Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 121909
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
209 PM CDT Thu Oct 12 2017

Forecast discussion for routine afternoon forecast issuance

.SYNOPSIS...
Issued at 208 PM CDT Thu Oct 12 2017

Relatively mild and quiet mid-autumn weather for the end of the
work week, then turning windy, wet, and colder (but really just
back to normal) this weekend.

The upper flow regime across North America was fairly amplified,
with a trough near the West Coast and downstream ridging mid-
continent. A series of short waves will eject out of the western
trough, resulting in a more zonal regime by early next week.
Reamplification is likely later next week, with the mean features
in about the same position.

Daily temperatures will vary between near and modestly above
normal throughout the period. Precipitation amounts are likely to
end up AOA normal, with the primary precipitation producer being
the cyclone that crosses the region this weekend.
&&

.SHORT TERM...Tonight and Friday
Issued at 208 PM CDT Thu Oct 12 2017

Low clouds remained across most of the area. Although a break in
the clouds worked into far northeast Wisconsin early this
afternoon, veering low-level flow should bring the main body of
the clouds back into the northeast and keep it in place area-wide
overnight. Overall, the set-up for drizzle looks better than last
night. The moisture depth may not be sufficient at all times as
some drier air around 850 mb shifts east across the area, but did
not attempt to resolve the drizzle/no drizzle times in the
forecast and just carried a chance throughout the night.

Drizzle could linger into Friday morning, then the chance for
precipitation will transition to the possibility of light rain
developing along the frontal boundary crossing the area. Models
seemed to be edging back from their previous runs in terms of the
rain chance tomorrow afternoon. So backed PoPs down from what we
had in the previous forecast, but left at least a chance of rain
in central and portions of east-central Wisconsin.

The widespread clouds will limit the diurnal temperature range.
Stayed close to a broad-based blend of guidance products for maxes
and mins.

.LONG TERM...Friday Night Through Thursday
Issued at 208 PM CDT Thu Oct 12 2017

Focus for this part of the forecast continues to center around the
active weather arriving this weekend as low pressure traverses the
region.  Comparing model solutions, have a preference for the ecmwf.
In general, models are trending stronger with the system this
weekend.

Friday night through Saturday night...A cold front will finish
crossing eastern WI on Friday evening before stalling over northern
Illinois late on Friday night.  Though moisture is in short supply,
should see spotty showers and cloudy conditions along and right
behind the front.  High pressure building in behind the front will
bring drier air to northern WI, which should lead to clearing skies
for that part of the state.  But cloud cover will hang tough over
central and east-central WI right through Saturday morning.  As flow
increases over the boundary and low pressure travels across the
central Plains, will see clouds and showers return north on
Saturday.  The main surge of precip will arrive from mid-Saturday
afternoon through Saturday evening when low pressure moves from
southwest to northeast Wisconsin.  Some elevated instability will
push into central and northeast WI during this time, which could
result in scattered embedded thunderstorms.  Though severe weather
is not expected, heavy rainfall over an inch is possible,
particularly over east-central WI where the best ingredients of
moisture and instability will reside.  Precip will be ending for
most locations overnight, though some comma-head precip could linger
over north-central WI.  If this occurs, colder air wrapping around
the low cold spell some wet flakes falling over north-central WI by
late in the night.

Rest of the forecast...Colder and blustery weather will linger
across the area on Sunday with a few rain/snow showers over north-
central WI in the morning.  The ecmwf continues to support a clipper
passing across the region on Sunday night, but the track has shifted
north and precip could now remain north of the U.P. border.  After a
cold start to the week, the upper pattern becomes more zonal through
the rest of the period.  This should result in above normal
temperatures returning by Tuesday.  Dry weather is then expected for
the rest of the period.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1229 PM CDT Thu Oct 12 2017

Low-end MVFR ceilings were predominant across the area at mid-day,
with a few sites reporting IFR/LIFR conditions. SSE flow above the
surface may bring a little drier air into the east and allow for a
brief improvement at MTW, but winds are forecast to begin veering
this afternoon. That will bring the main mass of the clouds back
across the area. So overall, ceiling trends will probably be
dominated by the typical diurnal oscillation of bases edging
down during the night and then rising tomorrow morning.
&&

.MARINE...
Issued at 208 PM CDT Thu Oct 12 2017

A potent system will be moving through the region on
Saturday and Sunday.  Northeast winds will be veering from the
northeast to southeast through the day on Saturday.  Waves are
likely to approach small craft criteria (4 ft) on Lake Michigan.
Then on the backside of a surface low, winds will rapidly shift to
the northwest and become gusty on late Saturday night into Sunday. A
brief period of gale force gusts appears possible, particularly
during the late Saturday night into Sunday morning period.
&&

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

$$

SYNOPSIS.......Skowronski
SHORT TERM.....Skowronski
LONG TERM......MPC
AVIATION.......Skowronski
MARINE.........MPC



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