National Weather Service Text Product Display

Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
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FXUS63 KMKX 010230 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
830 PM CST Tue Jan 31 2017

.UPDATE...

Area of moderate to sometimes heavy snow showers continues to
push southeastward into the forecast area this evening. This is
associated with 500 mb differential cyclonic vorticity advection
and upper divergence with left exit region of 300 mb jet streak.
There is some low level confluence as well. Area forecast
soundings show saturation in the dendrite snow crystal growth zone
into later this evening.

As a result, these snow showers have been producing snow
accumulation rates of 1/2 up to 2 inches per hour, per reports
from upstream locations. Look for these snow showers to continue
to slide southeast through the rest of the forecast area this
evening, exiting the far southeast around or soon after midnight.
A quick 1/2 to 1 inch of snow is expected, with 2 inch amounts not
out of the question. Areas toward Lafayette County may not see as
much of this activity as the rest of the area.

After the snow showers move out of the area, expect mainly cloudy
skies overnight with west northwest winds. There are some breaks
in central Minnesota that may move through later tonight.

&&

.AVIATION/06Z TAFS/...

Area of moderate to sometimes heavy snow showers will continue to
slide southeast across the area this evening, exiting the far
southeast around or soon after midnight. Expect snowfall rates of
1/2 to 1 inch per hour during this period, with some 2 inch per
hour rates not out of the question. These will be the total
amounts as well, given their movement across the area.
Visibilities may be reduced to 1/4 to 1/2 mile in the heavier snow
showers, with ceilings at or below 1000 feet.

After the snow showers move out of the area, expect ceilings in
the 2500 to 3500 foot range later tonight into early Wednesday
morning. There may be some clear areas at times. Skies should
become more scattered out as the day goes on. West northwest winds
will remain over the area overnight into Wednesday evening. Some
gusts to around 20 knots are expected.

&&

.MARINE...

Persistent west northwest winds are expected to linger across the
area for the rest of the week. There may be gusts to 25 knots at
times during this period, especially Wednesday into Thursday. A
Small Craft Advisory may be needed at times during the rest of the
week. Any high waves will remain near and over the open waters of
Lake Michigan.

&&

.PREV DISCUSSION... /Issued 249 PM CST Tue Jan 31 2017/

TONIGHT AND WEDNESDAY...Forecast confidence is high.

Broad troughing and cyclonic flow will prevail aloft, with southern
Wisconsin located along the poleward extent of a 140 knot speed max
nosing in from the northern Great Plains. There remains a chance for
some flurries or snow showers into tonight, as steep low-level lapse
rates combine with synoptic forcing via jet-level divergence and
differential cyclonic vorticity advection to produce some weak lift.
Any additional accumulations should be minor. Gusty winds will taper
off late this evening, but expect some blowing/settling of snow
cover until they do. Despite continued cold advection, temperatures
shouldn`t fall too much tonight given mostly cloudy skies.

A cold front brings a reinforcing shot of cold air Wednesday
morning, with falling temperatures by afternoon. The trade-off for
these colder temperatures will be a bit of sunshine as we head into
the afternoon and evening. Wind should pick up similar to today, as
the pressure gradient tightens due to strong high pressure building
towards us from the northern Rockies and Great Plains.

THURSDAY THROUGH FRIDAY NIGHT...Forecast confidence is high.

We`ll be under a fast nearly zonal flow aloft with high pressure
maintaining control at the surface. There is some short wave
energy moving through in that upper level flow, but there isn`t
much lift and, more importantly, there isn`t any deep moisture
that would justify any pcpn chcs at this point. Temps will be
cold, dropping to below normal for a few days before recovering
this weekend.

SATURDAY AND SUNDAY...Forecast confidence is medium.

Light snow chances have increased a bit with the weekend system
moving through. That trend will probably continue with subsequent
forecasts as confidence is likely to build. For now, it is an open
wave/trough moving through with some speed, so snowfall amounts
are still looking on the lighter side of things. About an inch or
two, with the highest amounts looking to stay north of Milwaukee
and Madison. Saturday morning looks dry, with the snow spreading
in from west to east during the afternoon, then exiting from west
to east during the late evening and overnight hours.

This system will push temps back up to above normal by Sunday.

MONDAY AND TUESDAY...Forecast confidence is medium.

The GFS/ECMWF/Canadian all agree that we should see a fairly
intense low pressure system form over the Central Plains early in
the week and head northeast toward the Great lakes on Tuesday.
Some leading troughing could bring light precip in Monday
afternoon that could be some drizzle/freezing drizzle. The track
of the low and the thermal profile put this storm more on the warm
side of a winter storm for us. Thus, look for a wintry mix,
changing to rain, then back to snow as this system evolves. Way
too early for that kind of detail, but for now it looks like the
better accumulating snow will be north of our forecast area, over
central and northern Wisconsin.

AVIATION/00Z TAFS/...

Flurries and snow showers are possible late this afternoon into
tonight. Confidence is low of any impact at the TAF sites, so only
added a VCSH mention for now. Gusty northwesterly winds should ease
late this evening, with more gusts to around 20 knots expected
Wednesday afternoon. Prevailing MVFR ceilings and VFR visibilities
are expected. The only possible exception would be brief IFR
visibility reductions in any snow showers this evening and tonight,
but confidence in this occurring is low.

MARINE...

The Small Craft Advisory will remain in effect until 6 pm this
evening, with diminishing winds and waves thereafter. Wind gusts
will approach Small Craft criteria for a time tomorrow afternoon,
especially towards the open waters. Confidence is not yet high
enough to issue an Advisory, but mariners will want to exercise
caution during this time.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

UPDATE...Wood
TONIGHT/Wednesday AND AVIATION/MARINE...SPM
Wednesday NIGHT THROUGH Tuesday...Davis
National Weather Service Regional Headquarters
