Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 012025
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
325 PM CDT Fri Aug 1 2014

.DISCUSSION...
ISSUED 325 PM CDT Fri Aug 1 2014

Very little change to our overall weather pattern is expected into
the middle of next week as the upper level northwest flow
continues. This will result in temperatures at or just below
seasonal normals, with shortwave troughs providing a focus for
showers/t-storms Tuesday and Wednesday. Medium range models
showing a shift in our pattern by Thursday, but there are quite a
few differences regarding how this will take place and what the
associated sensible weather will be.

SHORT TERM...Tonight through Sunday Night

Diurnal convection this afternoon has been getting a boost from a
shortwave trough moving into the area. The surface reflection was
only a weak wind shift, but this was enough to combine with the
instability and convective updrafts to produce several funnel
clouds in central and east central IL this afternoon. The radar
indicated a myriad of outflow boundaries with scattered
thunderstorms east of the IL River and very isolated showers to
the west. Will keep the mention of scattered t-storms in the
forecast for this evening generally along and east of I-55, with a
mention of isolated showers/few t-storms to the west.

The scattered rainfall, some of which was heavy in spots, will
contribute low level moisture to help produce patchy fog overnight
and into Saturday morning. The shortwave moving across the Midwest
tonight could linger just long enough in extreme eastern IL to
produce scattered showers/t-storms early Saturday afternoon.

Otherwise, weak high pressure will begin to approach later
Saturday and settle into the area Sunday with mostly sunny
conditions and temperatures in the lower 80s.

LONG TERM...Monday through Friday

A southerly wind will develop Monday ahead of the next approaching
cold front from the northwest. This will give us gradually
increasing humidity and temperatures closer to normal for early
August.

There are some model differences with the speed of the cold front,
with the GFS being quicker and the European and Canadian on the
slower side. The GFS may be a bit too quick with its frontal
depiction, so will keep the chance for thunderstorms north of I-74
for Monday night, and gradually drop them southward with the front
Tuesday.

As the models start to depict a breakdown in the northwest flow to
more of a zonal flow, their differences start to show up with the
position of the front Wednesday through Friday. The Canadian model
is farther north while the GFS drops it south toward the OH valley
Wednesday then lift it back north as a warm front by Friday.
Prefer the European solution of settling the front into southern
IL then pretty much keeping it there through the end of the week.
This would result in periods of showers and thunderstorms with
high temperatures in the lower to middle 80s.

Miller
&&

.AVIATION...
ISSUED 1230 PM CDT Fri Aug 1 2014

Short wave tracking se across central IL this afternoon and
interacting with unstable airmass to produce isolated to scattered
showers and thunderstorms this afternoon over central IL. Added
VCTS and tempo groups for 4SM TSRA BKN050CB next few hours
especially along I-72 at SPI, DEC and CMI where a weak surface
boundary lingers this afternoon. Isolated to scattered showers and
thunderstorms that have recently developed over central IL at
midday should dissipate at sunset with loss of daytime heating.
Some MVFR vsbys possible with convection while ceilings should
stay in the VFR range. MVFR vsbys with fog to develop overnight
and lift by mid Sat morning as scattered cumulus clouds again
develop. Isolated convection to develop by Sat afternoon mainly in
eastern IL after 18Z/1 pm so kept central IL TAFs dry Saturday
morning. Winds to stay quite light next 24 hours, generally near
5 kts during daytime hours and near calm tonight after sunset.

07
&&

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

$$






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