Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 222326
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
626 PM CDT Tue Aug 22 2017

Updated aviation portion for 00Z TAF issuance

.SYNOPSIS...
Issued at 220 PM CDT Tue Aug 22 2017

Generally quiet late-summer weather into early next week.
Seasonably cool the next couple days, then temperatures close to
normal.

The large scale pattern will complete an amplification cycle the
next couple days as a rather strong upper trough becomes
established from eastern Canada into the lower Great Lakes region.
Jet energy working east across Canada will cause the trough to
begin weakening by late in the week. By early next week, the main
westerlies will recede north into Canada, leaving just a weak
remnant of the trough lingering across the forecast area.

Temperatures will begin the period below normal, then rebound to
near normal levels by the weekend. Rainfall will be limited with
precipitation events consisting of just scattered showers. As
such, amounts for the period are likely to end up below normal.
&&

.SHORT TERM...Tonight and Wednesday
Issued at 220 PM CDT Tue Aug 22 2017

The latest RAP analysis and satellite/radar imagery show upper
troughing settling over the western Great Lakes early this
afternoon.  A widespread cu field has developed across the region,
though cu has the most vertical extent over far northwest WI and
northeast MN where the highest capes reside.  Some of this more
enhanced cu and even a few showers will move into north-central WI
later this afternoon. As cold air continues to funnel across the
region, forecast concerns revolve around light showers early this
evening, followed by lake effect showers/drizzle late tonight.

Tonight...As a secondary surge of cold air arrives from the
northwest tonight, high res models continue to indicate that
scattered showers will persist over north-central WI through the mid
evening hours.  Then attention turns to precip off western Lake
Superior overnight. 1000-850mb flow veers around to the NNW
direction after midnight, which is a good trajectory for showers or
drizzle to move into north-central WI. Increased cloud cover some
late as a result, but 10-15 kts of low level flow should not be
strong enough for these clouds to move into central or east-central
WI. With enough wind to prevent temps from tanking, should see lows
ranging from the mid 40s north to mid 50s south.

Wednesday...Broken cloud cover along with patchy drizzle/showers
will likely linger into the mid-morning hours over northern WI. With
day time heating, however, think mixing will cause these clouds to
scatter by midday.  Elsewhere, should see scattered fair weather cu
develop, which will lead to a partly cloudy day for most.  Highs
ranging from the low 60s in the far north to mid 70s at Wautoma.

.LONG TERM...Wednesday Night Through Tuesday
Issued at 220 PM CDT Tue Aug 22 2017

At low-levels, a cool, dry Canadian air mass will settle across
the area and linger through the weekend. Some pretty chilly
nights are likely unless clouds move through during the nighttime
hours. The typical cool spots across the north will probably fall
into the 30s Wednesday night and Thursday night, and would not be
surprised if there is some patchy frost. The anticyclone and its
associated air mass will linger across the area for much of the
forecast period, but moderation of the air mass should allow
temperatures to rebound to near seasonal levels by the weekend.

While the dry anticyclone dominates at low-levels, the forecast
area will be at least brushed by some middle and upper level
shortwave energy at times. That will lead to some clouds and
maybe some showers. But given the limited moisture, any rains are
likely to be scattered and light.

Tweaked mins down in the typical cool spots Wednesday night and
Thursday night, but tempered the adjustments some due to uncertainty
about passing clouds. Otherwise, the standard forecast
initialization grids based on a broad blend of model output seemed
reasonable, so no other significant changes were necessary.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 626 PM CDT Tue Aug 22 2017

Scattered showers continue to move through north-central and far
northeast Wisconsin early this evening. This activity will mainly
affect the RHI TAF site before diminishing with the loss of
daytime heating in a few hours. Otherwise, cool north-northwest
flow off Lake Superior will bring some low clouds and patchy light
showers or drizzle to north central WI late tonight, but
conditions should remain VFR farther south and east. Gusty
northwest winds will diminish after sunset. VFR conditions and
winds below 10 kts will prevail during the day on Wednesday as
high pressure settles in across the region.
&&

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

$$

SYNOPSIS.......Skowronski
SHORT TERM.....MPC
LONG TERM......Skowronski
AVIATION.......Kurimski



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