241
FXUS63 KDVN 180517
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1217 AM CDT THU JUN 18 2026
KEY MESSAGES
- QUIET AND SOMEWHAT COOLER THAN NORMAL WEATHER WILL BE SEEN
THROUGH THE SECOND HALF OF THE WORK WEEK, WITH THE PATTERN
BECOMING ACTIVE AGAIN THIS WEEKEND AND BEYOND.
UPDATE
ISSUED AT 1135 AM CDT WED JUN 17 2026
OUR FOCUS IS NOW ON THE ASSESSMENT OF MORNING STORMS AND THEIR
EFFECT ON THE AFTERNOON ACTIVITY. WHILE THERE IS A NOTABLE
IMPRINT ON THE TEMPERATURE FIELD, ONE CHALLENGE WITH THIS EVENT
IS THAT IT IS FAR MORE SPRING-LIKE THAN SUMMERTIME. IN OTHER
WORDS, THE STRENGTH OF THE LOW PRESSURE (992 MB) WILL HELP DRIVE
PARAMETER FIELDS BY STRONGER ADVECTION THAN WE WOULD TYPICALLY
SEE IN JUNE. AS A TESTAMENT TO THIS IS AN IMPRESSIVE JUNE
TEMPERATURE GRADIENT ACROSS THE AREA WITH MID TO UPPER 50S NORTH
AND CENTRAL TO LOW 80S JUST SOUTH OF THE CWA.
THE SURFACE WARM FRONT MODULATED BY OUTFLOW FROM THE MORNING
STORMS IS DRAPED JUST SOUTH OF THE CWA BORDER. STRONG WAA ALOFT
AND MOISTURE TRANSPORT ARE RESULTING IN REGULARLY DEVELOPING
THUNDERSTORMS NEAR THE 850 MB FRONTAL ZONE OVER THE I-80
CORRIDOR, WITH MAINLY A FLASH FLOOD THREAT. ALSO IMPRESSIVE
CLOUD-TO-GROUND LIGHTNING EVEN WHEN RAIN RATES DIMINISH SOME.
NEAR THE SURFACE WARM FRONT, SATELLITE INDICATES FAIRLY SOLID
CLOUD COVER NEAR THE IOWA/MISSOURI BORDER. HOWEVER, SOME OF THIS
IS TRANSITIONING TO TOWERING CUMULIFORM CLOUDS FROM NEAR
OTTUMWA SOUTHWESTWARD ALONG A CONFLUENCE AXIS. WE ARE THINKING
THIS MAY BE THE START OF THE AFTERNOON ROUND OF STORMS AS IT
PROGRESSES EASTWARD ACROSS LOCATIONS NEAR/SOUTH OF U.S. HIGHWAY
34, AND LIKELY SOME GRADUAL NORTHEAST EXPANSION, POSSIBLY EVEN
NEAR TO THE I-80 CORRIDOR IN ILLINOIS.
AS UPPER FORCING FROM A 120 KT UPPER JET IMPINGES OVER THIS
AREA, MATURE CONVECTION SHOULD GRADUALLY DEVELOP. THESE STORMS
WILL BE AT LEAST CLOSE TO BEING ROOTED IN THE BOUNDARY LAYER,
BUT EVEN IF SLIGHTLY ELEVATED WILL HAVE SEVERE POTENTIAL. THE
PARAMETER SPACE REMAINS FAVORABLE FOR SIGNIFICANT SEVERE
WEATHER, INCLUDING HAIL EVEN THOUGH WE DID NOT HAVE MUCH WITH
THE MORNING ACTIVITY. OF GREATER CONCERN IS IF ROOTED IN THE
BOUNDARY LAYER THERE WOULD BE THE THREAT OF TORNADOES, SOME
POTENTIALLY SIGNIFICANT GIVEN A STOUT PARAMETER GRADIENT (AS
SHOWN BY A FORECAST STP GRADIENT OF 1-6 BY 3 PM). WHETHER THAT
TRULY MANIFESTS INTO SURFACE-BASED SUPERCELLS IN OUR CWA IS
STILL AN UNCERTAINTY.
NOW THIS IS NOT TO SAY THERE IS NOT A SEVERE, AND EVEN A LOWER
END TORNADO THREAT, FURTHER NORTH TOWARD IOWA CITY AND THE
QUAD CITIES, SIMPLY BECAUSE OF THE DYNAMICS WITH THIS SYSTEM.
DEW POINTS IN THE MID 60S HAVE RETURNED TO CENTRAL IOWA ON
SOUTHEAST WINDS, AND CONTINUED PRESSURE FALLS WILL HELP KEEP
THAT LOW-LEVEL THEAT-A ADVECTION INCREASING AHEAD OF THE LOW
PRESSURE. IN TANDEM WITH EFFECTIVE SHEAR IN THE 1-6 KM LAYER OF
50+ KTS, AT LEAST SOME ORGANIZATION FOR SCATTERED SEVERE IS
PLAUSIBLE, AND WE'LL HAVE TO KEEP A CLOSE EYE ON THE LOW-LEVELS.
AS LONG AS STORMS KEEP REGENERATING ALONG THIS I-80 CORRIDOR,
IT MAY PREVENT TRUE LOW-LEVEL WARMING AND CAPE FROM BUILDING UP
TO THE I-80 CORRIDOR IN OUR CWA.
CONFIDENCE IS HIGH IN ANY SEVERE WEATHER THREAT CLEARING OUR
AREA NEAR 7 PM. ISOLATED SHOWERS AND STORMS IN NORTHWEST
ILLINOIS MAY CONTINUE TO 9 PM BEFORE THE FORCING HAS PUSHED
EAST.
