Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 221715

Area Forecast Discussion
National Weather Service Lincoln IL
1215 PM CDT Sun Apr 22 2018

Issued at 938 AM CDT Sun Apr 22 2018

Battle of the dry air underway in central and southeast Illinois,
as showers try to come up from the southeast. Lowest cloud levels
in the area are only around 10,000 feet, and RAP soundings only
showing it decreasing a couple thousand feet today, so any rain
will be light. While radar mosaics show it rather widespread over
the southern third of Illinois, surface reports are a little more
sporadic due to the high cloud bases. Short range high-res models
largely keep the showers to our south through the afternoon. Have
made some minor tweaks to the PoP trends, mainly limiting them to
areas well south of I-70. Further north, changes were made to
introduce a little more sunshine through the midday hours.
Temperatures look on track and only needed some tweaks over the
next few hours.


.SHORT TERM...(Today and tonight)
ISSUED AT 320 AM CDT Sun Apr 22 2018

Easterly winds continue today and most of tonight for Central
Illinois. Weak ridging from the Great Lakes back into the High
Plains as a surface low skirts to the south along the Gulf States
today, bringing storms along the southern tier of the country. The
upper level low associated with those storms is more or less cut
off from the more progressive flow to the south. Cyclonic flow and
some moisture from the system to the south expected to keep mid/high
clouds in place for the region today. That being said, the last
two days are any indication, in concert with pretty dry soundings
below 12kft, any precip will likely be mostly a virga issue to the
north through today. South of Interstate 70 has a better chance of
maybe seeing a shower before tonight. Better chances for precip
will come with a slow saturation of the column as the moisture
lifts into Central IL. Some concern that the models may be rushing
it somewhat, as well as being a little too far north with the
showers in the overnight hours.

.LONG TERM...(Monday through Saturday)
ISSUED AT 320 AM CDT Sun Apr 22 2018

Extended forecast remains largely unchanged. Precip chances with
varied solutions of small waves moving into the region around the
main upper low moving into the Ohio River Valley early this week.
Best chances for Monday as the low wobbles a bit to the north,
but overall, precip is a scattered threat into mid week. GFS and
ECMWF differing somewhat in the kicker low mid week, with the NAM
coming down on the side of the ECMWF. Both models kick the weekend
low out, but the GFS phases a wave in the northern stream with a
wave out of the Rockies closing in and bringing precip with it
Tues night/Wed. The NAM and the ECMWF maintain a split flow,
pushing a large chunk of energy to the north, phasing with the
first low well to the east. This leaves the Colorado low a little
weaker and moving into the Gulf States as an open wave aloft about
24 hours later in a more NWrly flow set up. ECMWF a little drier
as a result, with the precip moving to the north and to the south.
Not yet seeing any consistency from the models enough to weigh one
a little heavier than the other. As a result, the blended forecast
has several rounds of low chance pops. A little drier than prev
forecast and that may be the better choice for now.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1214 PM CDT Sun Apr 22 2018

Mainly looking at ceilings above 10,000 feet through the night
across central Illinois, as a fetch of dry air in the lower
atmosphere continues. Main concern will be after about 12Z, when
rain to the south finally starts to make some headway northward.
KDEC/KCMI most likely to be impacted toward the end of the TAF
period, with ceilings dropping to near MVFR conditions by midday.
Any lower conditions north at KPIA/KBMI wouldn`t be until after
18Z. Winds expected to remain east/northeast through the period,
due to a slow moving storm system centered just south of Illinois.




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