059
FXUS63 KGRB 180247
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
847 PM CST WED DEC 17 2025
NEW INFORMATION ADDED TO UPDATE SECTION
UPDATE
ISSUED AT 846 PM CST WED DEC 17 2025
THE LATEST RAP ANALYSIS SHOWS A DYNAMIC LOW PRESSURE SYSTEM
STRETCHING FROM SOUTHERN SASKATCHEWAN TO NORTH DAKOTA. WHILE LARGE
DEWPOINT DEPRESSIONS IN THE 0-2 KM LAYER CURRENTLY SUGGEST LITTLE
TO NO CHANCE OF PRECIPITATION, LOW-LEVEL MOISTURE IS SURGING
NORTH OVER SOUTHERN MISSOURI AND ILLINOIS AND WILL ARRIVE LATE
TONIGHT. LIGHT RAIN FALLING OUT OF A MID-LEVEL CLOUD DECK IS ALSO
REACHING THE GROUND OVER MINNESOTA. WIDESPREAD MID- LEVEL CLOUDS
WITH BASES ABOVE 9-10 KFT WILL PERSIST THROUGH 3-4 AM. CURRENTLY
ACROSS NORTHERN WISCONSIN, TEMPERATURES HAVE BOTTOMED OUT IN THE
LOW TO MID 30S AND WILL SLOWLY RISE THROUGH THE REMAINDER OF THE
NIGHT AS SOUTHERLY WINDS INCREASE. TO THE WEST, A POTENT SHORTWAVE
TROUGH IS MOVING THROUGH THE NORTHERN ROCKIES AND WILL ACT AS THE
PRIMARY DRIVER FOR AN INTENSE SURFACE LOW EXPECTED TO CROSS LAKE
SUPERIOR ON THURSDAY.
THE FIRST PHASE OF THIS SYSTEM INVOLVES INCREASING LOW-LEVEL
SATURATION AFTER 3-4 AM. SATURATION APPEARS DEEP ENOUGH IN
FORECAST SOUNDINGS FOR PATCHY DRIZZLE OR LIGHT RAIN BETWEEN 4 AM
AND 6 AM OVER MOST OF THE AREA. WHILE SURFACE TEMPERATURES ARE
EXPECTED TO REMAIN STEADY OR WARM SLIGHTLY, ROAD TEMPERATURES
REMAIN A CONCERN. LATEST RWIS DATA AND FORECAST ROAD TEMP DATA
NEAR THE U.P. BORDER SUGGEST LIGHT ICING POTENTIAL OVER NORTH-
CENTRAL WISCONSIN, GENERALLY NORTH OF A STEVENS POINT TO
ATHELSTANE LINE. THE GREATEST POTENTIAL FOR HAZARDOUS TRAVEL DUE
TO LIGHT ICE ACCUMULATIONS IS ESTIMATED TO OCCUR BETWEEN 4 AM AND
9 AM. TIMING HAS SLOWED SLIGHTLY, BUT A BAND OF LIGHT RAIN IS THEN
EXPECTED TO SLIDE RAPIDLY EAST ACROSS THE REGION BETWEEN 6 AM AND
NOON. GIVEN THE SHORT WINDOW OF FREEZING POTENTIAL, WILL HOLD OFF
ON AN ADVISORY FOR NOW, THOUGH A SHORT- FUSED WINTER WEATHER
ADVISORY MAY BE NEEDED IF PRECIPITATION DEVELOPS FASTER OR SURFACE
TEMPS LAG.
