Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 201801
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
101 PM CDT Sat Sep 20 2014

.UPDATE...
ISSUED AT 1045 AM CDT SAT SEP 20 2014

Forecast overall looks in good shape and just a few adjustments
for addressing the increasing chances of showers and thunderstorms
from the nw during the afternoon. SPC continues the slight risk of
severe storms along and nw of a Shelbyville to Mattoon to Paris
line where 15% risk of damaging wind gusts and large hail along
with 2% risk of tornadoes. Had isolated showers and thunderstorms
nw of IL river earlier this morning and have dissipated during mid
morning as its outflow boundary raced se to near I-72. Main area of
convection is tied closer to cold front over central IA. Cold
front to push se into nw IL late this afternoon and move through
central IL tonight and through southeast IL early Sunday morning.
Highs in the low to mid 80s this afternoon along with dewpoints
rising from the lower 60s into the upper 60s with breezy sw winds
this afternoon ahead of the cold front to make airmass more
unstable. CAPES to elevate to 1500-3000 j/kg and highest over
northern MO into west central IL. Bulk shear of 35-40 kts over
northern half of IL later this afternoon and evening to support
this slight risk. Best chance of severe storms over mid and late
afternoon across IL river valley to along I-55 and early/mid
evening further se from I-72 to nw of I-70.

&&

.SHORT TERM...(Today)
ISSUED AT 318 AM CDT SAT SEP 20 2014

With the high pressure ridge well east of the area southerly winds
have returned to the area and this should bring above normal temps
back into the region, along with some increasing moisture. Models
continue to bring the front into the area with a line of
thunderstorms just ahead of the front moving into the CWA beginning
late this morning and then increasing to the southeast during the
afternoon. Satellite and radar loops already show this line of
storms across central Iowa and WI. Chance pops will be over most of
the area as the pcpn comes through, but will have higher pops to the
northeast and north as that is where the best upper level dynamics
will be during the afternoon. With the front/pcpn coming through
around max heating, instability and other severe parameters look to
support the potential for some of the storms becoming severe. So,
agree with SPC on the slight risk area this afternoon and into this
evening.

&&

.LONG TERM...(Tonight through Friday)
ISSUED AT 318 AM CDT SAT SEP 20 2014

Severe weather threat continues into the evening hours for Central
and mostly southeastern Illinois in advance of the front moving
through the area. WAA through the day keeping plenty of
instability in front of the advancing showers. Convective activity
expected to continue into the early evening hours at least with
threat of damaging winds remaining the biggest issue. Precipitation
slowly coming to an end Sunday morning, with slight chance pops
south of Interstate 70 reflecting any lingering showers. Remainder
of the forecast is quiet with a surface high slowly drifting east.
Weak southerly flow at the sfc on the west side of the sfc ridge,
and very little flow aloft as the majority of the height gradient
is to the north of the region through the week. As a result,
temperatures on a slow warm up with no significant systems
bringing pops into the forecast beyond this weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
ISSUED AT 1255 PM CDT SAT SEP 20 2014

A cold front over central IA will push into nw IL late this
afternoon and push into se IL by early Sunday morning. Radar
mosaic shows showers and a few thunderstorms along and north of
I-80 over northern IL into se IA. Will have chance of showers and
thunderstorms moving into PIA from 19Z- 22Z to BMI 20Z- 23Z and
I-72 TAF sites at 21-24Z. Have MVFR ceilings and vsbys possible
with convection and could locally be lower in heavier rains.
Continue VCSH this evening with broken clouds of 4-5k ft then
scattering out toward overnight. Have scattered to broken clouds
of 3-4k ft spreading southward into central IL after 15Z/10 am
Sunday. Breezy sw winds 12-16 kts with gusts 20-25 kts to turn
west at 6-10 kts tonight and then breezy NW winds 13-17 kts with
gusts 20-25 kts developing during Sunday morning.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...07
SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...07






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