER THE
AREA AS THE SHORTWAVE TROUGH MOVES TO THE EAST. HIGHS ARE
FORECAST TO BARELY CLIMB INTO THE 80S WITH LIGHT AND VARIABLE
WINDS AREAWIDE. THESE CONDITIONS ARE NOT EXPECTED TO LAST LONG
THOUGH AS THE NEXT SHORTWAVE DIVES INTO THE NORTHERN PLAINS LATE
THURSDAY NIGHT, PUSHING ANOTHER WEAK COLD FRONT SOUTHWARD INTO
MINNESOTA AND THE DAKOTAS.
LONG TERM /FRIDAY THROUGH TUESDAY/
ISSUED AT 152 AM CDT WED AUG 5 2026
FRIDAY...ISOLATED TO SCATTERED STORMS (20-40% COVERAGE) ARE
BACK ON THE TABLE AS A SURFACE TROUGH MOVES THROUGH THE AREA.
LIMITED INSTABILITY DUE TO THE LACK OF PROLONGED RETURN FLOW AND
WAA SHOULD DAMPEN THE SEVERE THREAT WITH THESE STORMS, BUT THE
NORTHWESTERLY FLOW ALOFT DOES PUT THE SHEAR VECTOR PERPENDICULAR
TO THE FRONT, LEAVING THE DOOR OPEN TO A POSSIBLE MCS
DEVELOPMENT AS NOTED IN THE SPC'S DAY 4-8 CONVECTIVE OUTLOOK.
BY FRIDAY NIGHT, THE BOUNDARY CLEARS THE CWA AS ANOTHER WEAK
HIGH PRESSURE MOVES IN.
SATURDAY...A RINSE-AND-REPEAT OF THURSDAY IS LIKELY ON SATURDAY
AS CONVERGENCE ALOFT ON THE BACKSIDE OF FRIDAY'S SHORTWAVE
TROUGH AND LOW-LEVEL CAA KEEP THINGS DRY. HIGHS AND LOWS SHOULD
BE SEASONABLE, BUT ONCE AGAIN, THESE PLEASANT CONDITIONS WILL
NOT LAST.
SUNDAY-TUESDAY...THERE IS A LOT OF UNCERTAINTY IN POPS HEADING INTO
EARLY NEXT WEEK AS PERSISTENT WEST-NORTHWESTERLY FLOW ALOFT PREVENTS
ANY SIGNIFICANT MOISTURE ADVECTION INTO THE REGION. WHAT IS A LITTLE
MORE CERTAIN IS THE SHIFT IN LOW-LEVEL FLOW. ANOTHER WEAK SHORTWAVE
IS FORECAST TO DEEPEN A LOW PRESSURE ON THE LEEWARD SIDE OF THE
NORTHERN ROCKIES AND MOVE EASTWARD TOWARDS IOWA AND MINNESOTA
ON MONDAY. GENERAL CONSENSUS AMONG ENSEMBLE MODELS IS A
SOUTHERLY WIND SHIFT WHICH WILL KICK OFF A WARMING TREND SUNDAY
AND INTO EARLY NEXT WEEK WITH HIGHS LIKELY (60-80% CHANCE PER
04.12Z LREF GUIDANCE) IN THE MID-80S TO LOW 90S. ANY RESIDUAL
BOUNDARY LEFT ACROSS THE REGION ON TUESDAY WILL ALSO PLAY A HUGE
ROLE ON THE NORTHWARD EXPANSION OF THE HEAT.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 621 AM CDT WED AUG 5 2026
VERY SHORT TERM MODELS ARE STRUGGLING WITH STORM COMPLEX ALONG
THE IA/MO BORDER. SAID COMPLEX WILL MOVE EAST AND SLOWLY WEAKEN
AS IT MOVES AWAY FROM THE BETTER SUPPORT. THE LLJ IS FORECAST
TO SHIFT EAST TOWARD THE MISSISSIPPI RIVER AND DEVELOP A NEW
STORM COMPLEX AROUND 18Z/05. THIS NEW STORM COMPLEX WILL THEN
MOVE EAST INTO CENTRAL ILLINOIS. OUTSIDE OF SHRA/TSRA VFR WITH
POCKETS OF MVFR. MVFR/IFR CONDITIONS IN THE RAIN AND TSRA.
DVN WATCHES/WARNINGS/ADVISORIES
IA...FLOOD WATCH THROUGH THIS EVENING FOR IAZ076>078-087>089-098-
099.
IL...FLOOD WATCH THROUGH THIS EVENING FOR ILZ024>026-034-035.
MO...FLOOD WATCH THROUGH THIS EVENING FOR MOZ009-010.
SHORT TERM...DELAUNE
LONG TERM...DELAUNE
AVIATION...08
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