Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 230942
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
342 AM CST Thu Feb 23 2017
.TODAY AND TONIGHT...Forecast Confidence Is Medium.
Main issue will be precipitation types later tonight and potential
Strong upward vertical motion is expected to move into the area
later tonight, with strong east to west oriented low to mid level
frontogenesis response fields. Low level jet nose also points toward
or into the area for a time later tonight, aiding with the moisture
feed. Precipitation is expected to spread northward across the area
this evening, continuing into later tonight.
There will be quite a north to south temperature gradient in the low
levels tonight. Area forecast soundings continue to show potential
for a period of a rain/snow mix in the northern counties this
evening, then becoming more of a freezing rain issue with some sleet
and snow mixing in later tonight in the far northern and
Mainly rain is expected elsewhere. Weak elevated CAPE on soundings
continued to support a slight chance for thunder in the southwest
half of the area.
Light snow accumulations of 1 to 2 inches in the far northern
counties are forecast tonight, with some ice accumulations of up to
around 0.10 inches later tonight into Friday morning in that area.
Will issue a Special Weather Statement for now to highlight this
potential, with a winter weather headline eventually needed for
later tonight into Friday morning. This will impact the Friday
.FRIDAY AND SATURDAY - Confidence...Medium
Precip will be ongoing at the outset associated with isentropic
upglide ahead of 850 low in Iowa. Pronounced warm layer evident on
Bufkit soundings with 925 progs showing colder low levels reinforced
by a gusty northeast wind component. As always surface temps will be
key and the north and northwest cwa continues to look must vulnerable
to freezing rain during the morning hours while warm layer remains
present and colder surface temps linger. At this time it appears
temps will warm above freezing there into the afternoon hours so
any lingering precip prior to dry slot would change to rain. For
much of the CWA rain looks most prevalent until dry slot works in
during the late morning and afternoon. Lowered pops a bit in the
afternoon to account for the dry slot. Bufkit also showing
elevated instability so keeping some thunder mention going esp
during the afternoon in the southeast seems reasonable but not
looking like we will catch the warm sector so the better svr
threat being off to our south and southeast looks reasonable per
SWODY2. DCVA and passage of upper low occur later Friday into
early Saturday. Low level cold advection will then aid in a
changeover of def zone precip from rain to snow. ECMWF and GFS are
the favored models and qpf progs suggest potential for some cwa
wide accums of up to an inch in the far southeast and to as much
as 3 or 4 inches in parts of the northern cwa. As the low pulls
away on Saturday any lingering snow will end in the morning. But
it will be chilly with blustery northwest winds with many areas
hitting 30 tops.
.SUNDAY - Confidence...Medium
Models continue to show a weak mid level wave riding through with
light qpf. This does not look to be a big system at all but
potential for a little light snow.
.MONDAY - Confidence...Medium
Looks like there is consensus for a dry day with weak ridging
between departed weak system and organizing system in the Plains.
The GEM solution which spreads waa precip into the area quicker than
the ECMWF or GFS.
.MONDAY NIGHT THROUGH WEDNESDAY - Confidence...Medium
The GEM continues to be the faster solution on this low with precip
wrapping up later Tuesday. Meanwhile the ECMWF and GFS bring the low
and associated precip into the area later Tuesday into Tuesday
night. Consensus track on the low supports a north track which
suggests bulk of this event will be rain for us here in srn WI. Cold
advection regime takes hold for Wednesday with a dropoff in 850
temps and 1000/500 millibar thicknesses.
.AVIATION/12Z TAFS/...Area of low clouds with ceilings of 1000
to 2000 feet above ground level will continue to move east into
the area early this morning. They should linger today, possibly
rising above 3000 feet, before lowering to IFR and below alternate
minimums tonight into Friday morning. Visibilities near or below
alternate minimums are expected tonight with the arrival of
precipitation from the south.
Mainly rain is expected in the southern half of the forecast area,
including Madison, Waukesha, Milwaukee and Kenosha. A few rumbles of
thunder are possible later tonight. Areas to the north should see a
rain/snow mix this evening, then mainly freezing rain with some
snow/sleet mixing in later tonight. Light snow and ice accumulations
are forecast tonight in areas toward the Wisconsin Dells, Montello,
Fond du Lac and Sheboygan.
.MARINE...A tight pressure gradient with strengthening low pressure
will result in a period of gusty winds and building waves later this
afternoon into tonight. Gusty northeast winds are expected during
this time, which will build high waves. Frequent gusts up to 35
knots are expected later tonight.
Thus, a Small Craft Advisory will be issued from 3 pm this afternoon
until midnight tonight, followed by a Gale Warning from midnight
until 6 am Friday. Winds and waves should be high enough to keep
Small Craft Advisory conditions going into Saturday night. Gusty
winds are expected to back to the northwest Friday night into
LM...Small Craft Advisory from 3 PM this afternoon to midnight CST
tonight for LMZ643>646.
Gale Warning from midnight tonight to 6 AM CST Friday for
TODAY/TONIGHT AND AVIATION/MARINE...Wood
Friday THROUGH Wednesday...Collar