979
FXUS63 KDVN 212345
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
645 PM CDT TUE APR 21 2026
KEY MESSAGES
- WIDESPREAD SHOWERS AND STORMS WILL MOVE THROUGH THE AREA
THURSDAY INTO FRIDAY. SOME OF THESE STORMS MAY BE STRONG TO
SEVERE, WITH A LEVEL 1 OF 5 RISK OF SEVERE STORMS FOR EASTERN
IOWA, WEST-CENTRAL ILLINOIS, AND NORTHEAST MISSOURI.
- PLEASANT WEEKEND WEATHER AHEAD!
SHORT TERM /THROUGH WEDNESDAY NIGHT/
ISSUED AT 210 PM CDT TUE APR 21 2026
WHILE SUNSHINE HAS BEEN WIDESPREAD OVER OUR CWA THOUGH 1 PM IN
NEARLY ALL AREAS, A WEAK FRONT IS MOVING SOUTHEAST THROUGH THE
MIDWEST. A SHORT WAVE JUST AHEAD OF THIS FROPA, IS BRINGING A
VERY NARROW AREA OF SHOWERS AND STORMS MAINLY TO SOUTHEAST
WISCONSIN AS OF EARLY AFTERNOON. THE ACCAS CLOUDS ARE FOUND
SOUTHWEST OF THIS CONVECTION, AND EXTENDS DOWN THROUGH SOUTHEAST
IOWA. WITH DRY LOW LEVELS, THERE IS LITTLE IF ANY SURFACE CAPE
AVAILABLE FOR STORMS TODAY, BUT MUCAPE AROUND 500 J/KG IS
AVAILABLE FOR ANY STORM THAT FIRES. THE STEEP MID LEVEL LAPSE
RATES, AROUND 8.5C/KM WILL BRING A LOW, BUT STILL POSSIBLE
THREAT (~10%) OF STORMS THROUGH EARLY EVENING ALONG THIS
BOUNDARY, WHICH WILL BE IN OUR SOUTH THIS EVENING. ANY
THUNDERSTORM WOULD BE CAPABLE OF PRODUCING SMALL HAIL GIVEN THE
COOL AIR ALOFT. I DO THINK MOST IF NOT ALL OF THIS ACTIVITY WILL
BE EAST OF OUR CWA THIS EVENING.
LOWS TONIGHT, WITH VARIABLE CLOUD COVER ARE LOOKING MUCH MORE MILD,
WITH LOWER 50S NORTH TO UPPER 50S CENTRAL AND SOUTH. THIS MILDER
NIGHT WILL SET THE STAGE FOR ANOTHER MILD WEDNESDAY, WITH HIGHS IN
THE UPPER 70S TO NEAR 80. THE DRY WEATHER WITH SOUTH WINDS WILL
CONTINUE WEDNESDAY NIGHT, WITH LOWS DROPPING TO THE UPPER 50S IN
MOST AREAS.
LONG TERM /THURSDAY THROUGH TUESDAY/
ISSUED AT 210 PM CDT TUE APR 21 2026
UPPER-LEVEL RIDGING ACROSS THE UPPER MISSISSIPPI RIVER VALLEY BEGINS
TO BREAK DOWN WEDNESDAY NIGHT AS THE NEXT LONGWAVE TROUGH SETS UP
OVER THE ROCKIES. SURFACE CYCLOGENESIS OVER NORTHEAST MONTANA AND A
HIGH PRESSURE ACROSS THE SOUTHEAST WILL SUPPORT STRONG SOUTHERLY
FLOW AND MOISTURE ADVECTION ACROSS THE ENTIRE CWA THURSDAY INTO
THURSDAY NIGHT AS THE COLD FRONT APPROACHES. DIFFLUENT FLOW ALOFT,
CVA AT 500 MB, AND THE SURFACE FRONT WILL BE PRIMARY SOURCES OF
LIFT, BUT THE DISPLACED TROUGH TO THE NORTHWEST WILL KEEP MID-LEVEL
LAPSE RATES AT 7-8 C/KM, LIMITING OUR SBCAPE VALUES TO 500-700 J/KG
ACROSS EASTERN IOWA AND NORTHEAST MISSOURI. EFFECTIVE BULK SHEAR IS
ALSO EXPECTED TO BE WEAK AT 25-35 KNOTS. COMBINING THESE FACTORS,
THE SPC HAS A MARGINAL (1 OUT OF 5) RISK FOR DAMAGING WINDS THURSDAY
NIGHT AS THUNDERSTORMS FORM ALONG THE COLD FRONT.
