155
FXUS63 KGRB 111149
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
649 AM CDT Tue Mar 11 2025

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Temperatures fall back closer to normal today, then rise well
  above average the rest of the week.

- Warm temperatures along with melting snow will elevate flows on
  area rivers and streams, leading to an increased risk for ice
  jams and minor flooding. The potential for widespread rain
  Friday and Saturday will add to the risk.

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

&&

.DISCUSSION...
Issued at 408 AM CDT Tue Mar 11 2025

Short Term...Today...Tonight...and Wednesday

After a record setting day on Monday for many locations, much
colder air arrives today, but most spots will remain above/near
normal, with temps bouncing back well above normal on Wednesday.
Only small chances for light precip into mid-week.

Precip Chances: A moisture-starved cold front will complete its
passage through the area this early morning. Only a few sprinkles
or flurries are expected over northern WI as the front exits. Dry
conditions are expected the rest of today into this evening. A
push of WAA and weak shortwave will bring chances for light snow
or flurries to northern WI late tonight into Wednesday morning,
but chances for measurable precip remain between 10-30%. No
impacts are expected.

Temps: Strong CAA arrives behind the cold front today, ushering in
colder temps. Highs are forecast to range from the 30s in north
central WI and near Lake MI to the 40s elsewhere, which is near
or slightly above normal for this time of year (normal highs in
the mid and upper 30s). Temps tonight will fall mainly into the
20s. The shot of colder air will be brief as WAA begins on
Wednesday with highs climbing back above normal, with most spots
away from Lake MI seeing highs in the upper 40s to mid 50s.

Long Term...Wednesday Night Through Monday

The main focus in the extended period will be the return of highly
amplified flow which will bring another surge of much warmer
temperatures around the end of the work week followed by a strong
low pressure system Friday night through Saturday.

Temperatures...
An upper trough will dig into western CONUS early this week,
producing highly amplified flow across the Central Plains and
into the Great Lakes. As a result, steady warmth and moisture
flow into the region will bring a surge of much warmer
temperatures by the end of the work week, with widespread 60s for
Friday. Based on temperatures aloft at both 925mb and 850mb highs
getting into lower 70s during the day is not out of the question
for a few of the central Wisconsin sites.

Late-week System...
As the upper trough progresses into the Central Plains,
cyclogenesis is expected on the lee side of the Rockies, with the
resulting low pressure system then following the strongest warm
air advection northwards into western Great Lakes Friday night
through Saturday. By this time, the tightly wound low pressure
system will be in the process of occlusion, which may begin to
cutoff some of the better moisture, as evidenced by some strong
850mb cold air advection accompanying the first round of
precipitation into the region Friday night. Still, dynamics and
forcing along this initial surge are impressive and would likely
support some thunder chances, possibly as far as central
Wisconsin. That said, the timing doesn`t favor instability lasting
too long, so any thunder quickly disappears by Saturday morning.
Precipitable water values are greatest towards the Illinois
border, but a thin plume of higher values may still be in the
region for the initial round, which may boost some local rain
totals. Overall, current probabilistic guidance suggests a 70%+
chance of half an inch of rainfall for most of northeastern
WIsconsin, but only around a 30% chance of exceeding an inch of
rainfall only across a small portion of central Wisconsin.

Rain aside, winds may become a greater concern as the wind fields
around this tightly wound system are certainly impressive.
Inverted-V soundings would support some mixing and with winds
along around 60 knots at 850mb and 40 knots at 925mb, there
certainly is decent wind potential. This will be especially true
for any areas under the dry slot, which are often associated with
the better deeper mixing. Currently, the dry slot is expected to
again be further south, again towards the Wisconsin border, but
some widespread strong wind gusts are certainly possible (~50%
chance of greater than 30 mph gusts for most of the area).

The rain and winds will be around much of Saturday as the low
continues to occlude and drift northwards, with the but the bulk
of any wind and rain threat will pass by around Saturday
evening. As colder air mixes in behind the departing low, there
may be some brief snow mixed in for much of the area, but
accumulations should be minor. Temperatures behind this system
will be closer to normal, with highs expected to be in the upper
20s to upper 30s.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 649 AM CDT Tue Mar 11 2025

VFR conditions are expected through the TAF period as high
pressure builds into the Great Lakes. A few lower clouds around
3000-4000 ft, along with some mid-clouds, will exit early this
morning, with a mid and high clouds returning and thickening this
evening.

North winds will remain a little gusty this morning, up to around
25 kts, as a cold front exits to the south. Then winds will
slowly diminish later this morning. Winds will switch to the
east/southeast overnight and remain under 10 kts.

&&

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

&&

$$

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