Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 271732

Area Forecast Discussion
National Weather Service Lincoln IL
1232 PM CDT Mon Mar 27 2017

Issued at 957 AM CDT Mon Mar 27 2017

Upper low has entered west central Missouri this morning, with the
surface low not too far southeast. Initial bands of showers are
exiting the far northern CWA this hour, while the larger and more
predominant rain shield continues to overspread the forecast area
from the south. A bit of a curl is visible on the radar mosaics
between St. Louis and Mt. Vernon, and some of the radar returns
are starting to get enhanced there, although no lightning has been
observed as of yet.

Main surface low track continues to be projected across the
southern third of the state this afternoon, per the short term
high-res model guidance. Most of the MUCAPE available will be more
in areas along and south of I-70, and have done some refining of
the thunder mention in the forecast. Also adjusted the PoP trends
with indications of a dry slot moving into the western CWA later
this afternoon as the upper low opens up and reaches the area.


.SHORT TERM...(Today and tonight)
ISSUED AT 330 AM CDT Mon Mar 27 2017

Low pressure area in eastern OK will lift northeast toward the Ohio
river valley today. Showers and a chance of thunderstorms is
expected north of this track into central IL later today and into
this evening. Instability and shear parameters appear favorable for
some of the storms south of an I-70 to be strong enough for a small
threat for severe weather. So agree with SPC analysis of shifting
the slight risk for severe weather south of yesterday`s Day 2
forecast. All models, including the HiRes models agree that the
precip should end by 06z tonight. Temperatures will remain very warm
today and then mild tonight.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 330 AM CDT Mon Mar 27 2017

A brief break in the precip for Tues and Tues night as upper level
ridging keeps the region dry. Easterly winds through Wednesday
results in a rather neutral temp influence and max temps run very
close to climatological norms/degree or two above. 00Z runs have
sped up the approach of the system on Wednesday morning...with the
easterly winds holding off some of the advance of the precip across
western IL through the afternoon.   Precip dominates the forecast
through Friday this run...ending a bit quicker than last couple runs
as well.  This is altering how the early weekend looks (dry and cool
on Saturday), and although the models are starting to show more
similarities in the solution for the upper low over the southern
Plains late in the weekend, the models are hanging on to some
showery activity for Sunday.  Clearly moving through a pattern shift
in the first part of the work week and although the GFS and ECMWF
are showing mostly a dry forecast, the blends are picking up pops
from other solutions.  Not completely convinced, and although the
models do look better this run... there is still an adjustment
working through the the low gets kicked across the
southeastern quadrant of the country by the low diving into the Pac


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1232 PM CDT Mon Mar 27 2017

Rather challenging forecast for this TAF set. The arrival of
showers has resulted in a rising of the ceilings at many sites,
and areas from KSPI eastward are currently above 4000 feet. IFR
conditions persist near KPIA though, and that area is least likely
to see any significant improvements beyond low MVFR range. Have
removed the thunder mention as it appears the greatest threat will
be in southeast Illinois closer to the low track. As the low
starts to move away early this evening, wraparound low clouds
will bring ceilings back below 1000 feet, with only some modest
improvement expected later Tuesday morning.




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