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National Weather Service Lincoln IL
1140 PM CST SAT FEB 13 2016


Currently, radar shows a narrow band of light snow across mainly
Iowa. Some returns seen in western IL, but based on ILX 00z UA
sounding, low levels are very dry. Sfc dewpoints are in the single
digits and sfc winds are out of the southeast, which is a drying
flow. So it will still be several hours before snow begins to
reach the sfc in west central IL. Current forecast has chance in
the west and then slowly progressing east during the overnight
hours. So thinking is that current forecast still has a good
handle on the pop/wx timing in the forecast grids. Also believe
cloud cover will keep temps up some so will be raising overnight
lows a few degrees. Remainder of forecast looks fine. So with just
updating temps, update will out shortly.


.SHORT TERM...(Tonight)

1037 MB Canadian high pressure over IL at mid afternoon will move
into the upper Ohio river valley of WV/PA by 12Z/6 am Sunday. An
upper level short wave over MT and moving into the western Dakotas
mid afternoon will track into IA/northern MO by 12Z/6 am Sunday.
Isentropic lift starts after 03Z/9 pm tonight and increases more
so during overnight through 15Z Sunday and to develop light snow
from west to east later this evening and overnight. Snowfall
amounts overnight by dawn Sunday to range from 1-2 inches west of
highway 51 to less than 1 inch from highway 51 east with less than
a half inch near the IN border. Will continue the winter weather
advisory across CWA overnight through Sunday, starting at 3 am.
Was debating about starting the winter weather advisory at
midnight for western half of CWA, but snowfall amounts prior to 3
am should be less than 1 inch yet in western areas and se winds
still under 10 mph. Southeast winds pick up to 10-15 mph with
gusts 15-20 mph late tonight and could start blowing some snow by
dawn Sunday. Temperatures currently are in the upper teens and
lower 20s at 230 pm. Lows tonight range from 10-15F with coolest
readings ne counties, so not much temperature drop as skies cloud
up late this afternoon and evening and southeast winds increase
later tonight.

.LONG TERM...(Sunday through Saturday)

Snow should be falling across a majority of central and southeast
Illinois as day breaks Sunday. Moderate to strong isentropic ascent
will be in place for much of the day, although it will be
diminishing from the west by afternoon. The duration of the lift and
2-3 g/kg mixing ratios still supports 2"-5" snow totals (highest in
NW portion of forecast area). Remain concerned that a period of
freezing drizzle may occur in the late afternoon/night time hours
Sunday as the deeper moisture peels away and ice crystals are lost.
Have allowed for a brief period of freezing drizzle on the back edge
of the precipitation Sunday night. In any event, current Winter
Weather Advisory looks good and can easily be extended if confidence
grows in the freezing drizzle threat.

Quiet weather is anticipated Monday in between two weather systems.
Confidence is growing in a clipper impacting the area on Tuesday,
and most guidance suggests at least a quarter inch of liquid
equivalent falling across the area. However, there is still notable
disagreement with the track of the clipper, and this will have an
impact on thermal profiles while the precipitation is falling. The
most favored solution at this point starts out as snow late Monday
night, with a possible change to rain on Tuesday, especially during
the afternoon. In any event the evolution of this system will need
to be watched closely.

Behind Tuesday's system, mostly quiet weather is expected into the
end of the week, with temperatures trending well above normal. The
next weather system progged to impact the area will arrive by Friday
into Saturday, and temperatures will be mild enough for all rain
with this system.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)

Snow has begun in western parts of IL, but radar shows it is along
a narrow band. Believe this is just acting to moisten the lower
levels some. So thinking is not much snow will occur with this, so
will just have a TEMPO group at all sites overnight for 2hrs of
light snow with MVFR vis and cigs 3.5kft or above. Then as the
main wave reaches the area in the morning, more snow arrives,
starting around 15z at SPI and PIA with IFR vis and cigs in the
MVFR range. Based on HiRes models, that pockets of more intense
snowfall will be possible so will have TEMPO group at all sites
for vis below 1sm and cigs below 1kft...LIFR conditions. These
conditions will be in the late morning in the west to afternoon in
the east. As snow departs to the east, conditions will gradually
improve during the afternoon and then snow should completely stop
in the evening hours, though PIA and BMI may see light snow last
longer, being closer to the main mid level wave. Winds will be
southeast through the period. Wind speeds will around 10kts overnight
and into the morning hours, but then increase tomorrow with gusts
over 20kts. Once the snow begins to taper off, speeds will
decrease and winds will become more south-southeast.


.ILX Watches/Warnings/Advisories...
Winter Weather Advisory from 3 AM to 6 PM CST Sunday for 




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