ON FRIDAY, THE FLOW ACROSS THE CONUS RETURNS TO ZONAL AS TWO
SHORTWAVES OVER THE CANADIAN ROCKIES MERGE, STALLING THE
PROGRESSION OF THE LONGWAVE TROUGH. THE WEEKEND APPEARS TO BE A
NICE ONE WITH HIGHS IN THE UPPER 60S TO MID 70S WITH MOSTLY DRY
CONDITIONS THROUGH SUNDAY AFTERNOON.
ON SUNDAY, THE NEXT SHORTWAVE IN THE SUBTROPICAL JET ROTATES INTO
THE SOUTHERN PLAINS, SPAWNING THE NEXT LOW PRESSURE SYSTEM NEAR THE
COLORADO-KANSAS BORDER AT THE LEFT EXIT REGION OF A 110-KNOT JET
STREAK. THERE IS UNCERTAINTY IN THE EXACT TRACK OF THIS MID-LATITUDE
CYCLONE AS IT MOVES TO THE NORTHEAST. THIS WILL HAVE AN INFLUENCE ON
OUR SEVERE WEATHER RISK SUNDAY NIGHT INTO MONDAY, BUT ADDITIONAL
RAIN ACROSS THE REGION IS FOR CERTAIN. ONCE THE FRONT MOVES THROUGH
MONDAY EVENING, DRY AND COLD AIR ADVECTION WILL SUPPRESS POPS
ON TUESDAY.
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 635 PM CDT TUE APR 21 2026
PREDOMINANTLY VFR CONDITIONS ARE ANTICIPATED THROUGH THE PERIOD.
A WEAK COOL FRONT IS EXPECTED TO BECOME STATIONARY NEAR THE
HIGHWAY 30 CORRIDOR TONIGHT, THEN GRADUALLY LIFT NORTHWARD OF KDBQ
WEDNESDAY PM. THIS WILL LEAD TO W/SW WINDS BECOMING LIGHT AND VARIABLE
AT KCID AND KDBQ TONIGHT INTO EARLY WEDNESDAY AM. DESPITE THE LIGHT
WINDS, LARGE DEW POINT DEPRESSIONS PRIOR TO SUNSET OF 18-20+ DEGREES
SHOULD PRECLUDE ANY FOG CONCERNS. LATEST NBM AND 12Z HREF GUIDANCE
LARGELY MESH WITH THIS IDEA WITH LOW PROBABILITIES AT JUST 20-30%
FOR VISIBILITY <5 MILES. SOME OF THE RECENT HRRR VISIBILITY PLOTS
SHOW SOME FOG AND LOW CLOUDS POTENTIALLY FORMING IN THE VICINITY
OF LAKE MICHIGAN TONIGHT/WED AM, BUT VERY WEAK NE LOW LEVEL FLOW
SHOULD KEEP THIS FROM ADVECTING INTO KDBQ. OTHERWISE, SOUTH OF THE
BOUNDARY AT KMLI AND KBRL GUSTY WSW WINDS WILL DIMINISH TO
AROUND 10 KT TONIGHT AND THEN TURN OCCASIONALLY GUSTY TO 20 KT ON
WEDNESDAY. SOME LOWER STRATUS MAY FORM LATE TONIGHT/WED AM
MOSTLY TO OUR SOUTH ACROSS PARTS OF KS/MO WITHIN STRONGER 925-850
HPA MOIST ADVECTION. THIS COULD COME CLOSE TO KBRL PRIOR TO
DAYBREAK, BUT THE GREATER CONFIDENCE ON MVFR CEILINGS WILL BE
JUST TO THE SOUTH. STILL, CAN'T RULE OUT TRANSITORY MVFR CEILINGS
WEDNESDAY LATER AM THROUGH MIDDAY WITH ANY FURTHER CUMULUS
DEVELOPMENT IMMEDIATELY NORTH OF THIS MAIN ADVECTIVE AXIS, BUT
CONFIDENCE IS TOO LOW AT THIS TIME. LATEST NBM PROBABILITIES FOR
CEILINGS <3KFT AGL AT KBRL AND KMLI ON WEDNESDAY ARE AT 30-40%.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
SHORT TERM...ERVIN
LONG TERM...DELAUNE
AVIATION...MCCLURE
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