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000
FXUS63 KGRB 051127
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
527 AM CST Tue Dec 5 2023

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...
- A clipper system may bring a dusting to a half inch of snow to
  all but far northeast Wisconsin this morning. Some roads and
  sidewalks could become slippery.

- Well above normal temps (10-20 degrees), but below records, are
  likely on Friday.

- Low probabilities (10-20%) of significant winter weather on
  Saturday night and Sunday over northeast Wisconsin.

&&

.DISCUSSION...
Issued at 210 AM CST Tue Dec 5 2023

SHORT TERM...

A clipper system will track from northern Illinois to Indiana
this morning. The best moisture and lift from this system will be
well to the south; however, some modest low level warm air
advection will bring light snow and flurries across the area.
Given the limited moisture and lift, only a dusting up to a half
inch of snow is expected from this system across portions of
central, east-central and north-central Wisconsin.

Although the snow from this system should end by midday, lake
effect snow will continue across far north-central Wisconsin as
winds turn northwesterly. Highs today are mainly expected to be in
the middle to upper 30s under mostly cloudy skies.

High pressure will then build in across the area tonight, which
will end the lake effect snow across far north-central Wisconsin.
Some partial clearing is expected at times tonight, particularly
across northeast Wisconsin with some downsloping. Lows tonight
could be tricky depending on if areas clear out and for how long.
Lows are generally expected to range from the upper teens across
the north, to the middle 20s across east-central Wisconsin. Lows
could easily plummet further with prolonged clearing or be a bit
warmer if clouds hang in longer.

The high will slide east on Wednesday, allowing a warm front to
lift north as surface winds turn southerly by the afternoon and
become gusty, particularly across central and north- central
Wisconsin. Despite southerly surface winds, highs on Wednesday are
only expected to rise into the middle to upper 30s as model
soundings show a steep low level inversion just off the surface
with not much opportunity to mix into the warmer layer aloft. The
isentropic lift associated with the warm front could produce some
light snow or flurries/sprinkles on Wednesday across north-central
Wisconsin. Otherwise, conditions should mainly be dry across the
region.

LONG TERM...

Wednesday night through Friday night...Relatively quiet weather is
in store during this period.  A low pressure system will be tracking
from the northern Plains on Thursday to north of Lake Superior on
Friday night.  Warmer air will invade the region south of the
cyclone track and across Wisconsin on Thursday and Friday.  While
mixing looks shallow, temps will be on a warming trend with highs in
the 40s on Thursday and from the low 40s to low 50s on Friday.

Saturday through Monday...Focus then turns to a developing cyclone
over the mid-Mississippi Valley.  The ensemble means are generally
trending deeper with the shortwave located within the base of the
long wave trough in the Saturday-Sunday timeframe.  Cluster analysis
reveals that the stronger/deeper shortwave has higher potential for
precip across northeast Wisconsin.  In general, model spread remains
rather large due to a complex split flow pattern, so details will
likely change in the coming days.  With that said, eastern WI has
the greatest chance of seeing significant winter precip so will
monitor in subsequent forecasts.

In the wake of this storm system, temps will be trending colder with
signs of clipper energy traversing the region.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 527 AM CST Tue Dec 5 2023

Light snow showers from a weak Alberta Clipper will bring MVFR/VFR
conditions to the area this morning. Snow amounts will be less
than an inch in most areas, with little or no snow expected in far
NE WI. Conditions should improve to VFR across eastern Wisconsin
this afternoon and remain at MVFR across central and north-central
Wisconsin into tonight.

&&

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

&&

$$

DISCUSSION.....Kurimski/MPC
AVIATION.......Kurimski