Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 160929
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
329 AM CST Mon Jan 16 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 329 AM CST Mon Jan 16 2017

08z/2am obs continue to show temperatures hovering near 32F along
and north of a Rushville to Bloomington line.  With radar echoes
moving across the Illinois River Valley, cannot rule out some patchy
freezing drizzle for the next couple of hours before readings climb
above freezing by dawn.  Will therefore continue the Winter Weather
Advisory for the far N/NW KILX CWA, but this will likely be
cancelled shortly after sunrise.

The main short-term forecast challenge will be the development of
widespread fog today.  Thus far the lowest visibilities have been
centered from the St. Louis area northward to around Quincy.  HRRR
has been consistently showing dense fog spreading N/NE into central
Illinois: however, this has simply not materialized yet.  With warm
front well to the south and E/SE boundary layer flow expected to
persist all day, think visibilities will eventually decrease
across all of central and southeast Illinois this morning.  Based
on latest trends and HRRR signal, have expanded the Dense Fog
Advisory northward to include all locations along/south of a
Canton...to Decatur...to Robinson line.  If the HRRR verifies,
the Advisory may need to be expanded to include nearly the entire
CWA later this morning.  The only potential fly-in-the-ointment
will be the development of scattered rain showers that could mix
the atmosphere sufficiently to prevent widespread dense fog
northward to the I-74 corridor.

Showers will eventually become widespread this afternoon/evening as
low pressure and its accompanying warm front lift northward into the
area.  Forecast soundings indicate MUCAPE values increasing into the
200-400J/kg range this evening as the CWA punches into the warm
sector.  Will therefore carry categorical PoPs for showers and also
mention isolated thunderstorms.

&&

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 329 AM CST Mon Jan 16 2017

As low pressure tracks into the Great Lakes, it will pull a weak
cold front through central Illinois late tonight.  Most of the
precip associated with this system will exit Illinois by early
Tuesday morning: however, with a trailing upper-level wave not
expected to pass until evening, will continue slight chance PoPs for
showers across the far north through Tuesday afternoon.  High
pressure will build into the region on Wednesday, bringing sunshine
and mild temperatures in the 40s.

Once the high shifts off to the east, deep-layer southwesterly flow
will establish itself across the Mississippi/Ohio River Valleys,
leading to warm and unsettled weather for the end of the week.  00z
Jan 16 models have come into much better agreement concerning two
waves expected to impact the region...the first coming Thursday
night into Friday and the second arriving on Sunday.  Temperatures
will be warm enough to support all rain...as highs climb into the
50s through the period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1102 PM CST Sun Jan 15 2017

Cigs and Vsbys will deteriorate at all sites to LIFR with some
tempo VLIFR conditions in fog in the 08z to 12z time frame which
should last through at least 18z. A warm front will approach the
area by later in the day and that may bring cigs to IFR as rain
overspreads the area. Look for the poor cigs and vsbys (IFR to
LIFR) to hold into the evening along with occasional rain. Surface
winds will be light east to southeast tonight and then pick up
a bit from an east to southeast direction on Monday with speeds
in the 10 to 15 kt range during the afternoon and evening.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until noon CST today for ILZ036-040>042-
047>054-061-062-066>068-071>073.

Winter Weather Advisory until noon CST today for ILZ027>031-
036>038.

&&

$$

SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Smith


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