Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 231047
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
547 AM CDT Wed Aug 23 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 311 AM CDT Wed Aug 23 2017
Pleasant weather anticipated through the remainder of the week and
into the weekend as high pressure dominates the weather map. This
morning, a surface ridge stretches through the Plains, as
northwesterly flow aloft ushers some mild temperatures into the
region. Dewpoints are also dropping into the low to mid 50s as the
drier air filters in from the NW. A few cu possible across Central
Illinois, diminishing just before sunset. Another clear night
expected, with temps dropping a degree or two lower than this
morning.

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 311 AM CDT Wed Aug 23 2017
The quiet weather continues for the Midwest through the end of the
week for the most part. 500 mb map shows a deep trough over the
NE, and weak ridging over the western half of the country. The
northwesterly flow remains anchored over the region through the
end of the week and into the weekend. Currently a wave over
western Canada is expected to top the ridge and dive into the
broader trough, traversing ILX late Wed night/Thu morning.
However, the dry air being advected into the region will keep the
passage of that wave dry in the forecast. The wave itself will
reinforce the trough, and keep northwesterly flow over the region.

Towards the end of the week, the upper low just north of the
Pacific NW will push further inland, effectively narrowing the
upper ridge and starting to kick the low over the NE further
eastward. The high pressure at the surface shifts to the east as
the pattern progresses, with winds coming around to more southerly
just to the west...but flow across the forecast area remains
easterly. Around Sunday/Day 5, the forecast becomes problematic as
another wave dives into the Plains states, moving towards the
Midwest, collapsing the ridge...while the next tropical system
potentially moves into the coast and progresses eastward. Models
vary considerably with the solution. Previous runs brought a trof
early enough to pull that system to the northeast and out of the
region. But the 00Z runs are quicker with the trof, more or less
leaving the system over the Gulf Coast without a prominent
influencing system. Either way, the wave diving into the Midwest
for the end of the weekend/beginning of next week is working with
a questionable moisture profile in the models as they are pulling
most of it out of a system that could remain well to the south at
that point...not to mention a lack of southerly flow ahead of it
advecting any moisture or warmth into the region.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 545 AM CDT Wed Aug 23 2017

High pressure over the Plains keeping skies clear in the Midwest
as well with light northwesterly winds at the surface. Quiet and
VFR throughout the forecast with cu field anticipated today,
clearing just before sunset. Drier air mixing in from the NW
should keep dewpoints low enough to counter visibility drops.

&&

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

$$

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



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