Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 230320
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1020 PM CDT Mon May 22 2017

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Tuesday
Issued at 226 PM CDT Mon May 22 2017

The latest rap analysis and satellite/radar imagery show upper level
low pressure centered across Lake Superior, a compact shortwave
moving east over South Dakota, and a surface trough positioned over
southern MN into Nebraska.  Scattered showers will continue to move
east from northwest WI into north-central and far NE WI for the rest
of the afternoon.  Instability has been slow to build over central
and east-central WI so far today, but continue to see cu build up in
this area, and hi-res mesomodels continue to point towards some
showers developing.  Any thunderstorms will most likely be isolated
given the lack of forcing and instability.  More widespread shower
activity exists over SD with the compact vort max.  As this
shortwave moves towards the area late tonight into Tuesday, rain
chances and trends will be the main forecast concerns.

Tonight...Upper troughing will continue to reside across the
northern Great Lakes, while the shortwave trough over eastern South
Dakota moves into southwest Wisconsin late in the night.  A few
showers over far northern WI and also over east-central WI could
linger into the mid-evening hours.  Once the lingering showers
diminish, should see a lull in the precip chances until the
shortwave over SD and associated surface low move into southwest
Wisconsin late.  Did slow the chances down somewhat based on the
latest model data.  Low temps ranging from the upper 30s in the
north to near 50 over the southern Fox Valley.

Tuesday...The shortwave will swing northward across western
Wisconsin, and will lay out a convergence zone just west of the Fox
Valley and Bay of Green Bay.  Though some showers will likely be
moving northeast across central WI at the start of the morning, this
convergent zone looks to be the focus for shower activity for the
rest of the day.  Do not see much instability with clouds and precip
arriving in the morning, so left the mention of thunder out of the
forecast.  Temps will be cooler in many spots, and range from the
upper 50s to low 60s across the region.

.LONG TERM...Tuesday Night Through Monday
Issued at 226 PM CDT Mon May 22 2017

Precipitation trends are the main forecast concern.

An upper level trof and inverted surface trof will bring
showers to the entire region Tuesday night, and to the
southeast portion of the forecast area on Wednesday.

A weak ridge of high pressure will bring dry conditions
Wednesday night into Thursday evening, but small rain
chances will return as WAA develops late Thursday night
into Friday.

A series of weak short-wave trofs and associated cold fronts
will continue to bring periodic bouts of scattered showers
thunderstorms through the Memorial Day weekend, but the majority
of the period should be dry. Have sided more with ECMWF, as the
GFS has been exhibiting signs of convective feedback issues with
the weekend forecast over the last few days.

Below normal temperatures at the beginning of the period will
moderate to slightly above normal by Friday and Saturday, then
back to normal for the end of the holiday weekend.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1020 PM CDT Mon May 22 2017

Isolated convection noted along a boundary extending
over east central Wisconsin late this evening. This boundary
extends to a low pressure system and upper disturbance over
northeast iowa. Anticipate more isolated showers and storms along
this boundary overnight with mainly vfr conditions. Shower
activity may become more numerous over central and east central
Wisconsin Tuesday along with MVFR/IFR cigs developing. Since the
showers may be more scattered to isolated across northern
Wisconsin, mainly MVFR cigs anticipated through Tuesday afternoon.
&&

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

$$

SHORT TERM.....MPC
LONG TERM......Kieckbusch
AVIATION.......TDH


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