Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 100946

Area Forecast Discussion
National Weather Service Lincoln IL
346 AM CST Sun Dec 10 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 308 AM CST Sun Dec 10 2017
Pattern across North America remains deeply amplified as a storm
system moves off the New England coast. Northwesterly flow aloft
dominated the midsection of the country. This pattern will remain
in place and result in waves of cold air and precip chances off
and on through the week. Looking at the Arctic oscillation, the AO
remains negative, meaning the polar circulation is weaker than
normal and cold air is escaping southward and into the region.
A couple surges of cold air dominates the forecast, coming in
waves with a mostly neutral NAO. Northwesterly flow at 500mb
sends a series of weak waves with little agreement in model

This morning, a few echoes on radar not being caught with any
observations of snow as much of the ceilings are mid level clouds
and considerably drier underneath. A weakness in the surface
pressure gradient will result in a lull in the winds this morning
before they increase out of the southwest mid morning and gust
25-30mph through the afternoon with some moderate mixing. Temps
will climb up to the upper 30s/low 40s, but the wind will make it
feel like its still in the 20s/low 30s in the afternoon. Tonight,
slightly milder temperatures for the overnight with decreasing
winds, but increasing cloud cover.


.LONG TERM...(Monday through Saturday)
ISSUED AT 308 AM CST Sun Dec 10 2017
Smaller shortwaves moving along the northwesterly flow will bring
a series of light chances for snow and flurries Sunday
night/Monday morning, mainly in the north and northeastern
portions of the state...but a small shift in the forecast track
could result in some flurry mention showing up in the forecast in
future runs. Northwesterly flow continues at the surface and aloft
through the first couple days of the work week. Mondays highs
move into the 40s, but the trough/wave bringing snow chances to
the north and east is accompanied by the second round of deep cold
air and flurries with Monday night temps drop into the 20s.
Tuesday nights drop into the teens. With the deepening cold air
and continued northwesterly flow, have brought the winds up a knot
or two from blended guidance through midweek. Next chances for
snow now showing up in the model blends Wednesday, and small
showers through Friday. GFS is far more aggressive, but both ECMWF
and GFS have major timing issues with the waves. NAM has started
looking very similar to the GFS towards the end of its run, just
prior to the impact of the Wednesday wave...which could have a
major impact on the forecast for midweek. No large scale systems
are brewing, but periodic quick moving waves, with definite
timing issues. As for the end of the week, the AO is forecast to
become positive, and the forecast responds accordingly, with the
flow across the country starting to become less amplified.
Forecast should start to moderate with less drastic swings in the
temperatures, at least briefly, going into the weekend.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1134 PM CST Sat Dec 9 2017

VFR conditions will prevail at all TAF sites next 24hrs. High
cirrus is over the sites currently, but shortly after midnight,
mid clouds around 10kft will begin to move over the area and bring
a 10kft cig to all sites for 3-5 hours overnight. This patch of
mid clouds will not last long and all sites should have scattered
out by morning. Then it appears a dry sfc trough will rotate
through the area but clouds will remain scattered mid or high
clouds. The scattered mid clouds will remain over the area into
the evening hours. Winds will be southwest overnight and then
increase in speeds with gust of 20-22kts by morning once the mid
clouds move off to the east. Winds will diminish some during the
afternoon as the sfc trough goes by and winds become northwest for
the remainder of the TAF period.




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