Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 222016

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

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.



ISSUED 1243 PM CDT Tue Jul 22 2014
VFR early this afternoon, with cold front moving in later this
evening and showers and thunderstorms possible ahead of the sfc
boundary. Issues with the models...some of the shorter term higher
resolution models are actually downplaying the thunder potential.
With the amount of instability available to the boundary, and the
expected convergence along it...keeping the thunder in the TAFs
from near 00z into the evening. Winds shifting first to the east
and then to the north by morning. Timing issues abound with this
particular forecast so narrowing the time frame for the thunder is
problematic. Confidence is low and forecast is conservative as a




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