Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 230300
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
900 PM CST Wed Feb 22 2017

.UPDATE...
Issued at 853 PM CST Wed Feb 22 2017

A weak cold front is approaching central and southeast Illinois
from the northwest late this evening. The front is expected to
stall in the vicinity of the I-70 corridor by late tonight. While
the front does not currently have significant cloud cover or any
precipitation associated with it, there may be some fog/low clouds
developing along it later tonight as it stalls and winds are
light/variable in its vicinity. Do not expect widespread dense
fog again tonight, but this threat will need to be monitored,
especially in the vicinity of the stalled front later tonight.

&&

.SHORT TERM...(This evening through Thursday)
ISSUED AT 225 PM CST Wed Feb 22 2017

Leftover clouds from the morning fog have been wreaking havoc on the
temperature forecast for this afternoon. Upper 50s/lower 60s were
occurring between I-55 and the Illinois River as of 2 pm, but upper
60s noted west of the river and over eastern Illinois, where some
lower 70s were also noted. The residual stratus has rapidly been
fading the last couple hours, and there likely should be some decent
sunshine to get temperatures to rise several degrees (clearing in
Bloomington allowed a rise from 61 to 66 between 1-2 pm). However,
the original forecast of low-mid 70s may be bit of a stretch.

Latest surface map shows a surface low near Minneapolis, with a
trailing cold front extending southwest into central Kansas. The
front is progged to reach central Illinois after midnight, before
becoming stationary early Thursday. A shortwave digging across
northern parts of California and Nevada this afternoon will lead to
a developing surface low over eastern Colorado by late tonight,
which will lift toward Kansas City and drag the front back north as
a warm front. Showers will start developing along the boundary
during the afternoon, mainly affecting areas north of I-72. If any
formed south of there in the warm sector, some thunder would not be
out of the question as CAPE`s rise to around 500 J/kg. The front
will result in another wide range of temperatures Thursday, from
near 60 degrees around Galesburg to the lower 70s south of I-70,
although mid-upper 60s will be the general rule.

.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 225 PM CST Wed Feb 22 2017

Warm front over the state Thursday will push northward into northern
Illinois Thursday Night. The more significant precipitation along
and north of the front will be pushed north of the area with the
front.

Still some differences with respect to the evolution of the
potential convective event on Friday. Latest GFS has become more
slower and more vertically stacked with the low pushing northwest of
the area Friday. While the 00z ECMWF and 12z NAM are more
progressive with the system. The deeper GFS solution allows low-
level moisture to wrap up into the low by 18z Friday and develops
CAPE values around 1000 J/kg out ahead of the associated cold front.
The deeper solution also leads to higher shear values than the
ECMWF/NAM.  Either way, instability and shear are adequate for
thunderstorm development by midday near I-55 and then pushing east
during the afternoon. Models have been hinting at the development of
a second line out ahead of the front near the Indiana border during
the mid-late afternoon. Bottomline is that timing is in good
agreement, but intensity of the line is still somewhat uncertain. As
the event begins to move into the realm of the convective-allowing
models we should get a better handle on the evolution.

Much colder air advects into the region behind the front Friday
Night with 850 mb temps falling almost 25C in 24 hours. Models
continue to forecast wrap-around moisture into the northern forecast
area Saturday morning. With temps near freezing and 850 temps around
-10 precip will likely be in the form of light snow.
Given the warm ground conditions from this week`s record heat, any
accumulations should be light.

Models diverge as we head into the second half of the weekend as GFS
is phasing a northern stream wave with an initial shot of energy
from the latest west coast system. The merging of features brings a
slower and more substantial system than the more progressive ECMWF
which tends to move the northern stream system through late Sunday
with a chance for light mixed precip with the the more significant
forcing with the southern system remaining generally south of the
forecast area Monday.

Models remain divergent with timing through midweek as the western
trough sends a series of waves northeast into Illinois. However,
they are in agreement that temps should warm back above normal as
the ridge builds east of the western U.S. trough and the period
should be on the wet side as moist southwest upper flow continues.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 542 PM CST Wed Feb 22 2017

VFR conditions expected to start the period, but MVFR or IFR
visibilities and eventually ceilings will develop later tonight
as a weak cold front slips into the area and stalls out.
Visibilities should improve again Thursday morning after sunrise,
but MVFR CIGs may persist for much of the day in many areas. The
stalled front will begin to lift back northward by late in the
period, with a few showers possible by late Thursday afternoon.
However, expected coverage is too low to carry in terminals at
this time.


&&

.CLIMATE...
Issued at 925 AM CST Wed Feb 22 2017

Record Highs / Record Warm Lows - Wednesday Feb 22nd...
Peoria........ 71 / 51
Lincoln....... 71 / 52
Springfield... 71 / 53
Champaign..... 69 / 49
Bloomington... 70 / 53
Decatur....... 72 / 51
Danville...... 71 / 54
Galesburg..... 61 / 45
Charleston.... 71 / 52
Effingham..... 74 / 55

Record Highs / Record Warm Lows - Thursday Feb 23rd...
Peoria........ 64 / 49
Lincoln....... 68 / 50
Springfield... 70 / 50
Champaign..... 65 / 50
Bloomington... 66 / 52
Decatur....... 73 / 53
Danville...... 67 / 51
Galesburg..... 65 / 44
Charleston.... 69 / 52
Effingham..... 68 / 52

Record Highs / Record Warm Lows - Friday Feb 24th...
Peoria........ 71 / 54
Lincoln....... 74 / 53
Springfield... 78 / 56
Champaign..... 70 / 51
Decatur....... 75 / 52
Danville...... 71 / 54
Galesburg..... 68 / 47
Charleston.... 75 / 54
Effingham..... 75 / 54

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Bak
SHORT TERM...Geelhart
LONG TERM...Barker
AVIATION...Bak
CLIMATE...Geelhart



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