Area Forecast Discussion
Issued by NWS Central Illinois

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579
FXUS63 KILX 271031
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
531 AM CDT WED APR 27 2016

.SHORT TERM...(Today)
ISSUED AT 322 AM CDT Wed Apr 27 2016

The cold front that pushed across the area yesterday was located
over central Missouri east through extreme southern Illinois
early this morning. To the north of the front, temperatures
have dropped into the mid and upper 40s with a chilly northeast
wind, while over southern Illinois, temperatures were still in
the low to mid 60s. Main question for today will be just how
far north the warm front will be able to move as a wave of
low pressure approaches from the west this afternoon and
evening, which will dictate how far north the severe threat
will be in our area. 06z NAM-WRF continues to show the more
favorable MUCAPE instability axis will be roughly along and
especially south of the I-70 corridor this afternoon and
evening with the HRRR model suggesting the warm frontal
boundary may edge into southeast Illinois late today.

The first wave of showers and isolated storms is expected to
develop along and just north of the boundary over southern
Illinois this morning and arc northwest through our southwest
counties. Just how far north and east the rain will be able
to push into the drier air mass to our north this morning is
a challenge as we have already delayed the onset from previous
forecasts and really not confident that is slow enough. However,
models have been more consistent with the timing north this morning
with the first wave of rain, with even a hint of a break before the
main band of showers and storms tracks northeast into our area this
afternoon and evening. If there is going to be a severe weather
threat, this afternoon and evening would be the primary time frame
and especially along and south of the I-72 corridor. 0-6km shear
values around 45 kts could help to produce some wind and hail threat
in this area from mid afternoon through the mid evening hours before
the main area of forcing shifts off to our north and east.

Quite a range in temperatures across the forecast area today with
areas to our north having a tough time getting to 60, while over
far southeast Illinois, afternoon temperatures should climb into
the middle 70s. Have trended a bit cooler than guidance north of
the frontal boundary due to the extensive cloud cover, expected
rainfall and a cool easterly flow today, while guidance looked
reasonable over our southeast counties which had a decent chance
of seeing the warm front edge just to their north this afternoon.

.LONG TERM...(Tonight through Tuesday)
ISSUED AT 322 AM CDT Wed Apr 27 2016

Another similar round of models overall.  Deep low over the Plains
states this morning will not only drive the weather today, but into
the overnight and tomorrow as well. Showers and thunderstorms
continue through the overnight and begin clearing from SW to N/NE
tomorrow in the first half of the day as the upper low starts to
make its way through the region.  Should the low slow any more than
is currently forecast...the chances for precip could be a little
low...but for now the track of the upper low is further to the
north, allowing the southern tier of the state to be mostly dry on
Thursday. Showers come to an end briefly with a break Thur night and
into Friday before the next wave ejects out of the SW across the
Midwest for the weekend later Friday night.

Rain chances return for Friday night through the weekend with a
similar setup happening again with another slow moving storm system
out of the SW.  Warm sector showers and thunderstorms dominate the
weekend, with some clearing of the precip on Monday with drier air
wrapping around the system. Ultimately, will be interesting to see
how the current slow moving low is handled.  Models beginning to
show some wavering with the solutions as the low for the weekend no
longer looks like it clears the trof completely out of the SW.
Should that trof remain...shortwaves ejecting out over the Midwest
Mon-Tue could change up the forecast again.  For now, the models
shear out that energy in the wake of the main low...leaving the
first part of the work week with little threat.  Slight pops in for
now.  Expect some variability in the forecasts to come. Temperatures
throughout the forecast are in line with some expected seasonal
variance with rain/clouds/sun mix.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 525 AM CDT Wed Apr 27 2016

IFR and MVFR cigs/vsbys expected over most of the TAF sites thru
at least this morning before we see cigs rise into the MVFR to low
VFR category this afternoon. Periods of showers and TSRA can be
expected as well as a frontal boundary, currently to our south,
shifts slowly north into south central Illinois later today. The
first wave of rain and isold TSRA just west of STL this morning
will shift northeast into our area during the morning hours before
a temporary break in the rain moves in early this afternoon. That
will be followed by another wave of showers and possibly some
strong TSRA (especially for SPI and DEC) after 20z. Forecast
soundings do indicate enough turbulent mixing occurring with
the rainshowers and storms to bring the cigs to low VFR at times
this afternoon. Areas from PIA and BMI may stay in the IFR range
thru most of the day, while our southern TAF sites, SPI, DEC and
CMI may see the temporary cigs up to low VFR at times this
afternoon and evening before returning back to at least MVFR
category late tonight. Surface winds will be easterly at 12 to 17
kts today with a few gusts around 23 kts at times. Easterly flow
expected again tonight but with speeds diminishing to 8 to 13 kts
as the surface low approaches the area.

&&

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

$$

SHORT TERM...Smith
LONG TERM...HJS
AVIATION...Smith



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