Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 171552
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1052 AM CDT Thu Aug 17 2017

.UPDATE...
Issued at 1052 AM CDT Thu Aug 17 2017

15z/10am surface analysis shows 998mb low over western Wisconsin,
with cold front trailing southward along the Mississippi River.
Even though the actual boundary is just now entering the Illinois
River Valley, the best moisture has already been pushed to the
E/SE, as shown by 70+ surface dewpoints confined to areas
along/south of I-70. All model guidance suggests the front will
pass through much of the KILX CWA dry over the next couple of
hours, with scattered showers/thunder developing in the moisture
axis across the SE. Have adjusted PoPs accordingly, with isolated
to scattered wording along/southeast of a Danville to Effingham
line only. Elsewhere, skies will gradually become partly to
mostly sunny during the afternoon as W/SW winds gust to 20-25mph.
High temperatures will top out in the lower to middle 80s.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 253 AM CDT Thu Aug 17 2017

Showers continue to spread into the western half of the CWA early
this morning, but little instability at the moment and there is
only a stray lightning strike or two on occasion with this area of
rain. Latest high-resolution models continue to indicate that this
area should be out of the CWA before noon. However, both the NAM
and GFS indicate CAPE`s east of I-57 reaching above 1000 J/kg by
midday, ahead of the actual cold front, which is currently back
across eastern Iowa and northern Missouri. With a secondary surge
of moisture ahead of the front, will keep showers over the
southeast third of the CWA through the afternoon, with a mention
of isolated thunder as well. Any lingering rain should end toward
sunset.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 253 AM CDT Thu Aug 17 2017

Main upper flow will be coming out of the northwest late this
week, as ridging strengthens along the western Rockies. Timing of
the sharpening shortwave over the upper Mississippi Valley late
Friday has not changed much, and the main focus for us will be
Friday night, with a bit of rain lingering across the far eastern
CWA into Saturday morning as the wave exits the state. Remainder
of the weekend looks dry, as surface high pressure is sprawled
over the Midwest.

Eclipse update (Monday): Weak shortwave should be approaching the
Illinois/Missouri border Monday afternoon. Gulf moisture surge
will be setting up on Monday. with cu-rule off the GFS forming
scattered cumulus by midday over our area. Concern may be more
with higher level clouds spreading in from Missouri due to
potential for thunderstorms in that area. However, summertime
patterns are a bit finicky, so such high resolution details 5 days
out are rather hard to pin down.

Beyond Monday, the western ridge starts to strengthen again,
setting up the storm track across the Great Lakes region. The next
system will be originating in this flow, with showers and
thunderstorms spreading in Monday night and continuing Tuesday.
This upper pattern looks to continue past mid week, bringing some
cooler weather beginning on Wednesday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 537 AM CDT Thu Aug 17 2017

Challenging TAF set in the short term, as there are small pockets
of IFR/low MVFR ceilings embedded within otherwise VFR conditions.
Most of the lower stuff is associated with a band of showers that
extends from about KBMI-K1H2 eastward at 1030Z, and fluctuations
in heights are likely over the next few hours. More substantial
improvements are expected between 15-18Z as a cold front moves
into the area. In the wake of the front, winds will gust to around
20 knots due to the tight pressure gradient, but they should ease
off late in the afternoon.


&&

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

$$

UPDATE...Barnes
SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Geelhart


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