098
FXUS63 KDVN 181910
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
210 PM CDT SUN MAY 18 2025
KEY MESSAGES
- ACTIVE PATTERN SET TO DEVELOP LATE TONIGHT THROUGH WEDNESDAY WITH
PERIODS OF SHOWERS AND STORMS. HIGH LIKELIHOOD OF RAINFALL OF
GREATER THAN 1 INCH (60-90% CHANCE) WITH LOCALLY HEAVY RAINFALL
GREATER THAN 2 INCHES POSSIBLE (30-60% CHANCE).
- CONDITIONAL SEVERE WEATHER THREAT (LEVEL 1/2 OUT OF 5) MODULATED
BY THE LOCATION OF A WARM FRONT LATE MONDAY PM/NIGHT, WITH LARGE
HAIL AND DAMAGING WINDS THE PRIMARY THREATS, CURRENTLY FORECAST FOR
SOUTHERN PORTIONS OF THE CWA.
- A SHARP TEMPERATURE GRADIENT IS EXPECTED, ESPECIALLY NEAR
INTERSTATE 80, WITH COOL CONDITIONS NORTH, AND MILDER AIR TO
THE SOUTH THROUGH TUESDAY, FOLLOWED BY WIDESPREAD COOL WEATHER
WEDNESDAY.
SHORT TERM /THROUGH MONDAY NIGHT/
ISSUED AT 207 PM CDT SUN MAY 18 2025
SPECTACULAR SUNDAY WEATHER WILL CONTINUE INTO THIS EVENING, WITH
CLEAR SKIES GRADUALLY FILLING IN WITH MID CLOUDS AND AN NOTICEABLE
EAST WIND BY SUNSET. A BACK DOOR PUSH OF COLDER AIR IS EXPECTED
TONIGHT, AS FLOW BEGINS TO INTERACT WITH DEVELOPING PLAINS LOW
PRESSURE. COLDER AIR, FLOWING SOUTH THROUGH LAKE MICHIGAN IS SET TO
DROP INTO NORTHWEST ILLINOIS BY MID EVENING, AND SPREAD OVER THE
REMAINDER OF THE CWA OVERNIGHT, AS LOWS DROP TO THE LOWER 40S
NORTHEAST TO LOWER 50S SOUTH. THIS COOL LOW LEVEL AIR SHOULD CREATE
A STABLE AIR MASS FOR ANY STORM ARRIVING LATE TONIGHT, AND AT THE
VERY LEAST, LIMIT IMPACTS OF DOWNDRAFTS. MOST MODELS ARE NOW
SHOWING CONVECTIVE DEBRIS AND DISSIPATING RAINFALL ARRIVING FROM THE
WEST LATE TONIGHT, AND CONTINUING MONDAY MORNING IN THAT DISSIPATION
MODE. THE EXCEPTION TO THAT WOULD BE THE NAM WHICH HAS A MCS MOVING
THROUGH OUR AREA. THUS, WE'LL NEED TO WATCH CONVECTIVE TRENDS, AND
SEE IF THE FARTHER NORTH NAM SCENARIO GAINS TRACTION TONIGHT. EITHER
WAY, THE STABLE BOUNDARY LAYER REMAINS FORECAST.
MONDAY, WE'RE EXPECTING MANY MORE DRY HOURS THAN EARLIER FORECASTS,
BUT STILL SEEING CLOUDY SKIES AND EAST WINDS. TEMPERATURES IN THE
UPPER 50S TO LOW 60S ARE EXPECTED NORTH OF I-80, AND MID 60S TO NEAR
70 FARTHER SOUTH. SOME PASSING SHOWERS ARE POSSIBLE AT ANY TIME,
MAINLY FROM ELEVATED WAA PROCESSES.
THE MAIN FOCUS FOR STORMS AND HEAVY RAIN SETS UP MONDAY EVENING, AS
A LARGE AREA OF SHOWERS AND STORMS SPREADS ACROSS NORTHWEST MISSOURI
AND IOWA, SPREADING WIDESPREAD MODERATE TO HEAVY RAIN INTO OUR AREA
THROUGH THE NIGHT. PWATS IN THE 1.30 TO 1.8 RANGE ARE FORECAST TO
CONVERGE INTO OUR REGION, RESULTING IN WIDESPREAD RAINFALL OF 1-2
INCHES MONDAY NIGHT THROUGH TUESDAY MORNING. THE HEAVIEST RAINS
CONTINUE TO BE FORECAST IN OUR SOUTHWESTERN COUNTIES IN THIS PERIOD,
WITH LOWEST AMOUNTS NORTHEAST, BUT STILL OVER 0.5. THIS INITIAL
ROUND OF RAIN SHOULD BE ABSORBED MOSTLY, WITH DEVELOPING DROUGHT
CONDITIONS IN MUCH OF THE AREA. WE CAN'T RULE OUT SOME LOCALIZED
WATER ISSUES, ESPECIALLY WITH ANY HIGH RAINFALL RATES CONVECTIVELY
ENHANCED AND/OR REPEATED HEAVY RAIN OR CONVECTION WITH THE MAIN
CONCERN SHOULD THIS OCCUR IN ANY URBAN AREAS.
