051
FXUS63 KGRB 221058
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
558 AM CDT WED OCT 22 2025
UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE
KEY MESSAGES
- ON AND OFF RAIN SHOWERS REMAIN EXPECTED THROUGH TONIGHT. LAKE
EFFECT SHOWERS LATE TONIGHT INTO THURSDAY MORNING POTENTIALLY
MIXING WITH THE SEASONS FIRST SNOWFLAKES OVER FAR NORTH-CENTRAL
WISCONSIN.
- GUSTY NORTHWEST WINDS UP TO 30 TO 35 MPH ARE POSSIBLE THROUGH
TODAY, CREATING HAZARDOUS CONDITIONS FOR SMALL CRAFT ON LAKE
MICHIGAN AND GREEN BAY.
- A FROST OR FREEZE IS EXPECTED OVER THE FOX VALLEY AND LAKESHORE
AREAS ON THURSDAY NIGHT, LIKELY ENDING THE GROWING SEASON.
- BELOW NORMAL TEMPERATURES ARE EXPECTED THROUGH THURSDAY FOLLOWED
BY A SLOW WARMING TREND INTO THE WEEKEND.
DISCUSSION
ISSUED AT 210 AM CDT WED OCT 22 2025
SHORT TERM...TODAY...TONIGHT...AND THURSDAY
THE LATEST RAP ANALYSIS SHOWS A LOW PRESSURE SYSTEM SPINNING OVER
THE CENTRAL UPPER PENINSULA EARLY THIS MORNING. AN EMBEDDED
SHORTWAVE AND MID-LEVEL FRONTOGENESIS ASSOCIATED WITH THIS PARENT
LOW ARE CONTRIBUTING TO RAIN ACROSS MUCH OF EASTERN WISCONSIN,
WITH LAKE-ENHANCED SHOWERS OVER THE FAR NORTH-CENTRAL PART OF THE
STATE. WIDESPREAD MVFR ALONG WITH PATCHY IFR CEILINGS ARE PRESENT
ACROSS THE REGION. AS DEEP CYCLONIC FLOW CONTINUES, PRIMARY
FORECAST CONCERNS REVOLVE AROUND SHOWER TRENDS AND GUSTY WINDS.
THE LOW PRESSURE SYSTEM WILL TRACK ACROSS LAKE HURON TODAY AND
INTO QUEBEC TONIGHT, BUT DEEP CYCLONIC FLOW WILL REMAIN OVER THE
REGION THROUGH THURSDAY.
AFTER A RELATIVE LULL IN THE RAIN THIS MORNING, DIURNAL HEATING
WILL INCREASE THE COVERAGE OF SHOWERS ONCE AGAIN BY LATE MORNING.
SHOWERS SHOULD DIMINISH OUTSIDE OF THE LAKE EFFECT BELT OF NORTH-
CENTRAL WI BY EARLY EVENING. LAKE EFFECT SHOWERS WILL CONTINUE
OVER NORTH-CENTRAL WISCONSIN THROUGH THURSDAY MORNING. AS A
THERMAL TROUGH MOVES IN TONIGHT, 850MB TEMPERATURES WILL DROP TO
4C TO 5C BELOW. THIS CREATES FAVORABLE INGREDIENTS FOR LAKE
EFFECT PRECIPITATION OFF WESTERN LAKE SUPERIOR, INCLUDING
FAVORABLE WIND TRAJECTORIES, DELTA-TS OF 15-17C, AND HIGH RELATIVE
HUMIDITY IN THE 850-700MB LAYER WITH LAKE-INDUCED EQUILIBRIUM
LEVELS UP TO 12,000 FT. FORECAST SOUNDINGS AND PRECIPITATION TYPE
DATA CONTINUE TO INDICATE THE POTENTIAL FOR THE FIRST SNOWFLAKES
OF THE SEASON TO MIX IN WITH THESE LAKE EFFECT SHOWERS OVER FAR
NORTH-CENTRAL WI LATE TONIGHT INTO EARLY THURSDAY MORNING. THE
LAKE EFFECT SHOWERS SHOULD COME TO AN END BY EARLY AFTERNOON
THURSDAY.
STRONG WINDS AND BOATING HAZARDS: NORTHWEST WINDS WILL REMAIN
GUSTY AT TIMES THROUGH TONIGHT, WITH GUSTS OF 25 TO 30 MPH
EXPECTED. ISOLATED GUSTS TO 35 MPH ARE POSSIBLE OVER CENTRAL AND
EAST-CENTRAL WI. THE SMALL CRAFT ADVISORY WILL BE EXTENDED THROUGH
MIDNIGHT TONIGHT. UNSTABLE CONDITIONS WILL PERSIST OVER THE BAY
AND LAKE MICHIGAN, WITH 25 TO 30 KTS OF NORTHWEST FLOW IN THE
BOUNDARY LAYER CREATING HAZARDOUS CONDITIONS FOR SMALL CRAFT.
LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
THE LARGE SYNOPTIC SCALE TROUGH ACROSS THE GREAT LAKES IS
FORECAST TO FINALLY DEPART ON THURSDAY NIGHT AND FRIDAY. THIS WILL
ALLOW HIGH PRESSURE TO GRADUALLY BUILD INTO THE REGION.
FROST/FREEZE POTENTIAL: CLEARING SKIES BEHIND THE DEPARTING
TROUGH WILL LEAD TO FROST OR FREEZE POTENTIAL FOR MOST AREAS
THURSDAY NIGHT AND FRIDAY. CONFIDENCE OF WIDESPREAD FROST IS ONLY
MEDIUM DUE TO UNCERTAINTY ABOUT WHETHER WINDS WILL FULLY DECOUPLE.
WITH THE CENTER OF THE HIGH PASSING SOUTH OF THE AREA, FROST
POTENTIAL IS LOWER OVER THE FOX VALLEY AND LAKESHORE, WHERE THE
GROWING SEASON HAS YET TO END. A PERSISTENT BREEZE IN THESE AREAS
MAY RESULT IN A FREEZE OR NO FROST AT ALL, DESPITE LOWS IN THE
LOWER TO MIDDLE 30S.
REST OF THE FORECAST: A SLOW WARMING TREND WILL COMMENCE ON
FRIDAY AND CONTINUE INTO MONDAY. FORECAST PREDICTABILITY FOR
PRECIPITATION OVER THE WEEKEND REMAINS LOW DUE TO A SPLIT FLOW
PATTERN. WHILE MEDIUM-RANGE MODELS LAST NIGHT INDICATED A COMPACT
SHORTWAVE COULD BRING LIGHT PRECIPITATION FRIDAY NIGHT AND
SATURDAY, TONIGHTS MODELS HAVE SHIFTED THIS FEATURE FURTHER NORTH.
THE NEXT POTENTIAL FOR A LARGER SYSTEM ARRIVES LATE ON MONDAY
INTO NEXT TUESDAY, OCT 28, AS A TROUGH IS EXPECTED TO SPUR SURFACE
CYCLOGENESIS OVER THE CENTRAL/NORTHERN PLAINS.
AVIATION
FOR 12Z TAF ISSUANCE
ISSUED AT 557 AM CDT WED OCT 22 2025
DEEP CYCLONIC FLOW WILL PERSIST ACROSS THE REGION TODAY AS A LOW
PRESSURE SYSTEM TRACKS ACROSS LAKE HURON AND INTO QUEBEC.
WIDESPREAD MVFR CIGS, WITH PATCHY IFR, ARE IMPACTING ALL TAF SITES
(KGRB, KATW, KMTW, KAUW, KCWA, KRHI) THIS MORNING. CONDITIONS ARE
EXPECTED TO IMPROVE SLIGHTLY WITH DAYTIME HEATING THIS AFTERNOON,
BECOMING MVFR. SCATTERED -SHRA, CURRENTLY FOCUSED OVER FAR
NORTHERN WI, WILL INCREASE IN COVERAGE LATE THIS MORNING BEFORE
DIMINISHING BY EARLY EVENING. LAKE ENHANCEMENT WILL KEEP SHOWERS
GOING OVER NORTH-CENTRAL WI (MAINLY KRHI) THROUGH THE PERIOD. A
FEW SNOWFLAKES COULD MIX IN AT TIMES LATE TONIGHT INTO EARLY
THURSDAY MORNING, BUT NO IMPACTS ARE EXPECTED.
STRONG NW WINDS WILL GUST 20-25 KTS AT TIMES TODAY, CREATING THE
POTENTIAL FOR GUSTY CROSSWINDS. WINDS WILL SUBSIDE UNDER 20 KTS
TONIGHT.
TONIGHT, MVFR CIGS ARE EXPECTED TO PERSIST ACROSS CENTRAL
AND NORTH- CENTRAL WI. HOWEVER, VFR CONDITIONS COULD RETURN TO
NORTHEAST WI, INCLUDING THE FOX VALLEY (KGRB, KATW), LATE TONIGHT.
CONFIDENCE IN THE OVERALL CIG/VIS TRENDS IS HIGH, WITH MEDIUM
CONFIDENCE ON THE EXACT TIMING OF THE RETURN TO VFR CONDITIONS IN
THE FOX VALLEY LATE TONIGHT.
OUTLOOK...A MIX OF MVFR AND VFR CONDITIONS IS EXPECTED ON
THURSDAY. HIGH PRESSURE BUILDING IN THURSDAY NIGHT WILL BRING
CLEARING SKIES AND WIDESPREAD VFR FOR FRIDAY.
GRB WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION.....MPC
AVIATION.......MPC
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