421
FXUS63 KDVN 131052
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
552 AM CDT SUN SEP 13 2026
KEY MESSAGES
- ACTIVE PATTERN THIS WEEK TO BRING NUMEROUS ROUNDS OF SHOWERS
AND STORMS WITH HEAVY RAIN POSSIBLE.
- THERE IS A MARGINAL RISK, LEVEL 1 OUT OF 5, FOR SEVERE STORMS
NORTH OF I-80 MONDAY EVENING INTO THE OVERNIGHT HOURS. PRIMARY
HAZARDS WILL BE HEAVY RAIN AND DAMAGING WINDS.
- AN ELEVATED FLASH FLOOD RISK MAY DEVELOP MID-WEEK WITH
REPEATING ROUNDS OF STORMS. RAINFALL TOTALS OVER 2 INCHES ARE
LIKELY (60-80%), WITH LOCALIZED AREAS OF 5+ INCHES POSSIBLE
(10-20%), LEADING TO RISES ON AREA CREEKS AND STREAMS.
SHORT TERM /THROUGH TUESDAY/
ISSUED AT 131 AM CDT SUN SEP 13 2026
AFTER A MOSTLY DRY SATURDAY, SCATTERED SHOWERS (30-60%
COVERAGE) RETURN THIS MORNING AS CONFLUENT FLOW IN THE MID-
LEVELS SUPPORT AN F-GEN BAND ON THE BACKSIDE OF A STATIONARY
FRONT OVER NORTHERN MISSOURI. NORTHERLY FLOW FORCED BY A HIGH
PRESSURE OVER MINNESOTA WILL KEEP HIGH TEMPERATURES BELOW
AVERAGE IN THE UPPER 60S AND LOW 70S. HEADING INTO THE EVENING,
CONDITIONS DRY OUT AGAIN, BUT THIS WILL NOT LAST LONG WITH A
LONGWAVE RIDGE OVER THE MID-TO-UPPER MISSISSIPPI RIVER VALLEY
INTRODUCING SOUTHWESTERLY FLOW IN THE 850-TO-500 MB LAYER AND
CONVERTING THE STATIONARY FRONT INTO A WARM FRONT.
ON MONDAY, MORE SCATTERED SHOWERS AND STORMS (30-50% COVERAGE)
WILL FIRE ALONG THE WARM FRONT AS IT IS PULLED NORTHWARD BY A
DEVELOPING LOW PRESSURE CENTER OVER THE NORTHERN PLAINS. THESE
STORMS ARE EXPECTED TO BE ELEVATED AND COULD TAP INTO 1000-1500
J/KG OF MUCAPE AND 40+ KNOTS OF 0-6-KM SHEAR. WHILE THE OVERALL
SEVERE POTENTIAL IS LOW (LESS THAN 5%) WITH THIS MORNING ROUND,
ISOLATED HAIL CANNOT BE RULED OUT WITH THE STRONGEST CELLS. BY
THE LATE AFTERNOON AND EARLY EVENING, ANOTHER PERIOD OF DRY
CONDITIONS IS EXPECTED AHEAD OF THE APPROACHING COLD FRONT AND
SHORTWAVE TROUGH, BUT A STRONG LLJ OVER EASTERN IOWA MAY
SUPPORT SURFACE WIND GUSTS UP TO 30 KNOTS DURING THIS TIME.
OVERNIGHT MONDAY, A CLOSED HEIGHTS CENTER POSITIONED OVER THE
NORTHERN ROCKIES NEGATIVELY TILTS AS IT LIFTS INTO SOUTH-CENTRAL
CANADA. WIDESPREAD SHOWERS AND STORMS (80-100% COVERAGE) ARE
EXPECTED ALONG THE COLD FRONT MOVING IN FROM THE NORTHWEST, BUT
LACKLUSTER MID-LEVEL LAPSE RATES WILL PUT A HAMPER ON THE
OVERALL INSTABILITY (750-1500 J/KG OF SBCAPE). THIS IS
FORECASTED TO, ONCE AGAIN, LIMIT THE OVERALL SEVERE POTENTIAL.
