Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 082313
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
513 PM CST Mon Mar 8 2021

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Tuesday
Issued at 330 PM CST Mon Mar 8 2021

Main forecast concerns center around extent of fog tonight and how
warm temperatures can get on Tuesday.

The 19Z MSAS surface analysis showed a cold front that extended
southwest from eastern Lake Superior to southwest WI. Only a wind
shift from southwest to west-northwest marked this frontal
passage. A ridge of high pressure was located from the lower
reaches of the OH Valley northwest through the Upper MS Valley.
Temperatures were unseasonably mild, with readings roughly 15 to
20 degrees above normal.

The ridge of high pressure will slide across WI this evening and
reach the eastern Great Lakes region by daybreak. As this occurs,
a southerly return flow to set-up over WI. Mostly clear skies are
expected this evening, however some increase in clouds will occur
overnight as a warm front lifts north into southern WI and a mid-
level shortwave trough approaches from the Upper Midwest.
Anticipate a quick drop in temperatures this evening, then
readings to stabilize later at night with mins in the lower to
middle 20s far north, lower 30s south. Have included patchy fog as
melting snow adds moisture to the air or dew points get close to
actual air temperatures.

Middle and high clouds will continue passing over northeast WI
into Tuesday morning as both the warm front and shortwave trough
push across WI. Do not anticipate any precipitation to accompany
these features. By Tuesday afternoon, a gusty south-southeast wind
will pull warmer air into WI with 8H temperatures of around +5C
and 925mb temperatures around +10C. Winds should gust in the 20 to
30 mph range with max temperatures to range from around 50 degrees
along Lake MI, to the lower 60s west of the Fox Valley. A few
records may be broken if these values are indeed reached.

.LONG TERM...Tuesday Night Through Monday
Issued at 330 PM CST Mon Mar 8 2021

Main forecast concerns will be dealing with the mid-week system,
with questions regarding rain amounts/flooding issues, p-type
over northern WI, thunder chances and temps. Quieter weather
arrives for late in the week and weekend. Temps will be well above
normal on Wednesday, then fall back to near normal this weekend.

Tuesday night...a very mild early spring night is on tap with
southerly WAA flow continuing. Lows look to only drop into the 40s
to around 50. Could set some record high minimum temps,
especially across central and eastern WI. With dewpoints slowly
increasing and continued snowmelt, could have some fog and/or low
cloud issues both on land and on Lake MI. However, boundary layer
winds look to be high enough, along with clouds should help keep
dense fog from forming. Conditions look to start off dry during
the early evening hours, then light showers or drizzle will
develop as weak lift and initial shortwave energy toward the area.

Wednesday into Thursday...surface low will track from the central
Plains Wednesday morning into WI Wednesday afternoon/evening.
Models still vary on exact track and strength. Will lean toward
the farther north/stronger solutions. This will keep the precip
type mainly all rain for our area, with only a period of mixing
with freezing rain/sleet/snow across far north central WI
Wednesday night into Thursday AM. Right now any snow/ice
accumulation looks minor, but any southward shift could bring in
more wintry precip. Rain amounts look to mainly be in the
0.25-0.75" range. Locally higher amounts are possible if/where
some banding occurs and/or in a storm. This rain, along with
continued melting snow, could lead to some minor flooding issues.
Some ice jams could also develop as the ice begins/continues to
break up. South to southwest winds will be gusting up to 30 mph
across the Fox Valley and lake shore on Wednesday. The winds
could produce some ice shove issues on Lake Winnebago, along with
create some shifting ice on Green Bay. Thunder prospects still
look on the low side, but a storm or two can`t be ruled out
in/near the warm sector as steeper lapse rates push across the
area. Small hail and gusty winds up to 40 mph would be the main
hazards. Highs on Wednesday will be well above normal, with 50s to
around 60 in the warm sector and 40s north of the front. Precip
comes to a quick end Thursday morning as the cold front moves
through. Temps will still be above normal, but not as warm as
Wednesday.

Rest of the long term...quiet weather is expected Thursday night
into the weekend as large Canadian high pressure slides into the
western Great Lakes. An upper low will dive across southern Canada
late in the week which may clip our area, but any precip would be
very light. Temps will fall back to near normal.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 512 PM CST Mon Mar 8 2021

A warm front is expected to lift northward toward the area
tonight, which will allow east to southeasterly flow off Lake
Michigan. This may lead to fog development and possibly some lower
ceilings with upslope flow. Otherwise, patchy fog may also
develop over inland locations, especially northern WI due to
melting snow. VFR conditions should be predominant tonight,
however where fog does develop, vsbys would drop into the IFR
range.

Any fog that does develop will lift by mid-morning Tuesday with
south-southeast winds gusting into the 20 to 25 knot range by the
afternoon. VFR conditions to prevail through the day. LLWS is
forecast to develop late Tuesday afternoon/early Tuesday evening
across the entire region.
&&

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

$$

SHORT TERM.....Kallas
LONG TERM......Bersch
AVIATION.......Kurimski


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