Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 172338
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
538 PM CST Tue Jan 17 2017

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Wednesday
Issued at 344 PM CST Tue Jan 17 2017

Slowly improving conditions are expected over the next 24 hours as
the system responsible for the wintry precipitation continues to
pull away and a weak ridge of high pressure builds into Wisconsin.
That being said, there are still several concerns with the
forecast ranging from clouds trends tonight, potential of more fog
tonight into Wednesday morning and then both min and max
temperatures.

The 20z MSAS surface analysis showed low pressure situated over
southern Lake Huron with a trough extended west into southern
Wisconsin. A ridge of high pressure stretched from the central
Plains northeast through the Upper MS Valley. Visible satellite
imagery indicated clearing had taken place across northwest
Wisconsin, while the rest of state was shrouded in clouds and fog
with light rain or drizzle over the southern half of Wisconsin.

A weak shortwave trough, responsible for this afternoon`s light
rain/drizzle, will exit the area this evening, allowing for the
ridge of high pressure to move into the Western Great Lakes
tonight. The main question for tonight will be how much clearing
can take place? Models show lingering low-level moisture through
the rest of the night, thus any clearing may simply allow for a
stratocu deck to reform along with areas of fog. Prefer to go
mostly cloudy skies for most of the forecast area, with partly
cloudy skies at times over north-central WI where the least amount
of precipitation fell from the departed system. The amount of
cloud cover will also impact min temperatures with a potential
bust of 10 degrees. For now, have opted for readings from 15 to 20
degrees north-central, 20-25 degrees central/far northeast WI and
middle 20s across east-central WI. Lastly, with temperatures
falling below freezing tonight, any water on area roads will
freeze causing slick spots to develop, especially on untreated
roads and sidewalks.

Northeast WI to reside on the western flank of the surface ridge
on Wednesday which will allow for winds to be mainly from the
southwest. 8H temperatures are progged to be in the +6 to +8C
range and with mostly sunny to partly cloudy skies anticipated, we
are looking at a mild day by January standards. Expect most
locations to reach the 35-40 degree range for daytime highs, with
a few locations perhaps reaching the lower 40s. This would greatly
aid in attempting to melt the lingering ice issues over the area.

.LONG TERM...Wednesday Night Through Tuesday
Issued at 344 PM CST Tue Jan 17 2017

Latest NWP models indicate a fairly short quiet period across the
western Great Lakes as ridging on Thursday gives way to a series
of upper level lows tracking through the western Great Lakes from
late this week all the way through early next week. Although these
events appear to be fairly weak and minor given the lift and
dynamics tracking through the region, there are some opportunities
for mixed precipitation at times given the limited moisture.

The first of these events arrives Thursday night and Friday as a
weakening upper level trough tracks through the western Great
Lakes region. Given the lack of deep moisture there is a threat
for freezing rain late Thursday night and Friday morning until
surface and road temperatures rise above freezing. The NWP models
do offer different solutions with regard to placement and amount
of qpf associated so the amount and impact the freezing rain will
have is still in question. Weak lift will continue behind the
shortwave Friday night, continuing the threat for freezing rain or
drizzle as soundings show mid level dry air preventing ice
crystals from entering the column.

Warm air is expected to surge north this weekend, allowing daytime
highs to soar into the 40s and keep precipitation as mainly rain
across northeast Wisconsin as an upper level low lifts north
through the upper Mississippi Valley. Meanwhile, a strong low
pressure system developing over the southern Plains will track
east through the southeastern CONUS then lift north back over the
eastern Ohio Valley by early next week. Although the western Great
Lakes appears like it will be spared the brunt of this system, the
region will feel its effects as the northern edge of the trough
brings the chance for precipitation to the western Great Lakes
region. Precipitation type will depend largely on the amount of
low level cold air and how deep the moisture will be, with the
potential for additional freezing rain if surface temperatures
fall below freezing with a mid level dry layer. However that far
out will keep precipitation types a simple rain or snow mix.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 538 PM CST Tue Jan 17 2017

Clearing skies are expected from west to east this
evening, but it will be short lived, as low clouds will likely
form after several hours of clear skies due to abundant low level
moisture. The low clouds should mix out by midday Wednesday, but
it is not a sure thing as a temperature inversion sometimes inhibits
mixing. If skies do clear by midday Wednesday they should remain
clear through the evening hours. Pavement will likely get slippery
once again tonight as temperatures fall below freezing.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....AK
LONG TERM......Kurimski
AVIATION.......RDM



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