Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
332 am CDT Thursday Apr 2 2015
Today...forecast confidence medium.
Awaiting showers over NE Iowa in region of moisture convergence
along surface trough and stronger 700 mb Omega ahead of middle-level
trough axis that will accompany lead vorticity maximum across region this
morning. Leading line of showers and thunderstorms that moved into
west central Wisconsin last evening eroded as they moved away from
this better forcing and were outrun by outflow boundary. Wind gusts
should also diminish with approach of surface trough and as 60-70kt
low-level jet heels over to the east.
Have kept mention of isolated thunderstorms though elevated cape
almost non-existent on latest rap forecast soundings. However...
Storm Prediction Center mesoanalysis shows area of 500 j/kg most-unstable cape that
could brush southern Wisconsin so can/T rule out a rumble or two of
Have precipitation chances in the far southeast after 18z until 850
mb trough clears to the east. 925 mb temperatures rebound between 18z and
00z and enough afternoon sun to bring high temperatures in the 60s.
Actual cold front finally drops through southern Wisconsin after
midnight tonight after passage of weak secondary wave. Clouds and
mixing with west to northwest winds of 5 to 10 miles per hour will keep lows
int eh middle to upper 30s.
Friday and Saturday...forecast confidence...medium
Could see a little light rain clip the south Friday morning...as a
shortwave approaches. Rain chances then focus in the east during
the afternoon due to decent low level convergence. May even see a
mix with snow later in the afternoon toward the lake as colder air
Should be dry Saturday...with southern Wisconsin sitting between
high pressure to the south and a passing low to the north.
Temperatures will be cooler Friday...but will warm back to a few degrees
above normal for Saturday.
Saturday night through Wednesday...forecast confidence...medium
Could see some precipitation at times from Saturday through Tuesday...as
a series of systems move through a mainly stalled frontal zone.
There remains a bit of uncertainty with this portion of the
forecast due to model differences in frontal placement and thus
temperatures and precipitation chances. If the front sneaks farther north...would
expect much milder temperatures and a better chance for thunder. The
southern solution would result in persistent winds off the
lake...cooler temperatures...and less instability. Continued the down the
middle approach between the various model solutions for now.
Looks cool and dry Wednesday under high pressure.
Will make some adjustments prior to issuance on timing of showers
into taf locations and their impact. Expect VFR conditions with only
brief MVFR ceilings/visibilities per upstream observations under the showers
and isolated thunderstorms. Have kept mention of isolated
thunderstorms though elevated cape almost non-existent on latest rap
forecast soundings. However... Storm Prediction Center mesoanalysis shows area of 500
j/kg most-unstable cape that could brush southern Wisconsin so can/T
rule out a rumble or two of thunder.
Precipitation should clear kmsn by 18z...and eastern taf sites between 20z
and 21z. Looking for VFR conditions through the remainder of the
Fire weather conditions not as critical as yesterday with expected
0.2 to 0.3 inch rainfalls moistening fuels. Cooler temperatures and
lower winds also lowering the threat...though lower dew points will
bring relative humidity values down to around 25 percent in the west
Will keep current end time to Small Craft Advisory as winds are
beginning to ease with slackening gradient associated with surface
trough. Lowering winds and veering to an offshore direction after
passage of surface trough will allow waves to subside below criteria
Lm...Small Craft Advisory until 10 am CDT this morning for lmz643>646.
Today/tonight and aviation/fire weather/marine...rem
Friday through Wednesday...ddv