Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 171631
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1131 AM CDT Mon Apr 17 2017

.UPDATE...
Issued at 1131 AM CDT Mon Apr 17 2017

Current forecast looks good rest of the day with most of the area
seeing only high clouds. So, warming is still expected through
this afternoon over most of the CWA. Southeast CWA will see clouds
continue into this afternoon so their temps will be lower. Since
forecast looks good, no update necessary at this time.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 330 AM CDT Mon Apr 17 2017

08z/2am surface analysis shows stationary frontal boundary draped
along the Ohio River...while a weak bubble of high pressure is in
place further north across Iowa into northern Illinois.  Aloft...a
zonal pattern dominates the CONUS...with a number of short-wave
troughs embedded within the flow.  One wave is located over
Kansas/Oklahoma and is responsible for a cluster of convection along
the trailing end of the front across Oklahoma into the Ozarks.  As
this wave ripples eastward, a few showers may develop as far north
as the far SE KILX CWA later this morning: however, most model
solutions keep the bulk of the precip well to the south.  Have
included slight chance PoPs for showers south of I-70...with dry
weather expected further north across the remainder of the area.
Plenty of mid/high clouds will be in place early this morning, but
as the wave passes by to the south, skies will steadily clear from
north to south as the day progresses.  High temperatures will climb
into the lower to middle 70s...with the coolest readings around 70
degrees focused south of I-70 where skies will remain mostly cloudy
through the afternoon.  High pressure will bring clear skies and
cool conditions tonight...with lows dropping into the upper 40s to
around 50 degrees.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 330 AM CDT Mon Apr 17 2017

As the high slides off to the east, southerly winds will develop
across the region on Tuesday...allowing high temperatures to climb
into the middle to upper 70s.  A northern stream short-wave is
slated to track through the Northern Plains into the Great Lakes
Tuesday night, pulling a cold front southward toward central
Illinois.  Models continue to have differing opinions on how far
south the boundary will drop before becoming parallel to the upper
flow and stalling: however, consensus points to the I-74 corridor.
NAM/ECMWF/GEM all focus precip across only the northern CWA Tuesday
night into Wednesday, while the GFS takes the front slightly further
south and develops convection across nearly the entire CWA.  Based
on the zonal pattern in place, think the GFS is too far south with
the boundary...so have trended the forecast toward the model
consensus.  As a result, have kept highest PoPs across the northern
half of the CWA Tuesday night and Wednesday.

A more significant short-wave will eject out of the Plains Wednesday
night, giving the front a solid push southward at that time.
Scattered showers and thunderstorms will spread across the entire
area Wednesday night, then will end from west to east during the day
Thursday as the front pushes into the Ohio River Valley.  A much
cooler/drier airmass will filter into the region behind the front,
with high temperatures dropping into the lower 60s by Friday.

Considerable model spread still exists with the stronger system
expected late in the week, so forecast confidence beyond Friday
remains low.  A wave will come onshore across the Pacific Northwest
Thursday morning, then will amplify as it crosses the Rockies into
the Plains on Friday.  The exact degree of amplification and thus
the forward speed of the system remains in question: however, a
trend toward a more amplified and thus slower progression has been
noted.  The 00z Apr 17 ECMWF is the most progressive with the
wave...while the GEM is the most amplified and slowest.  The GFS
represents a middle-of-the-road solution and was therefore followed
closely.  End result will be dry conditions on Friday, followed by
low chance PoPs for showers arriving Friday night into Saturday
morning.  At this point, it appears the primary time frame for
widespread showers/thunder will be Saturday afternoon through Sunday
morning when likely PoPs are warranted.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 544 AM CDT Mon Apr 17 2017

VFR conditions will prevail through the entire 12z TAF period. An
area of mid-level cloudiness will linger along/east of I-55 for
the next couple of hours before shifting southeast of the
terminals by mid-morning. After that, only high/thin cloudiness is
expected. Winds will initially be light northeasterly early this
morning, then will veer to southeasterly this afternoon through
tonight.


&&

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

$$

UPDATE...Auten
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Barnes



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