Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 172034

Area Forecast Discussion
National Weather Service Green Bay WI
234 PM CST Fri Feb 17 2017

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Saturday
Issued at 234 PM CST Fri Feb 17 2017

Forecast challenge tonight and Saturday concern potential stratus
development and influence on temperatures. A patch of stratus did
develop over northeast wisconsin early this morning but did not
hang around long. Upstream over Minnesota, no stratus or even
patches of dense fog developed under the upper ridge. Likely too
much mixing with the surface trough sliding over this same region.
This surface trough with strong winds aloft slides over tonight
and will likely hold down stratus development overnight. Still
possible a band of stratus may develop due to convergence as the
trough slides over but likely would be minimal at this time when
considering upstream ground truth.

Weak caa for Saturday will lead to more mixing in the boundary
layer and inversion to keep the warming trend going.

.LONG TERM...Saturday Night Through Friday
Issued at 234 PM CST Fri Feb 17 2017

Highlights for this period is the stretch of well above normal
temperatures through mid week next week, and precipitation
potential Monday through Monday night and then again late next

Building upper ridge this weekend into early Monday will provide
a quiet and very mild pattern. Forecast max temperatures will be
dependent on cloud cover, but relatively low surface dewpoints
indicate more sunshine expected. High level clouds may start to
spill over the ridge late Sunday into Sunday night ahead of the
short wave trough. Clear skies will also provide cool overnight
low temperatures and morning inversions to overcome.

Dewpoints will be on the increase Monday ahead of a frontal system
and short wave trough working into the flattening upper ridge.
Latest progs suggest a band of rain ahead of a cold front to
sweep over the area mainly Monday night with up to a half inch of
rainfall on average. Even though the 925-850 mb air mass is
cooler Tuesday, warm start and mixing will continue the mild
temperatures. Easterly component of the wind Sunday and Monday
may lead to cooler by the lake wording for February.

A brief split flow regime develops mid week with a weak front
from the northern stream sliding over the state. Temperatures
will be still be above normal but slightly colder air settles
southward later next week ahead of a stronger system possible
late next week, to produce a mix potential at the onset Thursday
night into Friday.

Medium range models in somewhat better agreement with some
elements of the storm system late next week with the 850 low
sliding over the state and then colder air wrapping into the state
in its wake to end the mild trend. With the deepening 850 low,
thunder possible in the warm sector of the system or over the
southeast portion of the state. Total total values reach the
lower 50s over the Southeast portion of Wisconsin. This mornings
12z GFS run was becoming more aggressive with a warm front lifting
northward into the state Thursday night. Trends suggest a strong
dry slot sliding over the eastern half of the state, with more
snow over the northwest portion of Wisconsin and especially into

.AVIATION...for 18Z TAF Issuance
Issued at 1032 AM CST Fri Feb 17 2017

Early this morning satellite imagery showed a narrow region of
LIFR stratus from near Wittenberg to Iron Mountain with the rest
of the area observing clear skies and patches of mvfr vsbys due
to haze or light fog under the surface inversion. The stratus and
light fog diminished mid to late morning. The strong inversion
continues tonight to provide more opportunities for stratus
development as surface dewpoints rise into the upper 20s to lower
30s. But winds aloft become stronger and surface winds more
westerly to promote mixing. Any stratus development may be more
focused over central and northern Wisconsin due to snow cover and
more snow melt potential today. Increasing winds aloft tonight
also provide a stretch of LLWS conditions.

Issued at 234 PM CST Fri Feb 17 2017

Runoff due to snowmelt and rain early next week may produce
crests just below flood stage for a few of the main stem rivers.
More of an issue is the ice break up and unstable ice conditions
that could develop next week. Began adding ice break conditions
as per request of Central and Northcentral Wisconsin Hydro partners
in the HWO for starters today.



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