Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 141649

Area Forecast Discussion
National Weather Service Lincoln IL
1049 AM CST Sun Jan 14 2018

Issued at 1049 AM CST Sun Jan 14 2018

Clouds are quickly increasing from west to east across the area
this morning: however, 16z/10am visible satellite imagery still
indicates mostly sunny skies along/east of a Bloomington to
Effingham line. Clouds will overspread east-central Illinois over
the next 2-3 hours as warm advection increases ahead of an
approaching short-wave trough. Further west, light snow/flurries
have developed as far east as the Mississippi River and this
activity will be spilling into the Illinois River Valley by mid
afternoon. The airmass across central Illinois is initially quite
dry as evidenced by the 12z KILX upper air sounding, so top-down
moistening will be slow to occur. While flurries or very light
snow will likely spread all the way to the Indiana border by late
afternoon, little or no accumulation is expected during the day.
Stronger lift associated with another wave currently over North
Dakota will arrive late this evening into the overnight hours,
bringing accumulating snow at that time.


.SHORT TERM...(Today through tonight)
ISSUED AT 335 AM CST Sun Jan 14 2018

Forecast concerns this forecast package are snowfall amounts
tonight into Monday, and how cold wind chills get during 1st half
of this week, especially during Monday night into Tue morning.

09Z/3 am surface map shows strong 1040 mb arctic high pressure
over IL and lower Ohio river valley. This was providing light to
to calm winds over central/southeast IL with clear skies over all
but west central IL. Broken to overcast clouds with bases of
4.5-5.5k ft were streaming se into west central IL and approaching
Springfield. Cold temperatures were mostly in the single digits
and lower teens, but range from zero at Lacon to 17F in Flora.

One short wave pushing se into the central plains early this
morning was producing an area of light snows over western MO, nw
AR into central and eastern KS and eastern parts of NE/OK. This
band of light snow should stay sw of central IL this morning as it
track se. A stronger northern stream short wave (clipper system)
was over central Saskatchewan early this morning and will dive se
into the upper Midwest by sunset, and into central IL by Monday
morning. 00Z models have trended a bit further south with this
rather clipper system which is rather dynamic with mid level jet
around 90 kts. Expect clouds to spread eastward across central and
eastern IL during this morning and into the early afternoon. Then
light snow chances will increase over the IL river valley from
I-55 nw during mid/late afternoon, and into east central IL early
this evening. Southeast IL will see better chances of light snow
by overnight into Monday. Light snow will diminish from nw to se
during the day Monday, lingering longest into Monday afternoon in
southeast IL and near the IN border. With short wave tracking
further south, snowfall amounts are a bit higher, ranging from 1-3
inches over CWA, with highest amounts of 2-3 inches from I-74
north. This will be close to winter weather advisory criteria (3
inches) and will issue a special weather statement to address this
expected snowfall event. Highs today range from 20-25F, coldest ne
CWA. Temps do not drop off much tonight with lows in the upper
teens to near 20F, expect lower teens far nw CWA by Galesburg as
colder air starts to usher into areas nw of IL river toward dawn

.LONG TERM...(Monday through Saturday)
ISSUED AT 335 AM CST Sun Jan 14 2018

Brisk nw winds develop during Monday morning and could causing
some blowing snow especially from I-74 north. As the clipper
system pulls away from IL during Monday afternoon and into Monday
night, bitter cold air will usher into the area on brisk nw winds.
Temps in nw CWA expected to fall to zero to 5 above by sunset.
Southeast IL to see morning highs of 24-29F, then falling into the
upper teens by sunset. Lows Monday night of zero to 6 below over
central IL, and approaching zero in southeast IL. Wind chills to
lower to 15 to 25 below zero during Monday night into Tue morning
over central IL, with areas se of I-70 having wind chills
reach around 15 below zero later Monday night into early Tue
morning. A wind chill advisory will eventually be needed across
much of CWA Monday night and Tue morning.

Models dig a strong 529 dm 500 mb low into southern WI and central
Lake MI on Monday night and pivots a deep upper level trof se
across CWA during Tue. This could produce some more stratocumulus
clouds along with chances of flurries especially ne of I-74. Highs
Tue only 9-13F and wind chills still only in the single digits
below zero Tue afternoon. Another frigid night Tue night with lows
of 2 above to 5 below zero. Lighter winds Tue night will keep wind
chills from getting as cold as Monday night. But wind chills to
approaching 15 below zero overnight Tue night nw of the IL river.

Arctic high pressure over nw Canada to settle into AR and the mid
MS river valley as a 1040 mb high on Wed providing more sunshine
but continued cold with well below normal temps. Highs Wed of
15-20F. Lows Wed night of 6-12F, coldest near the Wabash river
closer to arctic high pressure ridge moving into the TN river

Dry stretch of weather expected from Wed thru Friday night as high
pressure settles into the southeast states and upper level ridge
shifts east into IL by sunset Friday. This to moderate temps late
this week. Highs of 29-35F on Thu elevate to upper 30s/lower 40s
Friday and mid 40s to near 50F on Saturday. Extended models show
IL getting in a sw upper level flow this weekend and more
unsettled weather pattern returning. GFS and GEM models seem too
fast/aggressive returning moisture/showers into IL on Saturday and
preferred the slower ECMWF model with just slight chances of
showers Saturday and Sat evening, possible mixed with snow if it
occurs early Sat morning. Shower chances to increase from the sw
overnight Sat night into Sunday as surface low pressure ejects ne
toward IL. Though big differences with track of this low as GFS is
much deeper and further north with low into central WI by sunset
Sunday, while ECMWF is weaker with surface low moving into eastern
AR by sunset Sunday. GEM model is closer to GFS solution. Will
stick close to model consensus for Sunday`s forecast which has
pretty high chances of rain showers overnight Saturday night into
Sunday morning. Highs Sunday range from lower 40s by Galesburg to
lower 50s by Lawrenceville.

A milder and more unsettled weather pattern looks to take shape
across central and southeast IL Jan 21-27th. Climate Prediction
Center (CPC`s) 8-14 day outlook has 50-60% chance of above normal
temperatures and 55-65% chance of above normal precipitation over
IL. CPC`s week 3-4 outlook continues this trend from Jan 27 - Feb
9 with 60-70% chance of above normal temperatures and about 55%
chance of above normal precipitation.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 559 AM CST Sun Jan 14 2018

Strong 1040 mb arctic high pressure over eastern IL and ridging
across the Ohio river valley at dawn, will drift eastward today.
As it does so, light southeast winds early this morning will
increase to 10-15 kts and veer SSE by mid/late morning and
continue through tonight. A northern stream short wave (clipper
system) moving se out of Saskatchewan into ND early this morning,
will track into central IL by 12Z/6 am Monday. Stratocumulus
cloud decks of 4-6k ft over west central IL including SPI early
this morning, will spread over rest of central IL during mid/late
morning. An area of light snow will move se to PIA during mid
afternoon, to I-55 during late afternoon and reach DEC and CMI
shortly after sunset. Cloud ceilings will lower to MVFR category
during mid or late afternoon and possibly to IFR during tonight.
Visibilities expected to range from 1-3 miles with light snow from
late afternoon and through tonight. An arctic cold front will
move se to around Galesburg by 12Z/6 am Monday and sweep through
central IL Monday morning shifting winds WNW and gusting 20-25
kts, so shortly after this 24 hr taf forecast.




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