Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 201725

Area Forecast Discussion
National Weather Service Lincoln IL
1125 AM CST Mon Feb 20 2017

Issued at 949 AM CST Mon Feb 20 2017

Dense fog has lifted and much of the forecast area is seeing
partly sunny conditions late this morning. Steady stream of
cirrus will be coming in from the west through the day ahead of
the next system. Regional radar mosaics have been showing movement
of the individual showers/storms just east of due north, while the
overall rain shield edges eastward with time. Based on this
movement, high-res models suggest a slower arrival in central
Illinois, mainly beginning this evening, although a few showers
may edge into the far western CWA late this afternoon. Have
updated the rain chances through tonight to reflect this thinking,
with the eastern CWA likely remaining dry until after midnight.

With the filtered sunshine and temperatures already approaching 60
degrees west of I-55, no changes were made to the highs for today.
Temperatures should reach near records once again, in the upper
60s to lower 70s.


.SHORT TERM...(Today and tonight)
ISSUED AT 323 AM CST Mon Feb 20 2017

Dense fog has once again developed across parts of central Illinois
early this morning...particularly along and east of the I-55
corridor. With southeasterly boundary layer winds on the back
side of departing high pressure, the fog has been steadily
advecting/developing northwestward toward the Illinois River
Valley. HRRR has been handling the fog quite well and shows it
spreading across the entire KILX CWA by 12z/6am. Based on
consistent signal from the HRRR and the latest satellite/obs
trends, will be expanding the current Dense Fog Advisory westward
over the entire area. Expect visibilities of one quarter mile or
less for the morning commute, with fog gradually eroding from
southwest to northeast as winds begin to increase by mid to late
morning. Once the fog lifts...a mostly cloudy, breezy, and
unseasonably warm day will be on tap. 00z Feb 20 models have
finally realized the strength of the upper ridge in place across
the Midwest and have delayed precip associated with an approaching
cold front until late afternoon/evening. Have therefore cut back
PoPs to feature just low chance along/west of a Peoria to
Jacksonville line after 22z/4pm. Despite cloud cover, afternoon
high temperatures will climb to near record values in the upper
60s and lower 70s. Better rain chances will arrive tonight as the
front nears and the atmospheric profile moistens. Will carry
likely to categorical PoPs for showers and will also mention
isolated thunder.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 323 AM CST Mon Feb 20 2017

Weak cold front will push into east-central Illinois by Tuesday
morning, then will exit into Indiana by afternoon.  Will therefore
linger rain chances east of I-55 through midday before going dry
everywhere by mid to late afternoon.  Despite FROPA and a shift in
wind direction to westerly...Pacific-origin airmass will offer
little in the way of cooling with afternoon highs again reaching the
upper 60s and lower 70s.  Warmest day of the forecast period still
appears to be gusty southwesterly winds develop in
advance of the next approaching boundary.  With thermal ridge axis
setting up and 850mb temps reaching 12-14C...record highs in the
lower to middle 70s will be likely.

Boundary will settle southward into central Illinois on
Thursday...with model consensus generally stalling it near the
I-72 corridor. As a result, a strong north-south temperature
gradient will develop...with highs ranging from the upper 50s far
north around Galesburg and 70 degrees far south around
Flora. As a significant upper wave ejects eastward out of the
Rockies, synoptic lift will increase along the boundary as the day
progresses, resulting in showers developing during the afternoon.
00z Feb 20 models are in relatively good agreement with the track
of an associated surface low from western Kansas Thursday evening
to the southern Great Lakes by Friday evening. This particular
track will place central Illinois within the warm sector of the
system and could potentially lead to strong to severe
thunderstorms Friday afternoon as a strong cold front pushes
through the area. Speed of the front still remains somewhat in
question, with the GEM showing a more amplified closed 500mb low
and therefore a slower frontal passage not occurring until late
afternoon/evening. Meanwhile both the GFS and ECMWF show a more
progressive wave and a slightly faster FROPA by early afternoon.
Right now it appears the greatest chance for strong to severe
storms will be along/east of I-57 Friday afternoon...but if the
slower solution pans out, the risk could be expanded westward.
Will carry just chance PoPs across much of the area, with likely
showers/storms across the east accordingly.

Once the front passes, a much cooler airmass will return to the
Midwest this weekend...with temps dropping back to near normal for
this of year in the lower to middle 40s.  The weekend will start off
dry, but another system passing south of the area will spread precip
into central Illinois Sunday into Monday.  Will have to keep a close
eye on the track/strength of that system...because it has the
potential to produce some snow across parts of the area Sunday
night into Monday morning.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1125 AM CST Mon Feb 20 2017

Mainly VFR conditions expected the remainder of the afternoon, as
the earlier low clouds and fog have dissipated. Higher level
clouds will be streaming in the west and gradually lowering this
evening, ahead of a cold front. Showers and a few thunderstorms
will start to spread into central Illinois early this evening and
work their way eastward. The storms currently appear to be limited
to areas from KPIA-KSPI westward but will be more isolated by the
time they arrive, so they have been removed from the TAF`s for
now. MVFR ceilings/visibilities will accompany the front late
evening and persist into Tuesday morning, with some IFR ceilings
likely at least from KPIA-KCMI late tonight and early Tuesday.


Issued at 312 PM CST Sun Feb 19 2017

Record Highs / Record Warm Lows - Monday Feb 20th...
Peoria........ 68 / 46
Lincoln....... 70 / 46
Springfield... 74 / 46
Champaign..... 71 / 45
Bloomington... 67 / 45
Decatur....... 70 / 47
Danville...... 70 / 48
Galesburg..... 64 / 41
Charleston.... 73 / 48
Effingham..... 68 / 54

Record Highs / Record Warm Lows - Tuesday Feb 21st...
Peoria........ 69 / 46
Lincoln....... 69 / 45
Springfield... 69 / 48
Champaign..... 67 / 47
Bloomington... 69 / 46
Decatur....... 68 / 48
Danville...... 67 / 50
Galesburg..... 68 / 40
Charleston.... 71 / 52
Effingham..... 73 / 52

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




LONG TERM...Barnes
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