Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 131102

Area Forecast Discussion
National Weather Service Lincoln IL
502 AM CST Wed Dec 13 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 330 AM CST Wed Dec 13 2017

Deep upper low moving into the Upper Midwest this morning on the
surface map. Predominantly northwesterly flow continues aloft as
the wave dives to the southeast. Southwest winds expected
throughout today to bring temps up to the upper 40s/lower 50s with
limited sunshine as mid level clouds stream across the region.
However, will be a very windy and blustery day. Winds are expected
to remain at sub advisory criteria as the storm moves into the
region bringing a much tighter pressure gradient. Winds just off
the surface come to a maximum before expect some of
the higher gusts from mid morning to early afternoon, once the
inversion breaks. A cold front moving through Central IL will
bring a round of sprinkles/flurries today before clearing the area
after sunset. Much colder air moves into the area behind the wave.
Whereas clouds tonight will help to keep the lows in the 20s,
tomorrows high temps will be about a 10-15 degree departure from

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 330 AM CST Wed Dec 13 2017
Cold air in place for Thursday keeps the high temps just below
freezing. North winds will remain relatively light and wind
chills will drop into the 20s in the afternoon. Weak warm air
advection kicks in for Friday with a west wind trying to pull some
of the warmer air into the region, and highs start to move into
the mid to upper 30s as another wave dives into the western
trough, altering the flow pattern aloft. The remainder of the
forecast centers around the interaction between the wave moving
onto the Pac NW coast on Friday, and an upper low over the Baja.
Either way, the westerly flow aloft allows for a slight warm up
and weak ridging over the eastern half of the country as the wave
digs in. The models are trying to resolve the two waves as to
phasing or ejecting the southern wave into more northeasterly
flow. Models are spinning up a sfc low and pushing precip into the
region for Sunday on this most recent run. Given the pattern
shift involved, expect details to start to come out in the next
few runs for the remains of the forecast pd.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 500 AM CST Wed Dec 13 2017

The initial concern this forecast period will be with the gusty
winds expected across the area today as low pressure tracks to our
north. The secondary concern will be with the timing of the low
VFR to MVFR cigs behind the cold front that is forecast to push
across the region this afternoon. We may see a few hours of LLWS
criteria cross the TAF sites but surface winds are expected to
increase quickly this morning, mainly after 14z with gusts up to
35 kts possible by later this morning through early this evening.
Initially winds will be south to southwest but quickly shift into
a west to northwest direction as the cold front approaches and
then passes to the east of a TAF site, starting at KPIA at or
shortly after 18z with FROPA expected at CMI around 21z.

Any lower VFR or MVFR cigs will be post frontal with cigs as low
as 2500 feet AGL possible this evening. As far as precip is concerned,
coverage appears rather limited again today so will only keep the
VCSH near or just behind the FROPA and not include any tempo groups
at this time. We may see some spinkles with the front and possibly
a few flurries as the colder air invades late this afternoon into
the early evening hours. The strong/gusty winds should begin to
slowly diminish across the area after 03z.




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