Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 101648
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1048 AM CST Sun Dec 10 2017

.UPDATE...
Issued at 1045 AM CST Sun Dec 10 2017

Updated the forecast for stronger winds into early afternoon along
with more cloud cover as a band of cirrus clouds quickly raced se
into central IL by late morning. This band of high clouds will
decrease from nw to se during the afternoon while low
stratocumulus clouds over WI drop southward into northern IL
during the afternoon and stay north of CWA through dusk. A cold
front entering far nw IL late this morning will push se dry across
CWA during the afternoon, reaching se IL by sunset as brisk sw
winds gusting 20-30 mph turn nw over central IL. Temps currently
in the low to mid 30s, will rise to seasonable levels in the upper
30s and lower 40s for highs this afternoon.

&&

.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
timing.

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 12Z TAFS through 12Z Monday morning)
Issued at 536 AM CST Sun Dec 10 2017

VFR and gusty throughout today with winds slowly veering from
southwesterly to northwesterly by sunset. Mid level clouds around
10k ft will move out this morning and get replaced by scattered
cirrus for the remainder of the day. Weak surface trough will
bring about the wind shift to near westerly by midday, and
northwesterly by sunset. Cirrus through the overnight as the winds
become much lighter and somewhat variable.

&&

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

$$

UPDATE...07
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...HJS



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