Scientific Forecaster Discussion
fxus63 kmkx 230808
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
308 am CDT Mon Sep 23 2019
Today and tonight...forecast confidence is high...
High pressure will build into the south as the low pressure
system continues to push northeast. This will keep US dry through
the period with clear skies expected by the mid afternoon. The
upper level low remains just to the northeast. Which will bring a
few waves of shortwave energy during the day. However, low and especially
mid level dryness will keep US precipitation free and by the late
afternoon and evening mostly cloud free as well.
Otherwise modest west/northwest winds are expected throughout the
day with temperatures expected to reach the upper 60s to low 70s
with some cooler overnight temperatures in the low to mid 50s. We
could see light enough winds overnight for a bit of patchy fog but
nothing dense is expected.
Tuesday through Wednesday night...forecast confidence is medium.
Much of Tuesday will be dry and with increasing south to
southwesterly flow, temps end up warmer. Highs on Tuesday could
reach into the upper 70s for much of southern Wisconsin. A
strengthening low level jet during the afternoon/evening brings low to mid
60 degree dewpoints back to the region. The biggest question for
this period will be in regards to the potential for any stronger
storms. Forecast soundings have been fairly consistent in showing
a strengthening capping inversion through the day as the low level jet ramps
up. Then during the evening hours as a quick moving shortwave
approaches lapse rates aloft steepen somewhat with MUCAPE topping
out around 500 j/kg. The better deep layer shear is lagging behind
the better instability. So, how would all of this play into the
severe threat? Think that further to the west parameters will line
up better to support robust convective development. Then as the
system kicks east, storms will be moving into a less favorable
environment. We may end up with a decaying line of convection with
the best chances for a stronger storm in the far western portion
of the area. Models continue to try and linger some precip into
Wednesday but think this is overdone and much of Wednesday will
end up dry and have trended the forecast in that direction. Expect
a cooler and breezy day on Wednesday with highs about 5 to 8
degrees below tuesdays values. The biggest change will be felt
in the low temperatures Wednesday night into Thursday morning.
Lows should dip into the 40s for the first time since early
Thursday through Sunday...forecast confidence is low to medium.
Guidance has trended stronger with the frontal passage on
Wednesday with a decent surface high building over the area
through Thursday. This is expected to have an impact on the
moisture recovery heading into Friday. Previous models were quick
to bring moisture back into the area. In addition to that, models
are trending to a more progressive solution and quicker frontal
passage on Friday. Rainfall totals would then end up lower and
this system may not be much of a flooding concern compared to last
nights runs. Since this is the first set of runs showing this
change, will wait before making large changes to the forecast
during this period.
High pressure builds over the area on Saturday providing a brief
round of mild air. Then as we head into Sunday and early next
week, the persistent ridge to the south is forecast to amplify.
This will allow for a return of above normal temperatures heading
into next week. It wouldn't be out of the question to have a few
80 degree temps to round out the month of September.
Showers have moved out of the area and we will thus will be dry
the rest of the day. Breezy west to northwest winds are expected
on today, with a few gusts to around 20 knots. A little fair
weather cu is expected, but should not be too widespread. Winds
will start to diminish with sunset. Some light fog will then be
possible late tonight, though it should remain patchy.
Light to moderate rain may persist over the northern half of the
lake this morning but will quickly push northeast with clearer
skies moving in by the evening. Some breezy west winds may pick
up, especially over the southern half of the lake, during the day
but will start to weaken by tonight. Otherwise waves will decrease
from 3-5 feet this afternoon to 1-3 feet overnight.