Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 040844
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
344 AM CDT Thu Jun 4 2020

Forecast discussion for routine morning forecast issuance

.SHORT TERM...Today...Tonight...and Friday
Issued at 343 AM CDT Thu Jun 4 2020

Precipitation trends are the main forecast concern.

MSAS analysis showed weak high pressure over the western Great
Lakes, with a cold front approaching from northwest MN and the
eastern Dakotas. Mid/high clouds were moving out of eastern WI,
and the resulting clear skies and light winds were causing patchy
fog to develop in north central WI.

The initial cold front is expected to weaken as it pushes into
northwest WI today, but an axis of marginal instability (CAPE
500-1000 j/kg) should set up over the northwest half of the
forecast area later in the afternoon. With little forcing
anticipated in the afternoon and evening, will just mention a
slight chance of showers and storms through about midnight.
Forcing increases overnight into Friday morning as a slightly
stronger cold front moves through, accompanied by mid-level short-
wave energy and the RRQ of an upper jet streak. Moisture is also
expected to increase ahead of the cold front overnight. POPs will
increase to likely during this period, along with the potential
for scattered thunderstorms. Although deep layer shear of 35 to 45
knots will be strong enough to support severe storms, weak
elevated instability and the unfavorable time of day should
mitigate the threat. Precipitation should decrease from northwest
to southeast Friday morning, with dry weather expected for the
afternoon.

Highs today will be in the lower to middle 80s, with lower to
middle 70s along the lakeshore. Lows tonight should be in the 50s
north and along the lakeshore, and in the lower 60s in central WI
and the Fox Valley. Highs will be a little cooler on Friday,
mainly in the middle 70s to lower 80s.

.LONG TERM...Friday Night Through Wednesday
Issued at 343 AM CDT Thu Jun 4 2020

The main highlights in the long term forecast are the near normal
temperatures this weekend, light precipitation early next week,
and the resolution of what is currently tropical storm Cristobal,
the remnants of which will possibly impact the forecast over our
area towards the middle of next week.

This weekend...a cooler and less humid airmass will be in place
under an upper level ridge. Highs will be close to normal,
ranging from the upper 60s to middle 70s Saturday, and just a few
degrees cooler on Sunday. Quiet conditions are expected into
Sunday, when a weak shortwave could set off some showers across
western and northern Wisconsin. Trended a little lower than
guidance early on Sunday, as instability may struggle to get
things going, but kept the inclusion of some showers and isolated
thunderstorms in through Monday morning. Most areas will remain
dry during this time.

Next work week... Return flow sets up for Monday through the end
of the extended, bringing back warmer and more humid conditions as
highs head back to the 80s. Much uncertainty is in the extended
period after this, as the remnants of what is currently tropical
storm Cristobal merge with the main upper level trough over the
Central Plains. The ECMWF has this system intensify as it heads
towards our region, bringing in high winds and even more
impressive PWATS. Other models are more moderate, merging the low
with the main flow, and then bringing a period of widespread
storms and showers to the region as the tropical airmass heads
northwards. How exactly this will impact the main flow and where
the heaviest precipitation sets up is still unclear, so kept winds
in line with guidance for now, but a period of heavy rainfall and
potential storms is likely for our region sometime in the middle
of next week.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1043 PM CDT Wed Jun 3 2020

Good flying weather is anticipated through much of the taf
period. Some mid and high level clouds will drift across the
region during the overnight and into Thursday morning. Clouds
will increase and a few showers or storms will be possible across
far northern WI on Thursday afternoon and across central and
north-central Wisconsin Thursday evening. The best chance for rain
appears to be later Thursday night when a mid level shortwave
arrives from the west, therefore will leave rain out of this set
of TAFs.
&&

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

$$

SHORT TERM.....Kieckbusch
LONG TERM......Uhlmann
AVIATION.......Kurimski


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