HOWEVER, THERE IS A BRIEF WINDOW WHERE A MID-LEVEL JET BOOSTS
THE 0-6-KM SHEAR ALONG THE FRONT TO 45+ KNOTS NORTH OF I-80. THE
SPC HAS MAINTAINED A MARGINAL RISK, LEVEL 1 OUT OF 5, FOR
SEVERE STORMS WITH PRIMARY HAZARD BEING DAMAGING WINDS. BY
TUESDAY, STORM COVERAGE AND INSTABILITY DECREASES AS UPPER-
LEVEL DYNAMICAL SUPPORT WEAKENS. THE COLD FRONT IS FORECAST TO
STALL OUT OVER NORTHERN MISSOURI, SIMILAR TO TODAY'S SET UP,
KEEPING STORM CHANCES AROUND THROUGH THE END OF THE WEEK.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
ISSUED AT 131 AM CDT SUN SEP 13 2026
THE SECOND HALF OF THE WEEK IS GOING TO REMAIN STORMY. A RIDGE
OVER THE SOUTHEAST AND A SLOW-MOVING SHORTWAVE TROUGH OVER THE
WESTERN CONUS IS FORECAST TO PULL MULTIPLE, WEAK SUBTROPICAL
TROUGHS NORTHEASTWARD INTO THE MIDWEST. WITH THE STATIONARY
FRONT FROM TUESDAY'S SYSTEM ACTING AS THE SOURCE OF LIFT,
SCATTERED SHOWERS AND STORMS WILL LIKELY DEVELOP DAILY. WITH
SATURATED GROUNDS EXPECTED AFTER THE ROUNDS OF RAIN TODAY
THROUGH TUESDAY, THE FLOOD THREAT WILL BECOME MORE ELEVATED WITH
EACH SUBSEQUENT ROUND. THE WPC ALREADY HAS A SLIGHT RISK, LEVEL
2 OUT OF 4, FOR EXCESSIVE RAINFALL MONDAY NIGHT INTO TUESDAY,
AND ANOTHER AREAWIDE SLIGHT RISK FOR WEDNESDAY. IN TERMS OF
RAINFALL TOTALS, LATEST LREF GUIDANCE HAS A 60-80% OF 2+ INCHES
ACROSS EASTERN IOWA AND 30-50% ACROSS NORTHWEST ILLINOIS AND
NORTHEAST MISSOURI THROUGH SATURDAY. THERE IS A LOT OF
UNCERTAINTY THOUGH IN THE AXIS (OR AXES) OF HEAVIEST RAINFALL
WITH THE LREF 10TH-90TH PERCENTILE SPREAD SHOWING A 2-3 INCH
DIFFERENCE AREAWIDE. THEREFORE, WHILE THE PROBABILITIES ARE LOW
(10-20%) FOR 5+ INCHES OF RAINFALL ACROSS EASTERN IOWA, THE
ENSEMBLE SPREAD IS SUGGESTING THAT LATEST MODEL GUIDANCE MAY BE
THE UNDERCUTTING THE HIGH-END TOTALS.
AVIATION /12Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 551 AM CDT SUN SEP 13 2026
VFR CONDITIONS TO START THE PERIOD. MID-HIGH LEVEL CLOUDS WILL
INCREASE THROUGH THE DAY, WITH SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS TRACKING EAST ACROSS IOWA. CONFIDENCE ON OVERALL
COVERAGE OF SHOWERS TODAY REMAINS LOW AND HAVE KEPT PROB30
MENTION FOR BRIEF MVFR VSBY REDUCTION AT ALL TERMINALS AND LEFT
OUT ANY THUNDER. THE LATEST RAP CEILING TRENDS WHICH IS
CURRENTLY DOING WELL WITH CLOUD HEIGHTS, BRINGS IN AN MVFR DECK
INTO DBQ LATER THIS AFTERNOON. HOWEVER, IT IS THE ONLY MODEL
THAT DOES THIS AND THUS HAVE LEFT OUT OF THE FORECAST FOR NOW.
WINDS TO REMAIN NORTHERLY UNDER 10KTS THROUGH THE TAF CYCLE.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
SHORT TERM...DELAUNE
LONG TERM...DELAUNE
AVIATION...GROSS
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