307
FXUS63 KGRB 111917
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
217 PM CDT WED JUN 11 2025
FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE
KEY MESSAGES
- SMOKE FROM THE CANADIAN WILDFIRES COULD REACH THE SURFACE AT
TIMES INTO THURSDAY, WHICH MAY IMPACT AIR QUALITY.
- LIGHT SHOWERS TONIGHT (40-60 PERCENT CHANCE) MAINLY SOUTH OF
HIGHWAY 29.
- MAJORITY OF SHOWERS STAY SOUTH ON THURSDAY, THEN SHOWERS AND
SOME STORMS LIKELY THURSDAY NIGHT THROUGH FRIDAY NIGHT. SEVERE
WEATHER RISK LOOKS LOW. HEAVY RAIN IS POSSIBLE, ESPECIALLY OVER
NORTHERN WI. PROBABILITY OF OVER 1 INCH OF RAIN IS 45-55
PERCENT, WHILE PROBABILITY OF OVER 2 INCHES OF RAIN IS 10-20
PERCENT. RAIN TAPERS OFF LATE FRIDAY NIGHT INTO SATURDAY.
- ACTIVE AGAIN NEXT WEEK WITH CHANCES OF SHOWERS AND STORMS.
DISCUSSION
ISSUED AT 211 PM CDT WED JUN 11 2025
SHORT TERM...TONIGHT AND THURSDAY
PARTLY TO MOSTLY SUNNY SKIES THIS AFTERNOON (MID CLOUDS AND A FEW
FAIR WEATHER CU) AND MUCH WARMER THAN THE MOSTLY CLOUDY AND COOL
DAY WE EXPERIENCED ON TUESDAY. TEMPERATURES EARLY THIS AFTERNOON
ARE ALREADY 15 TO 20F WARMER COMPARED TO THIS TIME YESTERDAY. A
TOUCH OF HUMIDITY AS WELL AS DEWPOINTS FROM FOX VALLEY TO THE
LAKESHORE ARE AROUND 60. WEST-NORTHWEST FLOW ALOFT AND DIVERGENCE
ALOFT COMBINED WITH MID-LEVEL FGEN AND A SHORTWAVE WILL TEAM UP
TO BRING IN SOME CLOUDS THIS AFTERNOON, THEN SOME SHOWERS AND
MAYBE A RUMBLE OF THUNDER THIS EVENING THROUGH EARLY THURSDAY,
MAINLY SOUTH OF HIGHWAY 29. RAIN OVER OUR AREA SHOULD BE LIGHT AND
SCATTERED AS MID-LEVEL FORCING WEAKENS AND THERE IS A LOT OF DRY
AIR TO OVERCOME AS SEEN ON THE 12Z GRB SOUNDING. POCKETS OF HEAVY
RAIN EXPECTED TO THE SOUTH OF OUR AREA, CLOSER TO SURFACE FRONT
FROM NORTHERN IA EAST ACROSS SOUTHERN WI.
ON THURSDAY, CLOUDS WITH A FEW SHOWERS MAY DRIFT WEST TO EAST
ACROSS SOUTHERN HALF OF THE AREA WHICH IS CLOSER TO 850MB WARM
FRONT. SURFACE FRONT ACTUALLY LOOKS TO BE SHOVED EVEN FARTHER
SOUTH ON THURSDAY IN WAKE OF THE SHOWERS AND STORMS THAT MOVE
THROUGH OVERNIGHT TONIGHT. OVER THE NORTH ON THURSDAY, SKIES
SHOULD BE MOSTLY SUNNY. THERE WILL BE ELEVATED WILDFIRE SMOKE,
EVEN DOWN BELOW 10KFT AGL AND PERHAPS AT THE SURFACE AT TIMES,
WHICH WILL KEEP IT HAZY. HIGH TEMPS WILL BE HELD DOWN OVER THE
SOUTH BY THE CLOUDS AND POSSIBLE SHOWERS AND EAST-NORTHEAST
WINDS OFF LAKE MICHIGAN TO THE NORTH OF THE SURFACE FRONT.
LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY
STRONGER SHORTWAVE TROUGH WILL BE OVER THE NORTHERN PLAINS ON
THURSDAY EVENING. AHEAD OF THE TROUGH, MAIN LOW-LEVEL FRONT WILL
STILL BE SOUTH OF OUR FORECAST AREA, SOUTHERN SD, EASTWARD ALONG
MN/IA AND WI/IL STATE LINE. ALONG AND SOUTH OF THE BOUNDARY IS
WHERE HIGHER MUCAPE WILL RESIDE. EVEN SO, MODELS AND NOW THE
ENSEMBLE CONSENSUS AS WELL PEGS AREA FROM THE TWIN CITIES INTO
NORTHWEST/NORTH-CENTRAL WI AS MOST FAVORED SWATH OF MODERATE TO
POSSIBLY HEAVY RAIN AS THIS IS WHERE THE STRONGEST FORCING/DEEP
LAYER LIFT TRACKS AHEAD OF NORTHERN PLAINS SHORTWAVE. THAT SAID,
THERE IS A LOT OF SPREAD IN THE MODELS WHERE AXIS OF HEAVIEST RAIN
OCCURS. AS MENTIONED YESTERDAY, THINK THIS IS BECAUSE THERE IS A
MISALIGNMENT BETWEEN GREATEST MUCAPE/INSTABILITY SOUTH, TO THE
STRONGER FORCING FARTHER NORTH. PWATS INTO THIS SYSTEM UP TO 1.5
INCHES ARE ABNORMALLY HIGH, BUT NOT EXTREME (125-150 PERCENT OF
NORMAL WHICH IS ABOVE THE 90TH PERCENTILE FOR THE DAY, BUT STILL
WELL BELOW THE DAILY MAX).
DECENT SPREAD IN MODELED 24HR QPF ENDING AT 00Z SATURDAY IS STILL
PRESENT IN LREF/NBM GUIDANCE. MAIN TREND THAT HAS EMERGED IN LAST
DAY IS A SHIFTING OF THE HIGHER "FLOOR" OF QPF FORECAST TO THE
NORTH, CLOSER TO THE STRONGER FORCING. FOR THOSE AREAS, A
ENSEMBLES AND NBM POINT TO REASONABLE HIGH-END AMOUNT (90TH
PERCENTILE) AROUND 2 INCHES. MANY HIGHER RESOLUTION DETERMINISTIC
MODEL SOLUTIONS ARE EVEN HIGHER THOUGH, ESPECIALLY OVER MN INTO
FAR WESTERN WI. THIS IS ALSO WHERE WPC CONTINUES TO HIGHLIGHT A
SLIGHT RISK FOR EXCESSIVE RAINFALL (ERO), WHICH IS A LEVEL 2 OF 4.
OUR FORECAST AREA AT THIS POINT IS IN A MARGINAL RISK (1 OF 4).
FRIDAY WILL BE A COOLER DAY NORTH OF THE FRONT WHERE IT WILL
REMAIN IN THE 50S ALL DAY. CLOSER TO THE FRONT AND IN AREA WHERE
SOME BREAKS WILL FORM IN THE CLOUDS AND SHOWERS WILL NOT BE AS
WIDESPREAD, READINGS MAY REACH INTO THE LOWER 70S SOUTH OF HIGHWAY
10. BULK OF SHOWERS WITH MODERATE TO HEAVY RAIN WILL PERSIST UNTIL
LATE FRIDAY AFTERNOON, BEFORE EXITING FRIDAY EVENING, LEAVING
SCATTERED SHOWERS FOR THE REST OF THE NIGHT. GIVEN THE SETUP WITH
WARM FRONT STAYING TO THE SOUTH, CANNOT RULE OUT BREEZY EAST WINDS
AND SOME FOG AT TIMES LATER FRIDAY INTO FRIDAY NIGHT.
