Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 100312
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1012 PM CDT Mon Oct 9 2017

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Tuesday
Issued at 219 PM CDT Mon Oct 9 2017

The latest RAP analysis and satellite/radar imagery show a dry cold
front over southeast Wisconsin. A broken band of clouds exists
behind the front over the southern Fox Valley and northeast WI.
More widespread mid-level cloud cover resides upstream over
northwest Wisconsin and Minnesota, behind a secondary cold front.
Temps are currently in the 40s behind the secondary boundary,
while mainly in the 60s ahead of it. As this front sags into the
area late tonight, forecast concerns center mainly around temps.

Tonight...The trailing cold front will slide across north-central
Wisconsin. Area of mid clouds and a northwest wind will likely
hold up temps for the evening, but then should see clearing skies
and calming winds occur overnight. With the incoming cold airmass,
temps are projected to fall into the low to mid 30s over north-
central WI, so will issue a frost advisory. Over northeast WI,
some clouds will likely persist into early this evening, before
partially clearing arrives. Low temps falling into the mid to
upper 40s over eastern WI.

Tuesday...As a storm system moves across the central Plains, will
see clouds on the increase from late morning through the afternoon
after a mostly sunny/partly cloudy start. Dry air will erode
precip as it tries to move northeast ahead of the system, but left
a slight chance in the forecast from southern Wood to southern
Winnebago counties. Cooler high temps in the mid 50s to near 60.

.LONG TERM...Tuesday Night Through Monday
Issued at 219 PM CDT Mon Oct 9 2017

The main forecast concerns will be precipitation chances for
the middle of the week and next weekend.

High pressure and a very dry air mass will reside over the
northern Great Lakes on Tuesday night. Farther south, an upper
level low is expected to track toward southern Lake Michigan,
and gradually weaken as it approaches. A tight moisture gradient
will reside across the region, with PWATS around 0.25 inch over
far northern WI, but increasing to 1 inch over parts of central
and east central WI. Models are still struggling with how far
north to bring precipitation Tuesday night into Wednesday morning,
but northeast winds should draw enough dry Canadian air into the
region to confine any significant rain to our far southern
counties. Across north central and far northeast WI, relatively
clear skies, light winds and the very dry air mass will support
cool temperatures, with lows in the middle 20s to lower 30s at
the typical cold spots. Would expect another widespread frost or
freeze there, but since frost/freeze headlines will be suspended
over northern WI after tomorrow, this should be a low impact event
with no headlines.

Expect a period of quiet weather from Wednesday afternoon through
Thursday night, along with near normal temperatures. Precipitation
will return Friday into Friday night, as post-frontal rains
develop in the wake of a cold frontal passage. The rain will be
supported by upper divergence in the RRQ of a 160 knot jet. POPs
have been increased significantly through this period.

Models are exhibiting timing issues with the weekend system,
with the GFS bringing the surface wave up the front Saturday into
Saturday night, while the ECMWF is about 12 hours slower. Both
models do agree that the system will track a bit farther southeast
than they have shown the past couple days, which would focus the
more significant rain over our southeast counties and push the
main threat of thunderstorms south of the forecast area. Will stay
close to the preferred model blend, at least until the models get
a better handle on the timing and track of the surface low. This
system has fairly potent dynamics and abundant moisture, so heavy
rainfall remains possible, especially over our southeast counties.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1012 PM CDT Mon Oct 9 2017

VFR mid level clouds will continue to slide over the
area overnight. A high pressure system over the Northern Plains
building into northwest Wisconsin through Tuesday will decrease
the mid level clouds over northern Wisconsin. Mid level clouds
may be more persistent over central and east central Wisconsin
tonight into Tuesday as a low pressure area tracks into Illinois
Tuesday into Tuesday night.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 8 AM CDT Tuesday for WIZ005-010>012-018-019.
&&

$$

SHORT TERM.....MPC
LONG TERM......Kieckbusch
AVIATION.......TDH



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