Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 311743
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1243 PM CDT Sun Aug 31 2014

.UPDATE...
ISSUED AT 948 AM CDT SUN AUG 31 2014

A low overcast persists across much of central Illinois along and
east of a Peoria to Jacksonville line this morning. 1430z visible
satellite imagery is showing thin spots developing in the cloud
cover, so am expecting it to dissipate within the next 2 to 3
hours. HRRR ceiling forecast shows this trend quite nicely,
resulting in a partly to mostly sunny afternoon. May see a few
showers/thunder pop up along/south of I-70: however, areal
coverage will remain spotty. Updated the forecast to better
reflect sky cover trends this morning and to confine PoPs to just
the far SE KILX CWA.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 358 AM CDT SUN AUG 31 2014

Shortwave trough and jet entrance region that brought banded
convection and some locally heavy precipitation to central IL last
evening has shifted northeastward with shower activity nearly ended
over the ILX CWA. With clearing skies and good radiational cooling,
patchy fog will continue to form overnight, mainly I-55
westward.

Moist conditions with enough instability will remain through the
afternoon today for a few showers and thunderstorms, mainly I-70
southeastward, but a relatively dry day expected. Highs in the mid
80s are expected.

After sunset, convection should end quickly across the CWA with the
loss of surface heating. Late in the night, chances for
thunderstorms will spread back into west central Illinois as another
cold front approaches from the west.

&&

.LONG TERM...(Monday through Saturday)
ISSUED AT 358 AM CDT SUN AUG 31 2014

SPC continues a slight risk (15+%) of severe thunderstorms across
central IL nw of a Flora to Robinson line Monday afternoon/evening
for damaging winds and large hail. This seems reasonable considering
surface to 6 km bulk shear values of 30-40 kts, CAPES of 2-3k J/kg.
Heavy rains also possible with thunderstorms in tropical airmass
ahead of frontal boundary. Short waves and 30-40 kt low level jet
moving into IL river valley later Sunday night into Monday morning
and then spreading into eastern IL Monday afternoon/evening. Upper
level trof over northern Rockies moves east into Midwest
Monday/Monday night and drives a cold front southeast across central
IL Monday night. Continued likely pops across much of area Monday
afternoon into Monday night, though diminishing pops overnight
Monday night nw of IL river. Best chances of showers and
thunderstorms lingers over areas from I-72 south on Tue especially
in the morning. The 5% risk of severe storms Tue is southeast of
Lawrenceville. Quite warm and humid Monday ahead of front with highs
82-88F and dewpoints 70-75F and warmest temps in southeast IL where
rain arrives later.

Frontal boundary to weaken as it moves se into Ohio River valley
Tue/Wed with near zonal upper level flow over the region. Carried
just slight chance of convection during midweek from Tue night
through Thu night. Highs in the low to mid 80s Tue/Wed climb into
mid 80s to around 90F Thu/Fri as dewpoints rise back into the low to
mid 70s with heat indices approaching 100F southern counties Thu/Fri
afternoon. Next frontal boundary press southeast into IL Friday
afternoon into Sat and bringing next best chances of showers and
thunderstorms and cooler temps during next weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1243 PM CDT SUN AUG 31 2014

MVFR ceilings will persist at the central Illinois terminals for
the next hour or two before gradually dissipating as the afternoon
progresses. Based on satellite trends, have scattered ceilings at
most sites by 19z, then at KDEC and KBMI by 20z. After that,
mostly clear skies will prevail through the evening before clouds
begin to increase from the west late tonight. A thunderstorm
complex currently developing across western Iowa/Nebraska will
track eastward tonight, with most model guidance keeping it west
of the Illinois River until 12z. Think storms will arrive in the
Illinois River Valley toward dawn in a weakening state, then
spread eastward across the area Monday morning. Have therefore
introduced low VFR ceilings and VCTS at KPIA after 12z, then
further east to KBMI and KDEC after 14/15z. Given plenty of
low-level moisture and relatively light winds, included slightly
reduced visbys down to 4sm at KCMI where skies will remain mostly
clear through dawn. Further west, think increasing clouds and wind
will prevent fog formation.

&&

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

$$

UPDATE...BARNES
SHORT TERM...ONTON
LONG TERM...07
AVIATION...BARNES





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