AS THE CYCLONE CROSSES LAKE SUPERIOR THURSDAY AFTERNOON, AN ARCTIC
FRONT WILL TRACK ACROSS THE AREA. SHORT-RANGE GUIDANCE SUGGESTS
FAVORABLE CONDITIONS FOR SNOW SQUALLS BETWEEN MID AND LATE
AFTERNOON. KEY INGREDIENTS INCLUDE SURFACE INSTABILITY UP TO 75
J/KG, LOW-LEVEL FRONTOGENESIS, STEEP LOW-LEVEL LAPSE RATES OF 7-8
C/KM, AND STRONG FORCING VIA THE SHORTWAVE TROUGH. SNOW SQUALL
PARAMETER VALUES BETWEEN 2 AND 6 IN THE NAM REFLECT THIS
POTENTIAL. A FLASH FREEZE WILL ALSO BE POSSIBLE AS SUB-FREEZING
TEMPERATURES SPREAD WEST TO EAST ACROSS WET ROADS THROUGH EARLY
THURSDAY EVENING. LIGHT SNOW AND MINOR ACCUMULATIONS WILL BE
POSSIBLE REGION-WIDE AS THE SYSTEM DEPARTS.
KEY MESSAGES
- MIX OF RAIN AND FREEZING RAIN EXPECTED TONIGHT INTO EARLY
THURSDAY, THEN RAIN CHANGING TO SNOW THURSDAY AFTERNOON AND
EVENING. SNOW SQUALLS POSSIBLE THURSDAY AFTERNOON AND EARLY
EVENING, FOLLOWED BY A POSSIBLE FLASH FREEZE. SIGNIFICANT
TRAVEL CONCERNS POSSIBLE LATE TONIGHT AND AGAIN THURSDAY
AFTERNOON AND EVENING.
- LIGHT SNOW POSSIBLE FRIDAY NIGHT INTO SATURDAY MORNING,
ESPECIALLY OVER FAR NORTHERN WISCONSIN.
- PERIODIC WINDY CONDITIONS AND A CHANCE OF GALES ON LAKE MICHIGAN
THROUGH THE FRIDAY MORNING.
DISCUSSION
ISSUED AT 347 PM CST WED DEC 17 2025
IT'S BEEN A QUIET AFTERNOON, WITH ONLY AN INCREASE IN MID-LEVEL
CLOUDS AND MILD TEMPERATURES IN THE 30S TO AROUND 40.
KEY POINTS/CHANGES FOR TONIGHT AND THURSDAY'S WINTRY SYSTEM:
1) SLOWED DOWN THE ARRIVAL OF PRECIPITATION UNTIL LATE TONIGHT
(AFTER 08Z/THU).
2) FREEZING RAIN POTENTIAL TONIGHT IS CONTINGENT ON ROAD
TEMPERATURES, AS AIR TEMPERATURES WILL BE RISING ABOVE FREEZING
AS THE LIGHT RAIN/DRIZZLE BEGINS LATE TONIGHT. FOLLOWED THE
SAME THINKING AS THE PREVIOUS SHIFT, KEEPING THE FOCUS FOR
FREEZING RAIN OVER THE NORTHWEST HALF OF THE FORECAST AREA. THIS
SEEMED REASONABLE AS AFTERNOON TEMPERATURES WERE IN THE LOWER 30S
IN THIS AREA (AND WILL DROP INTO THE MID TO UPPER 20S THIS
EVENING), AND CURRENT ROAD TEMPERATURES WERE ONLY IN THE MID 30S
TO LOWER 40S (BUT LOWER TO MIDDLE 40S FARTHER SOUTHEAST). ICE
ACCUMULATIONS SHOULD BE LIGHT AND ONLY A FEW HUNDREDTHS OF AN
INCH, BUT EVEN THESE AMOUNTS WOULD CAUSE SIGNIFICANT TRAVEL
CONCERNS.
3) HAVE ADDED THE POTENTIAL FOR SNOW SQUALLS TO THE FORECAST
DURING THE AFTERNOON AND EARLY EVENING, BUT PRECISE TIMING IS
UNCERTAIN AT THIS TIME. MODELS SHOW SIGNIFICANT SNOW SQUALL
PARAMETER VALUES MOVING THROUGH THE CWA ALONG THE ARCTIC FRONT,
REACHING NC/C WI DURING THE EARLY AFTERNOON 1-3 PM, AND THE FOX
VALLEY MID TO LATE AFTERNOON (4-6 PM). FALLING TEMPERATURES AND A
POSSIBLE FLASH FREEZE WILL FOLLOW AFTER THE SNOW SHOWERS/SQUALLS,
STARTING MID-AFTERNOON IN NC/C WI AND OVERSPREADING THE FOX
VALLEY AND LAKESHORE COUNTIES FROM 5-7 PM. POTENTIAL FOR
SIGNIFICANT TRAVEL IMPACTS DUE TO ICY CONDITIONS.
