Area Forecast Discussion
Issued by NWS Central Illinois

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KILX 150925
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
325 AM CST Sun Jan 15 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 325 AM CST Sun Jan 15 2017

08z/2am surface analysis shows 1034mb high centered over
Minnesota/Wisconsin...while frontal boundary remains draped from the
southern Appalachians to Texas.  A weak short-wave trough tracking
north of the front is currently triggering an area of freezing rain
across central/eastern Missouri.  This precipitation is tracking
E/NE and will eventually spread across the southern KILX CWA this
morning.  Based on radar trends and latest HRRR forecast...it
appears most of the precipitation will remain south of the I-72
corridor today...with only patchy drizzle further north.  Have
therefore focused high chance to likely PoPs across the southern
half of the CWA...while areas along/north of a Galesburg to Lacon
line remain dry through the entire day.  Precip type will
initially be a mix of freezing rain and sleet: however, as surface
temps slowly warm, it will gradually mix with rain.  Models seem
to be too warm today, with both the MET and MAV guidance
suggesting highs reaching the middle to upper 30s.  This seems
unreasonable based on extensive cloud cover and continued light
E/NE boundary layer flow.  Have therefore gone several degrees
below guidance, with afternoon highs ranging from the lower 30s
north to the upper 30s far south.  End result will be precip
transitioning to all rain along/south of a Paris to Taylorville
line this afternoon.  Given light QPF and marginal temps, ice
accumulations will remain under one tenth of an inch this morning.
The Freezing Rain Advisory will therefore continue through noon
to account for potential slick spots on mainly secondary and
untreated roads.

The initial push of light precip this morning will diminish as it
lifts further northward toward the prevailing high over the southern
Great Lakes this evening.  Meanwhile, the strongest forcing will
shift further south and west in association with the main upper
system lifting out of northwest Mexico.  As a result, have lowered
PoPs to slight or low chance tonight.  With temperatures hovering
around freezing, additional freezing drizzle or sleet will be
possible.  The current Winter Weather Advisory for the northern CWA
will remain in effect tonight through Monday morning and may need to
be expanded southward toward the I-72 corridor depending on how
surface temps respond this afternoon and if very light precip
lingers into the evening.  Any ice accumulations will remain very
light tonight, amounting to less than one tenth of an inch.

&&

.LONG TERM...(Monday through Saturday)
ISSUED AT 325 AM CST Sun Jan 15 2017

Temperatures will slowly begin to rise late tonight as boundary
layer winds veer to the southeast in advance of the approaching
system.  May see some lingering freezing rain along/north of I-74
into early Monday morning, but this will rapidly change to rain as
temps climb into the middle 30s.  As stronger forcing arrives from
the southwest, rain will become widespread across the area by Monday
afternoon.  With low pressure tracking from Oklahoma Monday morning
to southern Lake Michigan by Tuesday morning, central Illinois will
punch into the warm sector of the system Monday night.  NAM/GFS
forecast soundings show MUCAPE values of 200-400J/kg, suggesting the
possibility of isolated thunderstorms.  Once the low moves into the
Great Lakes, any lingering showers will come to an end Tuesday
morning followed by mild/dry weather through Wednesday.

After that, model consistency is quite poor and resulting forecast
confidence remains low.  One thing is for certain though...a big
warm-up is in store for the end of the week as southwesterly upper
flow establishes itself across the region.  Temperatures will climb
into the 50s Thursday through Saturday, with readings perhaps
reaching the lower 60s across the southeast CWA next weekend.  Main
questions will revolve around track and timing of waves embedded
within the flow.  Models have been flip-flopping on a potential wave
Thursday night into Friday.  The 00z Jan 15 GFS has backed off on
the wave, while the ECMWF has now latched onto it.  At this point,
have decided to go with a dry forecast through Saturday until better
model consistency is achieved.

&&

.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 today for ILZ040>057-061-
062-066-071.

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

&&

$$

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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.