Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 201802
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
102 PM CDT SAT AUG 20 2016

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Sunday
Issued at 353 AM CDT Sat Aug 20 2016

Showers and a few embedded thunderstorms continue to make their
way through the area as a mid level shortwave tracks through the
western Great Lakes early this morning. A much stronger shortwave,
associated with the main mid level trough, will make its way
through the area this afternoon as the main surface low and cold
front track through northeast Wisconsin. This system will have a
lot of forcing and fairly high pwat values on the order of 1.5 to
2 inches, which will make for a widespread 1 to 2 inches of rain
across the region. There could be some localized flooding as the
main system tracks through the region later today. There will also
be the threat for severe weather, mainly along and east of the fox
valley and bay of green bay, with afternoon MUCAPE values soaring
to around 1000 J/kg. The instability and dynamics could lead to
some severe storms across this area, with the main threat being
damaging winds and to a lesser extent hail.

The severe weather threat will diminish rapidly this evening as
instability values drop precipitously. However heavy rain will
still be a threat across the northern cwa as wrap around rain in
the comma head of this strong system continues to affect the
region.

High pressure will then build in behind the departing system on
Sunday as rain chances fall steadily through the night and into
Sunday. However a shortwave tracking through the western Great
Lakes will continue a slight chance for rain on Sunday across the
western Great Lakes. The main story with this system will be
temperatures, as highs will be a good 5 to 10 degrees below normal
for this time of year.

.LONG TERM...Sunday Night Through Friday
Issued at 353 AM CDT Sat Aug 20 2016

A high pressure system over the Great Lakes will bring dry
weather back to the forecast area for Sunday night and Monday.
00Z models had some QPF on Monday night in isentropic lift from
warm advection, but amounts and exact locations were not the most
consistent, so have a slight chance for showers across much of
the area. The area of QPF pushes north of the state by 12Z
Tuesday on the ECMWF and Canadian, but the GFS had it lingering
over northern Wisconsin into Tuesday morning. Have sided with the
dry ECMWF/Canadian solution.

A cold front and mid level short wave approaching from the Plains
will bring a chance for thunderstorms back to the area. The GFS
and ECMWF had it reaching the area about 12 hours faster than
does the Canadian. Have left the initial model blend alone for
the rest of the forecast/work week. This resulted in the chance
for thunderstorms mainly on Wednesday and Wednesday night, then
only slight chances Thursday and Thursday night as the system
departs.

Expect above normal high temperatures through at least Wednesday in
warm advection ahead of the system approaching from the Plains.
Highs should be close to normal on Friday behind the cold front.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 101 PM CDT Sat Aug 20 2016

Poor flying condition are expected this afternoon into tonight,
with the worst cigs over central and northern WI, as clouds and
scattered showers will linger across the area as low pressure
tracks across the state. A thunderstorm is also possible,
especially early this afternoon across eastern Wisconsin. Overall
coverage of showers will continue to be the greatest over northern
WI this afternoon and evening, with more scattered activity
farther south. Northwest winds will pick up through the afternoon
behind a cold front and as the low pressure system deepens as it
moves into Lake Superior. Some gusts over 20kts are expected. The
clouds and wind will keep fog in check, but due to the recent
rains can`t rule out some patchy fog overnight.

On sunday, northwest winds will continue to be a little on the
gusty side with lingering showers possible over mainly northern
WI, along with plenty of clouds, as the low pressure system
continues to pull away from the area.
&&

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

$$

SHORT TERM.....Kurimski
LONG TERM......MG
AVIATION.......Bersch



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