Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 201544
Area Forecast Discussion
National Weather Service Lincoln IL
1044 AM CDT Sun Jul 20 2014
ISSUED 1039 AM CDT Sun Jul 20 2014
Warmer and a bit muggier to start the day...with some early
morning fog burning off quickly for the region. Light southerly
winds today and more fair weather clouds and some cirrus streaming
in overhead. Forecast doing well, including hourly temps. Have
refreshed the grids with a slightly denser cloud cover in the
southeast with an earlier cu field developing. No major updates
necessary at this time.
ISSUED 628 AM CDT Sun Jul 20 2014
Localized IFR ground fog around CMI should dissipate by 13z. Brief
MVFR fog conditions could still affect DEC or PIA through 13z,
otherwise VFR conditions will prevail for most of the next 24
hours. A return of MVFR fog is indicated in the forecast soundings
for CMI later Sunday night, so 4SM BR was included after 21/10z.
Weak high pressure will slowly drift east of IL today and tonight,
so another day of light south-southeast winds is on tap. Sustained
winds will remain below 10kt at all terminal sites.
Cloud cover will remain VFR, with mainly SCT040-060 developing in
the heat of the day, and dissipating with sunset.
ISSUED 225 AM CDT Sun Jul 20 2014
Stagnant weather pattern resulting in another quiet early morning
across the forecast area. Have been seeing some locally dense fog
mainly along the Wabash River in the far southeast CWA, although
local visibilities are down to 1/2 mile as far west as Flora at 2
am. Latest upper air analysis showing zonal 500 mb flow along much
of the U.S./Canadian border to the northern Plains, then opening
up into a broad upper trough across the Midwest.
The main forecast challenge remains with rain chances from late
Tuesday through Wednesday afternoon, as a cold front pushes
through the area.
SHORT TERM...Today through Wednesday:
Not much change in the forecast through Tuesday. Large 500 mb high
over New Mexico will continue to build to around 600 dm by late
Tuesday evening, resulting in a gradual expansion of hot and humid
conditions eastward into the Midwest. The hottest day will be
Tuesday, with highs in the lower 90s widespread, with heat index
values near or just above 100 across the Illinois River Valley.
Upper trough riding along the top of the ridge will drop southeast
later Tuesday, dragging a surface cold front through the Midwest.
The NAM tries to make the front stationary Tuesday night over the
area, while the remaining model suite is more progressive with the
front generally moving through Wednesday morning. Highest PoP`s
will be west of I-55 Tuesday night and have increased them to
around 60% there. The southeast CWA should remain dry until
Wednesday morning as the front approaches. Not expecting a
significant severe threat given the arrival time. Some lingering
showers/storms will continue through Wednesday across the
southeast CWA, but areas I-72 north should be dry by midday as
high pressure begins to build from the north.
LONG TERM...Thursday through Saturday:
Brief shot of cooler conditions on tap Thursday and Friday, with
temperatures and humidity similar to what we have seen over the
last day or two. High pressure over the Great Lakes will keep us
dry through Friday. Past there, focus shifts to potential MCS
activity Friday night sliding down the upper ridge, which will be
re-establishing itself along and west of the Rockies. Latest ECMWF
has shifted a bit further west with the track of the MCS and
largely misses us, but the GFS has kept it over us the last couple
runs. Have kept the trends essentially in place for now.