Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 281755

Area Forecast Discussion
National Weather Service Lincoln IL
1255 PM CDT Tue Mar 28 2017

Issued at 1044 AM CDT Tue Mar 28 2017

Despite a ridge of high pressure in place across the region,
boundary layer moisture trapped beneath a subsidence inversion is
resulting in overcast conditions across much of the KILX
CWA this morning. The exception is across east-central Illinois
where a large break in the cloud cover has developed and is slowly
spreading southward. Skies are currently mostly sunny from Paris
and Mattoon southward to Marshall and Newton. While no model is
handling the clearing particularly well, it is apparent from
satellite loops that much of the E/SE CWA will remain partly to
mostly sunny into the early to mid afternoon before cloud cover
slowly advects back into that area from the north later in the
day. Have therefore updated the forecast to feature partly sunny
skies south of I-72 and along/east of I-57. Further north and west
across the remainder of central Illinois, cloudy skies will
prevail for the balance of the day. High temperatures will mainly
be in the lower to middle 50s, with lower 60s along/south of I-70
where partial sunshine will be observed this afternoon.


.SHORT TERM...(Today and tonight)
ISSUED AT 319 AM CDT Tue Mar 28 2017

As the low pressure area that brought rain to the CWA yesterday
moves off to the east, a brief period of dry weather is expected as
a high pressure ridge slides across the area today through tonight.
Winds will remain north to northeasterly through tonight, which
should keep cloud cover over the area the whole time. This cloud
cover and northerly-northeasterly winds will keep temps down as
well. Expecting highs mainly in the 50s, with lower 60s in the
southeast. Overnight lows will be in the 40s.

.LONG TERM...(Wednesday through Monday)
ISSUED AT 319 AM CDT Tue Mar 28 2017

An active weather pattern is expected to persist across central and
southeast Illinois over the next several days. While not every day
will see rain in the area, there will be a frequent risk. Expect
mostly cloudy conditions to persist as well, along with the
precipitation risk. Temperatures through the period will average a
little warmer than normal, with the warmest readings expected ahead
of each system to impact the area.

Quiet conditions will persist into early Wednesday as upper/surface
ridging slowly drift east of the area. Then, increasing
WAA/isentropic ascent ahead of a slow moving upper low/trof
(currently pushing into the Four Corners region) will return the
threat of showers to the area. However, most of the heavier/more
widespread rainfall should hold off until late Wednesday night into
Thursday evening as the system moves through the area. Instability
increases as the system draws closer, peaking around 1000 j/kg over
the southeast 1/2 of the forecast area Thursday afternoon, and
supports at least scattered thunderstorm development. Rainfall
chances should be tapering off on Friday as the system moves east of
the area. While model guidance is pretty good that the main upper
wave will pass through the area Thursday into early Friday, there is
still spread with the exact track of the system, individual short
waves moving through the mean trof, and how quickly the system
departs. Expect current forecast to need additional adjustments as
model consensus hopefully builds around the details.

Quiet weather returns for Friday night into Saturday night, but it
will not last for long as another system should be in our vicinity
for Sunday into Tuesday. However, model agreement during this period
is quite poor with the specifics, resulting in low forecast


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1255 PM CDT Tue Mar 28 2017

Low VFR/high MVFR ceilings will prevail across central Illinois
this afternoon. Once the sun sets, all models are showing cloud
bases lowering to MVFR by this evening. The big question will be
whether or not IFR ceilings will develop late tonight into
Wednesday morning. Rapid Refresh and NAM forecast soundings both
suggest they will indeed drop to IFR after midnight, generally
in the 08z-10z time frame. Meanwhile, a storm system will
gradually approach from the southwest, spreading light showers
into parts of central Illinois Wednesday morning. Based on speed
of system and overall lack of deep-layer moisture within the
profile, will only mention VCSH at KPIA/KSPI after 15z. Winds will
initially be from the N/NE at less than 10kt, but will veer to
the E/NE and increase to 10-15kt ahead of the approaching system
Wednesday morning.




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