Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 190305
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1005 PM CDT Tue Apr 18 2017

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Wednesday
Issued at 259 PM CDT Tue Apr 18 2017

A band of showers across central and north-central Wisconsin
was moving into northeast Wisconsin as of mid afternoon.
Temperatures were in the upper 40s across the far north
to the middle 60s at Oshkosh, Wautoma and Appleton. Winds
were from the southeast 10 to 20 mph, except at locations
that warmed into the 60s where wind gusts of 30 to 40 mph
were noted.

Gusty winds should shift northward into the central and northeast
Wisconsin for the remainder of the afternoon and into northern
Wisconsin towards sunset. The strongest winds will be across
portions of central and east-central Wisconsin, with lighter
winds across the north and lakeshore region. The models continue
to show steep mid level lapse rates and most unstable capes of
around 500 j/kg based on the latest local meso analysis page.
Will continue to mention slight chance of thunderstorms for
the remainder of the afternoon and across east-central Wisconsin
into the early evening hours. The front should exit east-central
Wisconsin around midnight. The models continue to show some
lingering shower activity across the north for a few hours
after midnight, thus have added a small chance of showers.

On Thursday, most of the morning should be dry across the
region as weak high pressure slides north and east of the
area. Only have a small chance of rain over the far southwest
just in case the rain returns quicker than expected. The latest
changes to Thursday will the lower or no chances of rain until
evening along the Michigan border. Latest model trends would not
have rain arriving until sunset or shortly after. High
temperatures on Thursday tricky due to winds turning northeast
and most of the day will be cloudy, along with the steadier rains
arriving across our southern forecast area during the afternoon.

.LONG TERM...Wednesday Night Through Tuesday
Issued at 259 PM CDT Tue Apr 18 2017

Precipitation trends, QPF amounts and potential for snow
accumulations over northern WI Wednesday night through Thursday
night, are the main forecast concerns.

Models continue to track the low pressure system a bit farther
north than was indicated a couple days ago, with the low moving
into southern or central WI by Thursday morning, then toward
Lake Huron Thursday evening. This system will have potent dynamics
and moisture, with strong WAA/isentropic lift on the nose of a
30-40 kt LLJ Wednesday night, then a potent short-wave trof moving
through northern WI on Thursday. PWATs will increase to 1.00-1.25
inch across the southeast half of the forecast area Wednesday
night, setting the stage for heavy rainfall there. Have increase
QPF amounts to 1+ inch over much of central, northeast and east
central WI. With a track farther to the north, warmer air will
move into far northern WI Wednesday night, which will delay any
mix or changeover to snow. The changeover is now more likely to
occur in the late morning and afternoon over the far north, which
will further limit accumulations. Have lowered snowfall amounts
to less than an inch. Kept a chance of thunderstorms over central
and east central Wisconsin Wednesday night into early Thursday.
Precipitation will gradually taper off from southwest to northeast
Thursday afternoon and night.

Generally dry conditions are anticipated from Friday through
Sunday night, with rain chances returning with a frontal system
Monday into Tuesday.

Aside from below normal temperatures on Thursday, temperatures
are expected to remain near normal levels for the remainder of
the extended period.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1005 PM CDT Tue Apr 18 2017

Isolated showers will depart eastern Wisconsin late this evening
as a cold front slides over eastern Wisconsin. MVFR/IFR cigs will
drift into the area overnight on west to northwest winds. A ridge
of high pressure will then drift over the northern Great Lakes
late tonight into Wednesday morning. Drier air on north to
northeast winds will spread into northern Wisconsin to improve
conditions to mainly VFR levels. What clearing that does occur
will likely be brief as clouds will be on the increase again
Wednesday with the approach of another frontal system. Showers and
storms may reach central and northcentral Wisconsin mid to late
afternoon and then widespread rain with lowering cigs will spread
over the area Wednesday evening.
&&

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

$$

SHORT TERM.....Eckberg
LONG TERM......Kieckbusch
AVIATION.......TDH



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