NWS-Green Bay Forecast Discussion
FXUS63 KGRB 061806
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
1206 PM CST Fri Mar 6 2026
Updated aviation portion for 18Z TAF issuance
.KEY MESSAGES...
- Patchy dense fog will impact travel across much of the region
this morning.
- Widespread rain (80-100%) impacts the region today and tonight,
with most of the area receiving between 0.50 to 1.25 inches.
Minor snow and ice accumulations may impact travel in far north
central WI late tonight into Saturday morning.
- Thunderstorms possible this afternoon and tonight. The best
chance of storms occurs from 10 pm to 3 am. Heavy rainfall and
a few strong storms with hail and gusty winds. Localized
flooding possible.
- Above normal temperatures expected through most of the period.
The warmest days occur Sunday and Monday, with highs reaching
into the 60s in some areas.
- Warmer weather may lead to ice breakup on rivers, resulting in
ice jam flooding. Ice floes could also be a concern, especially
from Sunday into Monday.
&&
.DISCUSSION...
Issued at 148 AM CST Fri Mar 6 2026
Widespread low stratus, fog and drizzle covered the region early
this morning. Locally dense fog was reported, especially in east
central WI. A Dense Fog Advisory has been issued for roughly the
southern two-thirds of the forecast area, and conditions will be
monitored for a possible expansion this morning. Since
temperatures are all above freezing, and expected to remain
above freezing, any mention of freezing drizzle has been removed
from this morning's forecast.
Main Changes for the Friday/Saturday System:
- More definition in pops has been added to better delineate the
two separate periods of more significant rainfall, with the main
lull occurring mid-afternoon through early evening. Rainfall
amounts for the first round have been lowered a little bit.
- While thunderstorms will be possible from this afternoon through
tonight, CAMs and SPC HREF 40 dBZ paintballs show the main round
of thunderstorms moving through the forecast area from 10 pm
through 3 am. This will be the best period for strong storms
with small hail, brief gusty winds, and heavy rainfall. Minor
urban flooding could occur in localized areas.
- Have increased snow/ice accumulations across far north central
WI late tonight into Saturday morning, as a significant band of
deformation zone precipitation occurs in conjunction with
surface temperatures dropping below freezing. A mixture of
freezing rain and sleet will eventually change to snow Saturday
morning, with up to 1 to 2 inches possible over northwest Vilas
County.
A generally dry period is expected from Saturday afternoon
through Monday night, with a couple clipper systems passing by
well to our north. Breezy southwest winds on Sunday and Monday
will bring very mild temperatures, with readings in the 60s in
our typical warm spots.
Another low pressure system arrives Tuesday and Tuesday night,
but models have generally trended farther southeast with the
track, keeping the forecast area in a colder air mass. Light mixed
precipitation will be possible during this period.
Ice Jam/Ice Floe Potential...In addition to the previously
mentioned potential for runoff flooding from heavy rainfall
tonight, there is a low threat of ice jam flooding. Continued mild
temperatures will increase the threat of ice break-up into
early next week. The ice jam threat will be reduced a bit due to
low water levels, though this may change after the expected heavy
rainfall occurs tonight. An increased threat of ice floes on
Green Bay could also develop, especially on Sunday and Monday,
when gusty southwest winds will occur.
&&
.AVIATION...for 18Z TAF Issuance
Issued at 1205 PM CST Fri Mar 6 2026
Low pressure system and approaching warm front will result in
rounds of light rain into this evening. Otherwise, low clouds,
fog and some drizzle will prevail with cigs AOB 003 and vsby
mainly 3SM or less. Fog may become widespread and dense late this
afternoon into the evening before round of rain and storms arrive
late this evening into the overnight hours. Strongest forcing will
be focused over east-central WI and this is where warm front will
reside as well. As a result, have included TEMPO mention of wind
gusts to 30 kts for GRB/ATW/MTW as the showers and storms cross.
LLWS will be present at all the TAF sites until cold front just in
wake of the showers and storms moves through late tonight.
Once widespread showers and storms end late tonight, a few widely
scattered showers will linger into Saturday as cigs begin to lift
to IFR/MVFR. More widespread precip in the form of fzra/sleet
switching to snow will occur over far north-central WI, eventually
making it to RHI by mid morning Saturday. Most of the accumulating
snow will remain north of RHI though.
East winds north of the warm front will remain light. Once the
warm front arrives later this evening into the overnight, winds
will shift southwest late tonight and become gusty, even aside
from the storms moving through. Winds will then shift northwest on
Saturday as cold front moves through, with gusts of 20+ kts across
the area by afternoon.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 6 AM CST Saturday for WIZ022-040-050.
