Area Forecast Discussion

FXUS63 KGRB 161136
Area Forecast Discussion
National Weather Service Green Bay WI
536 AM CST Sat Feb 16 2019
Updated aviation portion for 12Z TAF issuance
.SHORT TERM...Today...Tonight...and Sunday
Issued at 219 AM CST Sat Feb 16 2019
Cold early morning temperatures were had across much of the
region, with many locations across central and north-central
Wisconsin falling below zero with locations across east-central
and northeast Wisconsin in the single digits. Given the lack of
wind, wind chill values were in check across the region.
Partly to mostly sunny skies will be had today as high pressure
drifts across the western Great Lakes region. Some northeasterly
winds could bring some lake effect flurries to the lakeshore later
this afternoon and this evening, however these should be of 
little consequence. Highs today will generally be in the lower to
middle 20s.
The high then shifts to the northeast tonight, allowing a low
pressure system to develop over the mid Mississippi Valley. The
snow from this system looks to hold off until very late tonight,
therefore lowered POPs a bit for the late overnight periods. Lows
tonight should once again fall to below zero across the far north
with mostly clear skies for much of the night, with lows around 10
across central and east-central Wisconsin given more cloud cover
advecting in sooner with the low.
The aforementioned low will pass through central Illinois on
Sunday, with the northern extent of the snowfall affecting central
and east-central Wisconsin. Areas to the north should mainly stay
dry during this event given dry northeasterly winds from the high
to the north. Some lake enhancement is possible across the
lakeshore counties Sunday afternoon, which could help boost
snowfall totals. Snowfall from this event will not be very
impressive as the main forcing and moisture will be well to the
south as the snowfall fights the dry northeasterly winds. Overall
only a few tenths of an inch of snow are expected on Sunday, with
amounts possible reaching an inch across the far southern cwa. 
Daytime highs on Sunday will rise into the upper teens to lower 
.LONG TERM...Sunday Night Through Friday
Issued at 219 AM CST Sat Feb 16 2019
The stagnant mid-level pattern to persist through next week with
upper ridging over the eastern Pacific/western Atlantic and a
positive-tilted upper trough from central Canada to the southwest
CONUS. Models continue to show systems topping the Pacific ridge,
diving southeast through the base of the upper trough, then
ejecting northeast across the rest of the CONUS. This is an active
pattern for northeast WI with one system exiting Sunday night,
system #2 Tuesday night into Wednesday night and a potential third
system for next weekend. Temperatures are expected to be below
normal through Wednesday, then moderate a bit closer to normal for
late week.
The chance for light snow will continue over central/east-central
WI into Sunday evening as the shortwave trough moves toward the
eastern Great Lakes. Any additional accumulations would be very
light. While snow chances end across central WI by midnight, focus
turns to more of a lake effect threat for east-central WI
(especially Kewaunee and Manitowoc counties) as northeast winds
and moderately cold air move over Lake MI. Depending on the exact
trajectory of the wind, it is conceivable that areas from Kewaunee
southward could pick up an additional one inch of snow. Otherwise,
cloudy skies to prevail with min temperatures from zero to 5 
above north-central WI, 10 to 15 degrees east- central WI.
Lake effect snow shower threat to linger into Monday morning
across Kewaunee/Manitowoc counties with a north-northeast wind.
Models all show the wind will back to the north-northwest Monday
afternoon and this would end any lake effect from Lake MI.
However, these north-northwest winds may briefly open the door to
a little lake effect for Vilas County, although a good chunk of
Lake Superior has ice which would severely limit amount of snow
showers. For the rest of northeast WI, Monday will have a good
amount of cloud cover with perhaps a few peeks of afternoon sun.
Max temperatures to be in the upper teens to lower 20s.
An area of Canadian high pressure is forecast to build toward the
Upper MS Valley on Monday night, however model time sections
indicate moisture may be hard to displace, thus partly to mostly
cloudy skies to hold through the night. Despite these clouds, min
temperatures are expected to fall to around zero north, zero to 5
above south except around 5 above near Lake MI. The high pressure
will be situated over the Great Lakes on Tuesday, keeping quiet
and cool conditions intact. Any breaks in the clouds will continue
through Tuesday morning before clouds begin to become more
widespread late in the day in advance of our next system. Max
temperatures should again be in the upper teens to lower 20s.
This next shortwave trough to have ejected northeast out of the
western upper trough and is forecast to reach the central Plains
by 12Z Wednesday. Meanwhile, an associated surface low to have
moved toward the TN Valley. Expect the leading edge of light snow
to reach central/east-central WI by daybreak. As the mid-level
shortwave trough tracks toward the Upper MS Valley on Wednesday,
the surface low to move into the Ohio Valley with an inverted
surface trough extended northwest toward the WI/IL border.
Increasing lift from this surface trough and a nearly coupled
upper jet structure, combined with increasing mid-level Q-G and
frontogenetical forcing, should bring a broad area of snow to
northeast WI. While the models have the timing in good agreement,
the strength of the lift and forcing differ, making potential snow
accumulations rather difficult at the moment. Have gone along with
the consensus pops for now, but this system bears watching. Max
temperatures Wednesday to mainly be in the 20 to 25 degree range.
The snow would continue through Wednesday night as the shortwave
trough and the inverted surface trough sweep into the Great Lakes.
Anticipate additional accumulations, especially through the
evening hours. We finally get out of the snow on Thursday with
high pressure trying to push into the region. This should provide
for some sunshine during the day with max temperatures in the
middle to upper 20s. This area of high pressure to remain our main
weather feature through Friday, therefore another dry day on tap
with max temperatures edging closer to normal (upper 20s to around
30 degrees) with the help of more sunshine.
.AVIATION...for 12Z TAF Issuance
Issued at 536 AM CST Sat Feb 16 2019
MVFR ceilings and scattered flurries were still being reported
over parts of far northern and eastern WI this morning, and 
appeared likely to impact the RHI/GRB/MTW TAF sites for the first
hour or two of the new TAF period. Decreasing clouds are expected
this morning in northeast WI overnight as high pressure builds 
into the region. VFR conditions are then expected for the 
remainder of the TAF period as some high clouds move through the 
Clouds will then thicken and lower later tonight as a low pressure
system tracks through the mid Mississippi Valley region. Any snow
from this system and low clouds look to hold off until after 12Z
on Sunday.
SHORT TERM.....Kurimski
LONG TERM......Kallas