Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 221921
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
221 PM CDT Fri Mar 22 2024

.KEY MESSAGES...

- Gusty winds and sub-freezing temps will filter into the region
  this evening behind a sharpening cold front. Chances for a hard
  freeze range from greater than 70% north of a Macomb to
  Bloomington line, to less than 30% south of I-72.

- A spring storm system will bring a 40-50% chance for south wind
  gusts of 45 mph or higher on Monday, which would make travel
  difficult for high profile vehicles on east-west oriented
  roadways.

- Monday night, the same system will bring the potential for heavy
  rain, which could cause localized ponding of water in
  agricultural fields and in urban areas with limited drainage.
  The chance for widespread flooding rains (more than 2 inches in
  6 hours) is generally less than 20%.

- Mainly north of I-70, there will be a 40-60% chance for a hard
  freeze again Wednesday morning, climbing to a 50-80% chance by
  Thursday morning. This could damage newly emerged sensitive
  vegetation if protective precautions are not taken.


&&

.DISCUSSION...
Issued at 218 PM CDT Fri Mar 22 2024

Latest surface observations show a rather tight temp gradient across
the ILX CWA, with upper 30s in Galesburg to 60+ along the I-72
corridor. A developing cold front will bring gusty northwest winds,
a burst of moderate rain (and, in some spots mainly north of I-72,
perhaps mixed with some wet flakes and/or sleet), and a rapid drop
in temps as it sweeps northwest to southeast through the region this
evening. Tonight, wind chills are forecast to bottom out in the
teens in many locations mainly north of I-70, but working against a
sufficient temp drop for a hard freeze will be (1) winds, which will
be slow to ease overnight, and (2) widespread stratus, with HREF
probabilities for cloud bases lower than 3kft of 75-90% mainly
along/east of the IL River through 9-10am. NBM suggests that chances
for a hard freeze are generally greater than 70% north of a Macomb
to Bloomington line, while those probabilities fall to less than 30%
south of I-72. Given the greatest vegetation vulnerability (mainly
fruit trees) is generally south of an Astoria to Hoopeston line,
we`re going to forgo an SPS highlighting hard freeze potential,
but would still encourage folks to take precautions to protect
newly emerged sensitive vegetation today.

Despite the cold start and continued cool advection throughout the
day tomorrow, temps should rebound for several hours during the
afternoon with prolific sunshine to radiationally warm a dry
airmass. That being said, if the morning stratus is slower to burn
off than currently expected, the high temp forecast of mid to upper
40s could be overdone a bit. Thus highs north of I-74, where some
locations might struggle to reach 40 degF, were knocked down a
couple degrees.

Tomorrow night into Sunday, deterministic guidance is in agreement
heights rise across the region in advance of an upper trough and
associated intense sfc low lifting northeast across the central
Great Plains. Temps here will rise into the 50s Sunday, and then
further increase into the 60s on Monday as strong warm advection
overspreads the region in advance of the occluding sfc low. EPS mean
brings wind gusts to just over 40mph on Monday, when NBM gives a 40-
50% chance we hit advisory criteria (45mph). The EPS and GEFS means
bring PWATs to more than an inch across the entire region
- upwards of 200% of climatological normal - providing fuel for
efficient rain-producing showers and storms. Fortunately, the area
can still take quite a lot of water before having significant hydro
issues; NBM suggests the probability of exceeding 2 inches of rain
(a smidgen lower than the lowest 6h FFG across the area) ranges from
less than 10% northwest of I-55 to 15-20% at any given location
south of I-70. However, training storms are favored given the slow
progression of the cold/occluded front and nearly parallel cloud
bearing (850-300mb) flow, so localized ponding of water in
agricultural fields and urbanized areas with limited drainage is a
distinct possibility Monday night. Also, don`t want to try ruling
out severe potential, though at this point that continues to look
limited given poor overlap between favorable thermodynamics (south)
and kinematic fields (north). The CSU MLP continues to advertise a
5% chance for severe weather area-wide.

Behind the aforementioned front, the region will turn sharply cooler
with below normal highs, in the upper 40s to low 50s, forecast
Tuesday and Wednesday. NBM even gives a 40-60% and 50-80% chance for
a hard freeze mainly north of I-70 on Wednesday and Thursday
mornings, respectively.

Bumgardner

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1224 PM CDT Fri Mar 22 2024

A cold front will push across central Illinois this afternoon and
early evening. A narrow band of light showers is expected to
accompany the front. Behind the front, winds will turn northerly
and gust to around 20-25kt as MVFR ceilings overspread the
terminals. MVFR ceilings will persist overnight with improvement
possible mid to late Saturday morning.

Deubelbeiss

&&

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

$$


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