792
FXUS63 KGRB 162317
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
617 PM CDT Mon Sep 16 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Summer-like temperatures continue through Thursday with highs in
  the 80s. Temperatures to stay in the 70s near Lake Michigan.
  Slightly cooler temperatures are expected this weekend.

- Other than a small chance (15 to 20%) of a thunderstorm over far
  north-central WI through this evening, the next chances for
  rain arrive late this week and carry into the weekend.

&&

.DISCUSSION...
Issued at 158 PM CDT Mon Sep 16 2024

Short Term...Tonight and Tuesday

Isolated instability showers and storms have developed within a
pocket of higher MLCAPEs values (1000-1500 J/kg) across northwest
and far north-central WI this afternoon. With weak vertical wind
profiles expect storms to be pulsy in nature with little to no
severe weather threat. As evidenced by the lack of cumulus cloud
development, a more stable air mass is in place south of a Wausau to
Marinette line. This portion of the CWA should remain dry through
this afternoon. Temperates across the region are once again well
above normal, with readings as of 2pm ranging from the lower to
upper 80s across the region.

Tonight...Instability showers that developed this afternoon across
north-central WI should diminish this evening with dry conditions
expected overnight. Scatted cloud cover across northern WI will lead
to slower cooler temperatures tonight resulting in lows in the middle
to upper 50s at most locations overnight. Light onshore flow may
lead to the development of patchy fog near the lakeshore early
Tuesday morning.

Tuesday...Dry conditions across the area are expected to remain
through Tuesday as a 500mb ridge and dry mid-level air mass continue
to sit over the region. Skies will be a mix of sun and clouds as
middle and high clouds generated by a trough digging over the
Rockies filter over the area. The combination of sun and light
southerly winds will allow for another day of well above normal
temperatues. Highs across most of the region are forecast to reach
the low to middle 80s, while onshore flow will keep lakeshore areas
about 5 degrees cooler.

Long Term...Tuesday Night Through Monday

An omega blocking pattern will remain across the CONUS this week,
with the ridge portion of the pattern across the Great Lakes
region. This will keep the weather dry through much of the week as
temperatures remain well above normal for this time of year. The
pattern will shift a bit east towards the end of the week into the
weekend, which will allow the troughs and subsequent army of PV
anomalies to make headway over the western Great Lakes region. The
first one looks to arrive Thursday night into Friday, which will
bring a good chance for rain (40-60 percent) to central and
north-central Wisconsin and lesser chances (20-30 percent)
further east closer to the influence of the high.

The low pressure systems tracking through the region this
upcoming weekend and into early next week are a bit more murky as
the long-range models differ on the influence the ridge will have
across the area. The stronger ridging in place would portend a
drier solution, while a more progressive trend would make for a
wetter weekend. Once a ridge is in place it can be difficult to
unseat; therefore, would bet on at least some dry periods this
weekend with the possibility for rain showers/thunderstorms at
times if the shortwaves can make it this far east. Despite the
pattern that eventually emerges, there continues to be consensus
on continued well above normal temperatures into at least the
weekend.

In addition to the warm temperatures, some ground fog will
continue to be possible at times as a moist atmosphere will be in
place across the western Great Lakes region on southerly flow.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 617 PM CDT Mon Sep 16 2024

An upper level disturbance will produce high clouds as it moves
across Wisconsin tonight. There is a slight chance that some
ground fog could form late tonight west of the bay and Lake
Michigan at OCQ and MTW. Otherwise VFR conditions are likely
across the area overnight.

VFR conditions will continue Tuesday, with some high clouds at times
and light surface winds from the south.

&&

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

&&

$$

DISCUSSION.....GK/Kurimski
AVIATION.......RDM