636
FXUS63 KGRB 140918
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
ISSUED BY NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
418 AM CDT WED MAY 14 2025
KEY MESSAGES
- DENE FOG ADVISORY IS IN EFFECT FOR SOUTHEAST PARTS OF THE CWA.
MARINE DENSE FOG ADVISORY FOR THE NEARSHORE AREAS OF LAKE
MICHIGAN.
- THERE IS A CHANCE (25-35%) FOR STORMS WEDNESDAY AFTERNOON FOR
CENTRAL WI.
- SHOWERS AND STORMS ARE MOST LIKELY (50-80% CHANCE) THURSDAY
AFTERNOON AND EVENING. SEVERE STORMS ARE POSSIBLE WITH THE
PASSAGE OF A COLD FRONT WITH ALL HAZARDS POSSIBLE.
DISCUSSION
ISSUED AT 418 AM CDT WED MAY 14 2025
DENSE FOG OF 1/2 MILE VISIBILITY OR LESS HAS PUSHED INLAND FROM
LAKE MICHIGAN BUT HAS ALSO BEGUN TO DEVELOP INLAND AS WELL.
DENSE FOG WAS ORIGINALLY TRACKED FROM THE LAKE BUT HAS BEGIN TO
DEVELOP ELSEWHERE FURTHER INLAND THAN ORIGINALLY EXPECTED. A
DENSE FOG ADVISORY IS IN EFFECT FOR MARINETTE, OCONTO,
MENOMINEE, SHAWANO, WAUPACA, WINNEBAGO COUNTIES AND EAST THROUGH
10 AM CDT WEDNESDAY. THE VISIBILITIES HAVE LARGELY STARTED TO
FALL ACROSS THE CWA WITH LOW CEILINGS MIXING IN AS WELL. THERE
HAS NOT BEEN MUCH SIGNAL FOR HOW THIS WILL PLAY OUT EARLY THIS
MORNING BUT GIVEN THE WORSENING CONDITIONS I HAVE CONTINUED TO
SPREAD THE DENSE FOG ADVISORY FURTHER WEST AS OBS CONTINUE TO
SHOW LOWER VISIBILITIES. IT DOES SEEM TO HAVE A PATCHY NATURE
TO IT AS SOME LOCATIONS ARE SHOWING UP AND DOWN VISIBILITIES.
HOWEVER, LATER THIS MORNING AS THE SUN RISES WE WILL START TO
SEE THE FOG AND LOW CLOUDS DISSIPATE AS WE WARM UP. ADVISORY IS
SLATED TO END AT 15Z BE MAY BE ABLE TO BE ENDED EARLIER
DEPENDING ON HOW QUICKLY THIS DISSIPATES.
ANOTHER ROUND OF POP-UP SHOWERS AND STORMS IS POSSIBLE THIS
AFTERNOON, PRIMARILY TOWARD CENTRAL WI AWAY FROM THE LAKE DUE TO
MORE STABLE AIR. SURFACE BASED CAPE INCREASES TO 500 TO 1000
J/KG FROM CENTRAL TO NORTH- CENTRAL WI BUT WITH BASICALLY NO
DEEP LAYER SHEAR ANY STORMS WILL REMAIN UNORGANIZED. THERE IS
NOT MUCH OUT THERE TO FORCE STORMS AT ALL EITHER OUTSIDE OF JUST
YOUR TYPICAL DIURNAL HEATING AND MAYBE A SOME WEAK PVA ALOFT BUT
IF WE CAN GET A FEW STORMS THE OUTFLOWS FROM DYING STORMS MAY
BE ENOUGH TO BRING MORE SCATTERED STORM ACTIVITY. ONCE THE SUN
GOES DOWN ACTIVITY WILL LIKELY DISSIPATE FAIRLY QUICKLY
INTO THURSDAY WE MAY SEE A FAIRLY SIGNIFICANT SEVERE WEATHER
SETUP FOR THE REGION AS AN EML WILL BE BUILDING INTO WISCONSIN
STARTING THURSDAY MORNING, AS A WARM FRONT SURGES NORTH ACROSS
THE REGION. THIS WILL KEEP US CAPPED IN THE MORNING HOURS BUT
WILL FEATURE STEEP 700-500MB LAPSE RATES AROUND 7.5-8.5 DEG
C/KM. THE CAP WILL BE LOCATED AROUND 800-700MB AND WILL BE
FAIRLY SIGNIFICANT AT FIRST. A FEW SHOWERS/STORMS MAY BE
ONGOING ALONG THE LEADING EDGE OF THE EML EARLY THURSDAY, MAINLY
ACROSS THE NORTHERN PORTIONS OF THE STATE, BUT FOR THE MOST
PART THE STRONG CAP SHOULD LIMIT SHOWER/THUNDERSTORM ACTIVITY
THROUGH AT LEAST EARLY AFTERNOON. THE LATEST CAMS GENERALLY SHOW
LITTLE TO NO ACTIVITY THURSDAY MORNING, WHICH WILL MEAN PLENTY
OF SUN TO WARM THINGS UP AHEAD INTO THE AFTERNOON. AT THE
SURFACE, SOUTHEAST WINDS WILL ALLOW FOR WARMER TEMPS AWAY FROM
THE LAKE, WITH UPPER 70S TO LOW 80S OVER THE CENTRAL AND
NORTHERN PORTIONS OF THE STATE. EXPECT COOLER TEMPERATURES
CLOSER TO THE LAKE. SURFACE DEWPOINTS ARE EXPECTED TO RISE INTO
THE UPPER 50S TO MID 60S, HIGHEST FURTHER SOUTH. THIS IS
EXPECTED TO RESULT IN A LARGE BAND OF 2000+ J/KG OF MLCAPE
ACROSS MUCH OF THE STATE BY EARLY AFTERNOON, GRADUALLY SLIDING
EASTWARD.
