Oshkosh, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

914
FXUS63 KGRB 221128
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
528 AM CST Sun Dec 22 2024

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Minor lake-effect snow accumulations are possible in Door County
  and along the Lake Michigan shoreline this morning. Amounts are
  generally expected to be less than 1 inch.

- The potential has increased for a band of patchy freezing
  drizzle or snow across the area late tonight into Monday. A few
  hundredths of an inch of ice is possible with 1 to 2 inches or
  more of snow, which could impact travel ahead of the Christmas
  holiday.

&&

.DISCUSSION...
Issued at 254 AM CST Sun Dec 22 2024

Short Term...Today...Tonight...and Monday

Surface winds will turn southerly this morning as high pressure
pushes off to the east. This will allow a lake effect band to set
up once again over Lake Michigan, which may brush the lakeshore at
times. CAMs models do show this happening at times, but don`t
maintain a band over an area for a long period of time. Therefore,
maybe a few tenths of an inch are possible along the lakeshore
from these bands today, mainly north of Kewaunee. Highs today are
expected to range from the middle 20s across the lower 30s near
the lakeshore.

A low pressure system tracking through the area from the northern
Plains will bring a swath of precipitation to the region later
tonight into Monday. The low itself moves through Wisconsin, with
mid level frontogenesis. Despite the cold surface temperatures,
model soundings show a pocket of dry air in the mid levels which
would interrupt the seeder-feeder mechanism at times. This will
mean intermittent freezing drizzle will mix in with the snow at
times. There are some indications freezing drizzle could occur for
several hours depending on the amount of dry air in place. Any
freezing drizzle would cut into the snowfall totals as a result.
The current forecast looks to be several hundredths of freezing
drizzle with slightly lower snowfall amounts than previous runs as
amounts range from a few tenths, to 1 to 2 inches across a wide
swath of the area, and locally higher amounts close to 3 inches
possible. Although there was contemplation on issuing a Winter
Weather Advisory for late tonight through Monday, there is still
enough uncertainty to hold off as less freezing drizzle would
lessen the impact from this event.

Lows tonight are expected to range from the upper teens across the
north, to the upper 20s across the lakeshore and Fox Valley. Highs
Monday are expected to generally be in the lower to middle 30s.

Long Term...Monday Night Through Saturday

Main highlights from this forecast period revolve around the
potential for precipitation sometime later in the week and
temperatures warming to above normal.

Precipitation...Before jumping to the late week precip potential,
there will be some lingering precip chances for Monday evening as
the system in the Short-Term discussion is departing. In addition to
some light snow lingering in far eastern WI, forecast soundings
suggest ice crystals in the mid-layer will decrease, leaving the
potential for freezing drizzle to occur. The extent of how far west
the freezing drizzle will occur is uncertain, compared to the
eastern extent. Therefore, added some low PoPs (15-20%) for freezing
drizzle/snow in far eastern WI where confidence is greater. Some
slippery travel may continue into Monday evening as a result.

Christmas Eve and Christmas Day....High pressure and mid-level
ridging move over the area for Tuesday into Tuesday evening, keeping
conditions dry. This ridging will give way to mid-level troughing
looking to phase over the Mississippi Valley on Wednesday. Models
appear to be in agreement with the moisture surging from the
southern stream portion of the trough sliding to the east of the
forecast area for Christmas Day. But, if the moisture does reach the
forecast area, only the southeastern portion could see a slight
chance of rain. Followed along with the NBM solution for now, which
keeps the forecast area dry.

Beyond Christmas Day, all guidance indicates a southern stream
system will lift into the Upper Midwest, but they do not agree on
timing/placement. Regardless, anticipate the forecast area will see
precip at some point late this week in the form of rain.

Temperatures...Above normal temperatures are expected for the long-
term forecast, with the potential to see highs nearing/reaching the
low 40s by late this week.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 528 AM CST Sun Dec 22 2024

A mix of VFR/MVFR clouds are expected this morning as a mid level
shortwave tracks through the western Great Lakes region.
Conditions should then return to VFR as the shortwave tracks off
to the east. A low pressure system tracking through Wisconsin
will bring a return of MVFR/IFR conditions later this evening and
into the overnight hours with a mix of snow and freezing drizzle.
It is uncertain how much freezing drizzle will accumulate due to
mid level dry air; however several hundredths of an inch of ice
accumulation is possible by Monday.

&&

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

&&

$$

DISCUSSION.....Kurimski/Kruk
AVIATION.......Kurimski