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fxus63 kilx 160425 
afdilx

Area forecast discussion
National Weather Service Lincoln Illinois
1125 PM CDT sun Sep 15 2019

Synopsis...
issued at 821 PM CDT sun Sep 15 2019

Clearing skies, light winds, and high pressure will lead to areas
of fog tonight, mainly where significant rain fell earlier on
Sunday. Unseasonably warm temperatures and dry weather will
dominate the region for the first half of the work week.

&&

Update...
issued at 821 PM CDT sun Sep 15 2019

Areas of fog are expected tonight where significant rain fell
earlier today, mainly near and north of I-72. Still some question
about how dense the fog becomes with some lingering cloud cover
and shallow depth of rich moisture (according to evening sounding)
potentially mitigating fog formation. Model guidance is relatively
consistent with this area as well, so will not update fog forecast
in the afternoon package at this point. Otherwise, expect light
winds tonight with high pressure building into the area and a weak
cold front moving in. Lows should generally fall into the upper
60s to perhaps mid 60s.

&&

Short term...(this evening through monday)
issued at 251 PM CDT sun Sep 15 2019

A weak surface front will track across the area tonight. Upper
level support is negligible and with the loss of diurnal
instability, expect a dry frontal passage. High pressure building
in from the west later tonight, will allow winds to go light/calm.
With lingering low-level moisture, added areas of fog where the
more substantial rains fell this morning, mainly north of a
Rushville to Danville line. Will need to monitor for potential
dense fog development late tonight through mid-morning across the
north, which latest high-res guidance is suggesting.

Fog and/or low clouds may be prevalent across the north half of
the County Warning Area through mid Monday morning, as forecast soundings show
shallow moisture trapped under subsidence inversion. This should
erode by late morning. Mostly sunny skies and light northeast
winds will dominate the day, with the surface ridge axis off Great
Lakes high shifting overhead. We will see a return to Summer
warmth with highs in the mid to upper 80s and mid 60s dewpoints.

Long term...(monday night through sunday)
issued at 251 PM CDT sun Sep 15 2019

A deepening West Coast longwave trough will allow upper level
ridging to strengthen from the lower Mississippi Valley, northeast
into the Great Lakes for the first half of the week. With
588-590 dm 500 mb heights through the period and 850 mb temps at
+16-20c, July- like warmth will prevail. 85-90 degree highs are
forecast, and with normal highs dropping into the upper 70s this
week these numbers will be around 10 degrees above normal. However
with east to southeast surface flow off high pressure to the
northeast, dewpoint will stay tolerable in the 60s, keeping peak
heat indices within a few degrees of Max temps.

Wednesday night into early Thursday, a shortwave disturbance will
temporarily flatten the ridge, with thunderstorms likely well to
our northwest. We have a low thunderstorm chance primarily
northwest of the Illinois River as this disturbance tracks east
Thursday. Beyond this system dry weather looks to dominate
through the end of the week, along with more unseasonably warm
temps.

For next weekend, medium range guidance is in good agreement that
the western trough lifts northeast through the plains and into
the Great Lakes. This would bring a more difluent southwest flow
and deeper moisture east into the region. With significant timing
differences on better periods of upper level forcing, low chance
pops from nbm look reasonable at this range.

&&

Aviation...(for the 06z tafs through 06z Monday night)
issued at 1125 PM CDT sun Sep 15 2019

Expect areas of fog developing overnight as a weak surface front
slowly slips southward through the area combined with high
pressure bringing light and variable winds. Very moist conditions
remain, especially north of I-72 where widespread rain fell
Sunday. Questions remain regarding visibilities and ceilings with
fog and/or stratus development, however have incorporated IFR
conditions from 10z-14z at kpia, kbmi, kcmi but only MVFR at kspi
and kdec where it appears likelihood and intensity of fog is
lower. Otherwise, expect VFR conditions with a band of cloud
cover around 5000 ft above ground level slowly moving southward overnight ahead
of the cold front. Scattered diurnal cumulus will re-develop late
Monday morning as fog dissipates. Winds light and variable then
becoming north-NE up to 7 kts after 15z.

&&

Ilx watches/warnings/advisories...
none.
&&

$$

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