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Area forecast discussion 
National Weather Service Lincoln Illinois
859 PM CST Tuesday Nov 24 2015

issued at 857 PM CST Tuesday Nov 24 2015

Southerly winds will increase across central and southeast
Illinois overnight. This warmer and more moist southerly flow will
keep overnight lows several degrees warmer than last night, with
most locations expected to stay above freezing. Otherwise, quiet
weather is anticipated. Going forecast is in good shape overall,
and only a few minor tweaks are needed for the latest hourly


Short term...(tonight)
issued at 303 PM CST Tuesday Nov 24 2015

High pressure is dominating the weather across the eastern half of
the country this afternoon. As the ridge axis slips further to the
east, the winds are becoming more southerly. An increasing pressure
gradient overnight with the next storm developing to the west will
result in the winds staying up a bit in the overnight, increasing to
10-15mph by morning. Cloud cover across the region will remain
mostly cirrus. However, after midnight or so, expect to see some
shallow patchy fog development over the northern tier of Illinois
with the melting snowpack and increased llvl relative humidity.

Long term...(wednesday through tuesday)
issued at 303 PM CST Tuesday Nov 24 2015

A steady southerly flow will develop across central Illinois Wednesday in
response to gradients between high pressure centered over New
England and developing low pressure over the central-northern
plains. This will bring a further warming of
temperatures...especially north of the I-74 corridor where the last
remaining snow cover dissipates...and south winds 15-20 mph. Most
highs should reach the mid to upper 50s across central and southeast
Illinois. Continued southerly flow Wednesday night will push increased
moisture into central Illinois...yielding dewpoints well into the 40s and
precipitable water reaching near 1 inch. As a result...chances for
precipitation will develop from northwest to southeast across
central Illinois...and temperatures will have difficulty dropping below
the upper 40s...or even some low 50s. Still...forcing looks to
remain weak with only light amounts of precipitation expected.

For Thanksgiving Thursday...a strengthening cold frontal zone will
edge southeastward toward central Illinois...approaching Galesburg late in
the evening...then weakening and reaching Lawrenceville mid-day
Friday. Precipitable water values around 1.25 inches look to precede
the front...approaching 99th percentile for this time of year.
Moderate rainfall preceding the front looks to result in rainfall
rates around 0.60 to 0.70 inches per 6-hours as it crosses central
Illinois...resulting in around 1.25-1.50 inches storm total rainfall
accumulation. The heaviest rainfall period should be Thursday
evening to Friday morning west of I-55...early Friday morning to
early Friday afternoon to the east. Highs should reach around 60
degrees Thursday ahead of the front...then cool back to the 40s
north of I-72 for Friday...still remaining in the 50s to the south.
Depending on the timing of the front...temperatures may peak in the
morning and lower through the afternoon Friday...especially I-72
northward. South winds will remain breezy around 15 to 20 mph
Thursday ahead of the front.

There should be a short break in precipitation for most of central
Illinois Friday night into Saturday...then another low looks to lift
northeastward out of the Southern Plains into the Ohio Valley region
by Sunday morning. Models are still not totally consistent with
amounts and timing of precipitation preceding this low with the
latest 12z GFS as well as previous runs bringing more widespread and
heavier precipitation back to much of central Illinois by Saturday
afternoon and the European model (ecmwf) keeping precipitation lighter Saturday
afternoon and lingering precipitation later into Sunday.
Temperatures looking more seasonable with highs in the 40s for the

Still some uncertainty for precipitation early next week as one
disturbance moves by to the south over the Tennessee Valley area in
latest runs...and another upper low tracks to the north into the
upper Midwest. Any variation to this solution and central Illinois
could see some more precipitation early next week...although current
European model (ecmwf)/GFS solutions keeping central Illinois somewhat between these two


Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 554 PM CST Tuesday Nov 24 2015

Winds across the central Illinois terminals will trend more
southerly and increase in speed through the period, becoming gusty
by late morning Wednesday. These southerly winds will transport
low level moisture across the area, which will result in low end
VFR ceilings by late Wednesday morning. This moisture is already
evident in satellite loops with the low clouds streaming
North/East from the southern and Central Plains.


Ilx watches/warnings/advisories...


short term...hjs
long term...Onton

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