Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
409 PM CDT Thursday Jul 31 2014
Tonight and Friday...forecast confidence is medium.
Scattered to numerous showers and thunderstorms will continue across
mainly the northeastern counties into the early evening hours.
Should also see isolated to scattered showers and a few storms to
the south and west of there into the early evening. These were being
driven by passing 500 mb vorticity maximum clipping the northeastern
portions of the area...along with surface trough from east central
to northwest Wisconsin. 500 to 800 j/kg mean layer cape and mixed
out low levels also helping out. Could see isolated large hail with
strongest storms in the northeastern counties...with pea to dime
size hail more likely.
Activity should diminish during the early evening hours. Left lower
end probability of precipitation in through the evening in the north for any stragglers.
Should see partial clearing by later tonight into early Friday.
Light winds with this may lead to light fog across portions of the
area. For now...did not mention in forecast...but may need watching
as dew points remain in the upper 50s. Lows should drop into the
upper 50s to lower 60s.
Another round of showers with some thunderstorms are forecast for
Friday afternoon...as another 500 mb vorticity maximum moves
southeast into the area...and combines with weak surface confluence.
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 expected...though isolated large hail could not be
ruled out. Highs should reach the upper 70s east to lower 80s West.
Lake breeze will cool things off near Lake Michigan in the
Short term...Friday night through Sunday night.
Friday night and Saturday...forecast confidence high
Short wave deepens/sharpens southern portion of trough over the Lake
Michigan region as center of upper low...that has been nearly
stationary over the James Bay/Hudson Bay area...finally begins to
lift away to the northeast. Initial forcing with short wave trough
lingers into Friday evening...then weakens overnight as vorticity maximum
dives southeast out of the region.
Main trough axis remains in the vicinity Saturday. Will keep low
chance probability of precipitation in the southeast where forcing associated with vorticity
maxima rotating around its base will affect mainly the southeast.
Lows in the upper 50s expected Friday night...with enough sun for
highs Saturday around 80 in the west... with clouds...onshore
winds and the scattered precipitation holding readings in the 70s in the
eastern third of the County Warning Area.
Saturday night through Sunday night...forecast confidence medium
High pressure and middle-upper level ridging finally move across
region bringing dry weather Saturday night through Sunday
morning. Then yet another short wave in the active west-northwest flow...and
a surface trough that begins to sag south through the
state...bring precipitation chances back to the northern County Warning Area by Sunday
afternoon...and all but the far SW by Sunday night.
Not much cooling so lows around 60 and highs in the 80s away from
Long term...Monday through Thursday. Forecast confidence medium
Off and on showers and thunderstorms through the extended as
occasional short waves move across the region while the surface
boundary slowly sags into southern Wisconsin...becoming a focus
for precipitation development. A low-amplitude wave deepens as it moves
from the plains into the western Great Lakes Wednesday and
Thursday...bringing a better chance of showers and storms. Near
normal temperatures Monday and Tuesday will cool Wednesday with
easterly winds behind surface boundary as it sags south of the
state and stalls. Boundary returns northward Thursday as a warm front
but highs will only reach the upper 70s with clouds and higher
VFR conditions are expected most of tonight and Friday across taf
sites. Scattered to broken diurnal cumulus will linger into early
this evening. Isolated to scattered showers and thunderstorms are
forecast into early evening. Most of the activity may remain north
of taf sites. For now...will just use vicinity shower wording in
tafs due to timing/placement uncertainty. Small hail and brief gusty
winds are possible in strongest storms.
Light to moderate west winds are expected into early evening. They
may back southeast briefly at Milwaukee and Kenosha after 22z due to
Quiet weather is then expected tonight into Friday morning. Light
winds and partial clearing should allow for MVFR category light fog
at Kenosha/Madison/Waukesha taf sites between 09z and 13z Friday.
Another round of scattered to broken cumulus...with scattered
showers and thunderstorms...are forecast for Friday afternoon.
Vicinity shower/thunder wording will be used again for this period.
Small hail and gusty winds are possible in the strongest storms.
Light south winds are expected...becoming southeast at the eastern
sites in the afternoon with lake breeze.
Tonight/Friday and aviation/marine...wood
Friday night through Thursday...rem