Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 162322
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
522 PM CST Tue Jan 16 2018

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Wednesday
Issued at 207 PM CST Tue Jan 16 2018

Weakening low level convergence and steep low level lapse rates
contributing to scattered light snow showers this afternoon over
eastern and northern CWA.  Further weakening of the convergence and
increasing mid-level ridging should end bulk of the -shsn by
evening, however a few flurries may persist.  Clearing skies and
fresh snow cover should allow temperatures to fall off rapidly this
evening before leveling off as low level winds increase.  Lingering
winds of 5 to 10 knots and temperatures falling below zero will
result in wind chills falling to 10 to 15 below zero for a time
overnight.

Tightening pressure gradient between low pressure passing well north
of the U.S./Canada border and strong high pressure sinking into the
southern plains will result in the increasing low level winds late
tonight and on Wednesday.  Forecast soundings show the likelihood of
15 to 20kt sustained winds on Wednesday, with gusts of 25 to 30
knots possible.  These levels would result in widespread drifting of
the fresh, powdery snow.  Some of the snow will become lofted,
resulting in patchy reduced visibilities, especially in Door County.
Gusty west winds will pick up momentum over the ice cover on Green
Bay so wind gusts may exceed 35 knots, possibly requiring a Winter
Weather Advisory or Warning for Door County.

.LONG TERM...Wednesday Night Through Tuesday
Issued at 207 PM CST Tue Jan 16 2018

Wednesday night and Thursday:

Quiet weather is expected Wed night under high pressure, except
for some blowing/drifting snow possibly continuing in the east.

A passing wave may bring a little light snow to the northern
forecast area Thursday, with the best chance occurring in the
morning. Little to no accumulation is expected. West to southwest
winds will push high temps to a few degrees above normal for mid-
January.

Friday and Saturday:

Dry weather is expected for late week, with a west to southwest
low level flow resulting in even milder temperatures. Highs could
crack 40 in the south by Saturday.

Sunday through Tuesday:

Attention then turns to the next big low taking aim at the region
early next week. Models are in decent agreement in taking the low
across or just to the south of the forecast area Sunday night into
Monday, though there are some impactful differences. The
northernmost track among models would result in primarily rain for
the bulk of precip, with maybe an inch or two of snow on the back
side of the low Monday. The farthest south solution would be
mainly snow across roughly the northern half of the forecast, with
rain or a rain/snow mix in the south. There is the potential for
significant snowfall accumulations for those in the favored areas
northwest of the low track. Where that area will be though is
definitely still up in the air. This storm continues to bear
watching, with plenty of time left for details to change.

Could see a little light snow Tuesday, as the GFS and Canadian
solutions bring a quick wave through. The ECMWF is dry for this
day though.

Temperatures early next week will largely depend on the track of
low pressure, with a northern track resulting in milder temps and
and southern track resulting in colder temps. It should be colder
Tuesday either way as the low departs the area.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 517 PM CST Tue Jan 16 2018

The main wx impact on aviation the next 24 hours will be
developing LLWS. The wind shear will expand southeast across the
area after midnight, continuing and strengthening during the day
tomorrow. Surface winds may increase enough to produce some
blowing snow tomorrow afternoon, especially in eastern Wisconsin.
&&

.MARINE...
Issued at 207 PM CST Tue Jan 16 2018

Tightening pressure gradient will result in gusty west
winds developing late tonight and Wednesday.  A few gusts could
reach Gale levels, especially east of Door County, but not enough
confidence to post Gale Warning at this time.  However, a Small
Craft Advisory goes into affect Wednesday morning and continues into
Thursday afternoon.
&&

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

$$

SHORT TERM.....MBK
LONG TERM......DDV
AVIATION.......Skowronski
MARINE.........MBK



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