000
FXUS63 KARX 231138
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
638 AM CDT WED APR 23 2025
KEY MESSAGES
- PERIODIC SHOWER/T-STORM CHANCES THROUGH FRIDAY. COVERAGE VARIABLE
TODAY THROUGH THURSDAY, HOWEVER WIDESPREAD PRECIPITATION IS FORECAST
THURSDAY NIGHT. RAINFALL AMOUNTS .10" OR MORE I90 SOUTH THROUGH
THURSDAY (70-90% PROBABILITY), BUT .50"+ THURSDAY NIGHT (60-80%) FOR
MUCH OF THE AREA.
- SEVERE RISK 1 OF 5 TODAY FROM NORTHEAST IOWA INTO SOUTHERN
WISCONSIN. LARGE HAIL IS THE PRIMARY RISK WITH A SECONDARY RISK OF
DAMAGING WINDS (5 TO 10%).
- POTENTIAL FOR FLOODING STILL APPEARS TO BE MORE LOCALIZED. CURRENT
RAIN OF .5 TO 1.25" IS FORECAST. SHOULD TRAINING OF STORMS OR
HEAVIER RAIN OCCUR IN THE 1.5 TO 2.5" RANGE, LOCALIZED FLOODING
COULD OCCUR.
- ANOTHER STRONG TROUGH COULD BRING SEVERE WEATHER AND HEAVY
RAINFALL TO THE REGION NEXT MONDAY AND TUESDAY ALONG WITH SEASONABLY
WARM TEMPERATURES IN THE 70S.
DISCUSSION
ISSUED AT 320 AM CDT WED APR 23 2025
OVERVIEW:
LATEST WATER VAPOR SATELLITE IMAGERY, HEIGHTS AND LIGHTNING SHOWED A
ZONAL FLOW FROM WEST TO EAST ACROSS THE CENTRAL PART OF THE COUNTRY.
AN AREA OF LOW PRESSURE WAS NOTED OVER MANITOBA, SOME TROUGHING
OVER THE NORTHWEST U.S. AND A RIPPLE OVER CANADA. SEVERAL
CONVECTIVE COMPLEXES WERE SEEN THROUGH THE PLAINS FROM TEXAS
NORTHEAST INTO EASTERN KANSAS AND PARTS OF IOWA. AT
04Z...ISOLATED CELLS NEAR MARSHALLTOWN WERE PRODUCING QUARTER
SIZED HAIL AND WERE MOVING EAST WITH MORE STORMS IN A WEST TO
EAST LINE ACROSS SOUTHERN IOWA. BY 08Z, A MORE WIDESPREAD AREA
OF STORMS WERE OVER CENTRAL IOWA IN NORTHERN IOWA. THE STORMS
WERE GENERALLY PUTTING DOWN HEAVY DOWNPOURS OF RAIN WITH SOME
SMALL HAIL. AT 08Z...THE 50S DEWPOINTS WERE NOT YET IN OUR
LOCAL AREA WITH 30S AND 40S LOCALLY.
ACTIVE WEATHER THROUGH FRIDAY:
THE 500MB LOW IS FORECAST TO CONTINUE TO MOVE ACROSS SOUTHERN CANADA
TODAY AND TONIGHT WITH SOME AMPLIFICATION AHEAD OF ANOTHER TROUGH
THAT TRACKS ACROSS SOUTHERN CANADA AND THE UPPER MISSISSIPPI RIVER
VALLEY THURSDAY INTO FRIDAY. THIS PATTERN WILL BE QUITE ACTIVE DUE
TO THE AXIS OF 1" TO 1.3" PRECIPITABLE WATER LIFTING NORTH INTO THE
FORECAST AREA THIS MORNING AND AGAIN THURSDAY INTO FRIDAY, WITH
RELATIVELY COLD AIR ALOFT/STEEP LAPSE RATES. THE NORTHERN
STORMS ARE ALONG THE MUCAPE GRADIENT, THE GRADIENT OF THE
EFFECTIVE SHEAR AND THE SOUTHERN GRADIENT OF THE 0-6KM SHEAR.
THIS FARTHER NORTH LOCATION COULD BE AIDED BY THE UPPER LEVEL 85
TO 90KT JET THAT IS CURRENT ACROSS THE DAKOTAS.
