Area Forecast Discussion
Issued by NWS Central Illinois

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KILX 200412
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1112 PM CDT Sat Jul 19 2014

.DISCUSSION...
ISSUED 840 PM CDT Sat Jul 19 2014

Pleasant weather conditions continue this evening as high pressure
holds firm to our east. Satellite data indicating a band of mid and
high level clouds tracking into our area this evening as a weakening
shortwave pushes across north central Iowa. Will have to watch for
some patchy fog which may form after midnight, especially along and
east of Interstate 57 where dew points were several degrees higher
than out west. Latest forecast soundings support this possibility
late tonight, mainly from 3 am til 7 am Sunday morning. Current
forecast on track early this evening, so a ZFP update will not be
needed.

&&

.AVIATION...
ISSUED 1105 PM CDT Sat Jul 19 2014

The main forecast issue remains the potential for a brief period
of MVFR or lower vsbys in fog from 09z-12z, otherwise, we are
expecting VFR conditions to dominate thru the remainder of the
TAF period (06z Mon). The higher probability for more widespread
fog and lower vsbys still appears to be along and east of I57
which would include CMI with progressively higher vsbys as you
head west. What fog that does form early Sunday morning should
be gone by 13z with some more cumulus forming around 16z. Surface
winds will be light and variable tonight and light southerly on
Sunday with speeds less than 10 kts.

Smith
&&

.PREV DISCUSSION...
ISSUED 326 PM CDT Sat Jul 19 2014

A weak mean trough remains over the eastern U.S. with Illinois in
a light and relatively featureless northwest flow aloft. The main
change over the next several days will be an amplifying ridge over
the West...initially extending into the Midwest increasing
temperature and humidity over Illinois. Midweek...a shortwave
will propagate over the western ridge pushing a cold front through
Illinois for a good chance for thunderstorms followed by a cooldown.

SHORT TERM...Tonight through Tuesday

Scattered cumulus development based around 4000-6000 feet covers
most of central and southeast Illinois as expected today. This
will diminish overnight with the loss of surface heating.
Overnight expect patchy fog mainly over areas east of I-57 as
easterly surface winds pull a more moist air mass in from Kentucky
and Indiana as seen on satellite trends and depicted on HRRR
model. Sunday and Monday a strong 500 mb ridge is progged to
develop over the West and extend into the Midwest. This will bring
a warm and stable air mass over Illinois. Southerly low level flow
will bring an increase in moisture yielding dewpoints over 70 by
Monday and Tuesday and heat index values approaching 100 by
Tuesday afternoon.

LONG TERM...Tuesday Night through Saturday

A shortwave propagating over the western ridge will flatten the
ridge somewhat and bring a cold front through Illinois. Models
tend to depict this scenario early Wednesday morning at this point
but there is still plenty of room for uncertainty in timing. This
will bring a good chance for showers and thunderstorms followed by
a cooldown and dry conditions by Thursday.

A stronger low pressure system moving in from the Pacific
Northwest looks to break down the ridge significantly late next
week. This should bring another surge of cooler air southward,
though not as cool as this past week.

Onton


&&

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

$$






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.