Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Milwaukee/Sullivan WI
337 am CDT sun Apr 20 2014

Today and tonight..forecast confidence medium

A stationary front will remain over central WI along with its surface-
850 mb frontogenesis. Low to middle level warm advection will continue
to the south with scattered high based virga showers already developing
over the northwest County Warning Area. The moisture transport along the front will drift
farther south this afternoon and tonight so have likely probability of precipitation over the
far northwest County Warning Area later this afternoon and over much of the north tonight. Most
of the southern half of the County Warning Area will remain dry today with slightly
better chances of rain tonight.

Warm temperatures still looking good but the degree of cloud cover does
complicate the temperatures somewhat. Have higher confidence for steady
cloud cover over the northern and western County Warning Area...but believe partly cloudy
conditions will exist for at least some of the day over the southeast. Thus
went with some middle 70s over southeast WI and near the Illinois border...away from
the lake. The lake breeze should develop during the afternoon but
temperatures near the lake should be able to warm well into the 60s before
the cooling occurs with the exception of eastern Sheboygan County.

Monday - confidence...medium
shortwave trough with embedded weak vorticity maxima will aid
vertical motion. A weak low pressure system will move across the
area and drag the cold front through in the afternoon. Models are
all develop precipitation with a convective look. BUFKIT soundings are
actually showing some convective available potential energy at or above 1100 j/kg. Any heating and we can
hit low/middle 70s per MOS guidance. Middle level lapse rates are not
impressive. Cips analogs are showing pretty high confidence of
temperatures over 70 and dew points over 55. However cips shows severe
threat low with only marginal hail potential and this fits with
current swody2 outlook of general thunder. Will carry high probability of precipitation
and certainly retain thunder potential.

Tuesday - confidence...medium
chilly airmass settles in with low level cold pool dominating.
850 temperatures drop off to 0 to -2c with a smidge cooler readings on
the GFS. Low level relative humidity forecasts suggest associated with the cold pool
which could hang around a bit especially in eastern County Warning Area.

Wednesday - confidence...medium
high pressure ridge shifts east with southeast low level flow. Middle level
ridge axis approaches. Low level warm air advection starts to increase. However
850 jet core well west of the area through 18z with dry airmass
still in place. Models in sync with keeping precipitation west of County Warning Area
through 18z so flexed out the morning for dry conditions and then
expanded probability of precipitation west to east with time as the low level jet
translates east with better moisture flux increasing with time.

Thursday - confidence...medium
models continue to advertise the approach of a decent shortwave
pivoting towards WI from a broad trough in the northern/Central
Plains. This has attendant downstream cyclogenesis with a
considerable moisture surge to the north. At this time the instability
parameters are skewing the most favored severe threat to the south
of WI...especially on the European model (ecmwf) and Gem. The GFS has some 60 percent values
sneaking into WI. The 0-6km shear is quite impressive but how far
north the warm sector makes it into our area is still a question
mark. At this time surface dews are only proggd into the low/middle
50s. So emphasis being placed to our south. Coordinate with Storm Prediction Center on
this. But still quite a ways off and this day is one to keep a
very close eye on.

Friday - confidence...medium
cold front will have shifted off to the east but low pressure
slow to depart the region. So expecting a showery regime to linger
with low level cold air advection. Several spokes of vorticity
likely to be enhancing lift in addition to the surface/850 trough
axes coming into play.

Saturday - confidence...medium
500 millibar forecasts show a trend towards negative vorticity advection with surface high
pressure building in. Low level thermal trough to linger with 850
temperatures slow to rebound from proggd morning values of -2 to -5c.
Will maintain the allblend probability of precipitation which lends some credence to the
wetter look of the European model (ecmwf) with a glancing shot of some return warm air advection
rain showers into the southern County Warning Area.

&&

Aviation/12z tafs/...VFR conditions expected today and tonight for kmsn
and the southeast WI taf sites. A stationary front will remain over central
WI where the majority of the showers will occur. There will be
relatively small chances for rain tonight from Madison to Milwaukee and
south with better chances to the north. Any showers would be
brief.

&&

Marine...south winds of 10 to 15 knots will allow the waves to be
near 4 feet in the nearshore waters of Sheboygan County this morning.
A Small Craft Advisory is not anticipated at this time but boaters
should remain aware of the marine conditions and forecast.

&&

Mkx watches/warnings/advisories...
WI...none.
Lm...none.
&&

$$
Today/tonight and aviation/marine...gehring
Monday through Saturday...collar