Scientific Forecaster Discussion
fxus63 kmkx 121711
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
1111 am CST Tue Nov 12 2019
The forecast through tonight remains on track. Highs stay in the
teens today, then drop quickly into the single digits this
evening. An increasing southwest flow tonight will bring in some
warm air advection, putting The Breaks on the temp fall by
midnight. Readings by sunrise Wednesday will have risen about 5
degrees from the earlier low mark. The new model guidance isn't
suggesting any major adjustments to snow amounts for Wed-Wed ngt.
We need to work out the best area for accumulation. Half the
guidance seems to focus on our southern cwa, while the other half
is to the north. More later.
VFR conditions are expected through the taf period. Look for the
brisk northwest winds to diminish this afternoon, becoming rather
light this evening as a high pressure ridge moves overhead. The
ridge slides east by sunrise Wednesday with winds backing to the
southwest and becoming brisk very quickly after 12z Wednesday. Any
snow with the next approaching system will likely hold off until
after 18z-21z Wednesday.
Previous discussion... (issued 858 am CST Tue Nov 12 2019)
No changes needed to the short range forecast. It remains on track
and it's cold.
Look for the northwest winds to steadily diminish today as a high
pressure ridge approaches and slides across the lake this evening.
Winds will become light for a time this evening, before backing to
the southwest by sunrise Wednesday morning as the ridge slides off
to the east. Another Small Craft Advisory will likely be needed
for the brisk southwest winds and a few gale force gusts are
possible across the open waters on Wednesday. Winds will diminish
again by Wednesday night as weak trough of low pressure moves
through the region. Winds will then turn northwest to west in the
wake of the trough for Thursday.
Previous discussion... (issued 542 am CST Tue Nov 12 2019)
no changes to the forecast.
VFR conditions are expected through the taf period as clear skies
will continue through the day today with slowly decreasing winds.
The winds will also turn to the west this afternoon. Into the
evening and overnight period we will start to see clouds slowly
push back in as another low pressure system begins to push in.
This will steadily increase winds and turn them to the south
Wednesday morning. Although snow is not expected during the taf
period we will start to see some snow by Wednesday afternoon which
should lower ceilings/visibilities at times.
Previous discussion... (issued 327 am CST Tue Nov 12 2019)
Today and tonight...forecast confidence is high...
Despite some breezy northwest winds early this morning
temperatures are expected to reach the mid single digits across
much of the County Warning Area with areas near the shoreline toward the upper
single digits. These expected lows are mainly due to clear skies
and fresh snowpack though winds may prevent some areas from
getting quite as low as expected. This may result in record lows
Although clear skies and decreasing winds are expected during the
day today the high albedo snowpack will keep high temperatures in
the mid to upper teens. This will bring potential for record low
highs today as well. Into the evening the high pressure will
begin to push out, which will bring in clouds and some increasing
southerly winds overnight. This will cause tonight's lows to be
reached in the late evening prior to clouds pushing in. However,
very chilly temperatures in the mid to upper single digits are
still expected though record breaking lows are not anticipated.
Wednesday and Wednesday night...forecast confidence is high.
Another chilly start to Wednesday with temps in the single digits
to lower teens across all of southern Wisconsin. A trough dropping
southeast out of the pac northwest Tuesday night into Wednesday will initiate
"warm" air advection as winds through the profile Switch Back to
the W/SW. These stronger west/SW winds transport deeper moisture
northward will start aloft with clouds increasing through
Wednesday morning. Lower level moisture arrives by late morning
into the early afternoon hours. The entire column is saturated as
the trough axis and positive vorticity advection arrives during the afternoon/evening
hours. We'll also see lift associated with the left exit region
the upper jet as well as tied to the warm air advection that doesn't really begin
to weaken until after midnight. Time-heights suggest that the
forcing doesn't ever line up with the dendritic growth zone and
with the colder nature of the profile, more of a dry snow is
Another round of accumulating snow is expected to start late
Wednesday morning across central WI and spread south through the
afternoon/evening. The better chances for widespread snow will
occur during the evening commute on Wednesday.
The model output for quantitative precipitation forecast has changed slightly with the European model (ecmwf)
focusing more on central WI for snow and lower amounts the further
south you go. Based on forcing and saturated profile think we'll
still end up with amounts of 0.10 in the south to 0.2 in north.
This is closer to the 75th percentile based on modelcertainty.
Even though quantitative precipitation forecast looks low, slrs are on the higher side with a
14-18 to 1. So, snow totals will range from 0.5 to 2 inches in
the south and 2 to 3 inches across central WI. This amounts are
right in the line with the 50th percentile.
Temperatures for Wednesday stay in the 20s for highs and then drop
into the teens as the snow exits late Wednesday night.
Thursday through Saturday...forecast confidence is medium.
A few lingering flurries are possible near Lake Michigan for
sunrise Thursday but things will dry out through the day as high
pressure moves into the Central Plains. Winds begin to shift to
the west/SW helping to moderate temperatures somewhat with highs for
Thursday in the lower 30s. This trend continues for Friday with
slightly warmer temps in the mid 30s. Lows both nights though will
be in the teens.
Strong low pressure moves across the north-eastern Great Lakes on
Friday and we could see a cold front nudge into the area. Not
expecting any precip with this as conditions remain on the drier
side and we may not see much of a change in temps with the front
either as the coldest temps stay to our east.
Saturday night through Monday...forecast confidence is low to
Solutions begin to diverge on the timing of a trough and frontal
boundary moving across the area over the weekend. The European model (ecmwf) was
showing a mostly dry forecast as the system passed through, but
has trended towards the GFS and showing another round of light quantitative precipitation forecast
for Sunday into Monday. Trend is also to slow the timing of this
system and that may allow for some moisture recovery. Warm aid
advection bring temps up enough that we end up with a rain/snow
mix. Will wait for guidance to come into better agreement and go
with a blend of models for this period. Temps remain below normal
through the weekend.
Mostly clear skies are expected through the early evening. Winds
early this morning will remain gusty from the northwest, though
the gusts should start to settle down by the mid morning.
Winds will become light and more westerly over the day today..
winds will eventually turn to the south and southwest late tonight,
increasing as we head into Wednesday morning.
A Gale Warning and Small Craft Advisory remain in effect until
15z and 18z respectively for breezy northwest winds across the
lake this morning. Higher pressure will push in today turning
winds to the west while slowly decreasing. This period of light
winds will not last long as high pressure will push out overnight
as another low pressure system begins to push in. This will
increase winds from the south by Wednesday morning with potential
for gales during the day. Winds will quickly decrease into the
overnight hours as winds turn to the northwest during the day
Lm...Small Craft Advisory until noon CST today for lmz643>646.