Area Forecast Discussion
Issued by NWS Green Bay, WI

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471
FXUS63 KGRB 192030
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
330 PM CDT Sat May 19 2018

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Sunday
Issued at 329 PM CDT Sat May 19 2018

Strong cold front has begin its journey across the area early this
afternoon. Impressive temp drop behind the front with Manitowish
Waters falling 22 degrees. Temps were struggling to climb across
eastern WI due to the cloud cover, but a little afternoon sunshine
allowed the temp to jump to near the forecast highs ahead of the
front.

The front should accelerate as it works into central and east
central WI late this afternoon and exit the area by around 8-9pm.
Although nothing has developed yet, meso models continue to show
some isolated showers developing along or just behind the front,
which seems reasonable as there is lingering moisture (dewpoints
in the middle 50s to around 60) so will keep some chance POPs
across central and eastern WI through the early evening hours. A
rumble of thunder is still possible, although instability looks
very marginal (with only 200 J/kg MUCAPE extending into Wood Co.
as of 3pm) and mid-level lapse rates of 5-6 C/km. Low level lapse
rates a little more impressive, in the 7-9 C/km, mainly across
central WI. As the front drops south of the area later tonight,
look for dry weather across most of the area. However, models
still showing a convection cluster passing just to our south
overnight into early Sunday. It could clip the southern counties,
but think the front will make enough progress that most/all of
that activity will stay out of the area. Other factor in play will
be a piece of shortwave energy, along with some weak forcing.
These could generate a few showers as well. So will continue to
carry some POPs over the far south to cover either scenario. The
north looks to stay dry. Look for plenty of clouds across the area
through Sunday morning, then the drier air will finally win out
(especially over northern WI) through the day on Sunday with
clouds clearing out.

Winds have gusted to around 20-25 mph along/behind the front.
Expect this to continue as the front drops south, with some higher
gusts expected as it accelerates, especially across the Fox
Valley. However, models show the pressure gradient a little
baggier over far eastern WI, but still think the bay/lake will
have some influence in accelerating the front. Won`t go crazy
with the winds, but a few gusts to around 25-35 mph are possible
as the front passes. Winds will remain a little gusty behind the
front.

.LONG TERM...Sunday Night Through Saturday
Issued at 329 PM CDT Sat May 19 2018

A weak shortwave will bring the chance for rain to the area on
Monday. However moisture will be fairly limited with the best
chances for rain across the south closer to the shortwave. There
are some models that are dry on Monday, so there is a chance the
rain will miss us completely.

Tuesday looks to be dry and warmer as high pressure moves through
the western Great Lakes. There will be small chances for rain,
mainly across the south, Wednesday and Thursday, as shortwave
ridge riders move through the area. The Canadian model develops a
fairly significant convective complex that moves through Wednesday
night, however this is the only model with this solution so
confidence in this scenario is fairly low.

The ridge breaks down by the end of the week, as low pressure
approaches the western Great Lakes region from the northern
Plains. This will bring the next widespread chance for rain to the
region Friday into Saturday. Timing will be an issue as there are
still model discrepancies, however there seems to be a general
agreement that this low will track through during this time period
with a good dose of rainfall. There is the possibility for some
strong storms Friday and Friday night as this low approaches as
instability increases in the warm sector, however given how far
out this system is the confidence in severe weather potential is
low.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1257 PM CDT Sat May 19 2018

Low clouds and patchy fog hung tough across eastern WI this
morning, but CIGS/VSBYS have come up early this afternoon (except
for MTW, which will come up soon). A period of mostly sunny skies
moved across portions of central and north central WI and was
approaching the Fox Valley early this afternoon. But daytime CU
started to develop along with clouds associated with a cold
front.

For this afternoon into tonight, the cold front will drop north to
south across the area, exiting by early to mid evening. The front
will bring mostly cloudy skies and a chance for a few showers. A
thunderstorm is also possible for the Fox Valley and lakeshore,
but chances seem pretty low. Once the low clouds exit the east
early this afternoon, expect the period to have VFR CIGS/VSBYS,
with brief MVFR conditions accompanying the scattered showers or
storm. Overnight into Sunday, the area is expected to stay dry.
However, a few showers may approach ATW and MTW, but will leave
out of the TAF for now.

Light and variable winds will abruptly switch to the north this
afternoon as the cold front sweeps across the area. Gusts to
around 25-30 mph will be possible as the front pushes through,
with gusts to around 20 mph through the early overnight hours.
&&

.FIRE WEATHER...
Issued at 329 PM CDT Sat May 19 2018

Rainfall amounts over the next few days are not expected to
alleviate the abnormally dry conditions across the north. Warm
and dry conditions are expected for much of next week across the
north, resulting in an elevated fire weather conditions and
worsening drought conditions. Relative humidities are expected to
be in the middle teens to lower 20s through Monday, with a slow
moderation to around 30 by the middle of the week as surface dew
points increase.
&&

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

$$

SHORT TERM.....Bersch
LONG TERM......Kurimski
AVIATION.......Bersch
FIRE WEATHER...Kurimski



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