854
FXUS63 KGRB 121126
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
626 AM CDT Wed Mar 12 2025

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Well above normal temps today into Friday, with some records
  possibly in jeopardy late in the week.

- A strong system arriving late in the week will bring our next
  chances for widespread rainfall, gusty winds, and a chance for
  thunder.

- The mild temperatures through late this week, in combination
  with melting snow will elevate flows on area rivers and streams,
  will lead to an increased risk for ice jams and minor flooding.
  The potential for widespread rain Friday and Saturday will add
  to the risk.

&&

.DISCUSSION...
Issued at 329 AM CDT Wed Mar 12 2025

Short Term...Today...Tonight...and Thursday

Pretty quiet mid-March weather continues today into Thursday with
temps climbing back to well above normal.

Only chances for precip will be early this morning as a weak
forcing associated with a shortwave and FGEN/WAA moves across far
northern WI. Best forcing and moisture will only clip far north
central WI, so will confine chance PoPs and some minor snow
accumulations (under a half inch) there. However, most of what is
showing up on regional radar is virga, as the precip is fighting
the drier low-level air, and this fight will continue until the
system departs by mid-morning. Further south, too much dry air to
get any precip so will continue with the dry forecast. Otherwise,
look for dry conditions the rest of today into Thursday.

Temps will return to well above normal as WAA sets up over the
western Great Lakes. 925mb temps of 0-4C today support highs in
the mid 40s to mid 50s and of 5-9C on Thursday should allow highs
to climb into the mid 50s to low to possibly mid 60s. Cool,
onshore flow will keep temps cooler near Lake Michigan, with highs
mainly in the 40s to low 50s.

Long Term...Thursday Night Through Tuesday

The main focus of the extended forecast will be on the strong low
pressure system expected for Friday night through much of Saturday
and the preceding surge of much warmer temperatures.

Active weather...
A deep upper trough will cross the the Rockies Thursday and
Thursday night, leading to rapid cyclogenesis over the Central
Plains. The resulting stacked low pressure system is then
expected to rapidly lift northwards into the western Great Lakes
by Friday evening. Although the low will likely be occluding by
the time it arrives in our region, which will keep the best
dynamics well to our south, there is a window Friday evening and
early Friday night where thunderstorms are possible supported by
the strong warm air advection, LLJ, instability aloft, and mid-
level lapse rates around 8 C/km. Given the dynamics at play, if
elements do align, a strong storm could be possible, but again the
best dynamics do remain well south. The main concern for any
storms that do develop will be the potential to mix the
aforementioned winds to the surface, as 45-55 mph winds around
925mb and 850 mb may be accessible. If gusts do mix, they should
be brief as soundings do still appear relatively unfavorable for
widespread mixing outside of rain during the overnight period. A
better period for mixing will arrive late Saturday morning through
Saturday afternoon as drier air wraps around the low pressure
system. Where the dry slot sets up will be something to watch as
this will be the area that will best support mixing winds to the
surface, but this appears to remain focused southwards in Illinois
at this time. That said, some of the dry air will make its way
into our region during the afternoon regardless and soundings
during the afternoon period show some low level inverted-v
structuring which would support better mixing. Wouldn`t be
surprised if the Saturday afternoon period sees at least periodic
gusts in the 35-45 mph range, especially in east-central Wisconsin
in the afternoon, which will be closest to the main core of
strong winds aloft Saturday afternoon. The intrusion of the drier
air and occluding nature of this system may in turn make rain a
bit on and off, and due to the limited nature of the convective
potential, rain amounts are generally expected to be less than an
inch, with most probabilistic guidance suggesting around half to
three-quarters for most of the area. If someone sees thunder
from Friday night, locally higher amounts are possible. Finally,
some snow may mix in on the backside of this system Saturday
night, which could bring some brief snow to the area. Snow amounts
at this time remain light, with most remaining under an inch.

Temperatures...
A surge of warmer temperatures will precede the active weather
system Thursday and Friday as the high amplitude pattern brings
warmth and moisture into our neck of the woods from the south.
High temperatures could get into the 60s on Thursday and possible
a few lower 70s on Friday. Behind the active weather a dip to near
normal is expected for Sunday with highs in the lower 30s to lower
40s before recovering upwards again on Monday and Tuesday with
highs in the 50s.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 626 AM CDT Wed Mar 12 2025

Any lingering flurries and MVFR ceilings over far northern WI will
exit early this morning, with VFR conditions expected through the
rest of the TAF period. Mid and high clouds are expected at
times. Winds will generally stay east/southeast/south today and stay
under 10 kts, but a few gusts to 15 kts are expected later this
morning and early afternoon. Light and variable winds are
expected tonight.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION.....Bersch/Uhlmann
AVIATION.......Bersch