Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 190504
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1104 PM CST Sat Feb 18 2017

.UPDATE...
Issued at 845 PM CST Sat Feb 18 2017

The storm system that brought the sprinkles to parts of southeast
Illinois this afternoon was starting to pull off to our east this
evening. The latest surface analysis indicated a weak trof or wind
shift line located along and west of the Illinois River Valley
with the air mass behind this feature a bit drier than to the
southeast. Dew points as of 8 pm were in the mid 30s behind the
wind shift line, while further southeast, dew points were able to
push into the low to mid 40s with upper 40s noted over far
southeast Illinois this evening.

The latest satellite loop was indicating the thicker cloud cover
from the aforementioned wave to our south was tracking off to our
east while a low level cloud deck was starting to track northeast
out of southern Illinois. Based on the current movement, it
appears the eastern half of the forecast area will see these
clouds later this evening. With the increased low level moisture
over about the southeast half of the forecast area, combined with
a mostly clear sky and light winds, some patchy dense fog will be
possible later tonight. Have already added that to the grids
earlier this evening and sent an updated ZFP out to address that
possibility. With the clear skies and light winds, temperatures
have dropped off rather quickly in a few locations, especially
across the east so will have to tweak the evening temperature
grids as well as a few early morning lows. Other than the threat
for fog across parts of the area tonight, the rest of the forecast
continues to indicate the unseasonably warm pattern to hold into
at least the first half of next week. We should have the updated
ZFP out around 915 pm.

&&

.SHORT TERM...(This evening through Sunday)
ISSUED AT 251 PM CST Sat Feb 18 2017

Central Illinois remains caught between an upper low to the south
and a weak boundary to the NW.  The low to the south has been
creating precip all day and will likely continue for  a few hours
before it drifts to the east.  Little more than sprinkles are
anticipated in the southeast under the thicker cloud cover.  Today
was cooler than yesterday, although well above seasonal averages.
Models have put in some fog for this evening in the southeastern
portions of the state.  However, the models were also expecting the
precip shield further north.  As it is running into the dry air over
central IL, the precip edge is remaining just to the south.  Patchy
fog may be possible in the southeast...but so far the sfc dwpts are
not surging northward...and there is a lot of dry air to overcome.
Will not put it in the grids just yet. For tomorrow...more sunshine
and warmer temperatures into the upper 60s/lower 70s as ridging
keeps Central IL dry again.

.LONG TERM...(Sunday night through Saturday)
ISSUED AT 251 PM CST Sat Feb 18 2017

Most of the coming week will continue to feature well above
normal temperatures across central and southeast Illinois. However,
Mother Nature will remind us that it is still winter by next
weekend.

Look for temperatures to top out 20-30 degrees above normal for most
of the week. Then, a strong system will push through the area on
Friday, with temperatures falling closer to normal by Saturday.

There will be two main periods this week where precipitation will be
a threat. The first will accompany a frontal passage Monday into
Tuesday. There are still timing discrepancies with respect to how
quickly the front and associated precipitation risk will arrive, but
feel slower is probably better given the strong upper-level ridging
the system will be trying to push into, and how dry the local
airmass will initially be. Modest instability (pre-frontal MU CAPEs
generally AOB 500 j/kg) support a few thunderstorms Monday afternoon
into Monday night. If the front is slow enough, east-central and
southeast Illinois may see the thunder risk linger into Tuesday.
Little cooling is anticipated behind this first system.

A strong system is expected to push through the area on Friday, and
model guidance has been fairly consistent with this timing. However,
model agreement with the other details is not as good (exact track,
strength, precipitation coverage, etc). Strong WAA is forecast to
activate the warm front to the east of the system as early as
Thursday, but exactly where the associated rainfall will develop is
still somewhat up in the air. The trailing cold front should come
through the area Friday, accompanied by showers and some
thunderstorms, although some recent model runs have the cold front
come through our area dry. These trends will need to be watched
closely. As moisture and colder air wrap in on the back side of the
system Friday night, any lingering precipitation will change over to
light snow.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1100 PM CST Sat Feb 18 2017

Coverage of dense fog across the forecast area Sunday morning the
main forecast challenge. Fog and stratus continue to track slowly
northward into central and now east central Illinois with
Champaign seeing the low clouds and lowering vsbys. Based on
short term guidance, it appears the lower cigs and vsbys will
shift north and northwest to just west of the Illinois River
early Sunday morning. The LIFR conditions look to affect all but
PIA, but even at that location will include some fog in the 06z
TAF. The big question is how long the fog will hold over the
area Sunday morning. The NAM soundings suggest areas east of
I-55 may see the fog dissipate in the 16z-18z time frame.
Elsewhere, the moisture profiles in the lower levels of the
atmosphere are forecast to be quite shallow so we will continue
to keep the timing around 15 or 16z. After the fog lifts Sunday
morning, we expect VFR conditions into the afternoon and early
evening hours. Light and variable winds tonight will become light
southerly on Sunday with speeds of 10 kts or less.

&&

.CLIMATE...
Issued at 339 AM CST Thu Feb 16 2017

Record Highs / Record Warm Lows - Saturday Feb 18th...
Peoria........ 63 / 42
Lincoln....... 63 / 39
Springfield... 65 / 43
Champaign..... 65 / 42
Bloomington... 63 / 44
Decatur....... 70 / 43
Danville...... 67 / 49
Galesburg..... 63 / 43
Charleston.... 68 / 48
Effingham..... 70 / 44

Record Highs / Record Warm Lows - Sunday Feb 19th...
Peoria........ 71 / 50
Lincoln....... 71 / 46
Springfield... 70 / 54
Champaign..... 68 / 46
Bloomington... 70 / 47
Decatur....... 66 / 48
Danville...... 70 / 54
Galesburg..... 63 / 52
Charleston.... 72 / 53
Effingham..... 70 / 45

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

&&

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

$$

UPDATE...Smith
SHORT TERM...HJS
LONG TERM...Bak
AVIATION...Smith
CLIMATE...07


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