Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 191145
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
545 AM CST Fri Jan 19 2018

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Saturday
Issued at 349 AM CST Fri Jan 19 2018

High heights and zonal flow favors mild and dry weather and that
is what we expect for the next couple days. Should be mild today
with 900 mb temperatures of +10C. Some middle and high clouds
will inhibit mixing and keep it from getting warmer than it could
be. We still expect high temperatures of 10 to 15 degrees above
normal.

The mild weather will continue tonight with some middle or high
clouds and mild boundary layer temperatures. Lows should be 15
degrees or more above normal.

Fair weather will continue Saturday. Light winds and mild temperatures
should make for a good conditions for winter sports or melting
snow and ice from the roads and sidewalks.

.LONG TERM...Saturday Night Through Thursday
Issued at 349 AM CST Fri Jan 19 2018

The primary forecast concern continues to revolve around the elusive
details in regards to the next winter storm due to impact the region
late this weekend into early next week.  The latest models have
trended slightly south with the track of the system over the past 24
hours.  Furthermore, the GFS and Canadian have trended slower,
closer to the timing of the ECMWF.  Will therefore put more weight
into the ECMWF solution.

Saturday night through Sunday night...Low level moisture will be
increasing across the mid-Mississippi Valley and southern Great
Lakes on Saturday night, as low pressure emerges into the central
Plains.  Across central and northern WI, will have enough dry air
wedged below 700mb to keep most of the area dry, except for possibly
far northern WI.  In this area, mid-level fgen will be present
within the right rear quad of a jet streak, which may provide enough
forcing/saturation for a chance of light snow or flurries.  The low
makes some progress to the east on Sunday while low level moisture
creeps farther north into central WI by late in the afternoon.  The
mid-level convergence zone holds pretty steady over far northern WI,
so think the best chance of precip will probably occur there.
Perhaps a dusting to a half inch of accumulations are possible.  The
start of widespread precip will likely occur on Sunday night as
upper divergence and isentropic ascent increases.  Precip should be
light to start out due to lingering dry wedges in the mid-layers.
Thermal profiles suggest a wintry mix north and west of the Fox
Valley, where 1 to 3 inches of snow to go along with minor ice
accumulations are possible. Temps will be close to freezing in
eastern WI, so cant rule out some ice, but thinking mainly rain
through 12z Mon.

Rest of the forecast...The low pressure system will travel across
Iowa to southeast or east-central WI on Monday and Monday night.  On
the northern flank of the cyclone, a large swath of precip will lift
northeast across the region during this time, and exit the area on
late Monday night into Tuesday.  Models continue to point towards an
ample surge of warm air ahead of the low into central and northeast
WI for precip type to be a real headache to forecast.  Most likely
looking at a wintry mix to rain scenario shaping up for Monday in
this area before precip turns back to snow once the low passes on
Monday night.  North-central WI stands the best chance of seeing
mostly snow, where could see significant accumulations.  CIPS
analogs suggest a corridor of mixed precip in between these areas,
which could result in ice accumulations. All this said, the track of
the cyclone has not settled down yet in the forecast models so
details like those listed above will undoubtedly change as we draw
closer to the event.  The main take away is that travel is likely to
be significantly impacted across most of the region on Sunday night
through Monday night.

In the wake of the cyclone, generally quiet and seasonable weather
is expected during the middle of next week.  There are some
indications that another storm system will impact the area late next
week.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 544 AM CST Fri Jan 19 2018

VFR weather expected through Saturday, with some middle and high
clouds. Low level wind shear is expected by midday continuing into
this evening. West southwest winds of 35 to 45 knots are expected
at 2000 ft with southwest winds at the surface around 10 knots.

&&

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

$$

SHORT TERM.....RDM
LONG TERM......MPC
AVIATION.......RDM



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