Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 150519
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1119 PM CST Sat Jan 14 2017

.UPDATE...
Issued at 850 PM CST Sat Jan 14 2017

No significant changes being made this evening in the short term
forecast or any of the headlines that are currently out.

Weak high pressure was centered over central Illinois this
evening with quite a bit of cloud cover across the forecast area.
Only exception was over our northern counties where skies have
cleared with a slow southward shift in the clearing trend noted in
the satellite data and surface observations over the past couple
of hours. Further south, we still have a solid stratus deck south
of I-72 with the possibility for some drizzle or freezing drizzle
coming out of the lower clouds at times overnight. However, have
not received any reports of that this evening but will keep an eye
out for that.

The next wave of freezing rain with even some isolated thunderstorms
was located over southwest Missouri this evening. Latest RAP and
HRRR models indicate the bulk of that precip will affect parts of
southwest through southern Illinois by morning. Will see some light
ice accumulations (less than a tenth of an inch) from that, but
like today, afternoon temperatures will be at or a couple of
degrees above freezing. Further north towards the I-74 corridor,
we will have a tough time getting much precipitation that far
north until late in the day or at night. For the most part, the
forecast has a good handle on the overnight trends but will make
some minor adjustments in the timing of the precip across our far
west tomorrow morning. We should have the updated zones out by 915
pm.

&&

.SHORT TERM...(This evening through Sunday)
ISSUED AT 300 PM CST Sat Jan 14 2017

Batch of light freezing rain exited east of east central IL early
this afternoon with a weak short wave. Though low stratus clouds
with bases of 500-1500 ft and a light fog from IL river southeast
could have patchy freezing drizzle with surface temps of 28-32F over
central IL at mid afternoon. Just patchy drizzle over southeast IL
along and southeast of I-70 where temperatures were 34-38F. 1035 mb
canadian high pressure was over eastern SD and ridging into the
Midwest and light nw winds trying to bring in drier air. Dewpoints
range from upper teens to mid 20s nw of the IL river, to the mid 30s
in southeast IL. Added patchy fog to southeast IL tonight and into
central IL as well overnight as temps cool toward dewpoints and
winds remain light with abundant low level moisture from recent
precipitation.

The second round of wintry precipitation will arrive across SW IL
including far SW CWA sw of Springfield and Lawrenceville late
tonight, and over rest of the CWA during the day Sunday, likely not
reaching the northern CWA until during Sunday afternoon. Cooler lows
overnight range from lower 20s nw of IL river, to the upper 20s to
near 30F in southeast IL. The latest forecast models continue slower
spreading qpf into central IL and cooler temperature profile trends.
850 mb temps are forecast to be zero to plus 2C over northeast CWA
on Sunday and may see more of a mix of light snow and sleet
especially from I-74 ne before changing to light freezing rain after
sunset Sunday. Surface temperatures rise to similar readings as
today, with lower 30s over IL river valley, and upper 30s in
southeast IL where mix pcpn Sunday morning turns to all rain Sunday
afternoon.

The freezing rain advisory for Fulton, Tazewell and McLean counties
will be cancelled as well as for Clark, Jasper, Richland, Lawrence
and Crawford in southeast IL where temps are above freezing thru
this evening. The Winter Storm Watch for northern CWA will be
converted to a Winter Weather Advisory Sunday night and Monday
morning and include areas from Fulton, Tazewell and McLean counties
north. Will continue the Freezing Rain Advisory for rest of CWA
through noon Sunday for light ice accumulations up to a tenth of an
inch or less, highest amounts in sw CWA where highest pops are by
Sunday morning.

.LONG TERM...(Sunday night through Saturday)
ISSUED AT 300 PM CST Sat Jan 14 2017

Precipitation expected to push northward Sunday night as increasing
southerly flow develops ahead of a low approaching via the southern
Plains, currently moving into northern Mexico. Southeasterly winds
at the surface will allow temperatures to start an increasing trend,
but still expecting freezing temperatures for at least portions of
the night from I-70 northward causing continued potential for
freezing rain as well as a mix of sleet and snow. Temperatures will
rise above freezing by about mid morning in the vicinity of I-74
then temperatures should remain above freezing for at least the next
day...until Tuesday night. Planning on issuing a winter weather
advisory from Sunday evening through Monday morning from Fulton to
Mclean county northward for the mix of ice, sleet, and snow.

With the strong low approaching the northwest corner of Illinois by
Monday night...increased chances for rain will also develop along
with the increased temperatures...with amounts around 1/2 to 3/4
inch likely from Monday morning to noon Tuesday. MUCAPE values in
the 200 J/kg range associated with the warm sector southeast of the
low imply thunderstorms possible so have included slight chance of
thunderstorms starting Monday afternoon southwest of Springfield,
then across central IL Monday evening...then shrinking down to I-70
southward Monday night.

Only a brief pocket of cooler air will affect central IL Tuesday
night through Wednesday night with lows in the upper 20s to mid 30s
and highs in the 40s followed by warm advection ahead of the next
low pressure system. Highs thursday through Saturday should increase
into the 50s. After dry weather midweek...there is a chance for rain
by Friday, although model inconsistencies this far out imply low
predictability.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1115 PM CST Sat Jan 14 2017

The clearing line has edged to just south of a PIA to BMI line
and continues to slowly push south late this evening. Further
south, MVFR cigs were observed over the remainder of the forecast
area. Patchy fog was forming, especially in areas the cleared off
this evening and further south where the more widespread stratus
was concentrated this evening. As the next wave of wintry
precipitation moves into the TAF area Sunday morning, we expect
IFR occasionally LIFR conditions to overspread the entire area by
early afternoon. As it appears now, the main band of freezing
rain/sleet looks to be affecting areas south of I-74 with mainly
VCSH in our northern TAF areas by late morning or early in the
afternoon.

As was the case today, we look for surface temperatures to be a
few degrees below freezing Sunday morning, but warm to or just
above freezing Sunday afternoon so any icing that occurs with the
precip Sunday morning should melt during the afternoon. LIFR
conditions will continue into Sunday night along with areas of
freezing rain and sleet, mainly across the north. Surface winds
will be light and variable tonight and then turn more into an
easterly direction on Sunday, but remain on the light side,
with speeds in the 5 to 10 kt range.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Freezing Rain Advisory until noon CST Sunday for ILZ040>057-061-
062-066-071.

Winter Weather Advisory from 6 PM Sunday to noon CST Monday for
ILZ027>031-036>038.

&&

$$

UPDATE...Smith
SHORT TERM...07
LONG TERM...37
AVIATION...Smith


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