Area Forecast Discussion
Issued by NWS Central Illinois

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175
FXUS63 KILX 020150
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
850 PM CDT SUN MAY 1 2016

.UPDATE...
Issued at 850 PM CDT Sun May 1 2016

Will be updating the forecast shortly to cancel the Severe
Thunderstorm in east central and southeast IL. Potent shortwave
moving through central IL this evening combined with unstable air
and increasing deep layer shear to produce the right conditions
for a couple of supercells to track across the forecast area. A
few t-storms will linger in southeast IL until 03z or so, but
these should be well below severe limits.

In the northern part of the forecast area, a few showers
associated with the cold pool/upper low in northern IL will also
linger for another couple of hours before they rotate to the
northeast out of the region.

The rest of the night will be cloudy in central IL with chilly
temperatures in the mid 40s. Partial clearing will be in store for
southeast IL in the wake of the departing t-storms, but then
clouds will be on the increase overnight.

&&

.SHORT TERM...(Tonight)
ISSUED AT 300 PM CDT Sun May 1 2016

19z/2pm surface analysis shows stationary frontal boundary extending
from central Indiana southwestward into the Ozarks.  Ahead of the
front, temperatures have climbed into the middle 70s and SBCAPE
values have reached the 1500-2000J/kg range south of I-70.  This
will be the area of the KILX CWA that will be monitored for
potential severe weather over the next few hours as an upper low
over northern Missouri/southern Iowa shears northeastward and
provides additional synoptic lift.  HRRR is showing scattered
convection across the SE CWA in the warm/unstable airmass...and
additional showers/isolated thunder further northwest in closer
proximity to the upper low between now and about 02z/9pm.  Given
good convergence along the frontal boundary and strong instability,
think a strong wind/large hail threat will exist with any storms
that fire south of I-70 late this afternoon into the early evening.
Once the sun sets and daytime instability wanes, the convection will
weaken and shift eastward into the Ohio River Valley by mid-evening.
After that, mostly cloudy and cool conditions will prevail for the
balance of the night, with low temperatures ranging from the middle
40s northwest of the Illinois River...to the lower 50s far southeast.

.LONG TERM...(Monday through Sunday)
ISSUED AT 300 PM CDT Sun May 1 2016

The upper level trough and surface cyclonic flow is forecast to
remain in place over the Great Lakes region, effecting central and
southeast Illinois through the first part of the week. This will
keep partly sunny and chilly conditions in the area through Wed. In
addition, the cyclonic flow will provide enough focus for
instability showers periodically Mon through Wed. There could be a
break in the scattered pcpn Mon night and Tue, but still keeping a
slight chance of pcpn in the forecast. As the main upper level
system drops down toward Ohio, colder upper level temps will also
arrive, increasing the instability in the area. So have added a
slight chance for thunderstorms, along with the showers for Tue
night and Wed.

Beyond Wed, the pattern should begin to change and sfc ridging
should begin to build into the area. This will push the upper level
system to the east and bring drier weather to the area for the last
half of the weekend. As the high moves across the area, another
weather system will begin to develop in the plains and bring the
return of showers and thunderstorms for possibly next Sunday.

Temps will remain on the cool side through most of the week with the
continued cyclonic flow and general cloudiness. Once the high
pressure moves over the area, temps will begin to warm back up and
should reach into the 70s by the end of the week and into the
weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1256 PM CDT Sun May 1 2016

IFR ceilings prevail at the central Illinois terminals early this
afternoon: however, latest visible satellite imagery is showing
an appreciable thinning of the overcast. HRRR has consistently
suggested ceilings rising into the MVFR category over the next
couple of hours and have followed this trend accordingly. Think
KPIA/KBMI will be the last sites to improve as cloud cover appears
thickest in this area. With partial sunshine breaking through and
an upper low providing modest synoptic lift, think scattered
showers/thunder will develop this afternoon/evening. Have included
VCTS to cover this possibility. Once daytime instability wanes,
any showers will come to an end after sunset. After that, the low
overcast will spread/develop back southward...with the HRRR
showing IFR ceilings back at all TAF sites between 04z and 06z.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...Miller
SHORT TERM...Barnes
LONG TERM...Auten
AVIATION...Barnes



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