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Area forecast discussion 
National Weather Service Lincoln Illinois
255 PM CDT Friday Oct 9 2015

Short term...(tonight)
issued at 253 PM CDT Friday Oct 9 2015

Cooler air filtering into the region and persistent cloud cover
blocking the sun, are both keeping the temperatures down in central
Illinois this afternoon. Northerly winds are expected to weaken
somewhat after sunset, as the high pressure ridge axis drifts closer
to the forecast area. Models do not have a good handle on the low
clouds that are out there, and concern is that the clearing may be
too quick. Have hung onto the clouds a little bit longer, but
eventual clearing after midnight should allow the temps to drop to
forecast lows, particularly west of I-55.


Long term...(saturday through friday)
issued at 253 PM CDT Friday Oct 9 2015

Expansive high pressure will be in control of the weather through
the weekend. The surface ridge axis will pass southeast of our
counties by late afternoon, allowing the southwest winds to increase
during the afternoon. Forecast soundings show plenty of dry air by
12z/7am Saturday, so we expect full sun and SW winds to help high
reach into the upper 60s. Gusty SW flow on Sunday will continue the
warming trend, with 850mb temps climbing into the 16-18c range.
Mixing those temps to the surface should yield highs in the upper
70s to low 80s.

There remains consistent agreement among the 12z models about the
next cold frontal passage late Sunday night and Monday morning. Despite a 3-5
hour period of focused lift with the front, evident in the Omega
time height analysis, very limited moisture will be present for
precip generation during the fronts time in Illinois. There
appears to be increasing support for rain showers Monday afternoon
once the front reaches Indiana and eastward, as the front taps
into moisture from over the southeast states. We will continue a
dry forecast in our counties for Monday afternoon, but showers
could be close by across the Indiana border. The cold air will lag
enough behind the front for high temps to reach the mid to upper
70s early Mon afternoon.

A brief shot of slightly cooler air will arrive behind that front,
keeping high temps on Tuesday in the upper 60s.

Northwest flow aloft will set up a series of fast moving shortwaves
for the rest of the week, with rapid periods of warming and cooling
ahead of and behind the waves. The next one is projected for Tuesday
night and another on Thursday morning. Neither of them are
expected to have sufficient moisture and dynamics to produce any
precipitation in our forecast area. The fast progression of the
systems will limit the affects of potential airmass changes, so
highs Wed and thur should generally remain in the low 70s.
Slightly cooler air behind the Thursday wave will limit highs on
Friday to the upper 60s, which is normal for this time of year.


Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1253 PM CDT Friday Oct 9 2015

Persistent stratus in the wake of the cold front passing through
central Illinois hanging right around the 3000ft mark, just on the
MVFR/VFR break. Expect to continue. Forecast models not doing well
with the cloud cover that is out there, and as a result, slow to
clear out as quickly from erosion/mixing. If cloud deck does not
clear before sunset, will likely hold on to it for a while until
the back edge of the shield (over Iowa now) makes its way through
the region. Beyond sunrise, skies clearing and light northerly
winds in the morning.


Ilx watches/warnings/advisories...


Short term...hjs
long term...shimon

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