Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 200338
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1038 PM CDT THU MAY 19 2016

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Friday
Issued at 244 PM CDT Thu May 19 2016

Main forecast challenge remains on temperatures as an area of
high pressure over the Great Lakes prevents any potential for
precipitation.

The 19z MSAS surface analysis indicated an area of high pressure
extended from the Central Plains NEWD into the Great Lakes. An
area of low pressure was situated over Central MT, with a tight
pressure gradient over the Northern and Central Plains. Visible
satellite imagery showed mainly scattered cu field over the
eastern half of WI with temperatures rising to above normal
levels.

NE WI will continue to reside on the backside of the high pressure
tonight. A weak return flow into WI will help bring at least a
modest uptick in low-level moisture (compared to previous nights)
and should provide for a milder night across the forecast area.
Other than some passing high clouds, the night will be mostly
clear with light/variable surface winds. Thus, temperatures are
still expected to quickly fall this evening with the colder
locations over North-Central WI flirting with frost once again
toward daybreak. Do not believe readings will be cool enough for a
widespread frost, so have passed on issuing any headlines tonight.
Instead, have mentioned patchy frost in the forecast for North-
Central WI and generally taken min temperatures into the lower to
middle 40s elsewhere.

A very weak shortwave trough is forecast to move SE through the
Upper MS Valley and merge with a weak shortwave trof expected to
lift toward NE southern sections of the Great Lakes on Friday.
Lift overall with these two systems remains negligible over WI and
with forecast soundings showing a dry mid-level of the atmosphere,
hard to see any precipitation reaching the ground. Therefore, have
maintained a dry forecast for NE WI with max temperatures similar
to Thursday (a bit warmer temperatures aloft, but more clouds
expected). Look for middle 60s near Lake MI, mainly 70-75 degree
range inland.

.LONG TERM...Friday Night Through Thursday
Issued at 244 PM CDT Thu May 19 2016

Temperatures through the period, dry conditions and elevated fire
danger over northern WI through the weekend, and pcpn trends for
the next work week, will be the main fcst concerns.

Surface high pressure will reside over the western Great Lakes
through the weekend, and a high-amplitude upper ridge will build
over WI Sat ngt into Sunday. This will keep the prevailing dry
conditions in place. Deep mixing will cause dew points and
relative humidity to drop off Sat/Sun afternoon, with min RH in
the 20s to lower 30s percent range. Parts of northern WI are still
experiencing high fire danger, and the continued dry weather and
low RH will be cause for concern over the weekend. Temperatures
will gradually warm through the weekend, with highs in the 70s on
Saturday, and upper 70s to lower 80s on Sunday. Lake breezes will
keep lakeshore communities in the 60s or lower 70s.

As the sfc high and upper level ridge edge east early next week,
return flow and increasing instability will bring a chance of
thunderstorms. Most locations should not see any pcpn until
Monday night, though sct thunderstorms may affect parts of central
and north central WI Monday afternoon. The storms may become
focused along a weakening frontal boundary as it shifts east
through the forecast area Monday night into Tuesday. However, the
ECMWF is much less aggressive with QPF than the GFS is. A low
pressure system is expected to approach the western Great Lakes on
Weds night and Thursday, but models differ on the track. Will
carry a chance of thunderstorms across the fcst area from Monday
night through Thursday, but we should be able to provide more
timing detail with subsequent fcsts.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1038 PM CDT Thu May 19 2016

VFR conditions to persist over the next 24 hours with diurnal cu
field in the 6K-8Kft range developing late Friday morning through
Friday afternoon, then dissipating Friday evening. Generally
light winds to also persist through Friday with high pressure
situated just to our east. Great flying weather conditions!.
&&

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

$$

SHORT TERM.....Kallas
LONG TERM......Kieckbusch
AVIATION.......Kurimski



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