Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Milwaukee/Sullivan WI
1143 am CDT Sat Mar 28 2015
High pressure over the region will continue to bring quiet
weather today. Winds will become southeast this afternoon near
Lake Michigan...with south winds developing inland. May see dew
points mix out somewhat this afternoon with daytime heating. This
should lower relative humidity values into the 25 to 35 percent
Highs should reach the upper 30s across most inland areas...with
a few lower 40s near The Dells. Highs should remain in the middle 30s
near the lake.
High pressure will slide east of the region this afternoon and
tonight. VFR conditions are expected at taf sites during this
period. Southeast winds will develop at the eastern sites by early
to middle afternoon...with south winds at Madison. Middle to high
clouds will gradually spread into the area tonight.
South winds will gradually increase in magnitude tonight...with
gusty southwest winds Sunday morning...becoming westerly later
Sunday afternoon. Southwest winds around 45 knots at 2000 feet
above ground level between 09z and 13z Sunday will bring low level
wind shear conditions...before frequent gusty winds mix down to
Cold front moving east through the region Sunday will bring a
round of mixed precipitation to taf sites. A mix of light
snow...light sleet and light freezing rain will move east into
Madison by 13z Sunday...and the eastern sites by 15z Sunday. Any
accumulations of light snow/sleet will be a few tenths of an
inch...with a light glazing possible as well.
Temperatures should warm enough for a changeover to all light
rain by 18z Sunday...lingering into the afternoon. Ceilings and
visibilities should be in the lower MVFR to IFR categories
Sunday...but above alternate minimums.
A tight pressure gradient will develop later tonight and linger
into Sunday night...as a cold front moves east toward and through
the region. Increasing south winds will develop by later
tonight...then veer southwest on Sunday...then west late Sunday
into Sunday night.
Frequent gusts of 25 to 30 knots are expected later tonight into
early Sunday morning from north to south across the nearshore
waters. Waves should build to 3 to 6 feet. A Small Craft Advisory
is in effect for this period.
Frequent gusts to 35 knot gales are then anticipated for most of
Sunday...where a Gale Warning remains in effect. Waves should
build to 4 to 8 feet. A Small Craft Advisory will be needed later
Sunday into Sunday night...as winds and waves slowly subside.
Previous discussion... /issued 344 am CDT Sat Mar 28 2015/
Today and tonight...forecast confidence high
It/S a chilly start out there this morning as high pressure brought
clear skies...calm winds and radiating temperatures. Temperatures this
afternoon will recover into the middle 30s to near 40 range...warmest
northwest of Madison. Look for full sunshine as well.
The high will slide east by tonight with the region getting into a
better pressure gradient overnight as a trough of low pressure
approaches quickly from the northwest. Low temperatures will likely occur
this evening with warm advection ahead of the trough overpowering the
normal diurnal curve after midnight. The column remains dry through
12z...so no precipitation expected before then...just steadily increasing
Sunday... forecast confidence medium.
A vigorous shortwave and associated surface low will swing through
the northern plains and cross Wisconsin on Sunday. This system will
bring a brief round of precipitation to southern WI. The tight pressure
gradient will also lead to strong southwesterly winds Sunday morning
that switch to west during the afternoon in the wake of the surface
trough. Total quantitative precipitation forecast should be a quarter inch or less. Highs will be in
There is quite a push of warm air within the axis of a 60-knot low
level jet. This will shift from west to east through southern WI
Sunday morning... basically at the onset of the precipitation. Morning
temperatures will begin below freezing... so freezing rain or sleet is
expected west of Madison. Elsewhere... there is less certainty about
precipitation type since it will depend on how quickly the precipitation spreads
east to the lake. Expect a wintry mix in the morning that
transitions to rain from late morning through the afternoon.
Precipitation will taper off quickly Sunday afternoon/evening behind the
shortwave. Drier air should scour out clouds overnight with lows
dropping down to around 30.
Monday through Tuesday... forecast confidence medium.
The European model (ecmwf) is holding on to the idea of another shortwave and
associated weak low pressure bringing precipitation into southern WI Monday
night. Other models keep this precipitation well to our north. It would be
rain if it happens.
High pressure will drift through the region Tuesday into Wednesday.
High temperatures will be in the 50s... and lows in the 30s.
Wednesday through Friday... forecast confidence medium.
Warm air advection ahead of the next shortwave will bump maximum temperatures
into the 60s Wednesday and Thursday. The system will be occluding...
so precipitation should be delayed until Wednesday night and linger into
Thursday. The GFS model soundings show weak elevated instability...
so a few rumbles of thunder could be possible.
The models diverge as we get to Friday. The European model (ecmwf) brings a strong
system with rain changing to snow over southern WI with a good
amount of quantitative precipitation forecast for next Friday and Sat. The GFS does not show this
system at this time.
VFR conditions expected through the taf period. Light winds and
clear skies through today as high pressure begins to slide east of
the region. A trough of low pressure approaches from the northwest
tonight. Look for increasing middle and high level clouds...along with
south to southwest winds. We could have some low level wind shear
issues beginning about 09z sun and continuing into Sun morning.
Increasing south to southwest winds ahead of an approaching trough of
low pressure will bring Small Craft Advisory conditions after 06z
sun. A Gale Warning then GOES into effect at 15z sun with winds
subsiding by middle afternoon on Sunday.
Dewpoints will likely mix out this afternoon with a few locations
possibly dropping into the single digits. However...winds will
remain light with temperatures holding in the middle to upper 30s.
Lm...Small Craft Advisory from 4 am to 10 am CDT Sunday for lmz645-
Gale Warning from 10 am to 4 PM CDT Sunday for lmz643>646.
Small Craft Advisory from 1 am to 10 am CDT Sunday for lmz643-
today/tonight and aviation/marine...Davis
Sunday through Friday...mrc