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fxus63 kgrb 170008 
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Area forecast discussion
National Weather Service Green Bay WI
608 PM CST Sat Nov 16 2019

Updated aviation portion for 00z taf issuance

Short term...tonight and Sunday
issued at 239 PM CST Sat Nov 16 2019

The latest rap analysis and satellite/radar imagery show high
pressure exiting over the eastern Great Lakes while low pressure
is moving east over southern Manitoba. Mid-level clouds continue
to move east across the region above scattered to broken MVFR
strato-cu. Think some of these low clouds will erode through the
rest of the afternoon. Precip is developing over South Dakota and
falling out of a mid-level cloud deck. As this storm system moves
east, timing and accumulations of wintry precip are the main
forecast concerns.

Tonight...low pressure and associated frontal system will continue
to track east into Wisconsin late. Timing has slowed a bit, and
the cold front may not move into northwest Wisconsin until closer
to 12z Sunday. Timing of precip has slowed as a result, arriving
into north-central WI in the 4 to 6 am time period. Could see up
to a half inch of snow accumulations by 6 am over western Vilas
County. Otherwise, will see clouds gradually thicken and lower
through the night. With a mild south wind and cloud cover, temps
should only fall into the middle to upper 20s.

Sunday...precipitation will continue to move east along the cold
front, but gradually diminish in the process. Temps should be cold
enough for precip to fall mainly as snow over central and north-
central WI. This should result in an additional accumulations of
up to an inch. By the time precip moves into northeast WI,
including the Fox Valley, temps are forecast to warm into the
middle 30s, making precip more of a rain/snow mix. With precip
forecast to thin out, accumulations continue to look minor in
this area, and perhaps a couple tenths are possible. Forecast
soundings indicate that mid-level moisture departs during the
afternoon on the trailing edge of the precipitation band. Could
therefore see precip mix with or change over to freezing drizzle
for a time, mainly over north-central WI where temps will be near
freezing. But don't think any freezing drizzle will lead to much
impacts with temps near freezing and time of day considerations.

Long term...Sunday night through Saturday
issued at 239 PM CST Sat Nov 16 2019

An upper level trough and associated cold front will be moving
through the forecast area Sunday evening, so will keep a chance of
precipitation in the east and north part of the cwa. Moisture will
be shallowing out, so any lingering light snow may change to
drizzle or freezing drizzle. Temperatures in eastern WI may also
be warm enough for a mix of light rain/snow early.

Generally dry conditions are anticipated as a ridge of high
pressure moves through WI Monday and early Monday night. A warm
front will impact the forecast area late Monday night into
Tuesday, but will not have much moisture to work with. For now,
will only carry low-end pops for light snow or freezing drizzle.

A potentially stronger system is expected to arrive Wednesday
night into Thursday, but there are strength and timing issues
with the medium-range models. The GFS is strongest and farthest
north with the surface low, and brings a significant rain to much
of the cwa, while the European model (ecmwf) is farther south, colder and not as
strong. Have bumped up pops to likely in the southeast part of the
forecast late Wednesday night into Thursday morning. Later
forecasts will be able to provide more details on the likely track
and strength of the low in upcoming days, with better estimates
on qpf, as well as potential snow accumulations on the colder
northwest periphery of the storm.

As this system exits, there will be potential for a brief period
of light lake effect snow showers over north central WI Thursday
night.

Models diverge for the weekend, with the GFS suggesting a
generally dry forecast, while the European model (ecmwf) supports a chance of
snow showers as an upper trough swings through the region.
&&

Aviation...for 00z taf issuance
issued at 608 PM CST Sat Nov 16 2019

Some MVFR clouds persisted across portions of eastern WI late
this afternoon, with mid-upper clouds across the rest of the area.
Look for the MVFR clouds to continue to dissipate/exit eastern WI
as winds become southerly, lingering the longest at kmtw.

Flying conditions will deteriorate on Sunday as snow spreads west
to east across the area. IFR ceilings and vsbys are expected for a
few hours in the heaviest precip. A period of LIFR conditions are
possible as well, mainly at kauw, kcwa, and krhi Sunday morning.
As temps climb through the day, look for the snow to mix with or
change to a period of rain, especially across central and eastern
WI. As the steady precip exits in the afternoon, a period of
drizzle and freezing drizzle is expected. Only minor improvements
in ceilings are expected in the afternoon.
&&

Grb watches/warnings/advisories...
none.
&&

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