AN UPPER LOW CENTERED OVER SOUTH DAKOTA WILL SWING A BAND OF
PVA INTO WESTERN WI INTO THE AFTERNOON HOURS. IN ADDITION,
A COLD FRONT AT THE SURFACE WILL BE SWINGING THROUGH AS WELL.
THUS, THE FORCING IS EXPECTED TO BE PLENTIFUL AND WILL HELP WITH
OVERCOMING THE CAPPING INVERSION FROM THE EML. WE WILL ALSO
START TO SEE INCREASING FLOW ALOFT OVERSPREADING THE AREA FROM
THE WEST, RESULTING IN 40-50 KT OF DEEP LAYER SHEAR ACROSS THE
REGION. THE GREATEST UNCERTAINTY WITH THE FORECAST REMAINS THE
DRY MIDLEVEL AIR DUE TO THE EML. MOST MODELS HAVE STORMS AT
THIS POINT ESPECIALLY ACROSS NORTHERN WI WITH THE CAPPING
INVERSION LARGELY ERODED BY THE MID AFTERNOON. EVEN IF WE DO NOT
FULLY ERODE THE CAP THE FORCING IS STILL ENOUGH TO BRING SOME
ELEVATED SUPERCELLS WITH LARGE HAIL. BUT IF WE CAN BECOME
SURFACE BASED THE CONCERN FOR ALL HAZARDS INCREASES. THE
QUESTION THEN TURNS TO WHAT THE MODE WILL BE.
INITIALLY DISCRETE SUPERCELLS MAY BE LIKELY AND WHILE IT COULD
GET A BIT MESSY (LESS-DISCRETE) FAIRLY QUICKLY YOU COULD EASILY
SEE THIS REMAIN MOSTLY INDIVIDUAL CELLS. THE NAM 3KM IS VERY
MUCH A MODEL THAT TRENDS TOWARD PRODUCING A LINE OF STORMS BUT
EVEN THIS MODEL KEEPS THINGS RATHER DISCRETE AND CELLULAR IN
NATURE. EVENTUALLY IT MAY BECOME MORE LINEAR LATER ON BUT THIS
IS DEFINITELY SOMETHING TO NOTE. ANY INDIVIDUAL CELLS WILL HAVE
ACCESS TO GREAT LOW LEVEL HELICITY PROFILES WITH VERY LARGE HAIL
AND EVEN SOME TORNADOES (POSSIBLY STRONG) WILL BE POSSIBLE.
SINCE FRONTAL AND UPPER LEVEL FORCING WILL BE STRONGER ACROSS
THE NORTHERN HALF OF THE STATE. THE RISK FOR STRAIGHT LINE WINDS
WILL INCREASE WITH ANY LINEAR SEGMENTS, ALONG WITH A CONTINUED
HAIL AND A QLCS TORNADO RISK.
AS THIS PUSHES EAST THE LAKE WILL COME INTO PLAY AGAIN WITH
SOUTHEAST FLOW AND LAKE BREEZE CIRCULATION POTENTIALLY CAUSING
STORMS TO GO ELEVATED. STORMS ARE LIKELY TO MOVE QUICKER THAN
EXPECTED WITH MOST OF THE SEVERE RISK OUT OF THE AREA BY THE
EARLY TO MID EVENING HOURS.
FRIDAY THROUGH WEDNESDAY:
UPPER LEVEL TROUGH PIVOTS ACROSS THE WESTERN GREAT LAKES ON FRIDAY
WITH ANOTHER SHORTWAVE CROSSING DURING PEAK HEATING AHEAD OF
SECONDARY COLD FRONT. THE FORCING AND SURGE OF CAPE OVER 500J/KG
MAY RESULT IN ANOTHER ROUND OF SHOWERS AND SOME THUNDERSTORMS
ESPECIALLY OVER EAST-CENTRAL WI IN THE AFTERNOON. SOUNDINGS SHOW
WELL MIXED BOUNDARY LAYER WITH INVERTED-V PROFILE, SO THERE IS
A POTENTIAL FOR STRONG AND GUSTY WINDS WITH STRONGER STORMS.
REALLY THOUGH, EVEN BESIDES POSSIBLE CONVECTION, IT WILL BE A
WARM AND BREEZY DAY AS 850MB WINDS OF 40-50 KTS SUPPORT PEAK
GUSTS OF 35-45 MPH IN THE AFTERNOON, STRONGEST FROM THE FOX
VALLEY TO THE LAKESHORE. HIGHS WILL REACH AROUND 80 EAST-CENTRAL
AND WELL INTO THE 70S ELSEWHERE.
