229
FXUS63 KARX 181029
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
529 AM CDT WED JUN 18 2025
KEY MESSAGES
- SHOWERS TODAY WITH SCATTERED STORMS POSSIBLE. HIGHEST RAINFALL
AMOUNTS ALONG SOUTHEASTERN PERIPHERAL COUNTIES IN NORTHEAST IOWA
AND SOUTHWEST WISCONSIN WHERE AREAS OF 1"+ ARE POSSIBLE.
- ANOMALOUS WARMTH THIS WEEKEND WITH HEAT INDICES ABOVE 100 DEGREES
PRIMARILY SOUTH OF INTERSTATE 94 LOCALLY.
- STORM CHANCES THURSDAY THROUGH FRIDAY MORNING PRIMARILY NORTH OF
INTERSTATE 90. STRONG TO SEVERE STORMS WILL BE POSSIBLE BUT EXACT
DETAILS REMAIN UNCERTAIN AT THE CURRENT FORECAST HOUR.
DISCUSSION
ISSUED AT 305 AM CDT WED JUN 18 2025
SHOWERS TODAY:
THE NEBULOUS STATIONARY FRONT DRIVING SENSIBLE WEATHER IMPACTS
LINGERS SOMEWHERE OVER THE UPPER MISSISSIPPI RIVER VALLEY EARLY THIS
MORNING. SIMILAR TO PREVIOUS FORECASTS, A SOUTHEAST SHIFT IN
MOISTURE IS EVIDENT IN GOES DERIVED PWATS NEARING 1.25" LOCALLY TO
1.75" ALONG THE EASTERN SHORE OF LAKE MICHIGAN; WHEREAS 17.00Z HREF
MEMBERS SUGGESTED 1.75" LOCALLY. A NORTHEAST TRAJECTORY OF THE MEAN
FLOW ON EARLY MORNING WATER VAPOR IMAGERY WILL BRING THE SURFACE LOW
TOWARDS THE AREA ALBEIT MUCH MORE SOUTH THAN PREVIOUSLY FORECASTED.
OVERALL AMOUNTS FROM 0.25" TO 0.5" EXPECTED WITH AREAS NEARING 1"
ALONG OUR SOUTHEASTERN PERIPHERY. HIGHER THAN 1" AMOUNTS POSSIBLE
WHERE STORMS FREQUENT. BESIDES THE LOCALLY LOWER MOISTURE, OVERALL
PRECIPITATION CHANCES HAVE ALSO DECREASED.
CAN EXPECT SHOWERS TO PROGRESS NORTHEAST THROUGH THE DAY PRIMARILY
AFFECTING SOUTHERN PERIPHERAL COUNTIES IN NORTHEAST IOWA AND
SOUTHWEST WISCONSIN. EVENTUALLY THE EASTERLY PROGRESSING TROUGH AXIS
LEE OF THE ROCKY MOUNTAINS ON EARLY MORNING GOES WV IMAGERY LOOPS
SHUNTS THE FRONTAL BOUNDARY SOUTHEAST INTO TONIGHT PROVIDING
STRONGER FORCING FOR PRECIPITATION POTENTIAL SLIGHTLY FARTHER
NORTHWEST INTO THE FORECAST AREA. UNKNOWN HOW MUCH MOISTURE WILL
RESIDE OR HOW QUICKLY THE FRONT WILL ERODE FOR TEMPORAL OR SPATIAL
IMPACTS SO WHILE POPS ON THE BACKSIDE HAVE INCREASED, NOT A LOT OF
CONFIDENCE. STORM POTENTIAL CAN'T BE RULED OUT BUT WILL CONTINUE TO
BE MONITORED AS THERE IS MUCAPE TO THE NORTHWEST.
POTENTIAL STORMS THURSDAY NIGHT:
WHILE TONIGHT WE BID FAREWELL TO THE STATIONARY FRONT THAT HAS
DRIVEN THE PATTERN OVER THE LAST FEW DAYS, THE ACTIVE PATTERN
CONTINUES THROUGH THE WEEKEND AS THE QUASI-STAGNANT PATTERN BREEDS A
STAGNANT WEAK LOW LEVEL TROUGH LEE OF THE ROCKY MOUNTAINS AND
EXTREMELY STRONG LOW LEVEL THETA E ADVECTION THROUGH THE UPPER
MISSISSIPPI RIVER VALLEY INTO NEXT WEEK.
THE SLOWING SYNOPTIC PATTERN CAUSES AMPLIFICATION OF A WEAK RIPPLE
OVER THE ROCKY MOUNTAIN WEST ON EARLY MORNING GOES WATER VAPOR
IMAGERY THROUGH THURSDAY. A RESULTANT "BACKDOOR" COLD FRONT AND
NORTHWEST TO SOUTHEAST STRETCHING AXIS PROVIDES PRECIPITATION
CHANCES INITIALLY IN NORTHERN TO CENTRAL WISCONSIN THURSDAY NIGHT. A
PREFRONTAL CORRIDOR OF CAPE, 0 TO 500MB BULK SHEAR, AND -CIN
POSITIONS ITSELF FROM NORTHERN MINNESOTA THROUGH THE OHIO RIVER
VALLEY. THE CONTENTION BETWEEN THE RIDGE ADVECTING THE ENTIRE
SYNOPTIC PATTERN NORTHEAST AND THE WAVE DARTING SOUTHEAST PRESENTS
DIFFICULTY IN NAILING DOWN EXACT AREA OF HIGHEST IMPACTS. HOWEVER,
HODOGRAPH PLUMES OF ALL LREF MEMBERS EXHIBIT EXTREMELY LONG PROFILES
SUGGESTING LARGE HAIL WHERE STORMS DO FORM. WILL BE IMPORTANT TO
MONITOR AS SUBSEQUENT HREF RUNS PEER INTO THE THURSDAY NIGHT WINDOW.
