415
FXUS63 KGRB 162021
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
321 PM CDT Tue Jul 16 2024

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

 - Below normal temperatures expected tonight through Wednesday
   night, then temperatures return closer to normal by the
   weekend.

 - Mainly dry weather is expected through Saturday morning. The
   next chance of showers and storms is on Saturday afternoon, and
   then again early next week. The risk of severe weather is low
   over the weekend, and uncertain next Monday and Tuesday.

&&

.DISCUSSION...
Issued at 320 PM CDT Tue Jul 16 2024

Short Term...Tonight and Wednesday

Minimal impacts are anticipated through this forecast period with
only slight chances for precip and below normal temperatures.

This evening and tonight...This afternoon`s water vapor imagery
indicated a vort max/shortwave dropping south into northern WI,
which has triggered isolated showers to develop across the
Northwoods. Meanwhile, the rest of the forecast area saw dry
conditions under an agitated cu field. The isolated showers will
continue to drop south with the vort max/shortwave and gradually
dissipate by early this evening with a loss of daytime heating.
Cannot rule out the low chance (10-15%) for some rumbles of
thunder given a couple hundred J/kg of CAPE around. Clearing is
expected for the first part of the night following these precip
chances before the main trough begins to move overhead and bring
the return of clouds. In addition to the clouds, a few showers may
also develop. Overnight lows will be slightly below normal with
values mainly in the 50s.

Wednesday...With the trough gradually shifting eastward into
Wednesday morning, low-level winds will turn north/northwest and
combine with delta Ts around 13C to generate lake-enhanced rain
showers across far northern WI throughout the day. Isolated showers
may also develop in far eastern WI as the trough exits during the
afternoon. This pattern will bring cooler temperatures to the region
with highs about 5 to 15 degrees below normal, ranging from the
middle 60s to middle 70s.

Long Term...Wednesday Night Through Tuesday

500mb ridge across the Rockies with downstream troughing across
the western Great Lakes will bring cooler than normal temperatures
Wednesday night into Thursday. The 500mb ridge will shift westward
and while the upper trough shifts eastward leaving the area with a
weak trough on Saturday which shifts southward on Sunday.

Below normal temperatures are expected Wednesday night with lows
in the 40s to lower 50s. Readings could be close to 40 at a few
of the colder spots like Land O` Lakes and Tomahawk. Temperatures
will rebound back into the 70s on Thursday. Another cool night is
in store Thursday night, but should be a few degrees warmer than
the previous night. Dry conditions will prevail Friday through
Saturday morning.

The first chance of showers and thunderstorms will arrive Saturday
afternoon as a weak frontal boundary sinks southward across the
area. The risk of severe weather is low. Any lingering showers or
storms should end early Saturday evening. Dry conditions will then
prevail late Saturday evening through Sunday morning. Another a
small chance of instability showers and storms are expected Sunday
afternoon.

For Monday and Tuesday, the models are in fairly good agreement
for diurnally driven chances of showers and thunderstorms with the
highest chances during the afternoon and evening. It is too early
to determine if any of these storms would become severe. Temperatures
over the weekend will be fairly close to normal. Normal high/low
temperatures are at the peak for the year and will start the slow
decline by the end of the month.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1258 PM CDT Tue Jul 16 2024

VFR conditions are expected in most places through at
least Wednesday night. There will be Cumulus clouds with bases
between 4000 ft and 7000 ft this afternoon and early evening, along
with isolated showers. These clouds should dissipate late this
evening.

Cool air flowing across Lake Superior could produce lake effect
clouds across northcentral Wisconsin late tonight through Wednesday
morning, mainly north of a RRL to IMT line. These clouds will likely
have bases between 2500 and 3500 ft, lowest near the Michigan border.

VFR ceilings are expected Wednesday, but those clouds should dissipate
Wednesday evening, with clear skies Wednesday night.

.OSH...VFR conditions are expected for the next few days. Cumulus
clouds with bases between 4500 and 8000 feet are likely this afternoon.
They should dissipate this evening, with clear skies overnight through
Wednesday morning. Scattered to broken Stratocumulus clouds are expected
Wednesday afternoon with bases above 4000 feet.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION.....Kruk/Eckberg
AVIATION.......RDM