Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 231143
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
543 AM CST Mon Jan 23 2017

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 305 AM CST Mon Jan 23 2017

300 am observations and available web cams indicate spotty dense
fog over far northeast Wisconsin but not enough for a dense fog
headline. Areas radars show patches of light returns, so will
keep a mention of drizzle going this morning.

Light winds and moisture trapped in the boundary layer will
continue to keep clouds around for most of the period through
Tuesday. Slightly cooler air on northwest winds will filter into
the area tonight, but still well above normal.

Weak surface troughing extending into lower michigan and part of
Lake Michigan from a low pressure system drifting over the Ohio
Valley tonight, may produce a few light showers toward the Door
County area, but 24 hour trends suggest any pcpn to be confined
east of the area.

Attention then turns to a developing storm system approaching from
the Plains on Tuesday. Warm air advection precipitation may begin
to work into central Wisconsin Tuesday afternoon. With surface
temperatures in the mid to upper 30s, expect pcpn type to be light
rain or mix of light rain/snow.

.LONG TERM...Tuesday Night Through Sunday
Issued at 305 AM CST Mon Jan 23 2017

The medium range models continue to shift their forecast track and
timing of the next cyclone due to move across the region Tuesday
night into Wednesday.  Model comparisons still suggest that a blend
of the ecmwf/gfs will offer a middle of the road approach.

Tuesday night through Wednesday night...Precipitation will be in the
process of spreading northeast from central into northern and
eastern Wisconsin during the evening.  Forcing via upper divergence
and mid-level fgen look moderate to strong from Tuesday evening thru
early Wednesday morning, when the heaviest precipitation will be
moving through.  At the onset of precipitation on Tuesday evening,
precipitation will probably start out as a rain/snow mix until evapo
cooling knock temps down into the lower 30s by mid-evening.  This
may cut down snow totals slightly, but its still looking like snow
will be the main precip type for most of the event.  Snow intensity
will diminish from west to east from mid to late Wednesday morning
through the afternoon as the low exits into lower Michigan. However,
ample mid-level moisture will lead to light snow and/or flurries
continuing Wednesday afternoon into Wednesday night.  It is possible
that some rain may mix with the snow on Wednesday afternoon over
northeast Wisconsin as snow intensity diminishes and temps warm into
the middle 30s.  Expected accumulations have increased some over
northern Wisconsin, and now portray a widespread 3 to 5 inch
snowfall. Think there is some potential for snow ratios to be higher
than advertised for central and northeast WI Tuesday evening, that
could push amounts into the 4 to 6 inch range.  With coordination
from surrounding offices, will defer headlines to later shifts.

Rest of the forecast...As winds turn to the northwest aloft,
shortwaves dropping southward will provide occasional light snow
shower and flurry chances to the region through the weekend.  Its
rather difficult to determine where and when, as models have
different ideas in regards to the details.  It appears that the best
chances would occur on Thursday and also Friday night into Saturday.
Trajectories also become more favorable for lake effect snow showers
over Vilas county during the Friday night through Saturday night
periods, but shortwave disturbances will likely cause this timing to
shift some.  In general though, temperatures will be returning
closer to normal for the 2nd half of the week.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 543 AM CST Mon Jan 23 2017

Morning observations indicate a wide range of conditions ranging
from LIFR cigs and vsbys due to dense fog over door county, to a
pocket of vfr conditions over central Wisconsin. Eventually,
anticipate mainly ifr cigs today with mvfr vsbys today into
tonight.
&&

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

$$

SHORT TERM.....TDH
LONG TERM......MPC
AVIATION.......TDH


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