Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 121738
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1238 PM CDT Wed Aug 12 2020

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Thursday
Issued at 312 AM CDT Wed Aug 12 2020

A weak short-wave trough was bringing some mid/high clouds to the
forecast area early this morning. The cloud cover was holding
temperatures up a bit, with most locations in the middle 50s to
middle 60s. Farther upstream, a well-developed MCS was tearing
across northern South Dakota.

Mid/high clouds will impact the region early in the day before
shifting east and eroding as they move through the surface ridge.
The upstream MCS is expected to weaken or dive south before
reaching the WI border, so dry weather will continue over GRB CWA.
Abundant sunshine is expected by afternoon, with highs warming
well into the 80s inland. Developing southeast winds will keep
lakeside locations a little cooler, in the upper 70s and lower
80s.

Dry conditions will continue under the influence of high pressure
tonight into Thursday. There could be a few patches of ground fog
overnight, but confidence is not high enough to include in the
forecast at this time. Lows tonight should be in the middle 50s
to middle 60s. High temperatures on Thursday should be a carbon
copy of today.

.LONG TERM...Thursday Night Through Tuesday
Issued at 312 AM CDT Wed Aug 12 2020

A pattern change is expected this weekend as a 500mb ridge
develops across the western United States. A downstream trough
will bring a cooler northwest flow pattern to the western Great
Lakes early next week.

For Thursday night, high pressure will remain in control of
the weather. Dry conditions are expected with lows in the 50s
to around 60. For Friday, will continue the dry conditions as high
pressure remains over the area and main area of convection remains
well west of the forecast area. The chances of storms arrive
Friday night. A cold front will move across the state on Saturday,
bringing the chances of showers and thunderstorms during the day.
Bufkit soundings indicated CAPE values of 500 to 1,000 J/KG. Shear
values were from 20 to 25 knots and total total values around 45.
Could be some stronger storms Saturday afternoon.

The chances of showers and storms will linger across eastern
Wisconsin Saturday evening. Dry conditions are expected late
Saturday night through Sunday night. Will need to watch Monday
and Tuesday as the GFS/ECMWF/Canadian model brings some light
precipitation across the north. With cooler cyclonic flow aloft,
may need to add a chance of rain for this period, especially
during the afternoon and early evening. The ECMWF indicated 850mb
temperatures dropping to +8C to +10C on Tuesday. This will result
in high temperatures in the upper 60s to lower 70s at most
places. Temperatures should begin to moderate by the middle of
next week.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1237 PM CDT Wed Aug 12 2020

An area of showers and thunderstorms in far western Wisconsin at
midday should largely dissipate before arriving in northcentral
Wisconsin late tonight. There is a slight chance of a shower north
of Rhinelander, but the rest of the region should be dry. VFR
conditions are expected tonight through Thursday night with some
middle and high clouds at times.

&&

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

$$

SHORT TERM.....Kieckbusch
LONG TERM......Eckberg
AVIATION.......RDM



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