Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 270402
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1102 PM CDT Sun Mar 26 2017

.UPDATE...
Issued at 832 PM CDT Sun Mar 26 2017

The upper low that produced the gloomy weather today was edging
slowly away from central Illinois this evening. Weak high pressure
was tracking across the state this evening and will be east of our
area by morning. The next storm system, already producing a complex
of severe storms over the Southern Plains this evening, will track
northeast towards the Ohio Valley on Monday bringing another round
of showers and thunderstorms to the area on Monday. Based on the
present movement of the precipitation to our southwest this evening,
it appears the leading edge of the showers will be approaching west
central Illinois by dawn, and then overspreading the entire area
during the morning. Current indications suggest the surface low
will track across southern Illinois, which should keep the warm
sector and severe threat along and mainly south of the I-70
corridor Monday afternoon and early evening. Will see if this
track holds with the 00z model runs this evening.

Extensive cloud cover across the state in the wake of the upper
system should hold through the night, especially across the
north, but the last few runs of the Rapid Refresh model suggests
some breaks in the clouds may develop late tonight along the I-72
corridor, which may lead to a bit more fog down in that area then
currently indicated. Have made some adjustments to the weather
grids across our central and southern counties to take into
account the possibility for some patchy fog late tonight,
otherwise, the rest of the forecast is in good shape. We should
have the update out by 900 pm.

&&

.SHORT TERM...(This evening through Monday)
ISSUED AT 235 PM CDT Sun Mar 26 2017

Vertically stacked low has moved into the northern third of Illinois
this afternoon. Still some lingering very light rain showers
scooting across the northern half of the forecast area, but they
will continue to diminish, and will go with a dry forecast for the
evening.

The next storm system is seen clearly on latest water vapor imagery,
entering southwest Kansas, and this will make a more rapid trek
northeast once our current storm system lifts across Michigan this
evening. Most of the guidance continues to favor a surface low track
more across the southern third of Illinois, although the NAM is a
little further north into the middle of the state. A few showers
ahead of this system may reach the far southwest CWA before sunrise,
with the bulk of the rain overspreading the forecast area during the
morning hours. Areas along and south of I-70 stand the best chances
of seeing any thunder, but a few stray lightning strikes possible as
far north as Springfield and Bloomington. Mildest temperatures will
be over the southeast CWA which stand a better chance of getting on
the edge of the warm sector, and highs 65-70 are expected there. The
northwest CWA should only reach the mid-upper 50s due to the more
persistent flow through the period.

.LONG TERM...(Monday night through Sunday)
ISSUED AT 235 PM CDT Sun Mar 26 2017

Low pressure will be moving ENE out of the state Monday evening with
with the trough axis progged to be roughly along I-57 at 7 p.m. As a
result, showers and thunderstorms will be tapering off during the
evening with just a slight chance of lingering showers after
midnight near the Indiana state line.

High pressure for Tuesday and Tuesday night should produce dry
conditions before moist warm advection ahead of a low advancing
through Oklahoma initiates a chance of showers over west central IL
Wednesday afternoon. This should spread across the state Wednesday
night. Although some track uncertainty remains...12Z models seem to
be converging on the low tracking through southern IL Thursday
evening. This would likely bring a chance of thunderstorms as far
north as the I-72 corridor for late Thursday morning to Thursday
evening. Showers should continue Thursday night before tapering off
west to east on Friday.

Saturday looks largely dry before some potential for rain develops
Sunday in warm advection ahead of the next system over the south
central U.S.

Temperatures should be mild and a few degrees above normal for most
of the forecast period. Highs Tuesday through Sunday ranging from
the mid 50s in Galesburg to the low 60s in Lawrenceville. Lows upper
30s to lower 40s in Galesburg ranging up to primarily mid and upper
40s in Lawrenceville.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1100 PM CDT Sun Mar 26 2017

Little change from previous thinking. One system departs, another
to make an entrance starting Monday morning. The main forecast
concern will be with cigs and vsbys overnight. How far north the
improving trend in the cigs will be and if any clearing does take
place, will that bring in lower vsbys in fog? Current satellite
data indicates the VFR cigs were currently along and south of a
SPI to DEC line and were edging slowly north this evening.
Forecast soundings indicate the areas along I-72 including SPI,
DEC and CMI will see some temporary improvements in the cigs
late tonight before the next system starts to move into west
central Illinois by dawn Monday. This will bring in additional
low cigs to those sites that did improve overnight. Most areas
tomorrow should be at MVFR/IFR with occasional LIFR conditions
across PIA and BMI in showers and fog as the storm system tracks
to the south of the TAF sites later Monday afternoon and evening.
The thunder chances (VCTS) would be mainly along our southern TAF
sites of SPI, DEC and CMI into the afternoon hours.

Light west to southwest winds will become easterly on Monday
morning and increase to 10 to 15 kts with winds backing more
into a northerly direction after 20z as the storm sytems shifts
across far southern Illinois. A northwest wind is expected
Monday night with speeds of 10 kts or less.

&&

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

$$

UPDATE...Smith
SHORT TERM...Geelhart
LONG TERM...37
AVIATION...Smith



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