Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 250451
Area Forecast Discussion
National Weather Service Lincoln IL
1151 PM CDT Thu Jul 24 2014
ISSUED 900 PM CDT Thu Jul 24 2014
Pcpn that was moving across Iowa continues to diminish as it moves
toward the area. Not expecting any pcpn from this in the cwa.
Skies remain partly cloudy as only high cirrus covers the central
part of the state. Winds are very light, but dewpoints are
relatively low, so not expecting any fog overnight. Current
forecast still looks good, so no update required at this time.
ISSUED 1151 PM CDT Thu Jul 24 2014
VFR conditions will continue overnight and through tomorrow at all
TAF sites. Scattered cirrus is over the area now, but an MCS could
develop out west and then move toward the area overnight. However,
as it moves into the area, expecting it to diminish, like the one
from this evening. So only expecting some showers and mainly in
the morning at PIA and BMI. Not confident about showers at the
other sites so will leave out for now. Outflow boundaries from
this pcpn could lead to more possible showers tomorrow evening.
For now will just have VCSH at PIA/BMI and CMI. Will leave SPI and
DEC dry. Main cloud cover will be mid clouds through the period
with some scattered CU during the daytime hours. Winds will be
light and variable overnight but then become southerly remainder
of the period.
ISSUED 210 PM CDT Thu Jul 24 2014
SHORT TERM...Tonight through Sunday
Main forecast concern this period will be timing and coverage of
convection as a series of shortwaves track southeast across the
region. Already seeing a band of elevated storms over parts of
northwest Iowa tracking south-southeast with additional clusters
of storms to the northwest over the Dakotas in a zone of low and
mid level warm advection. Will maintain low chance POPs for our
counties to the west of the Illinois River well after midnight.
Forecast soundings thru tomorrow morning characterized by a dry
and stable atmosphere over the entire region and that will steadily
change as a warm front shifts northeast into our area by late in
the day or at night. Still appears the better chances for showers
and storms will be across the north Friday, but based on the
movement of the storms over northwest Iowa, we may have to watch
our west and southern counties if the trajectories hold. Warmest
temperatures Friday will be across the south and west where cloud
cover and rain threat will be minimal. We should see temperatures
climb into the lower 80s there with upper 70s across the north and
east where cloud cover will be a little thicker.
Warm front should begin to lift north of the area tomorrow evening
with the better convection chances along and to its north. Will
maintain the higher pops across the north closer to the boundary
with progressively lower pops south Friday night. A rather stout
elevated mixed layer or cap will invade the region on Saturday
bringing hot and humid weather back into the region. Big question
becomes convection chances and coverage during the day Saturday
as the area will see a significant cap hold until late in the day.
Several of the forecast soundings indicating the cap weakening
after 20z on Saturday as a frontal boundary edges into the forecast
area so pops will be higher in the afternoon with likely pops
looking reasonable Saturday night with precipitable water values
above 2 inches and warm cloud depths of over 13000 feet indicating
the likelihood for heavy rainfall in parts of our area.
The upper wave should begin shifting across our area Sunday
morning with showers and thunderstorm chances gradually lowering
from west to east during the afternoon. Possible redevelopment
of storms across our far east but not very confident on that,
especially if a large MCS affects the area later Saturday night
into Sunday. Rain chances, other than our far eastern counties,
will diminish Sunday evening with much cooler and less humid air
filtering southeast into the forecast area on Monday.
LONG TERM...Monday through Thursday
Ensembles showing good agreement with the deep trof expected to
form over the eastern U.S. bringing another bout of unseasonably
cool weather for most of this forecast period. Only challenge,
other than how cool the night-time lows will get, will be if
the very cool temperatures aloft will be able to produce some
diurnally driven showers each afternoon. At this point, it appears
that is a low probability event, so will continue to hold on to
our dry and cool forecast thru Thursday.