STORM POTENTIAL OVERNIGHT THURSDAY INTO FRIDAY MORNING:
THE RIDGE OFF THE WEST COAST ON UPPER LEVEL WATER VAPOR IMAGERY
RAPIDLY AMPLIFIES AND ADVECTS NORTHEAST OVERNIGHT THURSDAY INTO
FRIDAY MORNING, RAMPING UP LOW LEVEL THETA E ADVECTION AND AN
ANTICYCLONICALLY CURVED MIDWEST ATMOSPHERIC RIVER OF 1000 KG M-1 S-1
THROUGH THE UPPER MISSISSIPPI RIVER VALLEY. LREF MEMBERS HAVE
MODERATE CONFIDENCE (75%) FOR 1.5" PWATS ADVECTED BY A 20-40KT LOW
LEVEL JET STREAK INITIALLY TO OUR NORTHWEST SAGGING SOUTHEAST
THROUGH THE FORECAST AREA ON FRIDAY. THE JET CONTINUES NORTHEAST
PUSHING PRECIPITATION CHANCES THROUGH THE GREAT LAKES OVERNIGHT INTO
SATURDAY.
RECORD BREAKING WARMTH THIS WEEKEND:
THE AMPLIFIED RIDGE ALSO USHERS IN ANOMALOUS TEMPERATURES NEAR 30C
AT 850MB (GEPS/GEFS/EPS) OVER THE UPPER MIDWEST THROUGH THE WEEKEND.
WHILE SOLUTIONS ARE /SLIGHTLY/ COOLER THAN PREVIOUSLY SEEN BETWEEN
AND WITHIN EACH MODEL, THESE ARE STILL 15C ABOVE NORMAL FOR THE TIME
OF YEAR. THE MORE NOTICEABLE DIFFERENCE IS A SLIGHTLY QUICKER
SOLUTION THAN PREVIOUS FORECASTS, INCREASING TEMP FORECASTS FOR
SATURDAY AND SATURDAY NIGHT WHILE KEEPING SUNDAY SIMILAR TO PREVIOUS
FORECASTS.
ECMWF EXTREME FORECAST INDEX VALUES ABOVE 0.8 FOR ANOMALOUS WARMTH
ARE SEEN FROM FRIDAY NIGHT THROUGH MONDAY; SUGGESTING A VERY UNUSUAL
EVENT IS LIKELY. SHIFT OF TAILS VALUES ABOVE 0 SUGGEST MORE THAN 10%
OF ENS MEMBERS FORECASTING ABOVE 99TH PERCENTILE MODEL CLIMATOLOGY
FOR THE 5 WEEK PERIOD.
HEAT IMPACTS THIS WEEKEND:
WARMEST TEMPERATURES ARE NOW EXPECTED SATURDAY ACCORDING TO LREF
MEMBER PROBABILITIES IN 6 HOUR APPARENT TEMPERATURES. THIS TEMPORAL
LIMITATION SHOULD BE TAKEN INTO CONSIDERATION REGARDING THE
FOLLOWING PROBABILITIES FOR 100+ DEGREE HEAT INDICES.
PROBABILITIES HAVE INCREASED TO 80-100% OVER THE SAME AREA FROM THE
MISSOURI RIVER VALLEY TO THE MISSISSIPPI RIVER VALLEY FOR SATURDAY.
SUNDAY LACKS SUCH AGREEMENT AS THE GEFS MAXES OUT AT 20%, LOWER THAN
IT'S PREVIOUS VALUE OF 50%, WHILE THE GEPS AND EPS CONTINUE 70-90%
PROBABILITIES THROUGH SUNDAY. THE GEPS CONTINUES TO BE THE WARMEST
SOLUTION HOLDING ON TO 50-70% PROBABILITIES THROUGH MONDAY. ALL WILL
BE DEPENDENT ON THE STRENGTH OF THE BUILDING RIDGE WHICH AT A LONGER
FORECAST HOUR LEAVES MUCH TO BE DETERMINED STILL YET.
STORMS & RAIN THROUGH NEXT WEEK:
WE WEREN'T KIDDING ABOUT THE ACTIVE PATTERN. THE RIDGE BREAKS DOWN
THROUGH NEXT WEEK, MAKING WAY TO AN AMPLIFIED WEST COAST TROUGH THAT
PASSES WAVE AFTER WAVE ALONG SOUTHWEST FLOW. CURRENT NBM POPS SHOW
50%+ FROM DAY 5 ONWARDS. NOT MUCH ELSE TO SAY EXCEPT RAISE AWARENESS
AT THIS TIME.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 529 AM CDT WED JUN 18 2025
VFR EXPECTED THROUGH THE TAF PERIOD FOR THE AREA. SOME
INSTABILITY GROWS IN THE AFTERNOON FOR TSRA CHANCES BUT WITH
COVERAGE, THOSE CHANCES SHOULD REMAIN LOW (20-30%).
CLIMATE
ISSUED AT 305 AM CDT WED JUN 18 2025
RECORD WARMTH THIS WEEKEND:
MAXIMUM WARM LOW
JUNE 21
LA CROSSE: 102 (1988) / 9474 (1943) / 78
ROCHESTER: 99 (1988) / 9372 (1943) / 78
JUNE 22
LA CROSSE: 97 (1995) / 9475 (1983) / 78
ROCHESTER: 94 (1911) / 92 71 (1983) / 77
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...JAR
AVIATION...BAUMGARDT
CLIMATE...BOYNE/JAR
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