Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 131626
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1026 AM CST Fri Jan 13 2017

.UPDATE...

Primary short-term forecast concern is the chance for light snow or
flurries later this afternoon and evening. Regional radar shows an
area of light returns to our south and west pushing east late
this morning. Most of the precipitation is not reaching the
ground, given a dry layer around 900 to 950 mb that must be
overcome. However, reduced visibilities over northwest Iowa
suggest that some of the precipitation is reaching the ground in
that area.

This precipitation is occuring in conjunction with a weak shortwave
moving through, with forcing provided by an area of focused 700 mb
warm advection, along with an increase in differential cyclonic
vorticity advection and jet-level divergence within the right
entrance region of a departing speed max.

Despite the relatively dry low levels suggested by the deterministic
models, believe enough saturation will occur later this afternoon
and evening for precipitation to reach the ground. Given recent
mesoscale model runs, such as the operational HRRR, considering
moving up the start time for light snow/flurries a few hours to
mid/late afternoon in the west and early evening in the east.
Amounts should be on the light side, from a dusting to perhaps up
to one half inch. Will continue monitoring upstream obs and make
adjustments to POPs and QPF through the morning as needed. Any
precipitation will come to an end by late evening as forcing wanes
and the upper wave departs.

Clouds should stick around for tonight into at least the first
part of Saturday with lingering moisture and a northeast fetch
off Lake Michigan for a time. Warm advection will bring high
temperatures on Saturday close to seasonal normals for this time
of year.

&&

.AVIATION/18Z TAFS/...

Returns on area radars to our southwest are not reaching the
ground due to the very dry low levels. Some low level saturation
may occur later this afternoon and evening with ceilings lowering
to 4 to 6 kft, and chances for light snow or flurries. Ceilings
could drop to MVFR for a time, with brief 3-5 SM visibilities in
light snow later this evening, but confidence in the lower
ceilings and visibilities is low. Any light precipitation should
end from west to east early tonight, with clouds lingering into
early morning. Saturday looks quiet with partial clearing for the
late afternoon or evening.

&&

.MARINE...

A quieter wind period is expected over southern Lake
Michigan through Sunday as several large high pressure systems move
through the area. Expect NNW winds to veer to the SE thru tonight
but become offshore again on Sat. There remains a chance for some
light snow late this afternoon and tonight. Otherwise, more
widespread light precipitation is expected from late Sunday night
into Tuesday. Precipitation may start out as wintery mix but will
transition to ocnl rain on Monday.

&&

.PREV DISCUSSION... /Issued 340 AM CST Fri Jan 13 2017/

TODAY AND TONIGHT...Forecast confidence medium.

Temperatures have not cooled as much as previously thought this
morning with high clouds continuing to increase. Thus high temps may
be able to reach the lower 20s in far se WI today with teens
elsewhere. The arctic high will shift across the nrn Great Lakes
today and reach New England on Sat. A weak upper wave will bring a
round of 700 mb warm advection and weak 850-600 mb frontogenesis for
tonight. There is plenty of low level dry air to overcome but
forecast soundings suggest it is possible in a narrow band from sw
WI through the Madison area to Sheboygan. Only went with chances of
light snow for now along with flurries in other areas across srn WI.

SATURDAY AND SUNDAY...Forecast Confidence...High

High pressure is expected to bring dry weather for Saturday and
Sunday. Temps should be right around normal for mid-January.

SUNDAY NIGHT THROUGH TUESDAY...Forecast Confidence...Medium

Low pressure will move through the region early next week,
bringing widespread precip to the forecast area. Models continue
to agree fairly well with the general track of the low. Precip
will probably start as light snow Sunday night, before a warm
layer aloft brings in a mix of sleet and freezing rain for a brief
period later Sunday night into Monday morning. Should see mainly
rain by Monday afternoon, with the rain likely continuing into
Tuesday.

Still looks like period of sleet and freezing rain will not be
that prolonged...maybe 3-6 hours.

WEDNESDAY AND THURSDAY...Forecast Confidence...Medium

Went with a dry forecast for Wednesday and Thursday. Models do
show a wrinkle in the flow here and there, so not out of the
question for a few sprinkles or snowflakes during this period.
Should see above normal temps both Wed and Thu.

AVIATION/12Z TAFS/...Broken to overcast high clouds today will
lower to 4-6 kft tonight with chances of light snow. MVFR vsbys with
the snow will be possible for a few hours from sw WI through the
Madison area to Sheboygan.

$$

MARINE...A Small Craft Advisory will expire at 6 AM north of North
Point Lighthouse. Gusty nwly winds will gradually subside through
the morning.

&&

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

$$

UPDATE...SPM/MBK
TODAY/TONIGHT AND AVIATION/MARINE...Gehring
Saturday THROUGH Thursday...DDV



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