Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 230456

Area Forecast Discussion
National Weather Service Lincoln IL
1156 PM CDT Tue Jul 22 2014

ISSUED 904 PM CDT Tue Jul 22 2014

A boundary and the main front will still move through the area
tonight. Any thunderstorms that have developed along these
boundaries have not amounted to much as ILX 00Z sounding shows
high cape, but also very high CIN/capping in the lower layers.
Middle layers of the atmosphere are also very dry. So
storms/showers fizzle quickly and do not get much vertical
development. So will be updating pops for the overnight period.
Will be keeping chance, but have removed likelies. Confidence is
lower than earlier this afternoon. Remainder of forecast looks
fine, including temps and winds. Update will be out shortly.



ISSUED 1156 PM CDT Tue Jul 22 2014

Except for a small period of time overnight when vis will be
around 5SM and cigs will be 2.5kft, MVFR, conditions should be VFR
for most of the TAF period. The front is still slowly moving
through the area, so all TAF sites could still see some
storms/showers. PIA could still see something for about an hour,
BMI and SPI for 2hrs, DEC for about 3hrs, and CMI for about 2 hrs,
though starting around 08z. Once the front goes through, winds get
light, and with low level moisture still being high, light fog
will be possible at all sites. So have 5SM BR during several hours
overnight at all sites. As is being seen at some sites, cigs
around 2.5kft could happen, but only going to have a TEMPO group
for this. Then expecting some CU development tomorrow, even though
drier air is advecting into the area tomorrow. This CU will
dissipate tomorrow evening, resulting in clear skies tomorrow
night. Winds will be southwest ahead of the front/s, but become
light; then northwest behind the front. Expecting north-northeast
winds tomorrow, with speeds around 10-12kts during the daytime hours.



ISSUED 228 PM CDT Tue Jul 22 2014

The main forecast concern for the next few days is a shortwave and
attendant surface cold front approaching central Illinois from the
northwest this afternoon. This will sweep across central and
southeast Illinois this evening through tonight bringing a period
of thunderstorms. Following the cold front, temperatures will
lower several degrees and humidity will decrease significantly for
Wednesday and Thursday, along with dry conditions. Chances for
thunderstorms will arrive again Friday through the weekend as
another low pressure system moves across the region.

SHORT TERM...Today through Thursday:

Cold frontal boundary moving toward the northwest corner of
Illinois is currently initiating scattered thunderstorms over
eastern Iowa. Ahead of the front, dewpoints range up to the mid to
upper 70`s yielding heat index values in the upper 90`s. This
evening the front will reach the Illinois River around mid-
evening...and southeast Illinois early Wednesday morning. A few
hours of scattered thunderstorms are likely at each location as
the feature moves through. Severe wind and hail remain as a slight
risk as a result of high surface temperature and dewpoint combined
with strong mid-level lapse rates in the region the front is
moving into. Mitigating the severe weather possibilities are a
strong cap evident in the KILX morning sounding which has
precluded convective activity from western Illinois this morning
from spreading into central Illinois.

For and dry northerly flow push into central
Illinois for drying conditions, cooler temperatures, and much less
humidity through Thursday. Nighttime temperatures should dip into
the 50`s again.

LONG TERM...Friday through Tuesday:

A strong 500 mb low will move across the northern Plains and
Canada before moving into the great lakes region and carving out a
deep trough over the eastern U.S. through early next week.
Models fairly consistent bringing MCS remnants through Illinois
late Friday into Saturday...then a cold front arriving around
Sunday should bring another chance for thunderstorms. Yet another
round of cooler and drier conditions expected to follow for early
next week.




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