Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 300915
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
315 AM CST Wed Nov 30 2016
.TODAY AND TONIGHT...Forecast Confidence Is Medium.
The stacked low pressure system over Minnesota will continue to
weaken, but also drift across the Great Lakes by tonight. A trough
will rotate around the low as it moves in, bringing more clouds
and the chance for some light precipitation to southern Wisconsin.
Temperatures will be near wintry precip thresholds later this
afternoon and tonight. The precip will probably hold off in
Madison until mid afternoon, and Milwaukee closer to 6 pm this
The lack of forcing will keep precip intensity light, and thus we
should favor more liquid than snow through the afternoon. Plus,
pavement temps will be above freezing this afternoon, so no
concerns about slippery pavement. Cooling sfc temps and overall
column temps should result in the precip transitioning over to all
light snow later tonight, but by then it should be diminishing.
Little or no snow accum expected.
.THURSDAY THROUGH FRIDAY NIGHT...Forecast Confidence Is Medium.
Models are in decent agreement with the last 500 mb vorticity
maximum rotating through the area Thursday morning and early
afternoon, within cyclonic flow. Kept low end PoPs for Thursday
morning to account for this feature.
Otherwise, the area remains in 500 mb cyclonic flow into Thursday
night, before more westerly flow develops for Friday into Friday
night. Area forecast soundings and low level relative humidity
products show fairly persistent stratus clouds lingering across
the area Thursday into Friday night. Bumped up the cloud cover
during this period as a result.
A rather tight pressure gradient Thursday will gradually relax
Thursday night into Friday night across the area. Temperatures
should be near seasonal normals during this period.
.SATURDAY THROUGH TUESDAY...Forecast Confidence Is Medium.
ECMWF/GFS are in decent agreement with a potent 500 mb shortwave
trough sliding east northeast through the region Sunday into
Sunday evening. The ECMWF is a little slower than the GFS with
this feature. Both models show some weak warm air advection in
the low levels just ahead of the shortwave trough, with generally
light QPF values. Continued with chance PoPs for Sunday, tapering
off Sunday night. A transition from light snow to light rain is
forecast at this time for Sunday, as daytime heating ensues.
Temperatures look to remain near seasonal normals.
ECMWF/GFS then are showing some kind of cyclogenesis for Monday
into Tuesday over the northern Plains into south central parts of
Canada. Both of these low tracks keep southern Wisconsin in the
warm sector airmass Monday into Monday night, with a cold frontal
passage Tuesday or Tuesday night. ECMWF is more aggressive with
the 500 mb vorticity maximum clipping the area Tuesday, with the
GFS further to the northwest. For now, continued with consensus
blended PoPs and temperatures for Monday into Tuesday, given the
uncertainty this far out in the forecast period.
MVFR CIGS will overspread southern Wisconsin this morning.
Moisture is wrapping around a weakening upper level low over
Minnesota. That low will drift east today and tonight, and bring
a chance of light precipitation along with it. The precip should
reach KMSN by about 21z this afternoon, and 00z Thu for
It should initially be all rain, but then gradually become mixed
with then change over to all light snow by later tonight. By the
time it changes over to all light snow, it should be diminishing
or ending, so little in the way of accumulation is expected. CIGS
may also drop to IFR levels tonight, but it may be straddling the
A broad area of low pressure will drift across the Great Lakes
today through Thursday, with the center of the low staying north
of the area. This will result in southwest winds gradually
shifting to westerly tonight. Those winds could approach Small
Craft Advisory levels for a time this evening, mainly south of
Milwaukee. But, given the offshore trajectory, the highest waves
will be out in the open waters.
TODAY/TONIGHT AND AVIATION/MARINE...Davis
THURSDAY THROUGH TUESDAY...Wood