COLD FRONT SWEEPS THROUGH FRIDAY NIGHT AS LOW PRESSURE TRACKS
ACROSS LAKESUPERIOR. COOLER TEMPS, ARRIVE FOR SATURDAY AS HIGHS
RANGE FROM THE MID 50S NORTH, TO AROUND 60 IN CENTRAL WI AND
INTO THE MID 60S FOR THE FOX VALLEY TO THE LAKESHORE. STILL
COULD BE SCATTERED SHOWERS OVER NORTHERN WI IN THE COLD AIR
BEHIND THE LOW.
HIGH PRESSURE THEN SETTLES FROM MANITOBA TO ONTARIO LATER IN THE
WEEKEND BRINGING DRY WEATHER. TEMPS COULD DROP INTO THE MID 30S
NORTH SATURDAY NIGHT AND/OR SUNDAY NIGHT. NBM PROBABILITIES OF
MIN TEMPS LESS THAN 35 ARE AROUND 40 PERCENT SATURDAY NIGHT OVER
VILAS COUNTY, BUT INCREASE AND EXPAND TO 40-65 PERCENT ON
SUNDAY NIGHT OVER MUCH OF NORTHERN WISCONSIN. IF WINDS BECOME
LIGHT, SOME FROST COULD OCCUR ONE OR BOTH OF THESE NIGHTS.
BROAD TROUGHING OVER THE WESTERN CONUS LATE THIS WEEKEND SHIFTS
EAST EARLY NEXT WEEK, BRINGING THE NEXT CHANCE OF SHOWERS AND
STORMS TO THE AREA MONDAY NIGHT INTO TUESDAY. EARLY, BUT MACHINE
LEARNING PROGS DO SHOW AT LEAST A SMALL CHANCE (5-15%) THAT
STRONGER STORMS COULD OCCUR.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1225 AM CDT WED MAY 14 2025
LIGHT EAST TO SOUTHEAST WINDS TONIGHT WITH DENSE FOG BEING THE
PRIMARY IMPACT EARLY THIS MORNING. VSBYS LESS THAN A MILE AND AS
LOW AS QUARTER-MILE HAVE PUSHED AS FAR WEST AS BROWN AND CALUMET
COUNTIES BUT LOOKS LIKELY TO PUSH A BIT FURTHER WEST THROUGH THE
EARLY MORNING HOURS. THERE DOES SEEM TO BE A LIMIT ON HOW FAR
NORTH THE LIMITED VSBYS HAVE BEEN ABLE TO REACH BUT DOOR COUNTY
AND EVEN PARTS OF FAR EASTERN OCONTO AND MARINETTE COUNTIES
CLOSER TO THE BAY MAY SEE VSBYS UNDER A MILE. THIS IS ALSO A LOW
CLOUD DECK WITH VLIFR CIGS AS WELL. KATW/GRB WILL LIKELY START
TO SEE IMPACTS FROM THIS OVER THE NEXT HOUR OR SO. THIS WILL LIKELY
REMAIN IN PLACE THROUGH DAYBREAK WITH THE SUN GRADUALLY ALLOWING
IT TO DISSIPATE IN THE MORNING. OTHERWISE INTO THE DAY EXPECT
SOME POTENTIAL FOR A FEW STORMS TOWARD CENTRAL AND NORTH CENTRAL
WI WITH NORTHEASTERN AND EASTERN WI LIKELY REMAIN MORE SO ON
THE DRY SIDE. ALL EYES WILL THEN TURN TO THURSDAY WILL POTENTIAL
FOR STRONG TO SEVERE STORMS IN THE AFTERNOON FOR CENTRAL WI
WITH CONTINUING POTENTIAL INTO THE EVENING NORTH NORTHEAST WI.
BREEZY SOUTHEAST WINDS ALSO EXPECTED THURSDAY, PARTICULARLY
TOWARD CENTRAL WI.
MARINE
ISSUED AT 418 AM CDT TUE MAY 13 2025
EXPANDED THE MARINE DENSE FOG ADVISORY TO INCLUDE ALL OF THE
NEARSHORE WATERS OF LAKE MICHIGAN AND THE BAY OF GREEN BAY. THE
MARINE FOG IS EXPECTED TO STICK AROUND THROUGH AT LEAST
EARLY THIS MORNING DUE TO LIGHT, MOIST EASTERLY FLOW OVER THE
COLD OPEN WATERS.
GRB WATCHES/WARNINGS/ADVISORIES
WI...DENSE FOG ADVISORY UNTIL 10 AM CDT THIS MORNING FOR WIZ013-
020>022-031-037>040-048>050-073-074.
MARINE...DENSE FOG ADVISORY UNTIL 10 AM CDT THIS MORNING FOR LMZ521-522-
541.
DENSE FOG ADVISORY UNTIL 1 PM CDT THIS AFTERNOON FOR LMZ542-
543.
DISCUSSION...
AVIATION...
MARINE...
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