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Area forecast discussion 
National Weather Service Lincoln Illinois
319 PM CDT Sat Aug 23 2014

Short term...(this evening through sunday)
issued at 319 PM CDT Sat Aug 23 2014

Southern flank of morning thunderstorm complex continues to impact
the northeast kilx County Warning Area around Champaign and Danville this afternoon,
with only minimal development noted further southwest along the
trailing outflow boundary. Models have once again handled the
situation poorly, with the NAM/GFS being too aggressive with
convective development and the hrrr keeping system too far north.
Think storms will gradually push into Indiana over the next 3 to 4
hours, followed by only isolated convection across the eastern County Warning Area
early this evening. Once daytime instability wanes, dry conditions
are expected overnight. With clearing skies and light winds, fog
will likely develop late tonight into Sunday morning. Forecast
soundings and numeric guidance both suggest at least some
restriction to visibilities, and based on what happened last night,
think its prudent to carry patchy fog late tonight. Upper ridge
axis will continue to control the weather across central Illinois on
Sunday, providing hot and mainly dry conditions. Some models are
hinting that widely scattered convection may fire along the Indiana
border by afternoon, but think this is a bit overdone. Will only
maintain slight chance pops across the far southeast, with dry
weather elsewhere. High temperatures will reach the lower 90s,
resulting in heat index values of 100 to 105 degrees.


Long term...(sunday night through saturday)
issued at 319 PM CDT Sat Aug 23 2014

Medium range models are generally in good agreement for the first
few days of next week, then they digress pretty rapidly for two
reasons. First is the difference in solutions involving the speed
and strength of the upper level trough expected to move from The
Rockies to Midwest. This looks like it is being caused by the second
main difference, which is a lot of uncertainty with the speed and
motion of a pending tropical system in the western Atlantic. These
tropical systems tend to back up the west-east progression of
weather systems in the middle U.S. Thus, there is a greater than
normal level of uncertainty with the forecast for Wednesday through
the end of the week.

In the nearer term period for Monday and Tuesday, it appears likely
that the hot and humid conditions will continue. Monday could end up
being one of the hottest days with highs from 93-95 in central Illinois
and 91-93 in east/southeast Illinois. This will keep heat index values in
the 105-108 range in much of central and southeast IL, so will keep
the heat advisory going through Monday. Considered extending the
advisory into Tuesday, but will hold off for now since there is some
level of uncertainty as to the amount of increasing cloudiness
during the day, which could keep temps down just a bit.

The movement of a cold front, associated with aforementioned
approaching upper level trough, will really depend on the East Coast
tropical system. The most likely scenario, which is not really
handled very well by any model, is that the front will slowly
approach - and may even get hung up in central Illinois for a day or two.
Thus, will stick with a prolonged period of scattered showers/T-storms
Wednesday into Friday. The cloudiness associated with this rain
potential will keep temperatures down in the 80s, ending the stretch
of hot weather. However, longer term trends indicate the possibility
that we may see a return to very warm conditions for Labor Day


Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1236 PM CDT Sat Aug 23 2014

Southern flank of storm complex tracking across northern Illinois
is skirting along the I-74 corridor early this afternoon. Storms
have already impacted kpia with heavy rain and gusty winds up to
around 25kt and will push through kbmi over the next hour. Still
some question whether they will hold together and reach far enough
south to impact kcmi, so have only gone with thunderstorms in the vicinity there. Elsewhere
around the area, will maintain dry conditions through the
afternoon. Once convection exits into Indiana, skies will
gradually clear by this evening. Due to light winds and very high
dewpoints, think fog will once again develop across the area
overnight. Have therefore included restricted visbys down to
between 2 and 4 miles between 09z and 14z.


Ilx watches/warnings/advisories...
heat advisory until 7 PM CDT Monday for ilz042-047>054-056-

Heat advisory from noon Sunday to 7 PM CDT Monday for ilz036-040-



Short term...Barnes
long term...Miller

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