&&
$$
DISCUSSION.....Kieckbusch
AVIATION.......JLA
FXUS63 KGRB 061850
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
1250 PM CST Fri Mar 6 2026
Forecast discussion for routine afternoon forecast issuance
.KEY MESSAGES...
- Areas of dense fog will impact travel at times into tonight.
Most persistent fog will be near the lakeshore.
- Rain comes in waves this afternoon, then again later this
evening into the overnight hours. Greatest chance for
thunderstorms will be from 10p this evening through 4a Saturday
morning. Primary hazards with storms late tonight are heavy
rainfall, gusty winds and small hail. Localized flooding
possible.
- Wintry mix far north-central WI late tonight into Saturday
morning. Minor snow and ice accumulations could impact travel.
- In addition to minor flooding tonight with thunderstorms, the
rain and warmer temperatures will result in ice shifting and
breakup on rivers, leading to a localized ice jam flooding
threat into the weekend. Ice floes could also be a concern
Sunday into Monday.
- Very warm and breezy Sunday and Monday. Highs reaching the 60s
in some areas. Turning cooler by midweek with potential for rain
and snow.
&&
.DISCUSSION...
Issued at 1249 PM CST Fri Mar 6 2026
Near term through early evening...
Showers and isolated storms over southern WI into lower Michigan
with light rain into especially east-central WI at present supported
by 700-500mb speed max moving into lower Michigan. Additional
showers and storms over central IA into far southwest WI are on
nose of 850mb jet, though still north of the warm front. Two areas
of elevated instability are noted, one feeding into the initial
cluster of showers and storms that mainly stayed south, the other
with activity moving into far southwest WI. Expect these showers
and a few storms to have better chance of making it into southern
areas this afternoon, though veering low-level jet likely will
keep the bulk of higher elevated instability to the south. Between
both rounds of rain today, expect total rainfall amounts mainly
0.50 inch or less, greatest amounts south of highway 10.
Other concern into this evening will be dense fog near the lakeshore
as flow remains onshore. The rain will likely cause the fog to
diminish briefly, but when steadier rain ends, expect it to expand
again as low-levels across Lake Michigan remain very saturated to
the north of approaching warm front.
Active weather tonight...
Late this evening through most of the overnight strong low-mid
level jet energy on leading edge of strong trough over the plains
arrives over WI. At the sfc, warm front lifting into southern WI
early this evening makes it to east-central WI by around midnight.
50 kt low-level jet will be aimed toward Fox Valley/lakeshore
which along the warm front present should allow blossoming of
showers and thunder given elevated instability (1-6km MUCAPE
500-1000J/kg). Appears that initiation of the showers and storms
occurs over western IA, so that will be area to watch by early
this evening. Latest forecast soundings back across our area
show inversion based at 1-2kft northern Fox Valley to lakeshore
and points west/northwest. Hint still there inversion could try to
diminish briefly southern tier of forecast area as warmest low-
level temps/dewpoints arrive from the south with the warm front.
Expect one primarily slug of moderate to heavy rain, gusty winds
40+ mph and possible small hail as wet-bulb zero heights are
5-7kft. Main concern is if stronger winds just aloft (50kt 850mb
and 60kt at 700mb, can be brought down to the sfc. Seems that sfc
based instability is too low and remains to the south, but if the
orientation of the line of storms ends up perpendicular to the
axis of low-level jet, chances of seeing stronger sfc gusts could
increase.
Hydro concerns are still present as rain tonight falls on at least
partially frozen ground, saturated from the rain that occurs today.
As we have mentioned in discussions recently, many of our rivers remain
ice covered, so the moderate to heavy rain falling on this could
cause at least localized flooding issues once the increasing flow
begins to break up and shift the ice. Given the strong winds aloft,
storm motion and motion of the overall cluster of showers and
storms will be fast. Thus, flooding issues should overall be minor
unless training of convective elements can occur. The wild card
is the ice on the rivers as runoff off this could lead to minor
localized flooding. At this point, appears the heaviest swath of
rain tonight occurs in parts of our forecast area that have no
snow on the ground, versus far north-central where 10-20" of snow
depth remains. Rates with the rainfall tonight should be high
given the elevated instability interacting with PWATs over 1"
which is near or above the maximum for the date. Rainfall that
occurs from late this evening to 6 am on Saturday could at least
locally exceed 1" and the reality is most of that will occur in a
2-3 hour time frame. Last issue tonight will be the lingering
areas of fog that could be dense, especially when rain is not as
steady. This fog really will not abate until cold front and
primary cluster of showers and storms sweep through late tonight.
