315
FXUS63 KGRB 100348
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1048 PM CDT FRI MAY 9 2025
UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE
KEY MESSAGES
- THERE IS AN INCREASED RISK OF FIRE ACTIVITY INTO TUESDAY OF NEXT
WEEK DUE TO ABOVE NORMAL TEMPERATURES, LACK OF WIDESPREAD RAIN,
AND LOW HUMIDITY VALUES (20-35%) EACH AFTERNOON. THERE IS
POTENTIAL FOR CRITICAL FIRE WEATHER CONDITIONS ON SUNDAY AND
MONDAY DUE TO GUSTY SOUTHERLY WINDS.
- PATCHY FROST IS POSSIBLE OVER FAR NORTHEAST WISCONSIN ON
SATURDAY NIGHT.
- BELOW NORMAL PRECIPITATION IS EXPECTED OVER THE NEXT WEEK. THE
NEXT CHANCE FOR A WIDESPREAD RAINFALL AND THUNDERSTORMS WILL BE
IN THE THURSDAY-FRIDAY TIME FRAME.
DISCUSSION
ISSUED AT 222 PM CDT FRI MAY 9 2025
SHORT TERM...TONIGHT AND SATURDAY
THE LATEST RAP ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW HIGH
PRESSURE DEPARTING THE REGION TO THE EAST WHILE A COLD FRONT IS
DIVING SOUTHEAST ACROSS NORTHERN MINNESOTA. LARGE 0-1 KM DEWPOINT
DEPRESSIONS (15-20C) EXIST OVER EASTERN MINNESOTA AND WISCONSIN
AND CONSEQUENTLY, CLOUD BASES ARE MAINLY ABOVE 10000 FT ALONG THE
FRONT. NO CONFIRMATION OF A BROKEN BAND OF SHOWERS REACHING THE
GROUND, BUT RADAR RETURNS WOULD SUGGEST SPRINKLES ARE POSSIBLE
OVER NORTHEAST MINNESOTA. OBS ALSO SHOW SURFACE SMOKE IS OCCURRING
BEHIND THE FRONT OVER NORTHWEST MINNESOTA AND EASTERN NORTH
DAKOTA. AS THE FRONT MOVES ACROSS THE AREA, FORECAST CONCERNS
FIRST REVOLVE AROUND SHOWER/STORM POTENTIAL. THEN ATTENTION TURNS
TO FIRE WEATHER.
SHOWER & STORM POTENTIAL TONIGHT: THE COLD FRONT WILL SLIDE
SOUTHEAST ACROSS THE REGION FROM ABOUT MID-EVENING THROUGH LATE
OVERNIGHT. WHILE CONVERGENCE IS DECENT ALONG THE FRONT, MODELS ARE
GENERALLY SPARSE IN GENERATING PRECIP ALONG THE FRONT. IT APPEARS
THAT MODELS THAT GENERATE DEEPER SATURATION IN THE COLUMN,
PERHAPS AS LOW AS 5000 FT, ARE THE GUIDANCE THAT GENERATE PRECIP.
BUT GIVEN THE HIGH CLOUD BASES AND DEWPOINT DEPRESSIONS IN THE
BOUNDARY LAYER, IT SEEMS THAT THE DRIER HRRR AND RAP ARE THE WAY
TO TREND. THIS WOULD PLACE A 20% CHANCE OF SHOWERS WEST OF THE FOX
VALLEY AND BAYSHORE. THUNDER HAS BEEN REMOVED FROM THE FORECAST.
FIRE WEATHER: AFTER ANOTHER DAY OF LOW HUMIDITY (RH'S 15-30%
NORTHWEST OF THE FOX VALLEY), HUDSON BAY HIGH PRESSURE WILL
REASSERT ITSELF ON SATURDAY BEHIND THE COLD FRONT. THIS AIRMASS
WILL NOT BE QUITE AS DRY (50-60% OF NORMAL) AS THE ONE MOVING
ACROSS THE REGION THIS AFTERNOON (20-30% OF NORMAL) AND FORECAST
SOUNDINGS SHOW RELATIVELY SHALLOW MIXING (4000-5000 FT) DUE TO A
COOLER AIRMASS ARRIVING BEHIND THE FRONT. THERE IS QUITE A LARGE
SPREAD IN FORECAST DEWPOINTS ON SATURDAY AFTERNOON. DUE TO RECENT
TRENDS, SIDED WITH THE DRIER SCENARIOS, WHICH PUT MIN HUMIDITIES
AROUND 20-30% WEST OF THE FOX VALLEY AND BAYSHORE. RELATIVELY
LIGHT SUSTAINED WINDS UNDER 10 MPH SHOULD MITIGATE THE FIRE
WEATHER THREAT IN THESE AREAS. WILL CONTINUE TO MENTION AN
INCREASED RISK OF FIRE ACTIVITY IN THE HWO.
