Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 121614
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1114 AM CDT Sat Jul 12 2014

.DISCUSSION...
ISSUED 1100 AM CDT Sat Jul 12 2014
Very busy morning as a wave initiated VERY slow moving
thunderstorms just after midnight. Efficient rain makers and large
raindrops resulted in rapid accumulations with the storms not
making much progress out of the area. Radar estimates are being
verified by real time reports with an area btwn Le Roy and
Champaign in excess of 6 to 7 inches. Area of 2 to 4 inches were
more widespread from Pontiac to south of Shelbyville. Forecast
just fine for the afternoon as the storms move out to the east.
Secondary convective initiation will likely be confined to areas
closer to the frontal boundary lifting through the region
today...and more across the northern half. Adjusted the hourly
temps for the day, but overall not messing with the afternoon
pops. Headlines are tricky because of the FF warning in eastern
Illinois will continue for a while as flooding continues even
though the rain is slowly waning. Any rainfall on top of this will
be problematic. Flood watch headlines are likely at some point
before the next round of rainfall.  Updates out momentarily.

HJS
&&

.AVIATION...
ISSUED 700 AM CDT Sat Jul 12 2014

Thunderstorms ongoing in the eastern half of the area effecting
only BMI/DEC/CMI this morning. Believe this will continue for 3-4
more hours and then should push off to the east. Thinking is that
PIA and SPI should be dry this morning and into the afternoon and
evening hours. After this morning, believe other sites will be dry
for remainder of the morning and into the afternoon and evening
hours. Believe the next chance of thunderstorms will be overnight.
So, have VCTS at BMI/DEC/CMI for this morning with 3-4hr TEMPO
group at each one with MVFR cigs and vis. Then VFR conditions are
expected remainder of the forecast period. However, models
indicate a cold front dropping into toward the area late tonight,
and believe this warrants a VCTS mention at all sites just after
midnight. Winds will be southwest to south through the period with
speeds at 8-13kts.

Auten
&&

.PREV DISCUSSION...
ISSUED 301 AM CDT Sat Jul 12 2014

SHORT TERM...Today through Monday

07z/2am surface analysis shows warm front extending from Nebraska
across far southern Iowa into south-central Illinois. Showers and
thunderstorms have developed north of this boundary across
Nebraska/western Iowa in conjunction with an approaching upper
wave...with latest radar trends showing widely scattered convection
developing further east along the front across central Illinois.
With area VAD wind profilers showing a 30-35kt low-level jet feeding
into the boundary, think areal coverage of convection will
increase over the next few hours as most model guidance suggests.
As a result, will carry scattered showers and thunderstorms across
the board for the morning hours. Warm front will lift northward,
with model consensus focusing strongest lift across the southern
Great Lakes later in the day. Have therefore lowered POPs for the
afternoon, with dry conditions expected across the S/SW KILX CWA.
Will be a very warm and humid day, with highs ranging from the
middle 80s north of the I-74 corridor, to around 90 degrees far
S/SW.

As upper trough deepens over southern Canada and wind fields
subsequently increase, strong to severe convection will likely
develop along/near frontal boundary across portions of Iowa into
northern Illinois/southern Wisconsin this evening. Latest Day 1
convective outlook from SPC highlights areas along and north of a
Galesburg to Lacon line for the potential for damaging winds,
although exact evolution and track of convective system still
remain in question. Have carried likely POPs across the northern
CWA during the evening, with dry conditions further south. Frontal
boundary will sag southward overnight, spreading showers and
thunderstorms across all but the far SE CWA. Storms will weaken
once daytime instability wanes, so severe threat will likely be
confined to the northern zones during the evening hours.

Cold front will drop southward into the heart of central Illinois
on Sunday, warranting chance POPs across the board. While
instability parameters will be suggestive of potential severe
storms across the S/SE CWA Sunday afternoon/evening, wind fields
will be quite a bit weaker. As a result, think only isolated
strong to severe storms will occur, mainly along/south of I-70.

Cold front will settle south of the Ohio River by Monday: however,
a secondary front/trough axis is progged to rotate around
unseasonably deep upper trough over the Great Lakes. With 500mb
temps dropping into -10 to -12C range and trough axis arriving
during peak afternoon heating, think low chance POPs are prudent
on Monday.

LONG TERM...Tuesday through Friday

Once trough axis passes, a long stretch of cool/dry weather will
be on tap through the extended. Coolest day appears to be Tuesday
when 6 to 8C 850mb temps support highs only in the lower 70s and
overnight lows in the lower to middle 50s. After that, upper
heights will slowly rise and the airmass will gradually modify day
to day, with highs climbing back into the lower 80s by the end of
the week.

Barnes

&&

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

$$






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