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711
FXUS63 KILX 180919
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
419 AM CDT Tue Jun 18 2024

.KEY MESSAGES...

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- Hot and humid weather will prevail across central and southeast
  IL through Sunday. Heat index values will peak in the mid to
  upper 90s each afternoon, and closer to 100 degrees on Friday
  and Saturday afternoon.

- Isolated showers and thunderstorms are possible today until
  sunset, especially in eastern IL. The risk of severe storms is
  low, though lightning hazards and isolated/brief heavy rains
  exist along with gusty winds especially in eastern IL.

- A better chance for thunderstorms arrives Saturday night into
  Sunday as a cold front moves southeast through Illinois.
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&&

.DISCUSSION...
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Issued at 400 AM CDT Tue Jun 18 2024

The 09Z/4 am surface map shows large high pressure off the East
Coast while strong 988 mb low pressure was over north central
Nebraska and east central CO. The frontal boundary extended from
central CO through central SD into nw MN. Warm front had lifted
well north of IL into southern MN and central WI. Water Vapor
loops shows tropical plume of moisture advecting northward from
the Yucatan Peninsula and central Gulf of Mexico across lower/mid
MS river valley and into central/eastern IL and Indiana.
Precipitable Water (PW) values were very moist, ranging from 1.6
to 2 inches southeast of the IL river with southeast IL just
above 2 inches. 850 mb SSW jet of 30-35 kts was over central and
eastern IL with an area of mainly light rain showers along and
east of I-57, though a few showers as far west as highway 51 east
of highway 51 and one shower near the Logan and Macon county
border. These showers were lifting northward. Broken to overcast
mid level clouds giving mostly cloudy to cloudy skies from Peoria
and Springfield eastward into Indiana, with clear to mostly clear
skies west of there over western IL/MS river valley. Mild temps
were in the 72-78F range with dewpoints 65-72F. Peoria tied a
record warm low of 76F on Monday June 17 that originally was set a
decade ago in 2014.

Deeper plume of tropical moisture continues to stream NNE over
central and eastern IL keeping chances of showers and isolated
thunderstorms especially in eastern IL today. SPC does not have
our area in a risk area today, though a could be an isolated cell
or two that produces gusty winds this afternoon in eastern IL. More
cloud cover today and not as hot as past two days with highs in
the upper 80s and lower 90s, coolest in eastern IL and warmest
west of the IL river where more sunshine possible. Dewpoints in
the lower 70s gives heat indices peaking in the mid to upper 90s
this afternoon, and near 100F nw of the IL river.

Isolated showers/thunderstorms possible near the Wabash river in
southeast IL early this evening until sunset, then quiet weather
expected rest of tonight with muggy lows in the low to mid 70s.

On Wed the frontal boundary to our nw will press southeast into
far nw IL and bring chances of showers and thunderstorms to areas
nw of the IL river by Wed afternoon. Still could see an isolated
shower or thunderstorm east of the IL river Wed afternoon mainly
in east central IL. SPC day2 outlook has marginal risk over
northern IL, from I-80 north Wed afternoon/evening. Highs Wed in
the lower 90s with dewpoints in the upper 60s/lower 70s and
afternoon heat indices peaking in the mid to upper 90s and near
100F over the IL river valley.

Strong subtropical mid/upper level ridge over the mid Atlantic
states to strengthen as it expands and strengthens into southern
New England and ridges back into the mid MS river valley during
2nd half of the week. This will likely bring back hotter
temperatures and higher high indices especially by Fri/Sat similar
to what were experienced yesterday with highs in the mid 90s and
even some upper 90s and heat indices around or even surpassing
100F. Will issue a special weather statement to address this
extended and early season heat wave. The experimental NWS
HeatRisk map shows much of IL in major to extreme category on
Friday and Saturday. Convection chances shift north of central IL
on Thu with just slight pops north of Peoria Thu afternoon closer
to frontal boundary in far northern IL.

Extended models continue to a shallow upper level trof moving into
the upper Midwest and Great Lakes region during this weekend and
pushing a cold front se into central IL by Sunday morning. Will
see increasing chances of convection during Sat night from nw to
se and lingering chances on Sunday especially se of the IL river.
Highs Sunday in the upper 80s and lower 90s, warmest in southeast
IL. Heat indices peak in the low to mid 90s Sunday afternoon.
Drier and less humid air arrives Sunday night and Monday, with
highs Monday in the upper 80s to near 90F.

The Climate Prediction Center (CPC) 8-14 Day outlook for June 25
to July 1st has much of the lower 48 states (excluding the Pacific
Northwest) trending above normal temperatures with IL having a
55-60% chance of warmer than normal temperatures.

07
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&&

.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1142 PM CDT Mon Jun 17 2024

Evening model suite has begun to hint at some potential MVFR
ceilings around KPIA toward sunrise. Upstream satellite imagery
does show some patches of ceilings 1000-2000 across southeast
Missouri advecting northward. Latest HREF guidance shows about a
40% probability of ceilings below 3,000 feet in the 10-15Z time
frame. However, coverage in Missouri doesn`t appear especially
solid quite yet, so will monitor for a couple more hours to see if
a low ceiling is needed. Elsewhere, ceilings may dip to around
5,000 feet for a period around sunrise into mid morning, before
rising once again.

South winds expected to remain fairly breezy through the period,
with frequent gusts 20-25 knots.

Geelhart

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$