Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 300335

Area Forecast Discussion
National Weather Service Green Bay WI
1035 PM CDT Mon May 29 2017

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Tuesday
Issued at 323 PM CDT Mon May 29 2017

A cold front that was in eastern Wisconsin moved out of the state
this morning.

The 00Z sounding at GRB was pretty much dry adiabatic above a
surface based inversion that topped out around 950 mb. There were
a few showers early in the morning and they rapidly increased in
coverage once temperatures warmed up a bit. Surface based CAPE
increased throughout the morning, reaching values in excess of
800 J/kg in north central Wisconsin by midday.

Expect showers and isolated thunder to diminish during the evening
and overnight hours due to the loss of daytime heating. Another
mid level short wave trough will be passing through the area on
Tuesday, so expect chances for showers to increase during the day.
It looks to be cooler on Tuesday than today. with highs generally
ranging from the lower 50s to the lower 60s.

.LONG TERM...Tuesday Night Through Monday
Issued at 323 PM CDT Mon May 29 2017

The models agree that northwest upper flow will continue
through Thursday night or Friday. Significant differences begin
Friday night and Saturday when the ECMWF and especially the Canadian
model forecast a closed low over Minnesota while the GFS just has
the sharp trough moving through. The ECMWF and Canadian models
would suggest cool and rainy days Saturday and Sunday while the
GFS would be would just have a few showers. Seeing that there have
been a lot of closed lows this spring would not discount the
Canadian and ECMWF solution.

The forecast offices in the central part of the United States use
a blended model forecast for the 3 to 7 day period, so the current
forecast for Saturday and Sunday is drier than it should be if
the closed low does form and move across Wisconsin.

Temperatures will start off slightly cooler than normal Tuesday
night and Wednesday, and then warm a few degrees above normal for
Thursday and Friday with dry air allowing for good diurnal
ranges. It will be cooler than normal if Saturday and Sunday turn
out to be rainy, otherwise near normal.

.AVIATION...for 06Z TAF Issuance
Issued at 1030 PM CDT Mon May 29 2017

Scattered showers and isolated thunderstorms should taper off
at the beginning of the new TAF period, as an upper level
disturbance shifts east of the region. Generally quiet conditions
are expected overnight into early Tuesday morning. The exception
may be the arrival of some MVFR ceilings over north central WI
toward daybreak Tuesday.

On Tuesday, another round of diurnally-enhanced showers is
anticipated in the late morning and afternoon, as another in a
series of upper disturbance tracks through the forecast area.
There will be less instability, so thunderstorms are not
anticipated. The best chance of MVFR ceilings will continue to
reside in north central WI. Gusty west winds will also pick up
again during the late morning and afternoon, but should not be
quite as strong as they were on Monday.

Issued at 323 PM CDT Mon May 29 2017

West winds with gusts around 25 knots this afternoon will
diminish during the evening and overnight hours.



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