Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 271457

Area Forecast Discussion
National Weather Service Lincoln IL
957 AM 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 12Z TAFS through 12Z Tuesday morning)
Issued at 657 AM CDT Mon Mar 27 2017

Challenging aviation forecast this morning as VFR to MVFR
conditions occurring south of a wind shift boundary, and IFR to
LIFR conditions north of this boundary. Precip will begin to
spread into the area and effect the TAFs starting at 15z at SPI
and DEC and 16z at the other sites. When precip arrives at the
sites, cig and vis will likely be effected SPI/DEC/CMI, becoming
more MVFR. Once precip arrives at PIA/BMI conditions may improve a
little at BMI, but remain about the same at PIA. Conditions will
change again once precip begins to wane over the sites. T-storm
parameters sufficient for predominate thunderstorms for the
afternoon and think thunder will remain south of the PIA and BMI
areas. At DEC and CMI, VCSH will linger til around midnight. All
sites will see a decrease in conditions after the precip stops and
the sun goes down. Winds will remain easterly, but become north to
northeasterly late this afternoon.




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