SEVERE WEATHER REMAINS CONDITIONAL, AS AMPLE SHEAR EXISTS FOR
UPDRAFT ORGANIZATION, BUT THIS IS WELL NORTH OF THE SURFACE WARM
FRONT. THUS, SOME STORMS MAY PROVIDE A LARGE HAIL THREAT MONDAY
NIGHT, IN OUR SOUTHER COUNTIES, BUT WIND AND TORNADO THREATS APPEAR
LOW GIVEN THE STABLE BOUNDARY LAYER. IF THE DEPTH OF THIS STABLE
LAYER IS THIN ENOUGH, SOME ISOLATED STRONG/SEVERE GUSTS WOULD BE
POSSIBLE IN THE SOUTH, BUT THAT IS FAR FROM CERTAIN.
LONG TERM /TUESDAY THROUGH SATURDAY/
ISSUED AT 207 PM CDT SUN MAY 18 2025
THE STORM SYSTEM CONTINUES TUESDAY INTO WEDNESDAY NIGHT.
TUESDAY, THE LATEST GUIDANCE SUGGEST THE BOUNDARY WILL LIFT UP NEAR
I-80 WHILE LOW PRESSURE RIDES EAST THROUGH THE CWA FROM CENTRAL
IOWA. AT THIS TIME, INSTABILITY APPEARS WEAK, BUT CERTAINLY ENOUGH
TO BRING SLOW MOVING SHOWERS AND THUNDERSTORMS ALONG AND NORTH OF
THE FRONT. WHILE OVERALL QPF IS LOWER IN THE TUESDAY NIGHT AND
WEDNESDAY PERIOD, CONVECTION WILL BE VERY SLOW MOVING, AND A NARROW
AXIS OF HEAVY RAIN IS POSSIBLE, RIGHT NOW FORECAST NEAR I-80 IN IOWA
AND ILLINOIS. THIS SEEMS TO BE A PERIOD WHERE WE COULD SEE SOME
ISOLATED FLASH FLOODING DEVELOP.
AS STATED ABOVE, TEMPERATURES APPEAR QUITE COOL TUESDAY NORTH, AND
MILD SOUTH, THEN COOL IN ALL AREAS WEDNESDAY, AS THE FULLY OCCLUDED
SYSTEM CONTINUE TO SPREAD SHOWERS AND WEAKER STORMS OVER THE AREA.
LOOKING BEYOND, INTO NEXT WEEKEND, PLEASANT TEMPERATURES ARE
FORECAST AS THE UPPER LOW SHIFTS TOWARDS THE EASTERN CONUS. THOUGH A
FEW SHOWERS COULD OCCUR IN NORTHWEST FLOW, THE DRY AIR IN PLACE
WOULD KEEP THE THREAT FOR RAINFALL LOW. HIGHS IN THE 60S TO 70S ARE
FORECAST.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1212 PM CDT SUN MAY 18 2025
VFR CONDITIONS WITH CLEAR SKIES LOOK TO HOLD ON INTO EARLY
EVENING TODAY, BEFORE A DEVELOPING LOW PRESSURE TO OUR WEST
INCREASES EASTERLY FLOW, WHICH THEN BECOME REINFORCED BY LAKE
MICHIGAN BACKDOOR FRONT THAT SHOULD HELP TO BRING OCCASIONAL
MVFR CIGS AND GUSTY EAST WINDS TOWARD MONDAY MORNING. SOME RAIN
SHOWERS ARE POSSIBLE, ESPECIALLY IN SOUTHEAST IOWA, AS WE EXPECT
RAINS TO BE IN A DISSIPATING MODE ON ARRIVAL. THERE ARE FEW
MODELS SUGGESTING A MORE ROBUST AREA OF RAIN AND STORMS BY
MORNING, BUT WE'RE LEANING TOWARD THE MORE DRY SCENARIO AT THIS
TIME.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
SHORT TERM...ERVIN
LONG TERM...ERVIN
AVIATION...ERVIN
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