Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 140159

Area Forecast Discussion
National Weather Service Lincoln IL
859 PM CDT Tue Mar 13 2018

Issued at 858 PM CDT Tue Mar 13 2018

The latest shortwave aiding diurnally driven afternoon/evening
snow flurries/showers over eastern portions of the state has moved
past the area and most snow flurries have ended across east
central and southeast Illinois. Just one more batch of flurries
looks to be headed toward Vermilion County late this evening.
Overnight surface high pressure will be moving from the upper
Midwest toward the southern Mississippi Valley region to promote a
continued decrease of surface winds across central IL along with
a shift toward westerly. Winds will continue to shift toward
southwesterly for Wednesday afternoon, becoming breezy and gusty
with 15-20 mph winds and gusts approaching 30 mph north of I-72.
Lows in the low 20s across the forecast area continue to look good
for tonight, with current temperatures ranging from the upper 20s
in the north to mid and upper 30s south of I-70. Have updated
forecasts this evening for the trends in shower activity as well
as an increase in winds/gusts for Wednesday afternoon.


.SHORT TERM...(This evening through Wednesday)
ISSUED AT 220 PM CDT Tue Mar 13 2018

Rather widespread rain and snow showers occurring across the
northeast quarter of Illinois this afternoon, as shortwaves
continue to rotate around the upper low over southwest Ontario.
Some heavier snow showers currently occurring over the Chicago
metro, and will be tracking southeast through sunset. Have made
some updates to the afternoon and evening PoP grids along and east
I-39/US-51, as the short-range models keep the showers going until
around sunset. Rather dry air in the lower levels over our area,
which would indicate some virga at times. Overall impact should be
minor, aside from some periods of reduced visibility in the
northeast corner of the CWA near the heavier showers.

Once the showers exit, quiet weather will prevail into Wednesday
as high pressure slides to our south. Weak boundary to our north
on Wednesday will provide little more impact than an increase in
winds. Western CWA should reach into the lower 50s with more of a
southwest flow during the day, with mid-upper 40s across the east.

.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 220 PM CDT Tue Mar 13 2018

Upper level blocking pattern will be in place for the next few
days, as the Great Lakes low will only slowly move east. The
prominent ridge over the Rockies will begin to flatten as it
enters the Plains. Thus, the bulk of the warmer air beneath it
will not get this far east. Our main issue will be with a piece of
energy that cuts off on the west side of the ridge, across the
4-corners region later in the week. Longer range models are in
good agreement with a closed low moving into Kansas by Friday
afternoon, before weakening some as it tracks into the mid-
Mississippi Valley early this weekend. This system will be
battling a rather stiff easterly flow, so not much is expected
over our area on Friday. However, the lower atmosphere will
finally moisten up Friday evening, with rain changing over to
snow. Some minor accumulations will be possible Friday night,
though they won`t last long as we get back into the 40s on
Saturday. Some additional light rain or snow will accompany the
upper low itself on Saturday, before ending by sunset.

Not much of a break anticipated early next week, before the next
system forms over the Plains. Longer range models are in a bit
more flux on this position, ranging from eastern South Dakota to
central Kansas at midday Monday, but all take a general southeast
track. The GFS has more of a split system, from a wave over the
southern Plains and the low further north, while the European and
Canadian models are more integrated and thus feature more
widespread precipitation. Going with more of the wetter solution
at this point, with likely PoP`s Monday afternoon and evening.
After that, high pressure builds in for the middle of next week.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 628 PM CDT Tue Mar 13 2018

VFR conditions across central IL terminals this evening although
SCT -SHSN with isold lower vsby/cigs continue from around KDEC-
KCMI eastward. -SHSN will diminish in the first few hours of the
forecast period this evening with VFR conditions the remainder of
the forecast period. Winds NNW 10-15 kts with higher gusts early
in the evening, decreasing to 5-10 kts and shifting toward SW
through morning. SW winds increasing to around 15 kt with gusts to
25 kts after 18Z.




SHORT TERM...Geelhart
LONG TERM...Geelhart
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