Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 201749
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1249 PM CDT Wed Aug 20 2014

.UPDATE...
ISSUED AT 1050 AM CDT WED AUG 20 2014

Several clusters of showers and thunderstorms continue to track
E/SE across the KILX CWA this morning, mainly impacting locations
along/southwest of a Galesburg...to Lincoln...to Paris line. Have
updated the forecast to carry likely PoPs across the central and
southwest CWA and chance PoPs elsewhere. Many of the storms have
been prolific rain and lightning producers, with observers in
Springfield measuring as much as 2 inches of rain since 7 AM.
Models have generally handled this convection poorly, although the
general consensus continues to shift the precip eastward and
weaken it as the day progresses. Still think the areal coverage
will greatly reduce by early to mid-afternoon, with very little in
the way of precip left by late in the day. Due to the clouds and
precip, temps will be held down a bit. Have therefore lowered
afternoon highs into the middle 80s in most locations, with
readings near 90 across the far southeast.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 333 AM CDT WED AUG 20 2014

Storms have developed along a boundary in northeast MO and southeast
IA early this morning. These storms should move into western and
southwest IL in the next several hours. These could get into western
parts of the CWA so will have some chance pops in the west this
morning. However, all models seem to indicate this area will not
travel very far and should dissipate during the morning hours. The
associated boundary will then slowly lift northeast as a warm front
through the CWA, and though convergence along this boundary will be
weak, some isolated showers or thunderstorms will remain possible in
the early afternoon. By late afternoon and into the evening and
overnight hours, the warm front will remain across the central part
of the CWA so the chance of showers and thunderstorms will continue
during the evening and overnight hours.

Temperatures will be a few degrees warmer than yesterday, with some
areas in the west and south getting to around 90. Overnight lows
will also be warmer as most of the CWA will be in the warm sector
overnight.


&&

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 333 AM CDT WED AUG 20 2014

Position of the boundary after lifting through the FA today and
tonight will have a signif impact on the location of the showers and
thunderstorms. Though most recent models are lifting the boundary
further to the northeast, some chance pops Thurs and slight chance
pops remain in place at least over the northeastern portions of the
CWA from Thursday night through Friday night. Pops increasing
somewhat for Saturday as models are collapsing the ridge somewhat as
a wave moves over the ridge and into the Ohio River Valley.  Though
the precip chances are scattered at best and low confidence...the
models have been very persistent with the very hot temperatures for
some summer like conditions that are well above normal for this time
of year. Models have also shown consistency with  850 mb temps in
the 19-25C range through Sunday.  This will drive the temps into the
upper 80s/lower 90s with heat indices in the upper 90s/low 100s.
Forecast dwpts into the low to mid 70s may be over representing llvl
RH enhancement from widespread precip in the models that may not
quite come to fruition as widespread.  Todays heat indices are more
borderline for Heat Advisory criteria...but far more likely to see
from Thursday into Sunday with subsequent forecasts, should the
trend continue. Into the extended, day 7/just into day 8, models
actually beginning to diverge into a solution to break down the
ridge with an upper system pushing a return of precip in for Tues
night into Wed.


&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED AT 1249 PM CDT WED AUG 20 2014

Most of the widespread convection from this morning has now moved
east of the central Illinois terminals, except for KCMI where rain
will linger through 19z. Elsewhere around the area, only widely
scattered light showers are noted on radar. The showers will
become less numerous in coverage as the day progresses and some
partial clearing will even be likely at both KSPI and KDEC. Next
big aviation question will be where/when the next round of
convection will develop. Models are showing a warm front lifting
northward through the region tonight into Thursday, with
showers/storms likely firing along/north of the boundary late
tonight. Still some uncertainty concerning exact placement of
convection, but general consensus focuses it across northern
Illinois between 08z and 14z. Will carry VCTS at the I-74
terminals during that time frame, but will keep both KSPI and KDEC
completely dry tonight into Thursday morning. Will also need to
keep an eye on fog potential tonight, as low-level moisture
remains high and winds are light.

&&

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

$$

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





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