Scientific Forecaster Discussion
fxus63 kmkx 150928
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
328 am CST Fri Nov 15 2019
Today through Saturday...forecast confidence is high...
Low level clouds will push southeast through southern Wisconsin
this morning. However, as high pressure builds to the north and
south expect clouds to dissipate during the day as we expect a
loss of moisture in the low levels. This should allow US to get
some sun today and help US warm up to the mid to upper 30s.
Into the evening we will see an upper level shortwave track
through southern Wisconsin that will have some associated moisture
aloft. This should allow for some upper level clouds to develop,
which could contain some precipitation initially. However, given
very dry low and mid levels, any precipitation would be likely to
sublimate as it falls through the drier air, thus not reaching the
Saturday looks to be mostly quiet with upper level clouds
persisting with light winds from the east. High pressure will
continue to build but will push out of the region through the day.
As it pushes out winds will change to the southeast and increase
as the pressure gradient strengthens.
Saturday night through Sunday night...forecast confidence is
High pressure over the northern Great Lakes kicks east Saturday
allowing for winds to increase out of the south Saturday night
ahead of an approaching system. Increasing clouds aloft and the
warm air advection will keep temps in the upper 20s.
Models have slowed the progression of the system and the arrival
of precip into the region for Sunday with more activity likely to
occur during the late morning to early afternoon period. There
are still some subtle timing differences that still need to be
worked out. But one of the bigger issues is going to be related to
precip type. The warm air advection ahead of the trough will bring a warm nose
aloft of up to 3c into the region. This warmer airmass though will
be quite moisture deprived at the initial onset. So as precip
begins to overspread the area from west to east it will be
falling through this dry sub-cloud layer and evaporating, which
will help to cool the warmer air aloft. May start out with a mix
then as temps warm through the day shift to more rain than snow.
As the upper trough moves through in the afternoon we do begin to
lose ice in the clouds. This would end the warm air advection and as temps fall
we could have a period of drizzle and freezing drizzle during the
evening hours. Even though there are questions about p-type, quantitative precipitation forecast
amounts have been trending downward with the past few runs. So any
accumulations would limited. Model certainty would put the 50th
percentile less than half an inch and this forecast will stick
close to those numbers. Lingering cloud cover and more westerly
winds will keep temps Sunday night into Monday in the upper 20s.
Monday through Thursday...forecast confidence is low to medium.
The blocking pattern across the western US begins to break down
early next week with the ridge shifting east. Guidance has been
struggling with the progression of the ridge and subsequently
the upper waves dropping east/southeast ahead of the ridge axis. Thus, the
start of the work week has become a bit more uncertain with
models trending weaker with the multiple waves that moves across
the region. The 00z runs keep much of the precip associated with
these waves either to our west/SW or to the north/NE and will carry
slight chance pops through this period.
Even though there is uncertainty in progression of the upper level
features, models have been consistent in the idea that temps
continue to moderate through the middle of the week. Highs could
climb above the 40 degree mark for both Tuesday and Wednesday.
A cutoff low sitting off the Baja Peninsula will eject east/NE into
the central US as the blocking pattern attempts to become
reestablished. Decent moisture advection ahead of this system will
bring increased chances for rain/snow for Thursday. The precip
type is going to be highly dependent on the track of the surface.
Due to the uncertainty will keep a mix in the forecast at this
Some MVFR ceilings are expected to push southeast into southern
Wisconsin this morning. The progression remains a bit slower than
initially anticipated but by around 11-12z we should see MVFR
ceilings push across the taf sites. MVFR ceilings are expected to last
through the morning before slowly scattering as we dry out in the
VFR conditions are expected thereafter with upper level ceilings
expected to develop by the evening and continue through Saturday.
Otherwise light west winds are expected to start the day but will
turn to the north and then to the east through the day. Saturday
winds will turn to the southeast and increase a bit as high
pressure pushes out.
Light west winds are expected to start the day but will turn to
the north and then to the east through the day. Saturday winds
will turn to the southeast and increase a bit as high pressure
pushes out. Overnight Saturday winds will remain primarily from
the south. This period will have the best potential for Small
Craft Advisory conditions as winds will be breezy across the
northwestern parts of the lake with waves likely increasing to 4
to 5 feet across the west central parts of the lake for at least a
few hours. Otherwise light winds are expected across the lake for
at least the beginning of next week.