Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 242353
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
653 PM CDT Wed May 24 2017

.SHORT TERM...(This evening through Thursday)
ISSUED AT 325 PM CDT Wed May 24 2017

Low level cyclonic flow around low pressure in central KY will
keep showers and a few t-storms in eastern Illinois the rest of
the evening. Diurnal showers and isolated thunderstorms in western
and central IL will continue early this evening and then dissipate
west of I-55 by 8-9 pm and in the rest of central IL after 10 pm.
The latest mid level water vapor loop shows that drying will work
its way very slowly into west central IL. This, along with the
loss of diurnal cloudiness may lead to a brief period of partial
clearing later this evening. Any clearing will be short lived
though as plenty of low level/surface moisture should result in a
development of a deck of stratus clouds from east to west across
the forecast area overnight.

Added patchy fog to the forecast tonight into Thursday morning
along and west of the IL River valley where the surface wind will
be a bit lighter and allow for fog and stratus to both develop.
Also have fog in much of east central IL where it has been raining
much of the afternoon into the evening, which will provide plenty
of low level moisture for fog.

The upper low in central MO and surface low in KY will push off to
the east overnight and early Thursday, resulting in ridging to
move in for Thursday. This will give us drier conditions with more
sunshine and temperatures in the 70-75 range.

.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 325 PM CDT Wed May 24 2017

The ridging for Thursday will be progressive, allowing for a WSW
upper level flow to develop on Friday. This will allow for
moisture return in west central and central IL during the day
Friday. The models are in fairly good agreement that low pressure
will track from the southern Plains toward eastern MO by Friday
evening. This will spread showers and t-storms into most of the
forecast area Friday afternoon. A southerly surface wind will
allow temperatures to climb into the upper 70s before the
convection moves in/develops Friday.

As the low moves roughly along the I-70 corridor later Friday and
into central IN by Saturday morning, the precipitation will
briefly come to an end. However, it appears that an MCS may
develop in KS/western MO late Friday night, so the remnants of
that system should move along the boundary in southern IL,
resulting in an increase in t-storm potential by late Sat morning
and into Saturday afternoon across central and eastern IL.

There is some uncertainty as to the postion of the aforementioned
frontal boundary for late Saturday and through Sunday. Thus, the
proximity of a boundary near the forecast area will result in
keeping at least a chance of convection in the forecast south of a
Springfield-Paris line for Saturday night/Sunday...and into all of
the forecast area later Sunday.

We should finally see a break in the precipitation Sunday night
into Monday, before deep cyclonic flow reintroduces the potential
for showers and a few thunderstorms north of I-74 on Monday, and
over the rest of central IL Monday night into Tuesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 653 PM CDT Wed May 24 2017

Showers will diminish this evening as daytime heating ends and low
pressure slowly heads eastward. A large area of MVFR ceilings
upstream of central IL will continue to spread over the area
bringing predominant MVFR cigs to all central IL terminals by
02-03Z. Clearing of upper level cloud cover overnight will allow
stratus and some fog development resulting in IFR/LIFR cigs and
some visibility reduction. Improving conditions expected after
13-14Z resulting in VFR conditions by around 18Z. Winds N-NW 10
kts or less with a few higher gusts this evening and tomorrow
afternoon.


&&

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

$$

SHORT TERM...Miller
LONG TERM...Miller
AVIATION...37



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