Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 272333

Area Forecast Discussion
National Weather Service Green Bay WI
633 PM CDT Mon Mar 27 2017

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Tuesday
Issued at 244 PM CDT Mon Mar 27 2017

The latest RAP analysis and satellite/radar imagery show a shortwave
trough moving over northeast Minnesota and western Lake Superior
early this afternoon.  Scattered showers continue to develop ahead
of the shortwave over north-central and far northeast WI.  Think
will see the showers continue to develop through the rest of the
afternoon. But drier air lies just to the west, with the leading
edge of the clearing approaching Rice Lake and Hayward.  Meanwhile,
high pressure is building south over Manitoba.  Forecast concerns
include shower potential extending into this evening, followed by
cloud trends and fog potential.

Tonight...Shortwave trough will continue to move northeast over Lake
Superior tonight. Mid-level moisture will depart with the shortwave
early in the evening, so think the light shower activity will have
mostly departed by 00z.  Attention then turns to cloud trends.
Nearly all guidance shows drying coming in from the north as
Canadian high pressure builds into the region.  How quickly that
occurs varies from model to model, and generally sided with the
slower RAP, which was not that different from the previous forecast.
If clearing does occur late in the evening into the early overnight
across northern WI, then there is potential for dense fog/low
stratus to redevelop as temperatures cool under light winds. With
the late departure of the clouds over central and east-central WI,
however, do not think will see those same trends further south.  Low
temps falling into the mid 20s north to the mid 30s south.

Tuesday...High pressure will continue to build south into the
region.  Any lingering low clouds and fog will look to dissipate by
mid-morning as dry air gets mixed down from aloft.  Then should see
ample sunshine for the rest of the day.  Quite a difference of 925mb
temps in the models, but trended warmer towards the ecmwf, since
think bias corrected grids may be influenced from the cooler/wetter
pattern of the past few days.  Highs ranging from the mid 40s near
the lake to the mid 50s over central WI.

.LONG TERM...Tuesday Night Through Monday
Issued at 244 PM CDT Mon Mar 27 2017

Quiet weather to start the long term, then a low pressure system
will bring precip chances to the area Thursday into Friday, but
the 12z/27 models have shifted south, keeping the bulk of the
precip south of the area. However, questions still remain if this
shift is temporary or if it will stick. Near normal temperatures
are expected Wed-Fri then above normal readings return for the

Dry conditions are expected Tuesday night into Wednesday as
surface high pressure slides across Ontario and mid-upper level
ridging pushes across the Great Lakes. Mostly clear skies are
expected to start Tuesday night, but mid-upper clouds will be
approaching as moisture increases ahead of the next system, so
not expecting much sunshine on Wednesday as mid clouds are
expected with highs mainly in the 40s.

Attention turns to the system ejecting out of the southwest U.S.
on Wednesday. GFS remains farthest south with the track and
associated precip, and now has the system completely missing the
area. Canadian trended south on its 12z/27 run, with most of
central and north central WI missing out on any significant
precip, but still brings up to 0.75" of liquid to east central WI
Thursday and Thursday night (seems to be the outlier now). The
12z/27 ECMWF trended to the south as well, keeping the swath of
heavier precip just to our south across southern WI and only a
tenth or two of liquid over far east central WI. Models are
trending south, but a flip- flop is always possible with these
systems so confidence on how this system will play out remains on
the low- medium side.

Bottom line...the chances for getting any accumulating snow and/or
heavy precip looks to be diminishing at this point, due to a
southern shift to the system keeping the bulk of the precip over
southern WI. Plus, ground temps will be pretty warm, with much/all
of the frost out of the ground across east central WI thanks to
the recent rain and above freezing temps. Would need to get into
the heavy precip to cool the boundary layer sufficiently for snow
and to get anything to stick on the ground. Will reduce POPs
significantly across central and north central WI and keep nearly
the entire area dry on Friday.

Canadian shows lingering moisture in the cyclonic which would
keep a few showers around Friday night into Saturday morning, but
other models are dry. Will lean toward the drier models. A mid-
level shortwave will cross the northern Great Lakes on Saturday,
with a secondary shortwave right on its heels for Sunday. Both
could touch of a few showers, but at the surface weak high
pressure will be in place, plus there will be no deep moisture to
work with so activity is expected to be isolated at best. In
addition, not much skill in trying to time these fast moving
features this far out. Will keep POPs on the low side or out of
the forecast all together until the picture gets a little clearer.

.AVIATION...for 00Z TAF Issuance
Issued at 631 PM CDT Mon Mar 27 2017

MVFR ceilings clearing from northwest to southeast overnight,
though low clouds could form where skies are clear for several
hours. So look for some clearing this evening but possible areas
of low clouds late tonight where skies do clear. Skies should
become mostly clear by 15z Tuesday with good flying weather
Tuesday afternoon and evening.




LONG TERM......Bersch
AVIATION.......RDM is the U.S. government's official web portal to all federal, state and local government web resources and services.