The last locations to lose the fog will be near the lakeshore due
to flow off Lake Michigan.
Wintry Precip Saturday North-Central...
Still have to watch far north-central late tonight through first
thing on Saturday morning. As widespread precipitation diminishes
that area will be on southern fringe of deformation over western
Lake Superior/western Upper Michigan and within right entrance of
departing jet streak. Steady precip starts off as rain, but soundings
show warmth aloft being undercut by cold air advection, suggesting
a brief period of freezing rain/sleet before a switch to snow occurs.
QPF for the entire duration of wintry precip is less than 0.10,
looking at minor impacts given marginal sfc temps even when wintry
mix to snow occurs. High-end of NBM not suggesting any more than
1-2" of snow in far northern Vilas County late tonight through
midday Saturday. This idea is roundly supported by deterministic
model snowfall output as well. At this point, do not foresee need
for an advisory, but more of a nowcast/SPS type event. Away from
north-central, a few rain showers may swing through the rest of
the area as last of mid-level jet wind max slides through as the
cold front finishes crossing the area. No thunder is expected as
elevated instability will be east of the area. High temperatures
Saturday reach upper 30s north and probably the low to mid 50s
east-central. Northwest winds behind the front may reach 25-30 mph
Fox Valley to the lakeshore.
Warm, Breezy on Sunday...
Strong cyclone with MSLP less than 985mb crosses central Canada.
Dry with this system, but warm and windy. If not for the rain into
tonight, would be more of a fire weather issue where no more snow
is on the ground. NBM probabilities of seeing wind gusts over 30
mph are 40-60% with little change in last 24 hrs. Chances of seeing
highs 60+ 50-90%, with again little change. Adjusted winds/gusts
upward on Sunday given deep mixed profile and stronger pressure
gradient.
Next System Tuesday/Wednesday...
Main trend continues with shifting primary track of the low
southeast, thus heaviest QPF into the system also stays mainly
southeast. Ptype becomes more of an issue, especially northern
forecast area. NBM mean/50th percentile for 24hr snow ending 12z
Wed nothing too noteworthy, but reasonable high-end (90th percentile)
shows potential for several inches over northern WI. Diving into latest
model output there is decent spread noted in how far south could see
snow. Upshot is this will be a period to watch for trends as we move
into early next week.
Ice Jam/Ice Floe Potential...In addition to the previously
mentioned potential for runoff flooding from heavy rainfall
tonight, at least a low threat of ice jam flooding will carry into
the weekend, and continued mild temperatures will further increase
the threat of ice break-up into early next week. Lower river
levels initially do lead to a lesser threat, though this may
change after the expected heavy rainfall occurs tonight. Given the
gusty southwest winds expected Sunday and potentially into Monday
as well, an increased threat of ice floes on Green Bay may also occur.
Already saw in local media that ice shoves occurred during stronger
winds yesterday (Thu) near Washington Island and we could be in
for more of this type of activity later this weekend into Monday
with the stronger winds and deteriorating ice conditions.
&&
.AVIATION...for 18Z TAF Issuance
Issued at 1205 PM CST Fri Mar 6 2026
Low pressure system and approaching warm front will result in
rounds of light rain into this evening. Otherwise, low clouds,
fog and some drizzle will prevail with cigs AOB 003 and vsby
mainly 3SM or less. Fog may become widespread and dense late this
afternoon into the evening before round of rain and storms arrive
late this evening into the overnight hours. Strongest forcing will
be focused over east-central WI and this is where warm front will
reside as well. As a result, have included TEMPO mention of wind
gusts to 30 kts for GRB/ATW/MTW as the showers and storms cross.
LLWS will be present at all the TAF sites until cold front just in
wake of the showers and storms moves through late tonight.
Once widespread showers and storms end late tonight, a few widely
scattered showers will linger into Saturday as cigs begin to lift
to IFR/MVFR. More widespread precip in the form of fzra/sleet
switching to snow will occur over far north-central WI, eventually
making it to RHI by mid morning Saturday. Most of the accumulating
snow will remain north of RHI though.
East winds north of the warm front will remain light. Once the
warm front arrives later this evening into the overnight, winds
will shift southwest late tonight and become gusty, even aside
from the storms moving through. Winds will then shift northwest on
Saturday as cold front moves through, with gusts of 20+ kts across
the area by afternoon.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 6 AM CST Saturday for WIZ022-040-050.
&&
$$
DISCUSSION.....JLA
AVIATION.......JLA