Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 242352

Area Forecast Discussion
National Weather Service Lincoln IL
652 PM CDT Thu Apr 24 2014

ISSUED 240 PM CDT Thu Apr 24 2014

Area of showers and thunderstorms across Missouri and northwest
Illinois has been having a hard time penetrating areas to the east
this afternoon. Surface dew points still in the upper 30s to lower
40s along the Illinois River and eastward as temperatures have
risen into the 70-75 range there, with little moisture advecting
in from the southeast. Have had some periods of sunshine,
especially in the southeast, which have helped boost the
temperatures. Main surface low still located just south of Kansas
City, with a cold front trailing into northeast Texas and a
secondary boundary extending north into Minnesota.

Initial forecast concern remains with the rain trends through
tonight, with the focus then shifting toward the extended period
of showers and storms for much of next week.

SHORT TERM...Tonight through Saturday:

Surface low progged to move to near Peoria by early evening, with
the front reaching the Indiana border in the 2-3 am time frame, so
it will still be a few hours before the eastern CWA starts to
rain. Have made some adjustments to better ramp up the rain
trends from west to east this evening, then decrease it again from
west to east after midnight.

Dry and warmer weather expected the next couple days over most of
the area. Still some question as to where exactly the frontal
boundary will stall out on Saturday, but general consensus is
focusing more on the I-72 corridor. Numerical guidance showing a
sharp contrast in temperatures across the boundary, ranging from
the upper 60s north to around 80 south.

LONG TERM...Sunday through Thursday:

Digging wave across the West Coast early this weekend still
expected to swing eastward, with the blocking pattern across New
England resulting in the wave closing off. The large upper low will
meander over the central U.S. much of the week as a Rex block
pattern sets up, resulting in an extended period of showery

Frontal boundary will drift a bit northward on Sunday, allowing
more of the forecast area to be in the warm sector. Extensive
showers and thunderstorms will move eastward into the area through
the day. Currently think the severe threat will stay west of the
Mississippi River on Sunday, but a better shot in our area Monday
as the storm system starts to occlude. After that, temperatures
will gradually lower as the large upper low spins over the central
U.S. Will see a chance of showers each day Tuesday through
Thursday, although coverage will gradually diminish with each
passing day as the low slowly weakens. With the core of the cold
air aloft, will need to monitor for potential low-topped
convection Wednesday and Thursday. However, will leave thunder out
of the forecast for now.



ISSUED 652 PM CDT Thu Apr 24 2014

A line of showers and very isolated thunderstorms will progress
across the terminal sites this evening. Lightning has been very
limited, and has mainly remained south of any of our forecast
area. SPC mesoanalysis graphics show some MUCAPE still available
toward SPI and possibly as far east as DEC, so a thunder threat
will remain for the southern portion of the line of showers. The
northern TAF sites of PIA/BMI/CMI will be hard pressed to see
enough instability for thunderstorms as the upper level MCV moves
across IL. We left a VCTS in the evening hours for all TAFs, but
may be able to pull that in the next hour or so as we monitor the
progress of the system.

MVFR ceilings will most likely be the lowest the clouds drop with
the heavier showers. IFR is looking unlikely at this point and was
removed from the TAFs.

Gusty southeast to south winds to 25 mph will precede the line,
with NW winds developing quickly in its wake. Wind speeds behind
the line will increase to 12-15kt with gusts to 20kt the rest of
the night. NW winds will continue around 12 kt through the day on



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