Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
338 am CDT Wednesday Apr 1 2015
Today...forecast confidence high
500 mb ridge axis will be centered over state at 18z today ahead of
short wave trough digging into the northern plains by late this
afternoon. Surface ridge is slowly shifting east with gusty winds
developing in tightening gradient ahead of surface low that deepens
as it tracks through the northern plains/Canadian prairie provinces
then consolidates over eastern Winnipeg tonight.
Warm advection brings 925 mb temperatures up to +16c in the west and 15c in
the east by 00z. This yields highs in the lower 70s far west...and
middle 60s in central sections with onshore southeasterly winds holding highs
in the 45 to 50 degree range far east to around 60 in The Kettle
Moraine. If mixing up to 40+ knots winds around 900 mb on the forecast
soundings occurs late in the afternoon west...it could bring a few
gusts close to Wind Advisory criteria. Will have to be monitored.
Tonight...forecast confidence high
All models are bringing precipitation into the western County Warning Area between 00z and 06z
with a lead impulse...with the GFS farthest east with quantitative precipitation forecast...then
bring stronger short wave across Thursday morning.
Strong warm air advection on strong low-level jet will keep
convection elevated tonight with steep lapse rates above 800 mb.
However elevated cape does not increase until 03z and after with
better 850-700 mb moisture advection ahead of the middle-level trough.
Will trim back beginning of quantitative precipitation forecast until better elevated cape comes
into forecast area. Not expecting any severe with developing
inversion preventing much intrusion of strong winds aloft down to
the surface. Could not rule out a few hail stones. Storm Prediction Center day 1 outlook
has kept marginal risk of severe back to the west...just clipping
the far west-central portion of the state.
Not much of a drop off in temperatures tonight with occluded front/surface
trough centered over County Warning Area at 12z Thursday.
Thursday and Friday...forecast confidence...medium
The cold front will clear the southeast forecast area by late Thursday
morning. Showers can be expected as the front moves through.
Seeing a little elevated instability lingering Thursday morning...so
kept thunder mention going.
Have some low probability of precipitation in the south Friday...as the European model (ecmwf) and Canadian
clip the southeast with some precipitation. The GFS and NAM remain farther
south and dry for this period.
Temperatures will be cooler...but still above normal Thursday. Below
normal temperatures are then expected Friday.
Saturday through Monday...forecast confidence...low
Should be dry Saturday...with southern Wisconsin sitting between
high pressure to the south and a passing low to the north. Could
then see some precipitation at times from Saturday night into Monday...as
a series of systems move through a mainly stalled frontal zone.
There remains a bit of uncertainty with this portion of the
forecast due to significant model differences in frontal placement
and thus temperatures and precipitation chances. If the front sneaks farther
north as in the GFS...would expect much milder temperatures and a better
chance for thunder. The southern European model (ecmwf) would result in persistent
winds off the lake...cooler temperatures...and less instability.
Continued the down the middle approach between the various model
solutions for now.
Afternoon winds and lower dew points helping to push conditions to
near-critical levels today. However minimum relative humidity values
are marginal and temperatures and fuel moisture levels will be below
warning criteria so will handle mention in fire weather discussion
and severe weather potential statement for now. Offices to the west will be closer to headline
levels with stronger winds...higher temperatures and lower relative
Aviation and marine...these sections will be added shortly.
Today/tonight and fire weather/aviation/marine...rem
Thursday through Tuesday...ddv