Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 170838

Area Forecast Discussion
National Weather Service Lincoln IL
338 AM CDT Mon Jul 17 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 321 AM CDT Mon Jul 17 2017

High pressure returning to control the beginning of the work week
as a front slowly moves through the southern extent of the state.
Even behind the boundary, however, summer-like temperatures in
the 80s can be expected today with light winds and mostly sunny
skies later in the morning. Some low level clouds across the
region just behind the boundary a little slow to move out. Very
weak pops over the southern portions of the state invof the slow
boundary. Otherwise, quiet in the short term, and overnight lows
in the 60s.


.LONG TERM...(Tuesday through Sunday)
ISSUED AT 321 AM CDT Mon Jul 17 2017

Story in the remainder of the forecast has not changed. Hot and
periodic chances of showers and thunderstorms with some
uncertainty with the trajectory of the waves from midweek on.
The ridge aloft over the southwestern portions of the country
starts broadening through the southern half of the country,
putting Central IL on the cusp between weak NW flow and weakly
zonal flow/very weak gradient. A general warming trend kicks in
again, resulting in another hot week. The mid levels maintain a
warming trend throughout...and have continued to bump the temps in
the latter half of the week a degree or two above most
guidance...which will result in heat indices back into the low
100s. Portions of Central IL will be moving into heat advisory
territory for Wed-Fri most likely...with heat indices around 105F
at peak heating. Not putting out headlines just yet as there is
still significant spread in the guidance...and not just the bias
corrected version. Should Saturday continue the heat trend, and
the temperatures move up too much more...the prolonged heat may
require a different headline. But plenty of time to hold for a few
more details.

The ECMWF and the GFS are slowly evolving into a more consistent
message as to the strength and northern extent of the ridging
aloft as a series of quick waves top the ridge. So far, Central
Illinois is on the edge of the precip for the most part, with a
glancing blow to the north and northeastern portions of ILX CWA
starting Thursday. The warm air out of the SW and the cooling
impact of the showers to the north and northeast will help to
further define a developing boundary at the surface...providing a
focus for waves into the weekend as the front settles into the
region. Entirely too early to call the location of that boundary
with any certainty at this point.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1249 AM CDT Mon Jul 17 2017

Models not necessarily handling the MVFR cigs over Central IL
tonight, so btwn now and sunrise, forecast will be dominated with
tempos to MVFR or right at the MVFR/VFR break. Winds more ENE this
evening...becoming more NNE by morning with the low clouds moving
off to the south...then VFR beyond 12z or so, given appropriate
eroding of the llvl clouds.




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