Area Forecast Discussion
Issued by NWS Green Bay, WI

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705
FXUS63 KGRB 192359
AFDGRB

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

Updated aviation portion for 00Z TAF 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 00Z TAF Issuance
Issued at 658 PM CDT Sat May 19 2018

A cold front was moving south across the area this
evening. It is followed by some MVFR ceilings and scattered
showers. The front will move into southern Wisconsin tonight,
allowing skies to clear from northwest to southeast late
tonight. VFR flying weather is expected Sunday.
&&

.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.......RDM
FIRE WEATHER...Kurimski



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