Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 191657
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1157 AM CDT Mon Jun 19 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 406 AM CDT Mon Jun 19 2017

Precipitation trends will be the main forecast concern.

The region will remain in west-northwest flow aloft for the next
couple days, with periodic short-waves and associated weak cold
fronts moving through. These features and diurnal instability will
be the primary factors in precipitation trends.

WV imagery showed a short-wave trof over northern MN headed
toward GRB CWA. Models show weak cyclogenesis occurring over
northeast WI as this wave interacts with a weak cold front today.
Convergence along the boundary, combined with upper forcing from
the short-wave, will generate showers and scattered thunderstorms
over the region during the late morning and afternoon. The showers
will be most numerous across the southeast half of the forecast
area, where the best instability (CAPE 500-1000 j/kg) will reside.
The cooler air mass and associated low wet-bulb zero heights will
be favorable for hail development, but weak deep layer shear (20
kts or less) should minimize any severe weather threat. High
temperatures will be in the middle 60s to lower 70s.

Showers and a few storms will linger into the early evening,
especially over eastern WI. Additional showers will return to
parts of north central and central WI late, as a more potent
short-wave trof aapproaches. Low temperatures should be in the
upper 40s to middle 50s.

The potent short-wave will move through the region Tuesday
morning, and should produce at least scattered showers and
a few thunderstorms. Given the strength of the incoming system,
we may need to bump pops up to likely with subsequent forecasts.
Showers will decrease as the wave departs in the afternoon. High
temperatures will be similar to today, ranging from the middle
60s to lower 70s.

.LONG TERM...Tuesday Night Through Sunday
Issued at 406 AM CDT Mon Jun 19 2017

This part of the forecast starts out dry with a surface ridge
over the region and an upstream trough aloft. A chance for
showers and some thunder returns for Wednesday afternoon in warm
advection ahead of an approaching cold front. The thunder
potential increases during the night as the cold front and a mid
level short wave move across Wisconsin. There could be a brief
break in the activity on Thursday morning before chances for
showers and storms return later in the day and into the evening,
mainly in the southern and eastern parts of the forecast area, in
the vicinity of the frontal boundary. There looks to be a break in
the activity again Friday night through Saturday morning before
the chance for showers and storms returns Saturday afternoon
through Sunday. Models have consistency issues by late in the
week, so confidence in the weekend forecast is low-medium.

Below normal highs are expected for Wednesday, but it looks like
warmer than normal temperatures return for Thursday as upper flow
becomes more west-southwest. Near normal highs return for Friday,
but cooler temperatures are in store for the weekend with the
clouds and rain in the area. Would expect warmer temperatures for
the weekend if there is less precipitation around than is
currently in the forecast.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1153 AM CDT Mon Jun 19 2017

An upper level disturbance will bring another round of showers
and scattered thunderstorms through early evening, with the best
thunder chances occurring at the GRB/ATW/MTW TAF sites. Showers
should taper off by around sunset. Another upper disturbance will
bring more rain and isolated thunderstorms to the western TAF
sites early Tuesday morning, and to the eastern WI TAF sites by
mid morning. Ceilings and vsbys will likely fall to mvfr within
the showers.

&&

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

$$

SHORT TERM.....Kieckbusch
LONG TERM......MG
AVIATION.......MPC



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