Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
328 am CDT Friday Aug 1 2014
Today and tonight...forecast confidence medium.
Another afternoon with scattered showers and thunderstorms is
expected today. The diurnal chance for pop-up showers and a few
thunderstorms will be there in southern WI for the whole afternoon and
early evening. The best chance for thunderstorms will be tied to the
leading edge of a 500mb shortwave dropping south through WI from
late afternoon through the late evening. Mean layer convective available potential energy will be in
the 800 to 1000 j/kg range with very weak deep layer shear.
Thus...more pulse storms with small hail and gusty winds are
There is some uncertainty with the timing of the best chance. The hi-
res models show more convection during the afternoon and quickly
diminish it during the evening...and the synoptic models focus more
on late afternoon and keep the chance going well into the evening.
Thus...lingered small chance probability of precipitation into the early morning hours.
Surface high pressure will slide overhead late tonight...leading to
light winds and clearing skies. Any areas that get rain this
afternoon/evening will be especially susceptible to fog. Dewpoints
should remain around 60 southwest of Madison and in the upper 50s
elsewhere...leaving small Delta T/dew point values. The MOS guidance is
hitting inland areas hard with areas of dense fog. Given the lack of
widespread fog upstream tonight and the shallow low level moisture
in forecast soundings...opted not to include dense fog in the
forecast for now...with the exception of the WI River Valley.
Highs should reach the upper 70s east to lower 80s West. Lake breeze
will cool things off near Lake Michigan in the afternoon.
Saturday through Monday...forecast confidence...medium
Northwest flow will persist over the weekend into early next week.
Daily shower and storm chances will continue under this pattern.
There is not a well defined synoptic scale trigger for convection
Saturday...though models do seem to be focusing precipitation a bit
within an area of lake breeze convergence.
An approaching shortwave will kick off more showers and storms
Sunday...with the precipitation possibly lingering Sunday night into Monday
as the shortwave moves though.
Should see temperatures right around normal for Saturday through Monday.
Tuesday through Thursday...forecast confidence...medium
Upper level pattern is forecast to become more zonal through the
middle of next week...allowing for a return of a higher moisture
airmass to the area. This could be a more active period of
widespread showers and storms...with some appreciable rainfall
VFR conditions expected once again today and this evening. Areas of
dense fog are possible early Saturday morning...mainly inland
locations. Scattered to broken diurnal cumulus will develop once
again late this morning. Scattered to numerous showers and
thunderstorms are forecast from middle afternoon through the late
evening. Small hail and brief gusty winds are possible in strongest
Today/tonight and aviation...mrc
Saturday through Thursday...ddv