FROST POTENTIAL SATURDAY NIGHT: GOOD RADIATIONAL COOLING CONDITIONS
WILL BE PRESENT OVER NORTHEAST WISCONSIN. LOW TEMPERATURES HAVE
TRENDED COOLER WITH SOME MIDDLE 30S POSSIBLE OVER FAR NORTHEAST
WISCONSIN. PATCHY TO AREAS OF FROST APPEAR POSSIBLE OVER SOUTHERN
MARINETTE AND OCONTO COUNTIES.
LONG TERM...SATURDAY NIGHT THROUGH FRIDAY
FOCUS OF THE FORECAST REMAINS ON FIRE WEATHER FROM SUNDAY THROUGH
TUESDAY BEFORE TRENDING TOWARDS PRECIP/THUNDERSTORM CHANCES
WEDNESDAY THROUGH FRIDAY.
FIRE WEATHER: THE DRY AIRMASS FROM THE HUDSON BAY HIGH WILL GET
RECYCLED ACROSS THE AREA DURING THE SUNDAY-MONDAY TIMEFRAME. WHILE
DEWPOINTS WILL BE SLOWLY CLIMBING OVER THIS PERIOD, INCREASING
SOUTH WINDS WILL BE PUSHING WARMER AIR INTO THE STATE. SUNDAY'S
HIGHS RANGING FROM THE MIDDLE TO UPPER 70S WILL WARM TO THE LOW
TO MIDDLE 80S ON MONDAY AND OFFSET THE INCREASING BOUNDARY LAYER
MOISTURE. THIS PUTS RELATIVE HUMIDITIES AS LOWS AS 25-30 PERCENT
EACH DAY WEST OF THE FOX VALLEY AND BAYSHORE. MIXING IS FORECAST
TO BE RELATIVELY SHALLOW (BELOW 5000 FT), BUT WIND PROFILES WOULD
SUGGEST DEEPER THAN ADVERTISED MIXING WILL BE POSSIBLE EACH DAY.
SINCE HUMIDITIES AND WINDS ARE BOTH BORDERLINE FOR CRITICAL FIRE
WEATHER CONDITIONS, IT WOULDN'T TAKE MUCH DEEPER MIXING TO PUSH
CONDITIONS INTO CRITICAL CRITERIA. WILL CONTINUE TO ADVERTISE IN
THE HWO.
BY TUESDAY, GULF MOISTURE WILL START INVADING THE REGION, AND
HUMIDITIES IN THE 30-40% RANGE ARE FORECAST. THEREFORE, CONDITIONS
DO NOT LOOK AS CRITICAL AS SUNDAY OR MONDAY.
PRECIP/THUNDER CHANCES: PRECIPITABLE WATER VALUES WILL BE TRENDING
ABOVE NORMAL BY LATE TUESDAY INTO WEDNESDAY. MODELS CONTINUE TO
ADVERTISE AN INCREASE IN SURFACE BASED INSTABILITY BY WEDNESDAY
THAT COULD RESULT IN A CHANCE OF DIURNAL SHOWERS AND STORMS. A
HIGHER CHANCE OF SHOWERS AND STORMS (40-50%) WILL THEN MOVE INTO
THE REGION ON LATE THURSDAY AFTERNOON INTO THURSDAY NIGHT ALONG A
COLD FRONT. A CORRIDOR OF INSTABILITY IN EXCESS OF 1000 J/KG AND
DEEP LAYER SHEAR IN EXCESS OF 30 KTS WOULD SUGGEST STRONG STORMS
WILL BE POSSIBLE SO TRENDS WILL HAVE TO BE MONITORED.
AVIATION
FOR 06Z TAF ISSUANCE
ISSUED AT 1048 PM CDT FRI MAY 9 2025
VFR CONDITIONS ARE EXPECTED THROUGHOUT THIS TAF PERIOD. A COLD
FRONT WILL CONTINUE TO DROP SOUTHEAST ACROSS THE FORECAST AREA,
PRODUCING SCT MID-CLOUDS ABOVE 8000 FT AGL. A COUPLE OF SHOWERS
WERE ALSO OBSERVED MOVING INTO CENTRAL WI LATE THIS EVENING,
HOWEVER WERE QUICKLY DISSIPATING WITH TIME.
SOUTHWEST TO WEST WINDS AHEAD OF THE FRONT LATE THIS EVENING WILL
VEER NORTH BEHIND THE FRONT LATE TONIGHT, AND BECOME NORTHEAST BY
MIDDAY SATURDAY. GUSTS TO 20 KTS ARE ANTICIPATED ON SATURDAY,
MAINLY AT THE EAST-CENTRAL WI TAF SITES.
GRB WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION.....MPC/MPC
AVIATION.......KRUK
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