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Area forecast discussion 
National Weather Service Lincoln Illinois
905 PM CST Sat Feb 13 2016

issued at 905 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 upper air
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 Illinois. 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)
issued at 252 PM CST Sat Feb 13 2016

1037 mb Canadian high pressure over Illinois 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 Montana and moving into the western Dakotas
mid afternoon will track into Iowa/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 County Warning Area 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)
issued at 252 PM CST Sat Feb 13 2016

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
northwest 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 00z tafs through 00z Sunday evening)
issued at 543 PM CST Sat Feb 13 2016

VFR conditions will start at all sites with just mid and high
clouds over the area currently. Lower levels still remain quite
dry and any pcpn seen on radar will not be reaching the ground for
a while. Light snow is currently in western Iowa and is very
light, but based on satellite trends and model forecasts, system
is expected to intensify as it moves this way this evening. So,
snow will begin after midnight and be MVFR only because of vis.
Should only take about an hour for the lower levels to moisten up,
so conditions will decrease rapidly overnight and reach IFR
conditions in about an hour. Looks as though heaviest snow will be
intermittent so will have tempo at all sites for LIFR conditions
due to vis at 1/2sm. Later in the morning conditions should begin
to improve as the main heaviest part of the system moves east of
the taf sites. Do believe light snow will continue into the
afternoon and should begin to end in the west by late
afternoon...around 21z. For now will not have another line for
that in the tafs. Dec/cmi and bmi will probably have light snow
til around 00z...end of taf period. Winds will be southeast
through the period with speeds of 16kts or less through the


Ilx watches/warnings/advisories...
Winter Weather Advisory from 3 am to 6 PM CST Sunday for



short term...07
long term...Bak

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