199
FXUS63 KILX 271056
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
556 AM CDT Fri Sep 27 2024

.KEY MESSAGES...

- Remnants of Hurricane Helene will impact central Illinois over
  the next couple of days.

- There is a high probability (greater than 70% chance) of wind
  gusts in excess of 45mph along and east of I-55 late this
  afternoon and evening.

- Storm total rainfall will be heaviest across the Ohio River
  Valley: however, amounts in excess of 1 inch are expected as far
  north as the I-70 corridor.

&&

.SHORT TERM...(Today through Saturday)
Issued at 331 AM CDT Fri Sep 27 2024

07z/2am surface analysis shows Hurricane Helene rapidly churning
north-northeastward across Georgia...with the center located near
Vidalia. NHC forecasts show the system gradually weakening as it
continues northward across the Appalachians before veering
northwestward into Kentucky this afternoon. Model consensus
suggests a very deep 980mb remnant low will be located near
Evansville, Indiana by early evening. Given the tight pressure
gradient, strong/gusty winds are expected...with the highest
momentum air remaining to the N/NE of the low. HREF probabilities
strongly suggest Wind Advisory gusts in excess of 45mph as far
west as the I-55 corridor late this afternoon and evening. Have
therefore added Logan, Christian, and Sangamon counties to the
advisory in order to cover all locations along/east of the I-55
corridor. Some raw model guidance shows wind gusts potentially
exceeding 60mph pivoting northwestward from southern Ohio/Indiana
into the far E/SE KILX CWA late this afternoon. Will therefore
need to keep an eye on later model data as well as upstream obs
for a possible upgrade to a High Wind Warning generally
along/southeast of a Paris to Effingham line where the current
forecast features gusts in the 50-55mph range. The winds will
gradually decrease late tonight into Saturday as the low steadily
fills...with projected gusts down to 30-35mph by dawn Saturday,
then to around 20mph by Saturday evening.

The other big impact from Helene will be the rain. As has been
noted by the past couple forecast cycles, the heaviest rainfall
will remain focused further south across the Ohio River Valley
where 3-4 inches will be likely. Further north, enough dry air
will be entrained into the system to keep things mostly dry
along/northwest of a Rushville to Bloomington line. 00z Sep 27
LREF shows a 100% chance of 1 inch or more of rainfall along/south
of I-70...but only a very low probability (20-30%) chance as far
north as a Hoopeston to Taylorville line. The official forecast
features greater than 1 inch along/south of I-70 and greater than
2 inches along/southeast of a Lawrenceville to Olney line.

Barnes

.LONG TERM...(Sunday through Thursday)
Issued at 331 AM CDT Fri Sep 27 2024

Showers will linger into Sunday: however, additional rainfall
amounts will be minimal. The remnant low will gradually get
shunted eastward by Monday as a cold front approaches. Thanks to
increasing amounts of sunshine and southwesterly flow ahead of the
front, high temperatures will climb into the upper 70s and lower
80s. The front will pass through the region dry, followed by
slightly cooler/drier weather for the remainder of the extended.
Highs will drop into the lower 70s and overnight lows will dip
into the 40s both Tuesday and Wednesday before readings moderate
by the end of next week.

Barnes

&&

.AVIATION...  (For the 12z TAFs through 12z Saturday Morning)
Issued at 556 AM CDT Fri Sep 27 2024

N/NE winds will increase markedly today as remnants of Hurricane
Helene approach from the southeast. Forecast soundings and
numeric guidance suggest gusts in excess of 40kt along/east of
I-55 during the late afternoon and evening...with gusts possibly
over 45kt at KCMI/KDEC. Occasional showers will be noted at the
I-72 terminals with ceilings temporarily lowering to MVFR at
KCMI/KDEC between 16z and about 23z. VFR ceilings will prevail
elsewhere...until MVFR ceilings develop/spread from east to west
across all of central Illinois late tonight into Saturday morning.

Barnes

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 1 PM this afternoon to 1 AM CDT Saturday for
ILZ038-042>046-051>057-061>063-066>068-071>073.

&&

$$