Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 270536
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1136 PM CST Mon Jan 26 2015

.UPDATE...
ISSUED AT 900 PM CST MON JAN 26 2015

Freezing drizzle continues across northwest portions of central
and eastern Illinois this evening and based on upstream obs and
radar trends, thinking that these conditions will continue
overnight as well. So issued a freezing rain advisory for the
remainder of the night ending at 6am tomorrow morning. Updated
forecast already sent and do not see any other updates needed at
this time. Will monitor obs and radar trends to see if another
updated is needed, but do not think an expansion in area will be
needed for the current advisory.

&&

.SHORT TERM...(Tonight)
ISSUED AT 255 PM CST MON JAN 26 2015

Today`s short wave diving into the mean eastern North American trof
ended up remaining a little more robust than anticipated, despite
indications yesterday that it would be much more sheared out and
weaker by the time it arrived. The result has been at least a few
hours of light snow across most of the forecast area. While the
threat area will continue to shift east tonight before pushing out
of the area, the channeled vorticity within the mean flow will keep
a risk light snow or flurries across east central and southeast
Illinois for several more hours. However, most areas will only see a
dusting of snow. Away from the snow threat, across the western
portion of the forecast area, clouds should continue to hold tough.

One thing that will be need to be watched closely across the entire
forecast area, at least through this evening, is the threat for
freezing drizzle. Forecast soundings suggest that a fairly thick
low-level moist layer will persist after the upper energy and
associated ice crystals depart. However, the shear within the moist
layer is not very impressive and there is minimal indication of
drizzle upstream. So, plan to leave the mention out for now.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 255 PM CST MON JAN 26 2015

One more cool day (but near normal for late January) is expected
across central and southeast Illinois on Tuesday as northerly low
level flow develops ahead of an approaching ridge of high pressure.
Temperatures will also be held down by considerable cloud cover.

Southerly low-level flow and a quick warm-up is expected for midweek
as the surface ridge departs and low pressure approaches from the
Plains. The approaching storm system is still on track to bring some
rainfall to the area Wednesday night into Thursday as it moves
through. However, the latest indications are that the rain will be
delayed a bit and lighter than previously anticipated. The reasons
for the delay and lighter amounts are two fold. First, whereas this
system was initially expected to be primarily driven by energy and
associated moisture from the cutoff low of Baja California, now a
drier northern stream wave looks like it will be more of a dominant
player. Second, it also looks like low level ridging along the Gulf
coast will be stout enough to preclude much moisture return until
the system pushes east of the forecast area.

After a brief lull, our next system is expected to arrive by the
weekend. However, considerable model spread exists with respect to
the details, and there has also been significant run-to-run
variability. This uncertainty is resulting in an extended period of
low chance PoPs from Saturday into Sunday. The models agree that it
will be cold enough for snow, but little agreement exists with
respect to explicit timing and amounts. Hopefully the snow threat
will become more clear soon.

Forecast guidance has continued to suggest for several days that a
period of below normal temperatures is on the way beyond our normal
7 day forecast. However, once the forecast period draws closer, they
have been backing down. So, it still looks like temperatures should
average at or above normal for the next seven days. We`ll just have
to see if the how long that can last.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1136 PM CST MON JAN 26 2015

MVFR to LIFR conditions will continue across the TAF sites
overnight. With area remaining in cyclonic flow and a surface
front being over the area through most of the TAF period, believe
clouds will remain over the sites next 24hrs. TAF sites along and north
of this boundary will see cigs below 1kft through most of the
period, and then rising during the evening hours tomorrow. Other
sites like PIA, DEC and SPI will remain MVFR through tomorrow
afternoon. All sites except for SPI have vis of 5SM or less but
will improve during the morning and afternoon hours. Conditions
could improve more during the evening hours, but only become
broken sky cover with cig heights about the same as during the
day, just becoming MVFR for BMI and CMI. Winds will be light from
the southwest and then become northwest in a few hours, then by
morning, northerly with gusts to near 15kts. Then lighter by
afternoon, then light and variable winds return for tomorrow evening.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
FREEZING RAIN ADVISORY until 6 AM CST Tuesday FOR ILZ030-031-038-
043>046-053>057-062-063.

&&

$$

UPDATE...Auten
SHORT TERM...Bak
LONG TERM...Bak
AVIATION...Auten





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