Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 231955
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
255 PM CDT Wed Apr 23 2014

.DISCUSSION...
ISSUED 253 PM CDT Wed Apr 23 2014

Plenty of dry air in place over Illinois early this afternoon, on
the periphery of a high pressure ridge, with dew points in the
upper 20s to lower 30s. Across the southeast half of the forecast
area, clouds have been eroding as they move into the drier air. Area
of showers has been advancing eastward from Iowa. Looks impressive
on radar, but surface observations are showing cloud heights well
over 8000 feet in many cases, indicating not much in the way of
measurable rain is reaching the ground. However, this is enough
that a mention of isolated showers across the northern CWA this
evening is warranted.

The first forecast concern is with the timing of rain over the
next day or so, as this storm system pushes eastward. In the
longer term, the duration of the rain is a concern as we get set
in a rainy pattern for the first half of next week.


SHORT TERM...Tonight through Friday:

Water vapor imagery and upper air analysis showing a deep trough
currently pushing east across the Rockies, and is progged to move
across the Mississippi Valley late Thursday. The dry air at the
lower levels will take some time to saturate, with the forecast
soundings still rather parched below 850 mb at mid afternoon. Have
limited Thursday morning PoP`s to areas west of I-55 and still
kept them below 50% during the afternoon east of I-57, otherwise
have maintained the categorical PoP`s over 80% in much of the
forecast area during the afternoon. Best instability looks to be
along and south of I-72 for any thunder, although some low CAPE`s
to around 200 J/kg progged as far north as Peoria, so have kept
some thunder mention that far north. With the system a bit slower,
will mention 80% or higher PoP`s into the evening across the east
half of the forecast area into the evening. Dry weather then on
tap for Friday.


LONG TERM...Friday night through Wednesday:

A cold front will push southward through the region Friday night.
Big question will be where it ends up, as it will likely not be
going anywhere for awhile. Most of the models do have it through
the forecast area by early Saturday, although the ECMWF and GEM
models linger it more toward the I-72 corridor. Saturday should be
dry. However, the main action will be later in the weekend, as all
the models continue to close off an upper low over the central
Rockies. This low will only slowly drift eastward, and will likely
linger in some form into the middle of next week.

Most of Sunday should be fairly decent, with the rain most likely
across the western CWA during the afternoon. After that, rain is
likely on and off, with PoP`s gradually diminishing Tuesday and
Wednesday as the cutoff low slowly weakens. By this point, as the
core of the colder air settles over the Midwest, temperatures will
be a good 15 or so degrees below normal, with highs Tuesday and
especially Wednesday generally in the 50s.

Geelhart

&&

.AVIATION...
ISSUED 1236 PM CDT Wed Apr 23 2014

Dry air in place expected to keep the precip out to the west from
working into the TAF sites more than possibly a sprinkle this
afternoon, so keeping from mention at this point. However...will
drop from 10kft cigs to 5kft cigs with the moisture advection
overall by later this evening. VFR through the fcst, but the next
problem is expected tomorrow morning as the wave pushes some
precip towards the FA. Much of the precip is expected to hold off
until mid morning in the west...and a bit later in the east...but
models are not consistent with timing or coverage early.
Mentioning VCSH for the morning to start the trend...and next
issuance will likely see more of a mention and contemplate the
timing/potential for thunder.

HJS

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$





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