Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 191719
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1219 PM CDT Sun Mar 19 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Monday
Issued at 337 AM CDT Sun Mar 19 2017

Low clouds continue to hang tough across north central Wisconsin
while stratus clouds over the lake are actually advecting back
westward over the lakeshore counties. In addition high clouds
ahead of an approaching low are advecting in from the west. This
leads to questions as to whether or not low clouds can dissipate
enough to allow temperatures to fall to previously forecast
overnight lows as areas that have cleared out have indeed fallen.
Given the uncertainty will raise temperatures this morning a few
degrees from the previous forecast.

The aforementioned low will bring a cold front through the western
Great Lakes tonight, with rain showers developing ahead of the
cold front across north central and central Wisconsin during the
afternoon hours, sweeping east this evening and into the overnight
hours. Rain chances will be low given the meager amount of
moisture available to this front and the weak nature of the
forcing associated with a fairly weak shortwave currently located
just east of the Rockies. The weak forcing and instability
associated with this cold front will keep thunder chances to the
south of the cwa for this system.

Highs today ahead of the front are expected to range from the
middle to upper 40s across the north, with highs in the lower 50s
across the south. Abundant cloud cover tonight will keep lows in
the 30s. Highs on Monday behind the weak cold front will be
similar to today, signaling the weak nature of the aforementioned
cold front.

.LONG TERM...Monday Night Through Saturday
Issued at 337 AM CDT Sun Mar 19 2017

Forecast concerns mainly revolve around precip chances and potential
impacts as a result of a cyclone passage at the end of the upcoming
work week.  Rather large model differences exists in regards to the
interaction between northern and southern streams in split flow, and
also the strength of Canadian high pressure located north of the
Great Lakes during this time.  Comparing operation model output to
the ensemble means, have a slight preference for the ecmwf, though
the track of its surface low may be too far south.

Monday night through Tuesday night...Canadian high pressure will be
building southeast into the region during this period.  Cold
advection is initially pretty weak and there will be some high
clouds around on Monday night, so do not think temps will plummet.
Colder temps will arrive on late Monday night into Tuesday with
strengthening northwest winds.  Should see a few lake effect snow
showers over Vilas county once this colder air arrives into Tuesday
evening. After temps in the 50s at some locals on Monday, readings
on Tuesday should fall back into the 30s to lower 40s. Arrival of
the high on Tuesday night should lead to clear and cold conditions.

Rest of the forecast... The high pressure system will ensure cool
and sunny conditions on Wednesday.  Confidence falls pretty quickly
thereafter, as models indicate warm/moist advection ramping up as
early as Wednesday night.  However, low level flow remains emanating
out of the dry Canadian high at this time, so precip chances will
most likely be holding off until Thursday.  When it finally arrives,
a wintry mix appears possible for Thursday into Thursday night
across at least parts of the area. Friday and Friday night appears
to be the best time for widespread precip as the low track towards
and across the area.  If the low tracks far enough south, wintry
precip may continue for much of the duration across northern WI, but
central sections of the state will likely see all rain for nearly
all of the period. Precip should be exiting on Saturday with a
potential for a brief change over to snow on the backside.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1208 PM CDT Sun Mar 19 2017

MVFR CIGS continued across portions of east-central and northeast
Wisconsin early this afternoon. These low clouds will linger
through much of the afternoon. Meanwhile, a weak cold front will
move across the region tonight, bringing a small chance of showers
and possibly a thunderstorm. The chances for showers/storm moving
across an airport site is very low, thus only went with VCSH in
the 18z tafs. Some mvfr cigs and fog are possible behind the
cold front late tonight into early Monday morning.

&&


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

$$

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



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