Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Green Bay WI
640 PM CDT Sat Oct 25 2014
Updated aviation portion for 00z taf issuance
Short term...tonight and Sunday
issued at 215 PM CDT Sat Oct 25 2014
Main forecast focus to be on temperatures over the next 24 hours as hi pressure
to provide dry and pleasant auntumnal conditions.
The 19z msas surface analysis showed a strong area of low pressure near
Hudson Bay...with an area of hi pressure over the northern plains. This was
producing a strong pressure gradient over the Great Lakes with
wind gusts surpassing 30 miles per hour at times (even a 40+ gust at imt). A
dry air mass over WI allowed for 100 percent sunshine this
afternoon and temperatures responded by reaching the upper 50s north...lower
to middle 60s south.
The area of hi pressure is forecast to move into the western Great Lakes tonight...
bringing mainly clear skies and diminishing winds to NE WI. Not an
ideal radiational cooling night though as boundary layer winds to only
subside to 20 kts and there is already some weak warm air advection underway
toward daybreak. Therefore...a cool night...but not below normal.
Look for min temperatures to range from near 30 degrees north-central WI (perhaps
a few upper 20s possible in the typically colder locations)...to the
upper 30s over Door County.
The surface hi slides to our east on Sunday and brings a return flow
into WI as winds back to the west in the morning and eventually
become S-southeast later in the afternoon. Warm air advection to continue through Sunday as 800 mb
temperatures rise to around +10c by 00z Monday. Low-level moisture still
lacking and warm front to still be situated well to our south over the
middle-MS valley...thus other than increasing hi clouds through the day...
a mostly sunny Sunday is anticipated. Despite the sunshine and
warm air advection...maximum temperatures will actually be cooler than Sat mainly due to the
cool start to the day. Readings are expected to top out in the middle
50s N-cntrl...to around 60 degrees over parts of central WI.
Long term...Sunday night through Saturday
issued at 215 PM CDT Sat Oct 25 2014
Relatively active period with progressive upper level pattern.
Main weather system early in period is strong trough and associated
surface low that move across northern lakes Monday. 25/12z GFS and
European model (ecmwf) more inline and close to current forecast with respect to
timing. Ahead of the system...some elevated precipitation expected
as strong warm air advection develops ahead of approaching low. Stability
weakens sufficiently such that isolated tstorm could develop.
Should see initial warm air advection precipitation end Monday morning with a break
occurring during the day. With the surface front stalling over
central Wisconsin...low levels will likely remain moist enough
under inversion to keep stratus/drizzle around...though a few
breaks possible. Monday high temperatures will be dependent on cloud
cover. Next area of showers moves across area late Monday/Monday
night ahead of cold front.
Additional showers then possible Tuesday as main upper system
moves through and low-level cyclonic flow behind departing storm
Another small chance of showers Wednesday night as weak clipper system
Much colder air is then set to move in by the end of the week as
Arctic high slides south into north U.S. Upper shortwave/jet energy
may produce rain-->snow showers late Thursday/Thursday night.
Aviation...for 00z taf issuance
issued at 637 PM CDT Sat Oct 25 2014
Clear sies and decreasing winds were found across the forecast
area early this evening. VFR conditions will continue through the
taf period...with only an increase in middle/high clouds expected
Sunday afternoon. Have continued the mention of low level wind shear at all of the
taf sites until 05z-06z...with northwest winds around 35 kts at 1000-1500
feet above ground level.