322
FXUS63 KILX 100453
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1153 PM CDT Tue Jul 9 2024

.KEY MESSAGES...

- The greatest impacts from post-tropical Beryl will be focused
  on areas near and east of I-55. There will be a sharp dropoff in
  rain amounts and wind speeds west of the Illinois River.

- Probabilities of over 2 inches of rain range from around 50%
  near the I-55 corridor, to 90% from Taylorville northeast to
  Rantoul, with late afternoon and evening the greatest period of
  concern. A Flood Watch remains in effect along and east of I-55.

- A period of strong winds is expected in eastern Illinois from
  around midnight through mid morning Wednesday, with about a
  70-90% chance of gusts exceeding 40 mph before sunrise.

- Longer term, heat and humidity return early next week, with
  increasing potential for heat index values over 100 degrees.

&&

.UPDATE...
Issued at 934 PM CDT Tue Jul 9 2024

Tornado watch was cancelled earlier, but have made some
adjustments to pops/wx grids for the rest of the night. The
strongest part of the system where the tornado threat was has
moved east of the CWA and no long posses a threat to southeast IL.
However, rain will continue during the overnight hours...mostly
light rain, but some moderate rain will occur at times as the
backside of the system moves east across the CWA. The higher wind
gusts are still a possibility in the east overnight and did not
make any adjustments to them. An update should be coming shortly.

Auten

&&

.SHORT TERM...  (Through Wednesday)
Issued at 313 PM CDT Tue Jul 9 2024

Post-tropical Beryl is centered early this afternoon near the
Missouri Bootheel, with a warm front arcing northeast along the
Ohio River. Rain has struggled to get much further northwest than
Peoria, but has been fairly steady south of there the last several
hours. Heaviest rainfall estimates were earlier today along the
northern edge of the rain shield, but more recently have been
focused between Decatur and Flora. As the low lifts northeast into
western Indiana this evening, the heaviest and steadiest rains are
expected near and east of I-55, with highest probabilities of
over 2 inches focused on a Taylorville-Rantoul corridor. LPMM
(localized probability matched-mean) values from the morning HREF
run suggest potential for 3-5 inches in this corridor, and QPF
amounts in this forecast package have been increased as a result.
By midnight, much of the rain west of I-55 should be quickly
fading, but may stick around until sunrise near Champaign and
Danville.

Second item of concern is with severe potential this evening. While
the bulk of the threat will be closer to the Ohio River, latest
WoFS model ensembles suggest a period focused from 5-8 pm down
toward our far southeast counties (Crawford, Richland, Lawrence).
HRRR forecast soundings near Lawrenceville at 5 pm show around
0-1km SRH of around 200 m2/s2, so some brief spinning storms
can`t be ruled out, and the latest SPC Day1 outlook maintains the
level 2 (slight) risk.

Last concern during this period is with the winds. As the low
passes by, wind gusts significantly increase across eastern
Illinois. Gusts of 25-30 mph should be common by mid evening near
and east of I-55, with chances of >40 mph increasing to around
70-90% near and east of I-57 by around 3 am. HREF probabilities of
over 45 mph are around 40% during this period, so there is enough
uncertainty to hold off on an advisory at this point, but a
Special Weather Statement was issued to address the issue. Winds
are expected to drop off by mid morning Wednesday.

Geelhart

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 313 PM CDT Tue Jul 9 2024

Longer range upper pattern has a broad trough over the Great Lakes
late this week, lifting out of the area as a 597 dm high builds
across the Rockies. With time, this high will morph eastward
toward the Plains early next week. Some potential for the
northwest flow over the Great Lakes to edge southward and bring
some showers/storms, but at the moment, the main concern is with
heat and humidity. High temperatures likely to return to the 90s
as early as Sunday, with WPC probabilities of >105 degree heat
index values around 40% on Monday.

Geelhart

&&

.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1153 PM CDT Tue Jul 9 2024

Complicated TAFs tonight. Remnants of Beryl continue to move
slowly east across the region and are affecting all TAF sites.
Precip is more convective looking on radar and should end at TAF
sites from west to east. Cigs are VFR at all sites except for CMI,
but will improve once precip ends. Some MVFR clouds are possible
at all sites late tonight so will have TEMPO group for a few hours
at each site. With all the precip tonight, expecting broken CU at
all sites during the day. By late afternoon, as the mid level
trough rotates through the area, there is the chance of convection
at all sites. Cu should remain broken in the afternoon so all
sites could see TS in vicinity. Around 2z, convection should
dissipate...as sunsets. Winds will be light at PIA and SPI, but
still expecting gusty winds out of the north at BMI, DEC, and CMI.
Gusty winds will continue at these sites into the morning with DEC
and CMI seeing gusts continue into the morning hours around
30-35kts. SPI might see some gusts around 25kts overnight, but
decrease during the day. Winds become lighter in the afternoon and
light and variable in the evening.

Auten

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Wednesday afternoon for ILZ038-042>046-
051>057-061>063-066>068-071>073.

&&

$$