Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 272259
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
559 PM CDT Wed Mar 27 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Snow showers and flurries through tonight, with a dusting across
  the Northwoods and up to around an inch in Vilas County.

- A fast moving shortwave could bring a wintry mix to the forecast
  area Friday night into Saturday morning. Potential for any
  wintry weather and freezing rain has shifted slightly southwards
  to areas from Wausau to the Upper Peninsula border.

- Another round of active weather is possible early next week,
  although the track and timing for this system is currently
  uncertain. This system has the potential to bring another round
  of wintry precipitation to portions of the area.

&&

.DISCUSSION...
Issued at 352 PM CDT Wed Mar 27 2024

Short Term...Tonight and Thursday

Precipitation...Cyclonic flow has kept scattered clouds and light
snow showers and flurries over the region this afternoon. The source
of the cyclonic flow (closed mid-level low over western Lake
Superior/western UP) will gradually shift northeast over James Bay
by Thursday evening. Until then, the best forcing and moisture will
be located across the Northwoods where light snow accumulations are
expected. A dusting to a couple tenths is expected for most
locations across the Northwoods, with the exception of Vilas County
where up to an inch is expected. Given the cyclonic flow and
lingering widespread low-level moisture, anticipate flurries to
continue at times across the remainder of the forecast area
throughout the evening and night. All snow activity should come to
an end Thursday morning across the forecast area. Dry air will
gradually filter into the area on Thursday and allow mostly sunny
skies for most locations, except across the far north where the dry
air will struggle to reach.

Winds and Temperatures...Weak CAA and a tight pressure gradient has
allowed west to southwest winds at 850mb to mix to the surface with
gusts of 25 to 35 mph this afternoon. The pressure gradient will
decrease into this evening and tonight, however, forecast soundings
indicate enough mixing overnight to allow for gusts up to 25 mph at
times. Daytime heating on Thursday will allow for mixing to around
850mb again, but low-level winds will not be as strong as today.
Have west winds gusting to 20 to 30 mph for Thursday. Below normal
temperatures are expected overnight with lows ranging from the mid
10s to mid 20s, and Thursday highs ranging from the mid 30s to low
40s. The gusty west winds will make for blustery conditions
overnight into Thursday morning with wind chills as low as the
single digits above zero in central and north-central WI, and low
10s elsewhere.

Long Term...Thursday Night Through Wednesday

The main concerns in the extended forecast will center around two
potential rounds of wintry weather, one to start the weekend
Friday night and the other arriving around the end of the weekend
into early next week.

After a quiet period Thursday night through Friday, attention
turns to the potential for active weather Friday evening into
Saturday morning. A warm front to our south will have primed some
of the mid-levels with moisture and temperatures above freezing
from around 800-mb. As a mid-level shortwave approaches from the
west around 850-700mb, some scattered precipitation will be
possible across the region. The main concern for any precipitation
will revolve around the aforementioned warm layer, which could
result in a wintry mix and/or freezing rain across a portion of
the area as surface temperatures overnight remain below freezing.
Complicating the forecast however, are some of the shorter term
models that either a delay the onset of this mid- level feature,
delaying precipitation until later Saturday morning, or missing
the area entirely (such as the NAM which keeps more robust dry
layer in place in the lower levels). All in all, there is
potential for some freezing precipitation overnight, but
confidence remains medium.

The next period of active weather potential arrives around the end
of the work week to early next week as a deep upper trough digs
into the Pacific region and then crosses the Rockies. A warm front
will lift northwards ahead of the upper trough, bringing a broad
area of active weather into the northern Plains to western Great
Lakes. The northern extent of the precipitation is uncertain, but
some precipitation will be possible across southern to central
Wisconsin Sunday night into Friday. A low pressure system will
follow behind the warm air advection, which could keep active
weather going through Tuesday. Most recent guidance has come to an
agreement in bringing the low south and east of our area, which
would keep us in the colder sector. If this track holds, this
would mean less precipitation overall, a more southerly track for
any snow and a period of lake effect behind the departing low as
winds turn north. That said, the track may still shift, which will
change the details of who gets what during this period.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 559 PM CDT Wed Mar 27 2024

An upper level disturbance may bring a period of snow
showers and MVFR conditions this evening north of a RHI to IMT
line. The remainder of the area will have broken clouds with
bases of 3500 to 4500 feet.

Skies should clear over most of the region Thursday, except north
of a RRL to IMT line where VFR ceilings may continue through the
afternoon.

&&

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

&&

$$

DISCUSSION.....Kruk/Uhlmann
AVIATION.......RDM


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