HOW FAR NORTH WILL THE STRONG TO SEVERE STORMS MAKE IT? PARTS OF
NORTHEAST IOWA INTO SOUTHERN WISCONSIN ARE IN THE MARGINAL RISK
(RISK LEVEL 1 OF 5). THIS SEEMS REASONABLE THIS TODAY AS THE
MOISTURE TRANSPORT OVER CENTRAL IOWA LIFTS NORTH ACROSS THE
FORECAST AREA/TOWARD I90 THIS MORNING, THEN BUILDING ACROSS
NORTHEAST IOWA AND SOUTHWEST WISCONSIN THIS AFTERNOON BEFORE
DECREASING THIS EVENING. THE AXIS OF MU/MLCAPE 1300J/KG IS WHERE
THE STORMS WERE AT 05Z. THIS INSTABILITY AXIS LIFTS NORTH THIS
MORNING THEN WEAKENS. THE UPPER LEVEL JET STRENGTHENS WITH UPPER
LEVEL SUPPORT MOVING ACROSS THE FORECAST AREA. THE 30 TO 35KT
LOW LEVEL JET OVER SOUTHWEST IOWA IS FORECAST TO STRENGTHEN TO
35KTS OVER CENTRAL IOWA BY 12Z, BUT WEAKENS SOMEWHAT TO 25KTS
15Z AND 18Z BEFORE STRENGTHENING AGAIN TO 40KTS BY 21Z OVER
EASTERN IOWA INTO SOUTHERN WISCONSIN.
THE MOST RECENT HRRR NEURAL NETWORK CONVECTIVE HAZARD FORECAST HAS 5
TO 12% PROBABILITIES FOR ANY SEVERE WEATHER ACROSS PARTS OF EASTERN
IOWA INTO ILLINOIS THROUGH 12Z AND 5 TO 10% PROBABILITIES FOR
NORTHEAST IOWA AND SOUTHWEST WISCONSIN TODAY. ISOLATED STORMS HAVE
PRODUCED PEA TO 1.25" HAIL TO THE SOUTH, THUS CERTAINLY CAPABLE
OF PRODUCING HAIL WITH ANY STRONGER STORMS THAT DEVELOP.
THE HI-RES CAMS HAVE THIS FIRST BATCH OF STORMS MOVING TO THE EAST
AND SATELLITE IMAGERY AT 0530Z WAS ALREADY SHOWING THIS NEXT BATCH
OF STORMS BEGINNING TO DEVELOP WITH THE INCREASING LOW LEVEL
JET. BY 08Z, THE SHOWERS AND THUNDERSTORMS WERE SCATTERED ACROSS
MUCH OF CENTRAL IOWA. THE CAMS HAVE MORE WIDESPREAD SHOWERS AND
THUNDERSTORMS OVER NORTHWEST/CENTRAL IA BY 09Z AND THESE PUSH
ACROSS NORTHEAST IOWA INTO SOUTHWEST WI BY 12Z AND LAST THROUGH
THE MORNING HOURS TOWARD GRANT CO. WITH THE HRRR. HOWEVER THE
RAP HAS MORE THUNDERSTORMS FARTHER NORTH, SCATTERED ACROSS THE
FORECAST AREA TO NORTH OF I94. THE CAMS THEN HAVE ANOTHER LINE
OF STORMS FROM AROUND 17Z THROUGH 22Z WITH ADDITIONAL SCATTERED
SHOWERS AND STORMS INTO THE EVENING AND OVERNIGHT. THE 50S
SURFACE DEWPOINTS ARE DRAWN NORTHWARD PER THE RAP13 ACROSS
NORTHEAST IOWA BY 12Z AND MAKE IT INTO SOUTHERN TREMPEALEAU CO
BY 15Z THEN SHIFT EASTWARD WITH THE FRONT, HOWEVER THERE IS A
SECONDARY FRONT WITH A TRAILING DEWPOINT MAXIMUM WITH THAT. THE
40S DEWPOINTS TRY TO SETTLE TOWARD I90 BY 06Z. THUS, SHOWERS
AND STORMS WILL LINGER AHEAD OF THE 850MB FRONT, THEN THE 850MB
FRONT PUSHES NORTH AGAIN THURSDAY AND AGAIN PUSHING SOUTH BY
26.00Z FRIDAY EVENING.
