Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 120322
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1022 PM CDT Tue Aug 11 2020

Updated aviation portion for 06Z TAF issuance

.SYNOPSIS...
Issued at 237 PM CDT Tue Aug 11 2020

Seasonably warm and becoming a little humid again throughout the
rest of the work week and the upcoming weekend, then cooler next
week.

The subtropical ridge will remain stretched out across the
southern CONUS throughout the forecast period. Meanwhile, the
initially zonal band of westerlies to the north will turn slowly
progressive and gain amplitude as a trough presently over the
British Columbia region slowly migrates into the James Bay/Lower
Great Lakes region by the end of the period.

Temperatures should remain slightly to modestly above normal
through the upcoming weekend, then drop to at least a little
below normal next week. The humidity will gradually edge upward
during the week, though it shouldn`t feel excessively humid as dew
points are forecast to top out in the 60s. Precipitation amounts
are expected to end up AOB normal, though all the standard caveats
related to the uncertainty in forecasting summer convective
precipitation apply.
&&

.SHORT TERM...Tonight and Wednesday
Issued at 237 PM CDT Tue Aug 11 2020

Quiet weather is expected for the short-term portion of the
forecast as a weak anticyclone passes south of the region.
Guidance suggests warming will already be occurring tonight. But
edged mins below guidance due to the dry air in place across the
area and with the expectation that and winds likely to go calm
across much of the area. Conversely, raised maxes a bit tomorrow
after looking where temperatures stood early this afternoon.
A few of the models generated scattered very light precipitation
over the far north/northeast part of the area tomorrow. But
considering the flow from the surface up through 850 mb will
still result in a feed of dry stable air out of the receding
anticyclone, opted to keep the forecast dry.

.LONG TERM...Wednesday Night Through Tuesday
Issued at 237 PM CDT Tue Aug 11 2020

A zonal flow will start off the long term, then the pattern
amplifies this weekend and early next week with a ridge building
across the northern Rockies and western Plains and troughing
digging across the Great Lakes. Main forecast challenge will be
timing out best precip/thunder chances. Temps will start off
near/above normal, then fall below normal by early next week.

Wednesday night and Thursday...surface high pressure will
continue to slide into the eastern Great Lakes, with return flow
setting up across the western Great Lakes. The surface high along
with weak mid-upper level ridging will bring dry weather to the
area. A few models try to bring in a shower/storm into central and
north-central WI, but thinking this will stay to our west. With
the WAA slowly ramping up, low temps look to be a little warmer
with lows in the upper 50s to middle 60s, with humidity levels
remaining on the comfortable side. Highs on Thursday will be
pretty close to Wednesday, with 80s for most spots.

Thursday night into Friday...the surface high slides a little
farther to the east, allowing minor height falls across the
northern Plains and western Great Lakes. This will bring chances
for showers and storms back into the area, mainly across central
and north central WI as weak shortwaves and a frontal boundary
will likely kick off activity from time to time. Bulk of the
activity looks to stay anchored with the more potent shortwave
across eastern MN and western WI. Humidity levels will be slowly
on the rise late in the week, with dewpoints climbing into the mid
60s across central and east central WI by Friday afternoon. 850mb
temps do nudge upwards on Friday, but some cloud cover will
likely limit full heating, so highs in the upper 70s to
lower/middle 80s are expected.

Rest of the long term...as the zonal flow breaks down, a return
to northwest flow will take over the western Great Lakes. The two
best chances for widespread showers/storms will be with a
shortwave late Friday night into Saturday morning, mainly
impacting central and north central WI, then a a cold front
sweeping across the area on Sunday. Timing will of course have to
be fine tuned. More humid conditions are expected for the weekend,
with dewpoints topping off in the middle to possibly upper 60s.
Temps will remain in the upper 70s to middle 80s ahead of the
front. Then, drop in the upper 60s and 70s behind the front,
along with very comfortable humidity levels.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1021 PM CDT Tue Aug 11 2020

Minimal changes to the TAFs this issuance. Confidence is somewhat
low on the patchy fog potential across central and north- central
WI tonight as guidance has backed down on fog development. Will
keep a limited mention at KRHI/KCWA/KAUW for a couple hours where
winds are expected to be nearly calm. Otherwise, VFR conditions to
prevail with light winds and scattered high clouds at times
Wednesday afternoon.
&&

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

$$

SYNOPSIS.......Skowronski
SHORT TERM.....Skowronski
LONG TERM......Bersch
AVIATION.......KLJ


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