Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 221137

Area Forecast Discussion
National Weather Service Green Bay WI
637 AM CDT Mon May 22 2017

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 430 AM CDT Mon May 22 2017

an upper low over northern Minnesota early this
morning will move across northern Wisconsin and the Upper
Peninsula today and bring some light rain showers to far northern
Wisconsin. Later today the left exit region of a strong upper jet
moves across southern Wisconsin and should produce steep lapse
rates and a chance of thunderstorms despite low level air.
Forecast wet bulb zero heights of 5000 to 7000 feet and an
inverted v sounding suggest that small hail and gusty winds could
accompany any storms that do materialize.

The upper jet will slowly move into lower Michigan and keep a
chance of showers or thunderstorms south of highway 29 this
evening. Another upper low dropping south across Minnesota late
tonight starts to produce upper diffluence across the Western
part of the forecast area late tonight and across the entire area
Tuesday while warm air and moisture advect northward over a slow
moving surface front. This should result in showers for most of
the day.

.LONG TERM...Tuesday Night Through Sunday
Issued at 430 AM CDT Mon May 22 2017

Precipitation chances and timing are the main concerns during this
part of the forecast.

Showers are possible across the area on Tuesday night but they
should begin to exit from the northwest on Wednesday as a 500 mb
low and surface low depart and surface and mid level ridge axes
reach Wisconsin. This should bring a period of generally dry
weather until Friday afternoon and evening when warm advection
ahead of an approaching surface cold front and the arrival of a
mid level short wave bring a chance of showers to central and
north central Wisconsin. A thunderstorm or two cannot be ruled
out. Showers and thunderstorms are possible again on Friday
afternoon, and PoPs increase through Sunday as a cold front moves
across the state and a surface low approaches from the Plains. At
the same time, a mid level short wave passes, with a more
significant mid level system approaching. Models have quite a few
differences by the weekend, so be sure to check the latest
information from the National Weather Service.

A warming trend is expected through Friday as the rain and clouds
depart and southerly flow brings warmer air into the area. Highs
should be near normal from Friday through Sunday.

.AVIATION...for 12Z TAF Issuance
Issued at 636 AM CDT Mon May 22 2017

MVFR ceilings should increase to VFR category by afternoon. Scattered
showers across northern Wisconsin should dissipate by noon. There
is a chance of showers and thunderstorms across central and east
central Wisconsin this afternoon and evening. A more steady
rainfall is expected Tuesday with IFR ceilings in most places.



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