TONIGHT THERE IS SOMEWHAT OF A BREAK IN THE ORGANIZED PRECIPITATION
TONIGHT AS THE MOISTURE TRANSPORT SHIFTS SOUTHEAST OF THE AREA
THEN INCREASES THURSDAY AFTERNOON/NIGHT INTO FRIDAY WITH THE
NEXT TROUGH PASSAGE. AGAIN, INSTABILITY IS LIMITED AND THE
STRONGER FRONTOGENESIS APPEARS JUST NORTH OF THE AREA. WE
CONTINUE TO SEE THE POTENTIAL FOR WIDESPREAD RAINS THURSDAY
NIGHT.
TEMPERATURES REMAIN MILD TODAY AND THURSDAY WITH HIGHS IN THE 60S
AND 70S (SOME 50S NORTH OF I94 THURSDAY), THEN COOLER WITH 50S TO
AROUND 60 FRIDAY.
RAINFALL AMOUNTS ARE CURRENTLY FORECAST IN THE .5 TO 1.25" RANGE,
HOWEVER THE 23.00 HREF 24HR ENSEMBLE MAX THROUGH THURSDAY SHOWS SOME
SPOTTY 1.5 TO 2.5" AMOUNTS COULD OCCUR. DUE TO THE WIDESPREAD
RECENT RAINS, WILL NEED TO MONITOR FOR TRAINING OF STORMS WITH
POCKETS OF .5 TO 1" RAINFALL RATES. THE 6HR FLASH FLOOD GUIDANCE IS
1.5 TO 2.75". THUS, MUCH OF THE AREA SHOULD BE ABLE TO HANDLE
THE CURRENT RAIN FORECAST, HOWEVER WHEREVER TRAINING OR HEAVIER
THUNDERSTORMS OCCUR, LOCALIZED FLOODING COULD OCCUR.
DRIER FRIDAY AFTERNOON THROUGH SATURDAY NIGHT:
THE FRONT PUSHES SOUTH DURING THE AFTERNOON FRIDAY WITH SURFACE
HIGH PRESSURE BUILDING IN WITH SEASONABLE TEMPERATURES IN THE
UPPER 50S TO MID 60S FOR SATURDAY.
MORE STORMS LATER IN THE WEEKEND INTO EARLY NEXT WEEK; SEVERE
POTENTIAL TOO EARLY TO DETERMINE, BUT WILL BE WATCHING HOW THINGS
COME TOGETHER WITH THE STRONG TROUGH:
A 500MB RIDGE BUILDS IN SUNDAY AHEAD OF THE NEXT APPROACHING TROUGH
WITH DEEP MOISTURE RETURNING, THUS SHOWERS/ELEVATED STORMS COULD
FORM WITH AND RIPPLE IN THE FLOW. AS THE LONGWAVE TROUGH APPROACHES
AND SOUTH FLOW INCREASES ALONG WITH THE INSTABILITY. THE
ECE/GEFS/GEPS HAVE A JOINT PROBABILITY OF MUCAPE GREATER THAN
500J/KG AND BULK WIND SHEAR >30KTS IN A SOUTH TO NORTH AXIS FROM THE
PLAINS TO THE FORECAST AREA MONDAY. IT IS STILL A WAYS OUT, BUT WE
WILL BE LOOKING INTO THE DETAILS FOR MONDAY AND TUESDAY RELATED
TO THE SEVERE WEATHER AND HEAVY RAINFALL POTENTIAL.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 639 AM CDT WED APR 23 2025
A MCS WILL MOVE SOUTH AND SOUTHEAST OF THE TAF SITES THIS
MORNING. ADDITIONAL SHOWERS AND STORMS WILL DEVELOP ALONG A
BOUNDARY TO THE SOUTH OF THE TAF SITES THIS AFTERNOON AND
TONIGHT. AT THIS TIME, BOTH TAF SITES LOOK TO BE DRY WITH VFR
CEILINGS AND VISIBILITIES.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...ZAPOTOCNY
AVIATION...BOYNE
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