Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 211951

Area Forecast Discussion
National Weather Service Green Bay WI
251 PM CDT Wed Mar 21 2018

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Thursday
Issued at 251 PM CDT Wed Mar 21 2018

High clouds continued to exit the area from west to east through
the late morning and afternoon hours as a weak upper trough
crossed the area. A few lower clouds were found across far eastern
WI due to the NNE flow over Lake Michigan. Temps this afternoon
climbed into the 30s.

Any low clouds across eastern WI should dissipate/exit the area as
flow become weak and more northerly, keeping any lake clouds over
the lake. High clouds over eastern WI will exit to the east as
well. Meanwhile, another area of mid-level clouds over MN and
western WI are making slow but steady progress eastward, but
they are bumping into drier air, so they are eroding as they
attempt to move east. These clouds could sneak into the area this
evening (especially central WI), but model RH fields indicate the
dry will eventually win out, so will keep mostly clear skies
going across the area. Mostly clear skies, light winds, and snow
cover on the ground will provide ideal radiational cooling
conditions tonight, so will lean toward the colder guidance
across north central WI, with lows mainly in the single digits.
Would not be shocked to see the favored cold spots to dip below
zero for a few hours overnight, assuming skies stay clear. Lows
will stay in the lower 20s for most of the Fox Valley and

On Thursday, another quiet day is expected as the Hudson Bay high
pressure system dominates the western Great Lakes region. Plenty
of sunshine is expected with highs in the upper 30s to middle 40s.

.LONG TERM...Thursday Night Through Wednesday
Issued at 251 PM CDT Wed Mar 21 2018

An amplified mean flow to begin the extended forecast with upper
troughs just off the West Coast/eastern CONUS and an upper ridge
over the Rockies. This ridge slides eastward into the east-central
CONUS and weakens with the time this weekend as the western trough
moves inland. Eventually, this western trough turns into a closed
upper low over the southwest CONUS with the upper ridge reaching
the eastern CONUs and strengthening. These changes aloft will turn
the mean flow from northwest to southwest into WI, thus bringing a
milder, more unsettled weather pattern into northeast WI for the
first half of the next week.

A ridge of high pressure is forecast to stretch from northwest
Ontario south-southeast through eastern WI, all the way to FL
Thursday night. This will bring clear skies, light winds and
another cold night to northeast WI. Min temperatures to range from
10 to 15 above north-central WI, to the lower 20s south. The
surface ridge slides a bit to the east on Friday and extend from
Hudson Bay through Lower MI. Northeast WI to remain under a dry
east-northeast wind, thus mostly sunny skies are anticipated
although we should start to see some clouds arrive late in the
day. Temperatures aloft do not change much through Friday, thus
readings should be similar to Thursday. Thus, max temperatures to
range from the middle to upper 30s near Lake MI, around 40 degrees
north and lower to middle 40s south.

Attention then focuses on an area of low pressure that is progged
to move from the central Plains toward the mid-MS Valley. The
majority of the models keep the northern extent of light snow just
to the south of central WI, but may keep a slight chance pop in
the forecast just in case there is a northern shift to the
precipitation. Otherwise, look for partly cloudy skies north and
east, with mostly cloudy skies over central WI. Min temperatures
to range from 15 to 20 degrees north, lower to middle 20s south.
This system is expected to move east-southeast into the OH/TN
Valleys on Saturday, while high pressure starts to build back into
WI. This should translate into an increase in sunshine through the
day, along with a blustery east wind at 10 to 20 mph. Max
temperatures to be in the middle to upper 30s near Lake MI, upper
30s north and upper 30s to lower 40s south.

A strong area of high pressure centered over eastern Canada is
forecast to extend southwest all the way into the western Great
Lakes region Saturday night through Sunday. Mostly clear to partly
cloudy skies Saturday night will give way to mostly sunny skies
and seasonal conditions on Sunday. An east-southeast wind will
keep areas near Lake MI/Bay of Green Bay a bit cooler than inland
locations. Look for max temperatures to range from around 40
degrees lakeside, to the upper 40s over parts of central WI. Quiet
conditions are expected Sunday night, although the upper ridge is
progged to slide to our east and bring a southwest flow aloft into
WI. Expect clouds to gradually be on the increase, however any
precipitation would remain to our west and south. A cold front is
forecast to move into the Upper MS Valley on Monday and try to
shove precipitation eastward into WI. This incoming moisture will
still have to fight the retreating dry air, especially over
eastern WI. May bring a small chance of light rain into central WI
Monday afternoon, but prefer to keep eastern WI dry through the
day. Max temperatures on Monday to range from the lower to middle
40s north-central/lakeshore, to near 50 degrees over parts of
central WI.

Winds turn to the south-southwest from the surface-5H mb Monday
night and should quickly pull gulf moisture north into WI, just as
the cold front arrives. PW values are expected to surpass one inch
over all but north-central WI and with increasing lift from the
cold front and a diffluent flow at jet-level, expect soggy
conditions Monday night. The question then becomes precipitation
type as the nocturnal drop in temperatures transitions the rain to
a mix, then to snow. Too early yet for accumulation numbers, but
potential is there for northern/central WI. Precipitation will be
likely through Tuesday morning over eastern WI as the cold front
pushes across the rest of the state. Precipitation type will
remain an issue after sunrise as snow transitions to a mix, then
rain from east-central to north-central WI. The rain should begin
to taper off across central WI Tuesday afternoon as the cold front
pulls farther away. Max temperatures Tuesday to be in the lower to
middle 40s north-central/near Lake MI, middle to upper 40s

Models are having difficulty resolving the movement of a northern
stream shortwave trough for the middle part of next week. Some
models focus small pops Tuesday night, while others favor
Wednesday. Prefer to follow the model consensus which only
mentions minimal pops for both periods. Max temperatures on
Wednesday to range from the lower to middle 40s near Lake MI, to
around 50 degrees over parts of central WI.

.AVIATION...for 18Z TAF Issuance
Issued at 1232 PM CDT Wed Mar 21 2018

Fairly quiet flying conditions expected through Thursday. Mid-
upper level clouds will continue to exit from west to east late
early this afternoon. Winds have turned enough out of the north
to keep any lake clouds near Lake Michigan, which will bring in
lower clouds between 3000-3500 feet into MTW through the
afternoon. Another area of mid-level clouds over Minnesota are
making very slow progress eastward, but they are encountering
drier air, so they are expected dissipate or scatter out before
reaching central and north central WI. If clouds do survive the
trip eastward, CIGS will remain VFR. Winds will remain light
through the period.



SHORT TERM.....Bersch
LONG TERM......Kallas
AVIATION.......Bersch is the U.S. government's official web portal to all federal, state and local government web resources and services.