Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Lincoln Illinois
1108 PM CDT Sat Jul 4 2015
issued at 854 PM CDT Sat Jul 4 2015
Weak high pressure will settle off to our east over the next 12 to
18 hours continuing to bring a rather quiet weather scene to
central through southeast Illinois. May see some patchy fog form
again towards morning with forecast soundings suggesting any
shallow ground fog will dissipate rather quickly Sunday morning.
After that...look for afternoon highs on Sunday a few degrees
warmer than today with most areas within a few degrees of 90.
Current forecast has a good handle on the situation for the
overnight hours...as a result...no evening update will be
issued at 252 PM CDT Sat Jul 4 2015
A nice 4th of July night lies ahead for central/southeast Illinois for firework
displays at dusk as weak high pressure 1017 mb over central Illinois
drifts slowly into the Ohio River valley on Sunday morning.
Scattered diurnal driven cumulus clouds of 4-5k feet will dissipate at
sunset leaving just some thin cirrus clouds along with some hazy
smoke from Canadian wildfires originating over the northern half of
Alberta and Saskatchewan. With fair skies...light to calm
winds...and temperatures settling toward dewpoints of 60-65f
overnight...patchy fog should once again develop after midnight
especially southeast of the Illinois River. Could even see patchy dense fog
appear in a few spots though hrrr not as aggressive with fog
formation as it was last night. Any shallow fog that does develop
should lift quickly by middle morning Sunday.
Long term...(sunday through saturday)
issued at 252 PM CDT Sat Jul 4 2015
Main concern remains with the track of the incoming frontal boundary
early this week. Latest NAM model has slowed down quite a bit and
has it just entering the forecast area at sunrise Tuesday...while
the remaining models continue with their earlier trends of being
just east of I-55 by that time. A blend of the GFS and European model (ecmwf) was
used for the early week weather.
Have limited mentionable pop's Monday afternoon to areas along and
west of the Illinois River...with the main show coming Monday night
and Tuesday. GFS continues to advertise copious moisture with this
system...with precipitable water values in the 2-2.25 inch range.
Such values linger across areas along/south of I-70 into
Wednesday... although it is also a bit further north than the European model (ecmwf)
on stalling the front in southern Illinois. Will need to watch the
heavy rain potential if this indeed stalls over our area...but in
the meantime will continue the likely pop's south of I-70 through
Wednesday. Any severe weather would most likely be Monday
night...but potential remains low (5% on latest Storm Prediction Center day3 outlook) as
the front would be arriving at an unfavorable time.
Longer range models are trending more toward a northward surge in
the front...in response to a shortwave trying to eject northeast
from the Southern Plains. However...the upper patterns are showing a
fair range in these models...with the European model (ecmwf) having more of a split
flow converging just to our south and the GFS with it more overhead
or just to our north. This will affect where exactly to focus the
higher pop's late in the week...but have limited them to around 40%
until more agreement comes into play.
Aviation...(for the 06z tafs through 06z Sunday night)
issued at 1105 PM CDT Sat Jul 4 2015
Main forecast concern will be with the threat for MVFR/IFR visibilities
in fog between 09z and 12z Sunday...with VFR conditions expected
for the rest of the forecast period. A mostly clear sky...light
wind and abundant low level moisture will lead to some patchy
fog across the terminal sites early Sunday morning. Latest short
term models suggest cmi...Dec and spi may see the lowest visibilities
in fog/haze. Forecast soundings suggest any shallow fog that does
form should quickly lift by 13z/8am...after which just some
scattered cumulus will develop with bases of 2500-3500 feet
expected by late morning/early afternoon. As has been the case
over the past couple of days...surface winds will not be a factor
again on Sunday with a southerly wind developing during the day
at 10 kts or less.