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FXUS63 KGRB 221223

Area Forecast Discussion
National Weather Service Green Bay WI
623 AM CST Mon Jan 22 2018

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 417 AM CST Mon Jan 22 2018

Low pressure over southern Iowa will move slowly to the east 
northeast today as the closed upper low moves east from the 
central Plains. Precipitation type is not usually a concern when a
storm moves along this track, but there is not an arctic high 
over southern Canada to deliver cold air in the low level this 
time, so precipitation type will be an issue. 

Model forecast soundings suggest that it will be cold enough for 
mostly snow roughly north of a Wausau to Antigo to Wausaukee line,
and six to eight inches looks possible. From Wisconsin Rapids to 
Shawano to Oconto there should be a mixture of snow, sleet, 
freezing rain and rain with some accumulation. Fox Valley and 
lakeshore areas will have largely rain based on forecast boundary 
layer temperatures, but it wouldn't take much cooling to get snow.
Temperatures today will only rise three or four degrees due to 
precipitation and cloud cover. 

The precipitation will change to all snow before it diminishes tonight.
The majority of the snow that falls will be in the evening hours. Lows
tonight will remain well above normal. Light snow is likely Tuesday
morning in eastern Wisconsin before the system exits the region. Some
small accumulation is possible. It will be blustery and colder that
today, but still milder than normal.

.LONG TERM...Tuesday Night Through Sunday
Issued at 417 AM CST Mon Jan 22 2018

Forecast concerns in this portion of the forecast revolve around 
temperatures, and precipitation potential late this week.  The 
medium range models are in good agreement so a general model blend 
will suffice.

Tuesday night through Wednesday night...Weak shortwave energy will 
be passing across the region on Tuesday night and Wednesday.  Mid 
and high clouds will be on the increase on Tuesday night with 
saturation occurring above 700mb.  Though this shortwave is 
disjointed, with low level moisture lagging behind moisture aloft, 
wouldnt be surprised to see some flurries or light snow fall out 
these mid-clouds late Tuesday night into Wednesday.  The multi-model 
blend is not optimistic about precip, so will keep the area dry 
until we get closer to this time period.  After the mid-level 
moisture departs Wednesday afternoon, low clouds will likely move 
across the area into Wednesday night, and progged soundings indicate 
that a low overcast deck or fog could stick around through much of 
the night.

Rest of the forecast...Dry weather is anticipated for Thursday and 
Thursday night as warmer air surges into the region.  Clouds will be 
on the increase on Friday ahead of the next cold front.  Some 
timing/detail differences in the models, but it appears that 
moisture will be quite limited, so precip chances will be low.  If 
precip does occur, is likely to be rather light, which will limit 
potential impacts to the region.  Colder air will push into the area 
behind the front for next weekend, with some snow showers possible 
over northern WI.

.AVIATION...for 12Z TAF Issuance
Issued at 623 AM CST Mon Jan 22 2018

IFR weather will continue through at least the evening
hours, with significant snow north of a Wausau to Marinette line
and a mix of snow, sleet, freezing rain and rain further south.
Mostly rain is expected at ATW/GRB/MTW/OSH with mixed precipitation

The precipitation will taper off tonight from west to east though
there may be some light snow in the east early Tuesday. Gusty
northeast winds could produce crosswinds on some runways.

Winter Weather Advisory until midnight CST tonight for WIZ020-

Winter Storm Warning until midnight CST tonight for WIZ005-

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