620
FXUS63 KARX 202342
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
642 PM CDT SUN APR 20 2025
KEY MESSAGES
- SOGGY WEATHER - WIDESPREAD RAIN (WITH EMBEDDED THUNDERSTORMS)
THIS AFTERNOON AND TONIGHT, EXITING MONDAY MORNING. MEAN
AMOUNTS GENERALLY .80" TO 1.80", HOWEVER MAX AMOUNTS RANGE
FROM 1.5" TO 3.0". 10TH TO 90TH PERCENTILE RAIN RATES ARE
MOSTLY TRACE TO 0.40" PER HOUR. THE 1" PER HOUR RATES ARE
CURRENTLY SOUTH OF THE AREA.
- WITHIN BANK RISES ARE EXPECTED FOR THE CURRENT RAIN FORECAST,
HOWEVER URBAN STREET FLOODING AND PONDING COULD OCCUR. WITH
HIGHER 2"+ AMOUNTS, SOME LOCALIZED RIVER FLOODING COULD OCCUR.
- MILDER TEMPERATURES FOR THE UPCOMING WORK WEEK WITH HIGHS IN
THE 60S. WEDNESDAY WILL LIKELY BE THE WARMEST DAY WITH HIGHS
IN THE 70S ALONG AND SOUTH OF I-90.
- SHOWERS AND STORMS MOVE (60-80% CHANCE) THROUGH THE AREA ON
TUESDAY. ADDITIONAL CHANCES (20-50%) FOR SHOWERS AND STORMS
LATE WEDNESDAY THROUGH FRIDAY.
DISCUSSION
ISSUED AT 240 PM CDT SUN APR 20 2025
OVERVIEW:
AT MIDDAY, WATER VAPOR SATELLITE IMAGERY AND HEIGHTS SHOWED A 500MB
TROUGH OVER THE CENTRAL U.S. WITH AND AREA OF CLOSED LOW PRESSURE
OVER OKLAHOMA AND A LARGE AREA OF HIGH PRESSURE OVER THE SOUTHEAST
U.S. THE LATEST SUBJECTIVE SURFACE ANALYSIS HAD SURFACE LOW PRESSURE
OVER NORTHEAST OKLAHOMA WITH THE WARM FRONT STRETCHED FROM WEST TO
EAST ACROSS CENTRAL MISSOURI INTO SOUTHERN ILLINOIS. AT
18Z...TEMPERATURES WERE IN THE 40S AND 50S WITH DEWPOINTS IN THE 30S
AND 40S, WITH MID 40S ACROSS PARTS OF NORTHEAST IOWA. THE LATEST
WSR-88D HAD AN AREA OF RAIN SPREADING NORTH ACROSS IOWA INTO
SOUTHERN MINNESOTA AND SOUTHERN WISCONSIN. THE THUNDERSTORMS WERE
MOSTLY PUSHING ACROSS NORTHERN ILLINOIS AND INCREASING ACROSS IOWA.
THREE-HOUR RAIN RATES WERE VARIABLE FROM 0.01 TO 0.40".
TONIGHT AND MONDAY:
THE CLOSED 500MB LOW OVER OKLAHOMA AT 18Z IS FORECAST TO LIFT
NORTHEAST ACROSS IOWA THROUGH 03Z BECOMING NEGATIVELY TILTED AND
MOVING ACROSS NORTHWEST WISCONSIN THROUGH 12Z MONDAY. STRONG
MOISTURE TRANSPORT IS ONGOING, BUT WILL STRENGTHEN ACROSS EASTERN
MISSOURI INTO EASTERN IOWA THROUGH 00Z, THEN ACROSS WISCONSIN
TONIGHT. MID-LEVEL FRONTOGENESIS AND PRECIPITABLE WATER VALUES OF .9
TO 1.30" ACCOMPANY THE STORM SYSTEM. THIS FORCING COMBINED WITH 35
TO 45KT LOW LEVEL JET ACROSS IOWA AND ILLINOIS, UPWARD VERTICAL
MOTION, AND BROAD WARM AIR ADVECTING IS RESULTING IN THE WIDESPREAD
BAND OF PRECIPITATION.
AS THE 500MB LOW/SURFACE LOW TRACKS NORTHEAST ACROSS MISSOURI THIS
AFTERNOON AND INTO IOWA THIS EVENING AND ACROSS PARTS OF MINNESOTA
TONIGHT. THE MUCAPE/MLCAPE AXIS REMAINS MORE ROBUST TO THE SOUTH
ACROSS PARTS OF MISSOURI/EASTERN IOWA/ILLINOIS. THE AREA OF MID-
LEVEL FRONTOGENESIS LIFT NORTH AND PIVOTS NORTHWEST. SOME INSTABILITY
WILL LIKELY WORK INTO PARTS OF THE FORECAST AREA DUE TO THE
STRENGTH OF THE LOW LEVEL JET AND WHERE THE DEFORMATION BAND
SETS UP. THE HI-RES CAMS SHOW THE CURRENT BAND OF RAIN LIFTING
NORTH AND PIVOTING NORTHWEST THEN A LINE OF STORMS DEVELOPS FROM
SOUTHEAST IOWA INTO MISSOURI TRACKING EASTWARD INTO ILLINOIS
THIS EVENING. THE CAMS ALSO SHOW THE NORTHERN EXTENT OF THE
STORMS WORKING INTO NORTHEAST IOWA AND SOUTHERN WISCONSIN.
