Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
255 PM CDT Friday Aug 1 2014
Tonight - confidence...medium
upper trough with the associated cold air aloft and ripples
within the flow will maintain rain showers/thunderstorms and rain into the evening hours.
With little shear and decent middle level lapse rates expecting hail
to continue to be the dominant threat. Lake breeze clearly seen on
kmkx radar translating westward could result in some boundary
interactions. Mesoscale models show a gradual decrease in activity in
the evening hours and this makes sense given the loss of heating.
However will need to watch for some of this hanging on a bit
longer with tail of Canadian vorticity maximum arriving into southern WI between
Saturday - confidence...medium
shortwave trough shifts to the east and middle level flow takes on
more of an anticyclonic look. At the surface weak high pressure
will be dominant. BUFKIT soundings still show 500-1000 j/kg of
cape. Forcing not clearly evident but models are showing
quantitative precipitation forecast...especially the GFS. Will have some small probability of precipitation in there for
now with some lingering cold air aloft and weak low level
convergence though expecting pretty spotty coverage if anything
probability of precipitation.
Sunday - confidence...medium
pressure pattern remains weak across the upper Midwest with weak
surface high shifting to the southeast. This sets up a subtle
return flow. In the upper levels the anticyclonic flow becomes
slightly cyclonic once again. The prominent forcing related to any
upper level speed maximum or vorticity action looks to remain more to the
north of the County Warning Area. Even the 850 flow looks somewhat anticyclonic.
Hard to latch onto much of a trigger. With all the models showing
quantitative precipitation forecast it is hard to ignore and if something develops to our northwest and
rides down in the flow...that is a scenario hard to ignore...so
will go with the consensus of the quantitative precipitation forecast and MOS guide and have a
chance in there.
Sunday night through Monday night - confidence...medium
forcing parameters become a bit better this period with upper
flow becoming increasing cyclonic. Low level convergence increases
as surface boundary gradually sags towards southern WI. Noting some
upper divergence as well with more favorable jet action within the
increasing upper flow.
Tuesday and Wednesday - confidence...low
Gem and European model (ecmwf) show an active northwest flow while the GFS is
essentially keeping things on the quieter side. Both the GFS and
Gem Show Low pressure passing south with potential for an mesoscale convective system to
ride along and near an 850 baroclinic zone. This would be helped
along by a stronger northwest-southeast jet maximum dipping south with associated
upper divergence. For now will ride with the allblend probability of precipitation
favoring the consensus of the European model (ecmwf) and Gem at this point.
Thursday and Friday - confidence...low
the Gem and European model (ecmwf) show high pressure and drier regime taking
hold. The GFS a bit quicker on bringing in some return warm air advection induced
precipitation. The GFS continues to look more aggressive on bringing
substantial convection in for Thursday night and Friday while the
European model (ecmwf) is less dramatic. With the upper flow looking overall
unsettled will not alter the allblend probability of precipitation at this time.
Aviation/00z tafs/...a mostly VFR period with a couple of
concerns. First will be the ongoing storms sliding southward into
southern WI with the cold upper trough still across the area. Shear
not conducive to impressive storm organization though middle level
lapse rates supportive of hail potential with any of these pop up
storms. After storms diminish this evening any lingering cloud
cover will clear off. With light winds...potential for some fog
development. This is handled well in going gridded forecast so no
major changes planned in this regard. Middle level flow becomes less
cyclonic though lingering low level boundaries and instability may
end up generating a few more rain showers/thunderstorms and rain on Saturday.
Tonight/Saturday and aviation/marine...collar
Saturday night through Friday...collar