Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
1021 am CDT Friday Jul 31 2015
Aviation/18z tafs/...west-northwest winds will continue to ramp up with
decent mixing but expect some dropoff this evening with loss of
heating. NAM/latest hrrr want to generate some light precipitation into
SC WI late tonight but will leave mention out of taf at this time.
With surface/850 ridge drawing closer on Saturday expect an
overall lighter wind regime.
Previous discussion... /issued 312 am CDT Friday Jul 31 2015/
Today and tonight...forecast confidence is high.
In the very early term...around or just before 7 am this
morning...there is a weak surface trough passing through coupled with
a middle level trough up above. Higher dewpoints are sneaking up just
ahead of the front and some of the hi res models quickly generate a
few showers across south central areas...then just as quickly wipe
them out as they move southeast. There isn/T much on satellite right
now...just a few clouds over southeast Minnesota. So confidence this is
going to happen is very low. Will be keeping an eye on it though.
Otherwise...look for a very similar day to the last couple. Plenty
of sunshine with very steep low level lapse rates with deep mixing.
Temperatures will be a few degrees cooler than yesterday...but still warm.
Dew points will mix out once again...producing low humidity.
Quiet and pleasantly cool tonight.
Saturday and Sunday...forecast confidence...medium
High pressure will slide southward on Saturday...but should have
enough of a remaining influence to keep it dry through the daytime
hours. Should see a good amount of sunshine...with highs in the 80s
Looks like a decent chance for storms at times Saturday night
through Sunday night. First round Saturday evening and overnight is
expected to come as low level jet strengthens and moves overhead
ahead of an approaching shortwave. Storm Prediction Center is highlighting the southwest
half of the forecast are with a marginal to slight risk of severe
storms. Not surprising given best forecast instability in the
southwest...with 30-40 knots of bulk shear across the forecast area.
Thinking thunderstorm complex will develop upstream and then roll
into the forecast area.
Sunday is a bit of a question mark with precipitation chances. Models
showing a weak wave during the day which could trigger
storms...depending on how quickly things recover after the overnight
round of storms. Currently...models showing quite a bit of cape
by afternoon. Better chance will probably be in the evening hours
as a cold front advances into the area. Given
shear...instability...and current timing of front...thinking some
strong to severe storms possible once again.
Temperatures for Sunday are a headache...with models all over the place.
Will depend on timing of shortwaves and precipitation...and resultant cloud
cover during the day. Pretty good spread in temperatures aloft between
really warm NAM/GFS solutions vs somewhat cooler European model (ecmwf). Stuck close
to consensus blend of solutions given uncertainty.
Monday through Thursday...forecast confidence...medium
Could see a lingering shower or two Monday morning...but otherwise
it looks dry as high pressure begins to build in from the
northwest. Should be dry then Tuesday under the high...with a
couple showers possibly clipping the southwest Wednesday as a weak
wave slides through. Have low probability of precipitation in for Thursday as another wave
traverses the area.
High temperatures Monday/Tuesday look to be within a couple degrees of
normal...cooling a few degrees for Wednesday/Thursday under persistent
northwest flow aloft.
VFR conditions are expected through the taf period. There is a very
small chance of a shower at kmsn before 12z this morning...
associated with the passing of a weak surface trough. Winds will
again be gusty out of the west to northwest from late morning
through the afternoon...diminishing quickly by early evening.
A Small Craft Advisory is in effect from late morning through the
afternoon due to gusty west to northwest winds of 15 to 25 knots.
Winds will diminish quickly early this evening.
Lm...Small Craft Advisory until 7 PM CDT this evening for lmz643>646.
Today/tonight and aviation/marine...Davis
Saturday through Thursday...ddv