ELEVATED STORMS COULD WORK FARTHER NORTHWEST. THERE IS LIMITED
INSTABILITY; MUCAPE OF 100- 400J/KG TO WORK WITH HOWEVER THERE
IS DEEP LAYER SHEAR OF 40-60KTS. THE HRRR/RAP/NAM SHOWS THERE IS
A BRIEF WINDOW AROUND 05-06Z WHERE STORMS COULD BE SURFACE
BASED OVER FAR SOUTHERN CLAYTON/GRANT COUNTY...THUS WILL NEED TO
MONITOR. THE PRECIPITATION EXITS THE AREA MONDAY MORNING,
HOWEVER NORTH OF I94, SNOW COULD MIX IN WITH NO ACCUMULATION
EXPECTED.
FOR HYDRO DETAILS, SEE THE HYDRO SECTION BELOW.
TUESDAY - WEDNESDAY: PERIODIC SHOWERS AND STORMS, WARMER WEDNESDAY
AS WE HEAD INTO TUESDAY, SOUTHWESTERLY RETURN FLOW WILL PUSH AN AXIS
OF 850MB MOISTURE TRANSPORT INTO THE AREA BEGINNING OVERNIGHT MONDAY
AND INTO TUESDAY AFTERNOON. OVERALL, INSTABILITY IN THE PROFILES IN
THE RECENT NAM SHOWING SOME SKINNY CAPE THROUGHOUT THE DAY ON
TUESDAY WITH MUCAPE VALUES OF 250-1000 J/KG. AS A RESULT, THINKING
THAT SHOWERS AND STORMS WILL LIKELY FORM ON THE NOSE OF THIS
MOISTURE AXIS AS DEPICTED IN SOME OF THE LONG-RANGE CAMS THROUGHOUT
THE DAY ON TUESDAY. THE QUESTION WILL BE LATER INTO THE DAY ACROSS
PORTIONS OF NORTHEAST IA AND SOUTHWEST WI IF STORMS CAN BECOME MORE
SURFACE BASED. CURRENTLY, THE 20.12Z NAM WOULD SUGGEST THAT SOME
SURFACE BASED INSTABILITY WOULD BE PRESENT TUESDAY AFTERNOON AND
EVENING WHICH COUPLED WITH 30-40 KTS OF BULK SHEAR AND DCAPE VALUES
OF 600-800 J/KG COULD RESULT IN SOME ISOLATED GUSTY WINDS AS THE
NOSE OF A SUBTLE LOW-LEVEL JET WORKS IN. OVERALL, THIS SEEMS TO BE
AN EXTREMELY CONDITIONAL THREAT WITH THE CSU GEFS-FV3 BASED MACHINE
LEARNING OUTPUT HAVING ONLY 5% PROBABILITIES FOR SEVERE CONVECTIVE
HAZARDS. REGARDLESS, THERE ARE FAIRLY HIGH PROBABILITIES (60-80%) IN
THE GRAND ENSEMBLE (GEFS/EC/CANADIAN ENSEMBLE) FOR MEASURABLE
PRECIPITATION ACROSS THE AREA WITH LOW-MEDIUM PROBABILITIES
(20-50%) FOR AMOUNTS OVER 0.1".
TEMPERATURES CERTAINLY WILL FEEL QUITE PLEASANT FOR WEDNESDAY AS
SOME MIXING TO 850MB WILL AID WITH SOME CLEARING AND ALLOW OUR
TEMPERATURES TO WARM SOME. AS A RESULT, THE NBM HAS MOST
PROBABILITIES (40-70% CHANCE) FOR HIGH TEMPERATURES TO REACH 70
DEGREES FOR AREAS SOUTH OF I-90 ON WEDNESDAY. SKIES SHOULD
INCREASE SOME LATER INTO THE AFTERNOON AND EVENING AHEAD OF A
PIECE OF ENERGY THAT PUSHES SOUTHEAST OF THE AREA LATE WEDNESDAY
AND INTO THURSDAY. CANNOT RULE OUT SOME SHOWER ACTIVITY TOWARDS
SUNSET WITH THE GRAND ENSEMBLE (GEFS/EC/CANADIAN ENSEMBLE)
SHOWING SOME LOW PROBABILITIES (15-30%) WEDNESDAY EVENING WITH
CURRENT CONSENSUS KEEPING THE BULK OF ANY PRECIPITATION ACTIVITY
UNTIL THE OVERNIGHT.
