Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 201712
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1212 PM CDT Sat May 20 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Sunday
Issued at 436 AM CDT Sat May 20 2017

An upper low over the central Plains will move towards northwest
Wisconsin today and tonight while the surface low over Kansas
City moves towards Minneapolis as the system becomes vertically
stacked and starts to weaken. The left exit region of a strong
upper jet will provide good support for rain this afternoon and
evening and perhaps some elevated thunderstorms.

The atmosphere is initially quite dry, but low level moisture
advection will be quite good just above the surface and produce a
rainfall of a half inch to three quarters of an inch over much of
the forecast area. That isn`t enough to produce flash flooding,
but is enough to bring some streams and rivers above bankfull or
flood stage again.

The rain should end late tonight or early Sunday, with perhaps
some scattered afternoon showers in the far north. Clouds, rain
and a wind off the lake will keep high temperatures today well
below normal for this time of the year, though Highs Sunday will
be close to normal.

.LONG TERM...Sunday Night Through Friday
Issued at 436 AM CDT Sat May 20 2017

00Z models had fairly similar solutions through early next week
before they started to diverge.

Rain chances continue across northern Wisconsin into Monday
morning in cyclonic flow closer to the surface and 500mb low
centers. Colder air wrapped around the system, in addition to
clouds and precipitation, will bring cooler than normal high
temperatures for Monday. Another surface low and mid level trough
in northwest flow will bring chances for showers back starting
late Monday night, and continuing through Tuesday night in eastern
Wisconsin. Even cooler temperatures will prevail during the day on
Tuesday, with highs at least 10 degrees colder than normal at most
locations.

A surface ridge moving into Wisconsin from the west will result in
generally dry conditions with decreasing clouds for Wednesday.
More sunshine will lead to warmer, though still well below normal,
high temperatures. A warming trend is expected for the rest of the
work week as the upper level flow becomes more zonal and
southerly winds increase ahead of an approaching surface low.
Highs on Friday should be near normal at most locations. Nothing
higher than slight chance PoPs for this part of the forecast due
to differences in model QPF fields.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1208 PM CDT Sat May 20 2017

Low pressure moving northeast from the central Plains
will bring rain and mvfr conditions from south to north through
the afternoon hours. Ifr/lifr clouds and showers will continue
overnight into early Sunday. Visibility should rise into VFR range
Sunday morning with passage of a cold front, but ceilings will be slower
to increase. Showers and IFR conditions could continue Sunday
afternoon across north-central Wisconsin.

&&

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

$$

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



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