Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 131118
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
518 AM CST Mon Feb 13 2017

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 319 AM CST Mon Feb 13 2017

Westerly winds will turn southwesterly later today, allowing for
warm air advection across the western Great Lakes region. Despite
the advection of warm air, an inversion will keep mixing heights
rather shallow this afternoon around 950 mb, which will keep
daytime highs in check. That being said highs are expected to get
to around 40 degrees across the forecast area, which will be a
good 10 degrees or so higher than normal for this time of year.

A weak surface boundary and mid level shortwave will bring
increasing clouds tonight with some light snow showers possible
across extreme north- central Wisconsin. Moisture will be fairly
limited so snowfall amounts should be light.

By Tuesday a more potent shortwave will track through the western
Great Lakes, bringing a cold front sinking south during the
afternoon hours. Model soundings show quite impressive low level
lapse rates over a deep layer and some decent moisture in the low
levels. Despite a lack of widespread QPF amongst the NWP models,
it appears that snow showers will impact most of the area during
the afternoon hours given the instability and dynamics in play on
Tuesday. Therefore will raise POPs to chancy across the entire
area during the afternoon hours. The best chance for accumulating
snow will be across north-central Wisconsin with better moisture,
however these snow showers could drop a quick few tenths up to an
inch in the more persistent bands.

.LONG TERM...Tuesday Night Through Sunday
Issued at 319 AM CST Mon Feb 13 2017

Upper trough at 500mb will continue to move away from the area as
500mb ridge will then build across the central United States by
the end of the work week. A more substantial upper trough
will move onshore the western United States over the weekend. This
system will bring more rain to California, while it will allow for
very mild air to move into the western Great Lakes region. This
system would arrive across the area next Monday and Tuesday.

One small change to the forecast is to add a slight chance of
snow showers outside far north-central Wisconsin Tuesday evening.
Otherwise, increased max/min temperatures Friday through Sunday
from the superblend output, and added the typical biases (warm
spots during the day and cold spots (across the north at night).
Like last night, ECMWF gridded guidance and 925mb temperature
forecast off the GFS/ECMWF would support highs well in the 40s and
50s for the upcoming weekend. Even can`t rule out a 60 degree
reading at some point during the upcoming warm spell as 925mb
temperatures would support highs in the lower to middle 60s. Went
conservative for highs now as some of the area could see fog and
stratus which could significantly alter high temperatures,
especially across the north. The 925mb temperatures off the
GFS/ECMWF would support high temperatures approaching all-time
February records in our area if the projected 925mb temperatures
forecast comes true. If the current projections are true, there
will be concern for dense fog at some point on the bay and lake
this weekend into early next week.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 518 AM CST Mon Feb 13 2017

Quiet weather is expected through mid-afternoon, with VFR
conditions prevailing. Only an increase in high clouds is
anticipated, with moderate southwest winds developing by midday.

Some LLWS is expected to develop as a weak cold front approaches
late this afternoon. Although the frontal passage is expected to
only bring a wind shift in most areas, it is possible that some
MVFR ceilings may work their way into north central WI by late
this evening or after midnight.
&&

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

$$

SHORT TERM.....Kurimski
LONG TERM......Eckberg
AVIATION.......Kurimski



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