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000
FXUS63 KILX 081743
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1143 AM CST Sat Mar 8 2014

.DISCUSSION...
ISSUED 850 AM CST Sat Mar 8 2014

14z/8am surface analysis shows slow-moving cold front along the
I-70 corridor. Large area of light precipitation behind the front
enhanced by upper short-wave over Minnesota is pushing through the
Chicago area into northern Indiana. Meanwhile further southwest,
another upper wave over the Texas panhandle is creating another
area of precip along the trailing end of the front across the
Ozarks. The northern precip area has exited the N/NE KILX CWA, but
we will have to keep an eye on the southern area as it will likely
enter the SE CWA along/south of I-70 this afternoon. In the
meantime, overcast conditions with patchy fog will persist through
midday. May even see a few light showers from time to time, but
rainfall amounts will be minimal. Made some updates to the
forecast to lower POPs and remove mention of snow/sleet across the
north. Will carry scattered rain showers and patchy fog instead.
Zone update has already been issued.


Barnes
&&

.AVIATION...
ISSUED 1143 AM CST Sat Mar 8 2014

Low clouds blanket central Illinois late this morning...with
mainly low MVFR ceilings noted. Frontal boundary continues to sag
southward into the Ohio River Valley: however, clearing will be
slow to arrive from the northwest due to weak cloud-layer flow.
Models do not have a good handle on the situation, as the GFS
scours out the clouds this evening, while the NAM holds on to
overcast conditions through Sunday morning. Even though flow is
weak, satellite trends suggest clearing currently taking place
over central/northern Iowa will arrive across the area this
evening. Will therefore break up the clouds at KPIA by 02z, then
further east to KCMI by around 04z. Once skies clear, ample
low-level moisture due to recent snow melt and very light precip
may lead to fog development as winds become light/variable beneath
ridge axis overnight. Will lower visbys to around 3sm after 09z
accordingly. After that, southwesterly winds on the back side of
the departing high will lead to improving visbys and mostly clear
skies by mid-morning Sunday.

Barnes
&&

.PREV DISCUSSION...
ISSUED 250 AM CST Sat Mar 8 2014

Initial cold front/wind shift has gone through about 3/4 of the
CWA as of 2 am, but colder air lingers further northwest, with
sub-freezing temperatures still back across Iowa and northern
Missouri. Band of light rain/sleet mix has pushed into the far
western parts of the forecast area, with radar presentation and
surface obs showing more of a snow signature in narrow bands from
southwest to east central Iowa.

General forecast concerns are threefold: the first being with
precip types this morning, secondly the much warmer weather early
next week, and the third and most significant being with potential
storm system at midweek.

SHORT TERM...Today through Tuesday:

For today, forecast soundings showing the sleet potential across
the western half of the CWA early this morning, changing to snow
north and rain south. Some very dry low levels across the
southeast half should hold off the precipitation until midday or
later, at which point it should be rain. Initial precip should be
in a weakening state ahead of an upper wave in the northern
stream, but a secondary surge will push out of southern Missouri
during the afternoon, where the southern stream starts to interact
with the northern one, and will linger some PoP`s into the evening
south of I-70.

Significant warming trend to start on Sunday as winds quickly
turn southwest, as high pressure pushes south into the lower
Mississippi Valley. 850 mb temperatures rising into the +10C range
early Monday. Have maintained highs in the upper 50s to lower 60s
on Monday ahead of a weak cold front, with slightly cooler
conditions on Tuesday but still well into the 50s most areas.

LONG TERM...Tuesday Night through Friday:

Main challenge remains with midweek system, due to phasing of
split upper flow near the central Plains. Medium range models in
good agreement with surface cyclogenesis over Oklahoma on Tuesday
with a general east-northeast track of the low into Kentucky
Wednesday morning. The GFS is much weaker with this feature than
the ECMWF or Canadian models, with just a glancing blow of some
precip Wednesday morning. It has had some inconsistencies in the
last few runs, so will lean away from that model for now. Precip
type will be critical, as 850 mb temps on these models are down to
around -6C by midday Wednesday. The resolution of forecast
soundings on these models is a bit on the coarse side, so it is
too difficult to fine tune the details that far out, but right now
will keep the southeast as all rain, with a rain/snow mix
elsewhere Tuesday night and Wednesday.

General upper flow to remain from the Pacific through the end of
the week, so temperatures should rebound again late in the week
following this storm system.

Geelhart


&&

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

$$