Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 180913

Area Forecast Discussion
National Weather Service Green Bay WI
313 AM CST Thu Jan 18 2018

Forecast discussion for routine morning forecast issuance

.SHORT TERM...Today...Tonight...and Friday
Issued at 311 AM CST Thu Jan 18 2018

A clipper system will pass by to the north today. It is fairly
dynamic and could produce some snow in northern Wisconsin if
moisture were available. The models all show very dry air below
10000 feet in the north and 15000 feet across central Wisconsin.
Since it is unlikely that any snow can fall through dry air like
that without sublimating, we decided to just keep a few snow
flurries near the Michigan border. Highs today will be 5 to 10
degrees above normal even with quite a bit of middle and high
clouds for the first part of the day. Lows tonight will be held up
by mild boundary layer temperatures. Highs Friday should be around
ten degrees above normal in most places. A good day for winter sports.

.LONG TERM...Friday Night Through Wednesday
Issued at 311 AM CST Thu Jan 18 2018

Focus of this forecast continues to revolve around the passage of a
cyclone late this weekend into early next week.  Both the GFS and
Canadian continue to trend north with the track of the system, while
the ECMWF remains slower, but with a similar track to the GFS
Ensemble mean.  A blend of the ECMWF and GFS will keep good
continuity with this system.

Friday night through Saturday night...Wisconsin will be located
between a cold front positioned over south-central Canada and high
pressure located over the southeast conus on Friday night.  Other
than scattered to broken mid and high clouds at times, should be
looking at a quiet and mild night.  Mid and high clouds will
increase on Saturday, though a dry wedge below 700mb should keep the
area dry.  Temps on Saturday should rise into the upper 30s.  Low
level moisture will lift northward into the southern Great Lakes on
Saturday night as low pressure emerges into the west-central Plains.
Think this moisture will remain south of the region.  Meanwhile, mid-
level fgen may be enough for a few flurries over north-central WI
and will keep a small chance of snow in the forecast.

Rest of the forecast...Low pressure will then be swinging across the
central Plains on Sunday and into the northern Mississippi Valley on
Sunday night.  Light precipitation is expected to develop on Sunday
as low level moisture increases.  Progged soundings indicate that
moisture will be deep enough for light snow over northern WI, while
dry layers in the mid-levels could spell drizzle or freezing drizzle
over central and east-central WI.  A band of heavier precip is then
expected to accompany the surface low late Sunday night into Monday.
Awfully difficult to project precip type this far out given the
uncertainty around the track of the surface low.  However it does
appear there is a chance of accumulating snow and a wintry mix along
and to the north of the surface low track during the time of heavier
precip from roughly the northern Fox Valley into central and north-
central WI.  Some accumulating snow is also possible on the backside
of the system on Monday night into early Tuesday over much of the
area.  At this stage, its probably more important to understand that
travel is likely to be significantly impacted at times from Sunday
through early Tuesday rather than get bogged down into the details.

Behind the system, more quiet and seasonable weather is anticipated
for the middle of next week.

.AVIATION...for 06Z TAF Issuance
Issued at 850 PM CST Wed Jan 17 2018

LLWS is still expected to ease some overnight into early
Thursday, then increase as a compact upper system passes just
northeast of the area. There are still a lot of questions about
the low cloud potential. A low cloud deck is shifting ESE from
Canada, but it just does not look like it will make it into the
area unless additional clouds develop to its south. This is
possible given the strong inversion across the region, but seems a
bit less likely than earlier. Will continue to monitor the latest
trends and make an issuance time decision on how to handle the
situation in the TAFS. Expect RHI to primarily be the site



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