Area Forecast Discussion
Issued by NWS Green Bay, WI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
FXUS63 KGRB 221423

Area Forecast Discussion
National Weather Service Green Bay WI
923 AM CDT Fri Sep 22 2017

New Information added to update section

Issued at 916 AM CDT Fri Sep 22 2017

Have adjusted pops to bring a greater chance of storms to our
northwest counties today. A large cluster of thunderstorms,
with a few embedded supercell structures, have developed in
northwest WI, within an axis of strong elevated instability
(MUCAPE 3000-3500 j/kg) and moisture convergence on the nose of
a 40-45 kt low-level jet. Some of these are likely to brush
through parts of north central WI, and will bring at least a
marginal threat of severe weather.

Have adjusted fog headlines, cancelling the advisory for Manitowoc
and Kewaunee counties, and extending Door county for another
hour. Also cancelled the marine fog advisory for the bay and Lake
Michigan south of Two Rivers, and extended the northern Lake
Michigan zones through mid-afternoon.

Issued at 627 AM CDT Fri Sep 22 2017

Updated thunderstorm coverage further southward today to include
more of north central and northeast Wisconsin as per storm trends
over far northwest Wisconsin and eastern Minnesota early this
morning.  Convection along the Wisconsin/Minnesota border south
of Duluth showing more of a west to east motion and if the storms
hold together, will move into north central wisconsin mid
morning. Even though storm motion winds and thickness plots
indicate a northeast movement, storms appear to be developing
toward the more unstable air mass, where 4000 MU capes are
centered over central MN early this morning. This more unstable
air will drift into northwest wisconsin as 850 winds turn more
SSW. Its possible later shifts may need to expand the convection
even further south into parts of central WI, but not confident of
this scenario at this time.

For fog headlines, MTW came back in at 1/4 mile, while web cams
indicate dense fog along the lake michigan shoreline. Will let the
headlines as is.

.SHORT TERM...Today...Tonight...and Saturday
Issued at 318 AM CDT Fri Sep 22 2017

Primary forecast issue today into Saturday centers on fog
potential along the lakeshore and bay, convection trends over
the northwest portion of the state, and max min temperatures.

As of 300 am, fog along the lakeshore has diminished with the fog
imagery indicating pockets of fog between Two Rivers and Kewaunee
at this time. Web cams have shown improvement early this morning
but will let the lakeshore fog advisory run for another few hours
to see if redevelopment occurs. Otherwise anticipate patchy fog
along the lake will continue into the weekend with surface
dewpoints well into the 60s.

For convection trends this morning, area radars show clusters of
mainly elevated thunderstorms moving northeastward over
Minnesota. The storms will be sliding near the DLH vicinity
through 5 am. Radar does show some weaker turns showing up over
northwest Wisconsin at 3 am, but still west and northwest of
Oneida and Vilas Counties. A few meso models do track convection
originating over northeast South Dakota, over north central
Wisconsin during the morning hours. Height 850 to 300 thickness
fields indicate a southwest to northeast flow before shifting west
to east over northern Wisconsin. Surface warm front appears to
have lifted north of the area but 925 mb progs indicate a frontal
boundary over the north this morning may be the main focus of
convection across the area. Mid level clouds increasing across
this area may also be pointing out this boundary location.
Anticipate convection to continue to move mainly northeastward and
west of the area, but will continue to keep a small chance of
elevated convection over at least northern Wisconsin due to the
increasing elevated capes through today.

For tonight into Saturday, will continue the dry forecast as the
upper ridge and cap dominates. Its possible a storm may pass near
north central Wisconsin, but the potential is too low at this
time to add to the forecast.

With the warm front lifting north of the area tonight into
Saturday, south winds will continue to pump in a very warm and
humid air mass into the area. Temperatures will continue to run
nearly 20 degrees above normal.

.LONG TERM...Saturday Night Through Thursday
Issued at 318 AM CDT Fri Sep 22 2017

500mb ridge across the eastern United States will bring record or
near record warmth across our area Saturday/Sunday with highs well
into the 80s. A few readings in the lower 90s are possible on
Saturday. Showers and thunderstorms to the north and west of the
state could spill into far north-central Wisconsin at times this

A major shift in the 500mb pattern will take place during the first
half of next week. A western ridge will build with a downstream
trough across the eastern United States. Temperatures will gradually
trend towards normal by late next week. Meanwhile, a cold front
will slowly push east towards the area on Monday, and then across
the area on Tuesday. Do have chances of showers and thunderstorms
on Monday, but confidence is low if the rain will materialize on
this day. Tuesday is looking a little bit more interesting with
stronger wind aloft (greater than 50kts) with the area being in
the right entrance region of a 100+ knot jet. If these wind fields
materialize, there may some potential for severe weather across
the area. Still pretty far out to mention severe wording, but it
is something to watch over the next few days. Continued the small
chances of showers on Wednesday with dry conditions on Thursday as
high pressure builds into the region. Temperatures on Thursday
will be close to normal.

.AVIATION...for 12Z TAF Issuance
Issued at 545 AM CDT Fri Sep 22 2017

Patchy IFR vsbys and cigs will linger over northeast Wisconsin
this morning, especially along the bay and lake shore. Also this
morning, mid level VFR clouds were drifting northward over parts
of central and north central Wisconsin. There is a chance for
storms over northern Wisconsin later this morning. Otherwise vfr
conditions expected today into tonight, with the exception of
patchy IFR vsbys due to fog along the lakeshore.

Dense Fog Advisory until 11 AM CDT this morning for WIZ022.


LONG TERM......Eckberg
AVIATION.......TDH is the U.S. government's official web portal to all federal, state and local government web resources and services.