RIDGING OVER THE CENTRAL CONUS THIS WEEKEND FLATTENS BY EARLY
NEXT WEEK, PUTTING THE REGION INTO SOUTHERN EDGE OF STRONGER
WESTERLY MID-UPPER FLOW. AT THE SURFACE, LOW PRESSURE AND FRONTAL
BOUNDARY DROP SOUTHEAST AS STRONGER NORTHERN STREAM WAVE CROSSES
THE NORTHERN GREAT LAKES. A CHANCE OF SHOWERS WILL LINGER ON
SATURDAY, BEFORE DRIER WEATHER ARRIVES SATURDAY NIGHT INTO SUNDAY
AS HIGH PRESSURE BUILDS IN FROM CANADA.
NEXT WEEK AS THE MID-UPPER FLOW FLATTENS, WINDS ALOFT ARE STRONGER
AND THERE IS GREATER INSTABILITY PRESENT ON EDGE OF ELEVATED MIXED
LAYER (EML) FROM THE PLAINS. GIVEN THAT SETUP, THERE IS POTENTIAL
FOR SEVERE WEATHER. HOWEVER, THE EXTENT OF THIS WILL DEPEND ON
STRENGTH OF SHORTWAVES WITHIN THE ZONAL FLOW AND TIMING OF THOSE
WAVES. TOO EARLY TO HONE IN ON SPECIFIC WINDOWS FOR GREATER RISKS
AND NO HIGHLIGHT FROM SPC YET ANYWHERE IN THE REGION.
TEMPERATURES...ROLLER COASTER FOR THE WEEKEND. TEMPS STAY ON THE
COOLER SIDE OF AVERAGE ON SATURDAY AS CLOUDS GRADUALLY CLEAR OUT.
SEASONAL AGAIN ON SUNDAY, THEN READINGS REBOUND BY NEXT WEEK WITH
THE 25TH PERCENTILE OF NBM STILL SHOWING HIGHS IN THE MID TO
UPPER 70S, WHILE 75TH PERCENTILE POINTS TO MID 80S. GFS AND ECMWF
MOS GUIDANCE SHOWING READINGS UPPER 70S TO LOWER 80S STARTING ON
MONDAY. ALSO LOOKS LIKE HUMIDITY WILL BE ON THE RISE.
AVIATION
FOR 18Z TAF ISSUANCE
ISSUED AT 1223 PM CDT WED JUN 11 2025
MID-LEVEL DISTURBANCE MOVING IN FROM THE NORTHERN PLAINS ALONG
WITH A MID-LEVEL FRONT AND SWATH OF MOISTURE WILL SUPPORT NARROW
BAND OF SHOWERS INTO CENTRAL WI THIS EVENING, SHIFTING TO FOX
VALLEY AND EAST-CENTRAL WI LATE EVENING AND EARLY OVERNIGHT. ALL
THE TAF SITES WITH EXCEPTION OF RHI HAVE A MENTION OF LIGHT
SHOWERS. CHANCES FOR ANY THUNDER LOOK TO STAY SOUTH OF THE TAF
SITES. RAIN WITH THIS WEAK SYSTEM EXITS BEFORE DAYBREAK ON
THURSDAY. SURFACE FRONT TO THE SOUTH WILL KEEP RISK OF A FEW LIGHT
SHOWERS ON THURSDAY, BUT TOO LOW OF A CHANCE TO INCLUDE IN TAFS.
DESPITE THE CLOUDS AND SHOWERS, CONDITIONS AT ALL TAF SITES WILL
BE VFR. SOME VISIBILITY REDUCTION (5-6SM AT TIMES) WILL BE PRESENT
DUE TO AREAS OF SMOKE DRIFTING ACROSS. MOST OF THE SMOKE WILL
REMAIN ALOFT THOUGH.
NORTHWEST WINDS WILL GUST TO 15-20 KTS INTO MID AFTERNOON. WINDS
WILL BECOME LIGHTER INTO TONIGHT WHILE SHIFTING TO THE EAST. THE
EAST WINDS ON THURSDAY WILL INCREASE BY MIDDAY, ESPECIALLY CLOSER
TO THE LAKE AT MTW.
GRB WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION.....JLA
AVIATION.......JLA
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