Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 171618

Area Forecast Discussion
National Weather Service Green Bay WI
1118 AM CDT Sat Mar 17 2018

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Sunday
Issued at 202 AM CDT Sat Mar 17 2018

High level clouds continue to drift over the south half of the
state this morning as a low pressure system tracks and weakens
from Missouri this morning to the Ohio Valley region this evening.
Surface high pressure ridge will remain over the northern Great
Lakes region this weekend while the upper ridge builds into the
area today through Sunday to produce milder temperatures. A week
low pressure system in the northern stream is progged to slide
northeast of the area tonight. A few clouds may be associated with
this weak system tonight, but likely only influence would provide
a wind shift to the southwest tonight and then back to the
northeast for Sunday as a cold front drops south over the area.

Plenty of sunshine with milder temperatures today will continue
to gradually work on the snowpack across the north. The melting
will be halted overnight as lows drop into the upper teens to 20s
across the north. Northeast winds along the lakeshore for part of
the day today and then for Sunday will provide cooler readings.
Cooler air also will begin to filter into northern and northeast
Wisconsin later Sunday in the wake of the cold front. If clouds
become more widespread later Sunday, max temperatures may need to
be lowered a little.

.LONG TERM...Sunday Night Through Friday
Issued at 202 AM CDT Sat Mar 17 2018

The medium range models continue to advertise a quiet weather
pattern continuing for much of next week.  Even though a dominant
mid-level ridge will be breaking down late this weekend, Hudson Bay
high pressure will continue to be a strong influence on our weather
over the period.  Models indicate that the next significant chance
of precip will not occur until next Friday or Saturday and will
continue to rely on a general model blend.

Sunday night through Monday night...The next low pressure system
will be moving across the central Plains and into the central
Mississippi Valley on Sunday night and Monday.  May see some high
clouds from this system, but too much dry air for any threat of
precip.  However, northeast winds in combo with unstable conditions
could lead to some lake clouds moving into north-central WI and the
Lake Michigan shoreline during the period.  Little changes into
Monday night except for a further increase of mid and high clouds
ahead of a weak system moving across the northern Plains.  Deeper
moisture should remain west of the region, with northeast flow
funneling in dry air in the 850-700mb layer.  Temperatures will be
10 to 15 degrees colder on Monday than on Sunday.

Rest of the forecast...Shortwave troughing will move across the
region on Tuesday and Wednesday.  This slow moving shortwave will
likely bring broken to overcast conditions, but precip chances will
depend on how much dry air can get eroded below 700mb.  Models are
not bullish in regards to this occurring, though would not be
surprised to see a few flurries occur over north-central WI.  Hudson
Bay high pressure will then reassert itself on late Wednesday night
through Thursday night, which supports less cloud cover and an end
to any light precip threat.  The next chance of widespread precip
now looks to occur late Friday into next Saturday.

.AVIATION...for 18Z TAF Issuance
Issued at 1100 AM CDT Sat Mar 17 2018

VFR conditions should continue into Sunday afternoon. Two features
to watch that will impact wind speeds and directions over the next
24 to 36 hours. For this afternoon, lake breeze expected to
develop along the Lake Michigan shoreline and then move inland
late this afternoon and this evening. Still some uncertainty if
the lake breeze would make it to KATW/KGRB although have included
this scenario in the 18z taf issuance. The other event will occur
on Sunday as a backdoor cold front drops southward across
northeast Wisconsin. These fronts typically race down the Bay of
Green Bay and the shoreline of Lake Michigan due to the colder
waters, or in this case the ice covered bay, and will reach
KATW/KGRB/KMTW before reaching KAUW/KCWA. Expected the front to
reach KGRB/KATW/KMTW between 18z and 21z Sunday. There should be
a sudden shift and increase in winds behind this front. The front
should reach KRHI around 18z and KAUW/KCWA around 21z Sunday.




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