Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
255 am CDT Wednesday Sep 17 2014
Today and tonight...forecast confidence is high.
A weak pressure pattern will continue across Wisconsin today as high
pressure has moved off to the southeast and weak surface troughing moves
into northern Wisconsin. An area of middle level clouds just upstream
early this morning is a associated with a middle level short wave that
will dive southwest of Wisconsin today. Some of the clouds should
spread across the area briefly...mainly west of southeast WI. Temperatures
will be about 5 degrees warmer today.
The surface trough and a cold front up north will drop south across the
area tonight...accelerating down the lake in typical fashion. The
front should reach Sheboygan by midnight and Kenosha to Madison by 4
am. The models show a decent amount of low level moisture that
should translate into some low cloudiness for a time behind the
front. That will continue into Thursday. High pressure will settle
in behind the front.
Thursday - confidence...medium
surface high ridging into the area in the wake of the back-door
cold front. Models have been consistent in showing higher low
level relative humidity indicative of stratus field associated with low level
Friday and Friday night - confidence...medium
with the high well to the east a southerly flow will ramp up and
bring warmer air into southern WI. 850 warm air advection is pretty
decent with lingering thermal trough of around 7c warming well
into the teens within the 850 warm axis by days end. 925 temperatures
modify to 16-17c. So going forecast of temperatures into the 70s looks good.
Bulk of precipitation chances north of the County Warning Area closer to stronger 500
westerly flow and shortwave activity. Models vary with respect to
location of precipitation. NAM has main focus to our southeast while the
other models slowly expand probability of precipitation into the County Warning Area as the surface/850
Trough Draw closer. Allblend probability of precipitation pretty much keying on the latter
scenario at this time so went that direction with respect to probability of precipitation.
Saturday and Saturday night - confidence...medium
the European model (ecmwf) and to a lesser extent the GFS show activity ongoing
from Friday night into early in the day Saturday with the aid of
the 850 low level jet. 00z Euro now shows later day/evening
development to our south. The GFS hints at this and extrapolate of the
NAM is trending that way as well. County Warning Area becomes situated within
entrance region of 850 jet. But there are still some timing
differences on the shortwaves in the flow so will not make major
changes to forecast at this point. With enough pre-frontal heating
prior to frontal passage...certainly plausible that storms refire
within County Warning Area.
Sunday - confidence...medium
upper flow proggd to be strongly cyclonic by the GFS and Euro and
much less so from the Gem. The GFS has precipitation in this pattern and
the European model (ecmwf) now hinting at some light precipitation as well. Thus hard to
ignore the slight chance pop generated by the allblend.
Monday and Tuesday - confidence...medium
lingering cyclonic flow proggd by the GFS/European model (ecmwf) suggests some
concern for rain showers potential Monday. May eventually need a pop
though GFS looks sheared with still some timing differences. Will
stick with the dry look for now. European model (ecmwf) shows a benign weakly
anticyclonic flow for Tuesday. GFS a bit more amplified and slower
with departing upper trough.
Aviation/12z tafs/...any morning fog will burn off shortly after
sunrise. A weak pressure pattern will continue across the area into
the evening hours...with VFR conditions continuing. A trough and
associated cold front will drop south into the area after midnight
tonight. The front will accelerate Down Lake Michigan resulting in
a period of brisk northeast winds for kmke/kues/kenw from about
06-09z Thursday. In addition...it looks like a period of IFR ceilings will
develop in the cooler...moist air behind the front and then linger
into Thursday before lifting and scattering out.
Marine...winds will quickly increase out of the northeast tonight as
a cold front drops Down Lake Michigan. Wind gusts will approach Small
Craft Advisory criteria for a few hours just behind the front and
diminish early Thursday morning. Waves are expected to rise to around
4 feet for up to 6 hours and then subside. Therefore at this time...
we are not planning on issuing a Small Craft Advisory for this
Today/tonight and aviation/marine...Davis
Thursday through Tuesday...collar