Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 011748

Area Forecast Discussion
National Weather Service Green Bay WI
1148 AM CST Wed Mar 1 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Thursday
Issued at 329 AM CST Wed Mar 1 2017

Ajustments to snowfall totals and winter weather headlines are
the main concerns for this forecast package.

Models have trended farther north with QPF for today, so have
increased pops, QPF and snowfall totals accordingly. Have stayed
fairly close to the ECMWF, which seemed to have the best handle on
the short-term trends early this morning. The GFS and NAM both
had frontogenetic snow bands near the far northeast corner of the
state, well north of where the actual pcpn was occurring. Based
on the expected axis of heavier QPF as depicted by the ECMWF and
the WRF-NMM and WRF-ARX, have expanded the winter weather advisory
farther north, to include areas south of a line from Wausau to
Antigo to Pembine. Expect widespread 3 to 5 inch amounts, with
perhaps a few spots approaching 6 inches toward MNM and northern
Door county.

A cold front had shifted southeast of the fcst area, and
early morning temperatures ranged from the middle 20s northwest
to the middle 30s southeast. Low pressure along the boundary was
quickly shifting ENE through lower MI. Rain was starting to
change to snow over parts of the Fox Valley, as evidenced by mixed
rain/snow here at NWS GRB. Most of the pcpn was occurring over
the southeast half of the cwa, but snow should expand and increase
in intensity by around daybreak as forcing associated with a s/w
trof in Iowa and the LFQ of an upper level jet arrive. The main
upper trof will move through during the early to mid-afternoon,
followed by a decrease in snow as it departs late in the day.
Gusty north to northwest winds will cause some patchy blowing
and drifting snow, which should persist until around sunset.
Falling temps are anticipated early in the day, followed by
steady readings in the 20s.

Will carry small pops for light snow showers or flurries in the
forecast late tonight into Thursday as a couple weak s/w trofs
move through. Some weak lake effect is also possible in far north
central WI. It will be chilly, with lows in the teens tonight, and
highs ranging from the middle 20s to lower 30s on Thursday.

.LONG TERM...Thursday Night Through Tuesday
Issued at 329 AM CST Wed Mar 1 2017

Models are in good agreement with the mean flow across the CONUS
into early next week. One prominent mid-level trough exits the
eastern CONUS this weekend as an upper ridge moves into the
central CONUS. The next impressive mid-level trough digs into the
western CONUS late this weekend and will eventually impact
northeast WI during the Monday/Tuesday time frame. Precipitation
amounts appear to be below normal through the weekend before
revving up with the next system. Temperatures will be below normal
through Friday, then move well-above normal Saturday-Monday.

A few snow showers may linger over eastern WI early Thursday
evening as the weak clipper system pulls away. The other feature
to watch will be the continuation of lake effect snow showers over
north-central WI as CAA overspreads the region and 8H temperatures
fall to around -22C. Have kept pops in the chance category, mainly
due to the approach of a surface ridge that would gradually back
the winds to the west-northwest and usher drier air into the
region. Accumulations for the Vilas County snowbelt may reach
one-half to one inch, but most locations in north-central WI will
not see more than a dusting. Min temperatures to range from zero
to 5 above north-central, to the middle teens near Lake MI. The
surface ridge axis slides across WI Friday morning and reside to
our east Friday afternoon. A good deal of sunshine can be expected
over northeast WI, however the air mass aloft is still quite cool,
therefore max temperatures will be below normal. Look for readings
to only reach the lower to middle 20s which is cooler than
previously forecast.

A return flow sets up across WI Friday night as south-southwest
winds take over. Expect to see an increase in mid/high clouds a
significant WAA overspreads the region. If the atmosphere can
saturate, there could be some light snow accompanying this warm
air surge, but models disagree on whether saturation can be
achieved. Therefore, will only mention slight chance pops with
little in the way of snow accumulation. Min temperatures will not
be nearly as cold as Thursday night, as readings only drop into
the lower teens north, middle to upper teens south. Models bring
the weakening upper ridge into the Great Lakes on Saturday,
bringing milder air in on south-southeast winds. These winds may
keep lakeshore areas cooler than inland locations, but readings
will be above normal nonetheless. Under a mix of sun and clouds,
expect max temperatures mainly be in the upper 30s to lower 40s.

Clouds are expected to thicken over the area Saturday night as a
warm front lifts north into the Great Lakes. This front may be
able to kick off some light shower activity with surface
temperatures dictating rain, snow or a mix. Once again, QPF
amounts look very light, thus any snow that would fall should not
accumulate to much, if anything. The mild start to Sunday, coupled
with a prevailing southwest wind, is forecast to bring mild
conditions to almost all of northeast WI. Max temperatures on
Sunday to range from the lower 40s over northern Door County, to
the middle 50s across parts of central WI.

As the next mid-level trough pushes across the Rockies Sunday
night, the models strengthen an area of low pressure that moves
across the northern Plains toward the Upper MS Valley. The GFS is
a bit slower/weaker with this surface low compared to the
ECMWF/CMC, thus keeps most of Sunday night dry over northeast WI.
Since the mean flow is progressive, prefer to lean the forecast
toward the ECMWF/CMC and bring increasing pops to northeast WI,
mainly after midnight. Surface temperatures will again be key to
precipitation type as a mix cannot be ruled out over northern WI.
The surface low is progged to track northeast into southwest
Ontario or northern sections of the Great Lakes on Monday. Models
are having some timing/track issues with the movement of this low
pressure. Anticipate additional rain showers through the day
(perhaps mixed early north) and cannot rule out thunderstorms as
mid-level lapse rates steepen. Will hold off on thunder wording
for now as level of instability is in question. Max temperatures
on Monday are going to be tricky depending on the timing of the
heavier rainfall. For the time being, have readings in the upper
40s to middle 50s.

Combination of strong CAA and cyclonic flow will turn the rain to
snow Monday evening over northern and parts of central WI with
rain or a rain/snow mix east. Eventually, any precipitation would
turn to all snow overnight, although QPF amounts are forecast to
diminish overnight as the surface low begins to pull away. Monday
night will also be quite blustery as winds veer to the west-
northwest and increase into the 15 to 25 mph with higher gusts.
Gradually improving conditions are expected on Tuesday as the low
pressure departs and a ridge of high pressure builds across the
Upper Midwest. Have carried chance pops into Tuesday morning, then
lingered potential lake effect for north-central WI through
Tuesday afternoon. Max temperatures for Tuesday to range from the
middle to upper 30s north-central, lower to middle 40s south (away
from Lake MI).

.AVIATION...for 18Z TAF Issuance
Issued at 1148 AM CST Wed Mar 1 2017

Snow, moderate to heavy at times, will end from west
to east during the afternoon hours. Ceilings and visibilities
should increase to MVFR or VFR range by mid evening and continue
tonight and Thursday. Gusty north winds will produce some blowing
and drifting snow through early evening.

Winter Weather Advisory until 6 PM CST this evening for WIZ013-


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