THURSDAY - SUNDAY: MILD, SHOWER AND STORM CHANCES THURSDAY & FRIDAY
LOOKING LATER INTO THE WORK WEEK, DETERMINISTIC GUIDANCE DISPLAYS A
FEW DIFFERENT WEAKER PIECES OF VORTICITY ADVECTION IN THE
SOUTHWESTERLY FLOW THAT WORK TOWARDS OUR REGION. AS A RESULT, HAVE
HELD ONTO PRECIPITATION CHANCES FROM LATE WEDNESDAY THROUGH FRIDAY.
CURRENTLY, THE BEST FORCING APPEARS TO SWING THROUGH THE AREA
THURSDAY AND INTO FRIDAY MORNING AS BOTH THE 20.12Z GFS/EC HAVE A
SHORTWAVE TROUGH DESCENDING OUT OF SOUTHERN CANADA. OVERALL, THE
PROBABILITY FOR ANY SEVERE WEATHER IS VERY LOW AT THIS TIME WITH THE
AI EC-BASED FENGWU AND PANGU SEVERE HAZARD OUTLOOKS HAVING VIRTUALLY
NO PROBABILITIES FOR ANY SEVERE CONVECTIVE HAZARDS. REGARDLESS,
WILL LIKELY SEE SOME PRECIPITATION THROUGH THE AREA DURING THIS
PERIOD WITH THE GRAND ENSEMBLE (GEFS/EC/CANADIAN ENS) HAVING
HIGH PROBABILITIES (60-90% CHANCE) FOR MEASURABLE PRECIPITATION.
AS FAR AS TEMPERATURES ARE CONCERNED, WITH ZONAL TO SOUTHWESTERLY
FLOW THROUGH THE AREA FOR THURSDAY, EXPECTING TEMPERATURES TO REMAIN
MILD WITH THE NATIONAL BLEND SHOWING SIMILAR TEMPERATURES TO
WEDNESDAY. ADDITIONALLY, THE RECENT NBM HAS RESPECTABLE
PROBABILITIES (30-60% CHANCE) FOR HIGH TEMPERATURES OVER 70 DEGREES
ON THURSDAY SOUTH OF I-90. AS THE AFOREMENTIONED TROUGH WORKS
THROUGH OVERNIGHT THURSDAY, COULD SEE A SLIGHT COOLING TREND WITH
SOME WEAK COLD AIR ADVECTION BEHIND THE TROUGH. HOWEVER, WOULD
LIKELY KEEP THINGS SEASONABLE WITH HIGHS STILL IN THE 60S FOR
FRIDAY AND INTO THE UPCOMING WEEKEND.
AVIATION /00Z TAFS THROUGH 00Z TUESDAY/
ISSUED AT 640 PM CDT SUN APR 20 2025
MVFR AND IFR CONDITIONS CONTINUE FOR MUCH OF THE NEXT 15-21
HOURS AS ONGOING RAIN KEEPS CONDITIONS LESS THAN IDEAL. CURRENT
THINKING IS THAT VFR CONDITIONS WILL EVENTUALLY OCCUR BY MONDAY
AFTERNOON, BUT WILL NEED TO KEEP A CLOSE EYE ON POTENTIAL FOR
LINGERING MVFR CUMULUS TOMORROW, PARTICULARLY IN OUR NORTHEAST.
OTHERWISE WINDS, INITIALLY OUT OF THE EAST, WILL BECOME OUT OF
THE NORTHWEST BETWEEN 06 AND 12Z.
HYDROLOGY
ISSUED AT 240 PM CDT SUN APR 20 2025
RAINFALL AMOUNTS HAVE TRENDED UPWARD OVER THE LAST DAY AND WILL BE
DEPENDENT ON HOW QUICKLY THE RAIN MOVES THROUGH, WHERE THUNDERSTORMS
OCCUR, AND WHERE THE BANDED PRECIPITATION PERSISTS. THE 20.12Z RUNS
OF THE MODELS HAVE GENERAL 0.80- 1.80 AMOUNTS ACROSS THE FORECAST
AREA. THE HREF 24HR ENSEMBLE MAX HAS 1.25 TO 3" AMOUNTS FROM SOUTH
TO NORTH ACROSS THE FORECAST AREA. THE 6HR FLASH FLOOD GUIDANCE IS
2.25 TO 2.75 INCHES OR MORE FOR MOST PLACES, THUS MOST AREAS SHOULD
BE ABLE TO TAKE THE CURRENT FORECASTED AMOUNTS. HOWEVER URBAN
STREET FLOODING AND POOR DRAINAGE AREAS COULD SEE LOCALIZED
FLOODING. THE NCRFC ENSEMBLE MODEL OUTPUT SHOWS THAT IF LOCATIONS
RECEIVE 2 TO 2.5" OF RAINFALL, RIVER FLOODING COULD OCCUR. SOME OF
THE RIVERS OF INTEREST WOULD BE THE BLACK RIVER, THE YELLOW RIVER,
THE TREMPEALEAU RIVER, THE KICKAPOO RIVER, AND TURTLE CREEK.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...NAYLOR/ZAPOTOCNY
AVIATION...FERGUSON
HYDROLOGY...ZAPOTOCNY
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page