SHORT TERM /THROUGH FRIDAY/
ISSUED AT 225 PM CDT WED JUN 17 2026
BUILDING UPON THE UPDATE DISCUSSION ABOVE, INCREASING SHEAR PROFILES
WITH THE ARRIVAL OF STRONGER WIND FLOW AT SEVERAL LEVELS IS
OCCURRING, WITH EFFECTIVE SHEAR PROFILES OF 50-60 KTS. A SECONDARY
WARM FRONT LIFTING UP TO THE I-80 CORRIDOR WHILE A COOL FRONT IS
SQUEEZING EASTWARD ACRS WESTERN INTO CENTRAL IA. BUT THE PRIME
INTERACTION WITH BUILDING/RE-BUILDING INSTABILITY/CAPES WITH A SHARP
TIGHT GRADIENT IS ALIGNING ALONG AN AGITATED CU FIELD SEEN ON THE
VIS SATELLITE LOOP FROM ACRS WEST CENTRAL ILWEST-SOUTHWESTWRAD ACRS
FAR NORTHERN MO AND WEST OF THE KANSAS CITY AREA. THIS IS WHERE NEW
SUPERCELLULAR STORM DEVELOPMENT IS EXPECTED SOON, THUS THE DVN
SOUTHERN THIRD TO QUARTER OF THE CWA WILL BE AT RISK FOR THIS
DEVELOPMENT, WITH THE ACTIVITY THEN SLIPPING SOUTH OF THE CWA
THROUGH LATE AFTERNOON. THE OTHER ACTION ZONE OF MAINLY ELEVATED
STORMS CLOSER TO THE UPPER LOW/TROUGH WILL ROTATE ACRS SOUTHERN MN,
FAR NORTHEAST IA AND INTO WI THROUGH MID EVENING, POSSIBLY MAKING
THE BULK OF THE DVN CWA IN BETWEEN THESE TWO MAIN CONVECTION ZONES.
THUS THERE MAY BE JUST A FEW STRAY ELEVATED SHOWERS OR STORMS MOVING
ACRS THE LOCAL AREA AFTER THE POTENTIAL STORMS IN OUR SOUTH MIGRATE
SOUTHWARD TO CAPE FEED, BUT MAY STILL HAVE TO WATCH THE STRENGTH OF
THESE "IN-BETWEEN" STORMS.
POST FRONTAL WEST-NORTHWESTERLY BOUNDARY LAYER FEED TO BRING ABOUT
LOW TEMPS DOWN IN THE 50S FOR MUCH OF THE AREA BY THURSDAY MORNING.
LATER ON THURSDAY LOOKS LIKE A BLUSTERY POST-FRONTAL DAY WITH PLENTY
OF CUMULUS DEVELOPMENT AND/OR WRAP AROUND FOR PARTLY TO MOSTLY
CLOUDY CONDITIONS FOR MUCH OF THURSDAY. WITH THE DIURNAL HEATING AND
CONTINUING CYCLONIC FLOW ALOFT, THERE MAY BE A FEW ISOLATED TO SCTRD
SHOWERS EMBEDDED IN THE CU FIELDS. CLEAR OUT AND SFC WIND DECREASE
MAKING FOR A COOL NIGHT INTO FRIDAY MORNING WITH WIDESPREAD LOWS
WELL DOWN IN THE 50S.
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
ISSUED AT 225 PM CDT WED JUN 17 2026
QUICK LOOK AT THE LONGER RANGE SUGGESTS SOME RETURN FLOW WARMING FOR
FRIDAY AHEAD OF A CLIPPER-LIKE SYSTEM THAT WILL LOOK TO DROP DOWN IN
NORTHWESTERLY STEERING FLOW ACRS THE WESTERN GRT LKS. THIS WILL
BRING A CHANCE FOR A SHOWER AND POSSIBLE STORM IN OR NEAR THE CWA
LATE FRIDAY AND FRIDAY EVENING. CONTINUED WARMING FOR SATURDAY
TRYING TO PULL SOME 80S UP ACRS THE LOCAL AREA. THEN EYES TURN TO
MCS GENERATION ACRS THE CENTRAL PLAINS SAT NIGHT, AND THE POTENTIAL
FOR THIS FEATURE TO PROPAGATE EASTWARD AND IMPACT THE LOCAL AREA ON
SUNDAY SOMETIME WITH STRONG STORMS AND HEAVY RAINFALL. BEYOND THAT,
UPPER JET ENSEMBLES SUGGESTS A RETURN TO NORTHWESTERLY STEERING FLOW
ACRS THE UPPER MS RVR VALLEY EARLY TO MID NEXT WEEK MAKING THE AREA
SUSCEPTIBLE TO CLIPPER-TYPE WAVE GENERATED PRECIP EVENTS EVERY OTHER
DAY OR SO, DEPENDING ON MOISTURE RETURN FOR THESE WAVES TO
UTILIZE.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 1214 AM CDT THU JUN 18 2026
WINDS WILL CONTINUE TO SLOWLY DIMINISH BUT PERIOD GUSTS TO
AROUND 15 KNOTS WILL BE POSSIBLE. ONCE THE INVERSION BREAKS
(APPROX. 14Z/18) ANOTHER ROUND OF GUSTS UP TO 15 KNOTS WILL BE
POSSIBLE UNTIL SUNSET THURSDAY.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
UPDATE...FRIEDLEIN
SHORT TERM...12
LONG TERM...12
AVIATION...08
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page