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Area forecast discussion 
National Weather Service Lincoln Illinois
907 PM CDT Fri Apr 18 2014

issued 907 PM CDT Fri Apr 18 2014

Skies are clear and should remain that way overnight. Could be
some high cirrus moving in, but not until morning. Current
forecast looks to be on track so no update planned at this time.


issued 612 PM CDT Fri Apr 18 2014

VFR conditions will prevail at all taf sites next 24hrs. Expecting
clear skies through the period as the high pressure ridge
continues to move to the east of the area tonight. Winds will be
light this evening but then begin to pick up some and switch to
the east overnight. Then winds will become southeast tomorrow with
speeds around 9-10kts.


Previous discussion...
issued 218 PM CDT Fri Apr 18 2014

Models in very good agreement today well into next week. Looks
like a nice Spring weekend on tap.

Short term...tonight through Wednesday

High pressure building into the Midwest will continue to advect a
dry airmass into Illinois through much of the weekend.
Temperatures at 850 mb will climb 4-8 degrees c between this
morning and Saturday afternoon which should be reflected by
temperatures significantly warmer on Saturday after a cool start.
Boundary layer moisture does increase somewhat late Saturday night
into Sunday and will likely lead to some cloud development which may
inhibit further warming on Sunday, but for now it does appear
that a warmer start to the day and a reasonable amount of sun
should allow temperatures to climb into the 70s.

A northern-stream shortwave approaches late Sunday night into
Monday. This system will be moving into a very dry air mass and
will likely take a while to saturate the column. Instability will
be somewhat limited due to the dry air in place. Cape values of
200-400 j/kg Max are the highest the operational models expect
and that should be after sunset. However, there are some sref
members with higher convective available potential energy to around 800 j/kg. Some scattered
thunderstorms may be possible, but should be limited in coverage
and intensity. Models may be a bit overdone in total qpf, but some
local amounts of 0.50 may be possible in locations that are
impacted by the thunderstorms.

Cold advection behind the system should be limited as shortwave
ridging moves in quickly and 500 mb heights climb quickly almost
100 meters between 12z Tue and 00z Thu in reaction to a stronger
system approaching late in the week.

Long term...Wednesday night through Friday

A stronger system is progged to move out of a broad trough along
the Pacific coast for the later half of next week. The models do
begin to diverge with the strength and timing of this system. As
often is the case, the differ on the amount of the overall energy
of the trough is associated with each ejected wave. European model (ecmwf) is
faster and weaker with this initial wave, while the GFS suggests a
more dynamic system holding off until late Thursday. The GFS would
suggest quiet a warm day Thursday with clouds and only a slight
chance of thunderstorms, while the European model (ecmwf) has a broad precip field
moving in early Thursday keeping temperatures on the cooler side.

Timing of this system will also have a huge impact on the
strength of convection. European model (ecmwf) suggests a lower potential for
strong storms given the ongoing precip on Thursday, while the GFS
suggests a more stormy Thursday late afternoon and evening.

For now will stick with a compromise as we are looking six days
out and will focus on run-to-run consistency as we look to
determine the overall trend.



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