605 
FXUS63 KILX 080910
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
310 AM CST Wed Feb 8 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 309 AM CST Wed Feb 8 2017

It will feel much more like winter across central and southeast
Illinois through the period, and in more ways than one. Temperature
readings that had been well above normal in recent days, will trend
below normal. Also, a quick shot of snow is expected across much of
the area today.

Cold air has been filtering into the area on northerly winds
overnight, and this trend will persist through the period. High
temperatures today will be in the lower 30s across much of the area,
with lows tonight mainly in the teens.

An area of snow is rapidly approaching the area from Iowa, and should
begin to impact western portions of the forecast area toward
daybreak. This area of snow is forecast to weaken as it tracks east-
southeast this morning. However, a second more expansive area of
snow is expected to begin spreading across the region toward midday.
This second area of snow should be east of the area by 00Z Thursday
(6 pm tonight). Southeast Illinois may warm enough this afternoon
that the snow mixes with or changes to rain for a time.

Today's snow is being forced by a couple short-wave trofs, and their
associated upper-level jet streaks. The second wave is stronger than
the first. Model guidance is fairly good on the track of the heavier
snowfall axis, which is expected to cut from west-northwest to east-
southeast across the northern portion of the forecast area. This
heavier snow area is associated with a fairly strong band of mid-
level frontogenesis. Have decided to post a Winter Weather Advisory
for today within this band for 2"-3" snowfall totals. These amounts
are marginal for an advisory in most cases. However, there has not
been much snow so far this winter. Also, and more importantly, model
guidance suggests there is the potential for convective snow bands.
If the banded snow occurs, local snow totals will be higher than the
current forecast.

&&

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 309 AM CST Wed Feb 8 2017

Sub-freezing temperatures will prevail Thursday and Thursday night
as an upper trough shifts east across the Midwest. However, a marked
warmup for late in the week. A warm front at 850 mb will edge into
western Illinois by sunrise Friday, and by midday, temperatures at
that level will be in the +8 to +10C range over central Illinois (as
opposed to -3C at midnight). The strong warm air advection should
help counter the lingering snow cover and boost temperatures into
the 50-55 degree range over the southwest CWA, with mid 40s over the
northeast areas where today's snow is expected to be a bit more
generous. 

Some discrepancies are developing with the weekend storm system. The
GFS has a surface warm front generally near the I-72 corridor
Saturday afternoon, while the Canadian and ECMWF models are a bit
further north. The latter models are about 6C degrees warmer at 850
mb and have highs more in the upper 60s/near 70 degree range. Opting
for a general blend at the moment with the discrepancies, but that
still yields a mild day with highs mid 50s north to lower 60s south.
In terms of the rain potential, main focus looks to be over the
eastern parts of the CWA, especially with the ECMWF and its
prominent dry slot accompanying the surface low's arrival in the
evening. Passage of the trailing cold front on Sunday looks to be
better for more widespread scattered showers. 

Early next week, a split upper flow will be converging over the Ohio
Valley, thanks to a prominent upper low that will take up residence
over Arizona this weekend. While temperatures cool off a bit, no
significant cold air surges are expected in this pattern, and highs
should still be in the 40s Monday and Tuesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1138 PM CST Tue Feb 7 2017

MVFR cigs across central IL should see some breaks in low cloud
coverage from 06Z-12Z before a rapidly approaching weather system
currently over the central Plains moves into the area. Have
included tempo groups for scattered low level cloud cover, however
predominant conditions still looks like it should be MVFR. Next
system should bring a return to widespread MVFR cigs by 10-12Z
along with increasing -SN with IFR vsby. Improving conditions
expected after 22Z-24Z. Winds N-NW 8-12 kts through the period.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 PM CST this evening for 
ILZ027>031-036>038-045-046.

&&

$$

SHORT TERM...Bak
LONG TERM...Geelhart
AVIATION...37