4) MOST PLACES SEE WELL UNDER AN INCH OF SNOW, BUT VILAS COUNTY
SHOULD RECEIVE 1-3 INCHES WITH LOCAL HIGHER AMOUNTS IN THE FAR
NORTHWEST PART OF THE COUNTY DUE TO LAKE-EFFECT.
REST OF THE FORECAST...A CLIPPER SYSTEM PASSES THROUGH THE REGION
FRIDAY NIGHT INTO EARLY SATURDAY, BRINGING A ROUND OF LIGHT
ACCUMULATING SNOW (1-2 INCHES) TO MAINLY FAR NORTHERN WI AND DOOR
COUNTY. NO OTHER SIGNIFICANT PRECIPITATION EVENTS ARE EXPECTED
THROUGH THE REST OF THE WEEK. TEMPERATURES WILL BE ON A ROLLER
COASTER RIDE, AS A COUPLE DIFFERENT COLD FRONTS MOVE THROUGH THE
REGION.
WINDS...SEVERAL PERIODS OF GUSTY WINDS ARE EXPECTED FROM TONIGHT
THROUGH FRIDAY MORNING. NOT REAL CONFIDENT WITH GALE POTENTIAL FOR
THE SOUTH WIND/WAA EVENT TONIGHT, BUT CONFIDENCE HAS GROWN HIGH
ENOUGH TO ISSUE A GALE WARNING FOR THE THU NGT/FRI AM CAA PORTION
OF THE SYSTEM.
AVIATION
FOR 00Z TAF ISSUANCE
ISSUED AT 534 PM CST WED DEC 17 2025
VFR CONDITIONS WILL PREVAIL THROUGH 08Z-10Z BEFORE A POTENT STORM
SYSTEM BRINGS DETERIORATING FLIGHT CONDITIONS. INCREASING
MOISTURE WILL LEAD TO LOWERING CEILINGS AND THE DEVELOPMENT OF
LIGHT RAIN AND FREEZING RAIN FROM WEST TO EAST AFTER 10Z. THE
GREATEST RISK FOR FREEZING RAIN EXISTS AT RHI/AUW/CWA WHERE
SURFACE TEMPERATURES REMAIN BELOW FREEZING LONGEST; HOWEVER, ANY
LIQUID PRECIPITATION MAY FREEZE ON COLD RUNWAYS. CONDITIONS WILL
QUICKLY DROP TO IFR/LIFR BY 12Z-14Z AS WIDESPREAD RAIN AND FOG
DEVELOP AND BEGIN TO MIX WITH SNOW BY MID TO LATE MORNING.
A POWERFUL ARCTIC FRONT WILL SWEEP THROUGH THE REGION THURSDAY
AFTERNOON. THIS WILL TRIGGER A TRANSITION FROM RAIN TO SNOW, WITH
A PERIOD OF SNOW SQUALLS LIKELY BETWEEN 19Z AND 23Z. THESE SQUALLS
MAY PRODUCE BRIEF LIFR VISIBILITIES AND GUSTY WINDS. A FLASH
FREEZE IS ALSO POSSIBLE AS TEMPERATURES PLUMMET BEHIND THE FRONT.
LOW-LEVEL WIND SHEAR IS A SIGNIFICANT CONCERN TONIGHT INTO
THURSDAY MORNING AS A 45-55 KT SOUTHWESTERLY JET MOVES OVERHEAD AT
2,000 FT. SURFACE WINDS WILL BECOME GUSTY FROM THE SOUTH-
SOUTHEAST TONIGHT, VEERING WEST AND REMAINING GUSTY BEHIND THE
FRONT THURSDAY AFTERNOON.
GRB WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE.........MPC
DISCUSSION.....KIECKBUSCH
AVIATION.......MPC
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