Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 192257
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
457 PM CST Fri Jan 19 2018

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Saturday
Issued at 337 PM CST Fri Jan 19 2018

Tranquil winter weather day in progress across the area with temps
10-15 degrees above normal. Mid-upper level clouds pushed across
the area providing for fair skies.

The quiet weather will continue tonight as the region resides in a
zonal flow pattern and no surface features or sufficient moisture
to produce precip. Strong 150+ knot upper jet over southern Canada
along with moisture above 10,000 ft will keep mid-upper level
clouds across the area. SW/W surface winds will help keep temps
well above normal tonight, with most spots only falling into the
20s to around 30 degrees. The light winds in combination with
slightly higher dewpoints and melting snow could lead to patchy
fog development.

Not much change on Saturday, with the upper jet slowly moving
east. Weak gradient will allow winds to be very light. Mid-upper
level clouds are again expected, which will limit heating somewhat
and provide for fair skies. Temps will run 10 to 15 degrees above
normal for most spots.

.LONG TERM...Saturday Night Through Friday
Issued at 337 PM CST Fri Jan 19 2018

The upcoming winter storm system is the primary concern during
this part of the forecast.

A mid level trough is forecast to move onshore, reaching the
western CONUS, tonight. A cutoff 500 mb low will then develop and
cross the Plains, approaching the Great Lakes region late this
weekend/early next week.

Onset of the main round of precipitation looks to be Sunday
evening, with PoPs then increasing during the day on Monday and
gradually decreasing Monday night before the storm pushes away
from the area on Tuesday.

The 12Z models have generally been showing the surface and 500 mb
lows passing a little farther south than they had on previous
runs. The ECMWF was still the farthest south and slowest of the
NAM/GFS/ECMWF/Canadian. Precipitation type issues remain due to
model differences with the exact path of the surface and mid level
cyclones.

The blended model solution showed quite a bit of ice accumulation
with some locations in central Wisconsin with just a little less
than a quarter inch. Heaviest snowfall was in far north central
Wisconsin. Ended up adjusting some of the forecast grids to yield
less ice and pushed the axis of heaviest snowfall a little farther
southeast. Confidence in exact precipitation type and totals at
any location is low due to model differences, so have decided to
hold off issuing any headlines but there should be some pretty
high snowfall totals over some part of the area by the time this
event is finished.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 456 PM CST Fri Jan 19 2018

LLWS conditions will linger this evening with 2000 ft winds around
40 kts. Otherwise VFR conditions to dominate overnight into
Saturday. Patchy MVFR fog possible late tonight. MVFR clouds may
be on the increase late Saturday but more likely towards Saturday
night.
&&

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

$$

SHORT TERM.....Bersch
LONG TERM......MG
AVIATION.......TDH



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