Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 281955
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
255 PM CDT Thu Aug 28 2014

.SHORT TERM...(This evening through Friday)
ISSUED AT 255 PM CDT THU AUG 28 2014

18z/1pm surface map shows warm front extending from northern
Missouri into western Kentucky.  Aloft...vigorous upper-level low is
evident on water vapor imagery over eastern Colorado/western Kansas.
Large cluster of showers/storms associated with the low developed
along the front across Iowa last night and has since weakened as it
lifted northeastward into drier air over the Upper Midwest/Great
Lakes.  Convection is still ongoing along outflow boundary from
eastern Iowa into northern Missouri: however, most of this will
remain W/NW of the KILX CWA late this afternoon into the early
evening.  Meanwhile, scattered convection is firing further south
along the front across western Kentucky and this is expected to
develop further north into central Illinois over the next couple of
hours.  HRRR has had a good handle on the convection and have
followed its solution closely for the immediate short-term.  Have
therefore gone with scattered showers/thunder across all but the far
NE CWA around Champaign and Danville this afternoon into the
evening.  Think convection will be diurnally driven and will
dissipate shortly after sunset.

As upper low slowly approaches from the west, corresponding
downstream ridging will help push the warm front northward tonight
into Friday.  With strongest upper support remaining west of
Illinois through the day, think convection will once again only be
scattered in nature and primarily occur during peak heating.  Have
therefore gone with a mostly dry forecast during the morning,
followed by chance PoPs during the afternoon.  Best rain chances
will be focused closer to the frontal boundary across the northern
two-thirds of the CWA.  High temperatures on Friday will be held
down a bit by clouds/precip, but will still rise well into the 80s,
with locations along/south of I-70 perhaps hitting the 90-degree
mark.


&&

.LONG TERM...(Friday night through Thursday)
ISSUED AT 255 PM CDT THU AUG 28 2014

Upper wave currently over the Rockies expected to slowly move out
and bring rain chances to the area, particularly Friday night and
Saturday as the upper trof moves through the Midwest.  Keeping the
precip around on Saturday may result in slightly cooler temperatures
by the afternoon.  Once again, the cold front associated with the
upper trof moves across the region, losing its distinct baroclinic
zone and becoming more diffuse as it slows considerably just to the
southeast near the Ohio River Valley.  The remaining boundary will
keep pops around for the areas in the southeastern portions of the
state through the remains of the weekend until another larger trof
moves across the country bringing more widespread rain and thunder
for Sunday night into Monday. Signif differences between the ECMWF
and the GFS with the GFS being weaker with the boundary and leaving
a more stationary focus for prolonged showers...whereas the ECMWF is
more progressive and dries out the region on Tuesday.   At this
point, the ECMWF builds a weak upper ridge into the Midwest and the
GFS stays more active.


&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
ISSUED AT 1235 PM CDT THU AUG 28 2014

Warm front currently across southern Illinois will be the main
weather-maker over the next 24 hours. 17z radar imagery continues
to show dry conditions across the KILX CWA, although scattered
showers/thunder are beginning to develop further south across
western Kentucky/far southern Illinois. This is shown quite nicely
by the 3-hr HRRR forecast, which also shows widely scattered
thunder developing further north into west-central Illinois after
20/21z. Will continue to feature a period of VCTS this afternoon
into the early evening before any diurnal convection dissipates.
Even after the afternoon showers fade away, forecast soundings are
showing mid-level cloud deck remaining in place tonight. This
should mitigate any potential fog development, with the Rapid
Refresh showing visbys at or above 6sm through 10z. Winds will be
from the E/SE at less than 10kt this afternoon and tonight, then
will become S/SE by Friday morning as the warm front lifts
northward.


&&

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

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BARNES






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