Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 262330
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
630 PM CDT Tue Mar 26 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Rain mixes with and changes over to light snow late this
  afternoon or early this evening. Minor snow accumulations are
  possible mainly across north-central Wisconsin, but with little
  to no impacts.

- Blustery conditions are expected across the entire area tonight
  into Wednesday. Gusts to 25 to 35 mph, locally higher at times.

- A fast moving shortwave could bring another round of rain, snow,
  or a wintry mix to the region Friday night into Saturday. Most
  likely to see the impactful wintry weather is north-central WI,
  near the Upper Peninsula border.

- Another round of active weather is then possible next week, but
  the track and timing for this system is unclear at this time.
  This system has the potential to bring another round of wintry
  precipitation to the area.

&&

.DISCUSSION...
Issued at 259 PM CDT Tue Mar 26 2024

Short Term...Tonight and Wednesday

Main forecast concerns to be on light snow accumulations tonight,
temperatures and light snow potential north Wednesday afternoon.

The 19Z MSAS surface analysis showed a strong area of low pressure
over western Lake Superior with a cold front that extended south-
southwest from the low pressure through north-central to southwest
WI, into central IA. High pressure stretched from south-central
Canada southward toward the central Plains. The radar mosaic
indicated a band of light to moderate rain showers were over
eastern WI and snow showers were over the Upper MS Valley/western
WI. Winds were gusting in the 20 to 35 mph range.

The strong surface low continues to track northeast into eastern
Ontario tonight with the cold front exiting eastern WI this
evening. Bulk of moisture to be shoved east by the cold front, but
the wrap-around moisture will bring a chance for snow showers to
much of northeast WI this evening with a lingering chance far
north into the early morning hours. Accumulations to remain minor
and focused over north-central WI where around an inch is expected
over the the Vilas County snowbelt. West winds of 10 to 20 mph
with higher gusts to persist through the night as the pressure
gradient remains tight between the departing low pressure and the
high pressure over the Plains. A good push of CAA will send min
temperatures down to 10 to 15 above north-central WI, middle 20s
near Lake MI. Wind chills could approach zero over north-central
WI by daybreak. This drop in temperatures may lead to some
slippery road conditions where any water remains on area roads.

As the high pressure slides southeast toward the mid-MS Valley on
Wednesday, drier air to work into WI and allow for some mixed
sunshine to occur, especially over central and east-central WI.
Models are consistent with the movement of a closed upper low into
northern sections of the Great Lakes Wednesday afternoon. Cyclonic
flow around this upper low, plus a shortwave rotating within the
upper low circulation, could bring snow shower chances back to
northern WI by the afternoon. Perhaps one-half inch of
accumulation would be possible, mainly over far north-central WI
by sunset. Gusty west winds to also persist across the area and with
max temperatures only in the upper 20s to upper 30s, there will
be a bit of a bite to the air when outdoors.

Long Term...Wednesday Night Through Tuesday

The main focus of the extended forecast will be the potential for
our next two weather systems, after a fairly quiet period in the
middle of the work week.

Fairly quiet conditions persist across the region from Wednesday
night through the afternoon Friday, as high pressure remains
dominant in the region. Temperatures during this time will be on a
steady increase, with highs in the middle to upper 40s by
Friday.

First active weather chance...A fast moving mid-level shortwave is
expected to cross northern CONUS and cross into the area Friday.
This will bring strong warm air advection through the mid-levels
ahead of the shortwave through the day Friday, although current
models keep the surface warm front somewhere in southern
WI/northern Illinois. With the majority of the moisture trapped in
the warm sector south of the area, any precipitation will be
fairly light. Models generally depict a couple tenths of qpf for
this system, starting sometime in the latter half of the day but
ending by the early overnight. The main concern and any potential
impacts will be mainly centered on the potential for freezing
rain in north-central Wisconsin, where surface temperatures may be
below freezing during or shortly after rainfall.

The second round of potential active weather will come early next
week. A large upper trough crossing the Rockies will spin up a low
pressure system over Colorado, which will then lift east and
north, potentially impacting the western Great Lakes region. The
exact track of this system remains highly variable, with the most
recent runs considerably more south than the last forecast update.
The main concerns for this system will be another round of wintry
precipitation, which would impact travel across the region early
next week. The details on who gets what will need monitoring in
future updates, as the variability at this time remains high.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 629 PM CDT Tue Mar 26 2024

MVFR ceilings are expected across the area through midday Wednesday.
Snow showers and IFR conditions are likely west of a IMT to STE
line early this evening. An upper level disturbance could produce
some snow showers Wednesday afternoon north of RHI, but elsewhere
drier air will bring rising ceilings and some clearing east of a
ESC to ATW to MSN line.

&&

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

&&

$$

DISCUSSION.....Kallas/Uhlmann
AVIATION.......RDM


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