Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 291750
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1250 PM CDT Fri Aug 29 2014

.UPDATE...
ISSUED AT 948 AM CDT FRI AUG 29 2014

Made a quick update to the forecast to raise PoPs from Lincoln
northward to Henry due to current radar trends. A cluster of
thunderstorms with high rainfall rates of 1.5 to 2 inches per hour
is lifting northward into Tazewell and western McLean counties at
this time and will continue northward across Woodford and Marshall
counties over the next couple of hours. Once this cluster
weakens/exits the KILX CWA toward midday, additional showers/storms
will develop along outflow boundaries as well as the synoptic warm
front as it pushes northward later today. Have gone with low
chance PoPs across the board this afternoon, with highs climbing
well into the 80s.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Frontal boundary from NW Missouri through southern Illinois into
Kentucky will push northward today as southwesterly flow increases
ahead of a trough currently over the central plains. For this
afternoon convection will be primarily driven by surface heating and
not well organized, therefore have ramped up pops through early
afternoon and trended them downward in early evening in eastern IL.
In the early evening, the upper level trough and weak surface cold
front associated with the plains system begin to move into western
IL. This will bring a good chance of showers and thunderstorms
pushing across central and southeast IL overnight. Temperatures for
today will be similar to Thursdays...generally mid to upper 80s with
dew points in the low 70s resulting in heat index values in the low
to mid 90s.

&&

.LONG TERM...(Saturday through Thursday)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Cold front accompanying current deep Plains upper trough will be
losing some of its punch as it comes into the mid-Mississippi
Valley, but will still be potent enough for showers and
thunderstorms to be likely on Saturday over our area. Some heavier
rains will be possible with the stronger storms, primarily over the
southeast CWA where precipitable water values will be around 1.8
inches Saturday afternoon, about 2 standard deviations above normal
for the end of August. The precipitation threat will continue
Saturday night and Sunday over the southeast CWA as moisture
continues to surge into the Ohio Valley. However, the northwest half
of the forecast area should be dry during this period.

West-east upper high to dominate the lower CONUS into mid week, as a
broad trough tracks across the northern states. Showers and storms
ahead of the surface front should begin spreading in northwest of
the I-55 corridor after midnight Sunday night. Most of the models
try to form some sort of dual MCS`s, one tracking east across
Wisconsin and the other southwest through Missouri, with some
potential for lesser amounts of rain Monday morning. However,
redevelopment is expected by afternoon as the front starts to hang
up in the upper flow, so have likely PoP`s over most of the CWA for
Monday. With the frontal boundary in the vicinity, the 00Z models
are trending more toward additional MCS activity tracking over our
forecast area Monday night. Have increased the PoP`s some,
especially across the north which had been dry Monday night. The
front should start to be dragged a bit further south on Tuesday as a
surface wave moves along it, but have kept PoP`s in the 30-40% range
into Tuesday night before the focus shifts more into the Ohio Valley.

Mid to late week, the upper high begins to ridge again across the
Mississippi Valley. 850 mb temperatures of 20-22C should allow for
highs to return to the 90s late next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 1250 PM CDT FRI AUG 29 2014

Widely scattered thunderstorms will continue to develop across
central Illinois over the next couple of hours as a warm front
lifts north of the area. Will carry VCTS at all terminals
accordingly. Meanwhile further upstream, regional radar mosaic is
showing a band of showers/thunder developing across western
Missouri into northern Arkansas. HRRR is showing this band lifting
N/NE this afternoon, eventually arriving in west-central Illinois
early this evening. Have therefore opted to carry predominant
light rain with VCTS for a 6-hour period at all sites this evening
into the overnight hours. Based on HRRR and observed trends, have
brought precip into KSPI after 02z, then further east to KCMI
after 05z. After this initial band lifts through the area, only
widely scattered showers will be noted Saturday morning.

&&

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

$$

UPDATE...BARNES
SHORT TERM...ONTON
LONG TERM...GEELHART
AVIATION...BARNES





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