Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
329 am CDT Monday may 4 2015
Today and tonight...forecast confidence is medium.
The cold front will be south and east of the area near sunrise
this morning...with any remnant rain in the far east exiting
quickly as well. Subsidence in the wake of this complex...which
has developed a mesoscale convective vortex...should bring most of
the area dry conditions this morning into about middle afternoon.
We start to see some Omega return later this afternoon with the
approach of the next middle level short wave for tonight. The low
level return flow will provide some warm advection north of the
surface boundary. So...will begin to introduce some small probability of precipitation across
the far south later this afternoon and steadily increase the probability of precipitation
overnight as the next wave and better warm advection moves in.
There are differences in the models with respect to how far north
the precipitation will get tonight...with the NAM/Canadian and high res
arw/nmm the most aggressive. The GFS and the European model (ecmwf) mostly keep the
precipitation across the far south. Will blend.
Short term...Tuesday through Wednesday night...forecast
confidence is medium.
Models are in general agreement with having stalled frontal
boundary south of the area Tuesday shift slowly northward Tuesday
night...then northward into the area Wednesday before moving north
of the area Wednesday night.
The models have a fair amount of focused warm air advection/850
mb convergence/frontogenesis response shifting northward through
the area Tuesday into Tuesday night. NAM more aggressive with
frontogenesis response than GFS Tuesday. 500 mb vorticity maxima
move through Tuesday as well.
Kept higher end probability of precipitation Tuesday morning in the south and east...with
the best upward vertical motion fields...then lower probability of precipitation in the
afternoon and night. Onshore winds will bring cooler temperatures
across the area...especially near Lake Michigan.
Warm sector airmass then moves into the region following the warm
frontal passage later Wednesday into Wednesday night. 850 mb low
level jet develops and focuses moisture transport later Wednesday
into Wednesday night to the west of the area.
Continued chance probability of precipitation for Wednesday with the frontal
passage...and lower Wednesday night with best upward vertical
motion fields to the west of the area. Warmer temperatures are
forecast Wednesday inland...with cooler readings again near the
lake. Hopefully the area will continue to get rounds of beneficial
rainfall during the Tuesday to Wednesday night period.
Long term...Thursday through Sunday...forecast confidence is
GFS/European model (ecmwf) are in some agreement with bringing a cold front
eastward toward the area Thursday...then across Thursday night or
Friday. The European model (ecmwf) is quicker than the GFS with the frontal
passage. Kept consensus model probability of precipitation going for Thursday into Friday
given some uncertainty. Warm temperatures are expected across most
of the area...with south to southwest winds.
GFS/European model (ecmwf) then try to bring low pressure slowly northeastward from
the southern High Plains Saturday into north central Iowa later on
Sunday. Several 500 mb vorticity maxima shift northeast through
the area during this time...with warm front approaching the area
Sunday. Kept consensus model probability of precipitation going for this period as well.
Mild temperatures look to continue...though it may be cooler near
A cold front has shifted just south of the state line early this
morning...and a light northwest flow remains.
An area of MVFR/IFR ceilings/visibilities has developed over southwest WI in
the wake of the rain early this morning. It looks like it will be
a threat for kmsn...but not confident it will move into
kmke/kues/kenw. These lower conditions should begin to improve
after sunrise...when increased flow and deeper mixing begin to
break it up. That might take until 9 am or so.
In general then...VFR conditions will prevail across the area
through this evening. Winds will turn to the northeast by early
afternoon along the Lake Shore. As always...there is a risk for a
brief reduction of ceilings...as cooler air flows in off the lake.
The taf sites should be dry through at least early evening.
Thereafter...the front to the south will begin to head north as
the return flow from the south increases. A middle level wave
approaching at the same time should result in another round of
showers and storms spreading north later this evening and
overnight. MVFR ceilings/visibilities are possible in the heavier showers and
Today/tonight and aviation/marine...Davis
Tuesday through Sunday...wood