Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 141140

Area Forecast Discussion
National Weather Service Lincoln IL
640 AM CDT Mon Jul 14 2014

ISSUED 258 AM CDT Mon Jul 14 2014

SHORT TERM...Today through Wednesday

Cold front has settled southward into the Ohio River Valley early
this morning, with convection ongoing across the far southern KILX
CWA. Based on satellite/radar trends as well as latest HRRR,
precipitation should exit into Indiana prior to 12z. As a result,
will go with a dry forecast across the southeast during the
morning hours. Further north, a second cold front currently
extending from southern Michigan into Iowa will sag southward this
morning. One small cluster of showers/thunder has already
developed along the front across Nebraska and additional
convection is expected to form further east later this morning as
colder air arriving aloft creates steep lapse rates along/ahead of
the boundary. Have opted to carry scattered showers/thunder across
the central and northern zones throughout the day and across the
southeast during the afternoon. Will still be a fairly warm day,
with highs ranging from the upper 70s far north to the middle 80s
south of I-70.

Secondary cold front will settle south of the area this evening,
with a few lingering showers possible across the far southeast
through midnight. After that, a much cooler/drier airmass will
filter into the region overnight. Current dewpoints behind this
front across the Dakotas and Minnesota are only in the 40s and
some of this airmass will arrive in central Illinois later
tonight. Have generally gone at or slightly below guidance
numbers, with lows ranging from around 50 degrees in Galesburg to
the upper 50s far southeast. Coolest day of the forecast period is
coming up on Tuesday as unseasonably deep upper low drops into the
Great Lakes. 850mb temps in the 6 to 8C range will support very
cool temps only in the lower to middle 70s. These readings will be
close to record low maximum temperatures in many locations. For
more details, please see the climatology section of this
discussion below. With surface high pressure in control of the
weather, another very chilly night will be on tap Tuesday night
with lows once again bottoming out in the lower to middle 50s.
Only slight airmass modification is expected on Wednesday,
resulting in highs a couple of degrees warmer than Tuesday in the
middle 70s.

LONG TERM...Thursday through Sunday

Quiet weather is expected through the extended, although the 00z
GFS is trying to put a fly in the ointment. As has been advertised
for several days, an upper-level wave currently spinning along the
Washington/Oregon coast is expected to cross the northern Rockies,
then dive southeastward along the western periphery of the Great
Lakes trough, then track eastward into the Tennessee River Valley
by late Thursday into Friday. All models have been in agreement
that any precip associated with this feature would stay well south
of the KILX CWA. Latest GFS is now bringing precip much further
north into parts of central Illinois Thursday night and Friday.
ECMWF/GEM remain dry and consistent with their previous solutions.
Since GFS is an outlier and rain pushing into a surface ridge axis
seems unlikely, have ignored the GFS in favor of the ECMWF/GEM
consensus. As a result, have continued with a dry forecast with
slowly moderating temps through the end of the week. After that,
model solutions vary as to timing of next northern stream wave and
associated frontal boundary. At this point, will only introduce
slight chance POPs for Sunday until better model agreement is



ISSUED 640 AM CDT Mon Jul 14 2014

VFR conditions will prevail at all sites next 24hrs. However, a
little bit of fog is at SPI this morning, so have added a TEMPO
group for 1hr with light fog and stratus deck at 200ft. This
should clear up and be completely VFR by 13z. A cold front will
move through the area today and this should kick off some
scattered showers and thunderstorms today and effect all TAF
sites. It will occur first at PIA and then progress to the
east/southeast next 1 to 2 hours. So should begin around 17z at
all sites. Since storms will be scattered, will just have VCTS at
each sites today through this afternoon. Storms will be diurnal
and should dissipate around 00z. Then expecting clear skies during
the night. Light and variable winds this morning will become more
southwesterly and increase in speed some. Once storms arrive in
the area, winds will be more west-northwesterly at around
10-15kts. Northwest winds will continue during the evening but
decrease in speed some. Believe skies will be clear tonight, but
with winds at or above 7kts and dewpoints dropping into the 50s,
thinking is that fog will not be an issue.



ISSUED 219 AM CDT Mon Jul 14 2014

Record low maximum temperatures will be possible on Tuesday, July
15. Here are the current records for selected cities:

Peoria:      72 in 1939 and 1990
Springfield: 73 in 1929 and 1993
Lincoln:     73 in 1996



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