Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 152031
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
331 PM CDT Fri Mar 15 2024

.KEY MESSAGES...

- Hard freeze conditions are likely (60% chance or greater)
  Sunday night in areas north of Interstate 70, and again Monday
  night in areas east of Interstate 57. Any sensitive early-
  season vegetation will be susceptible to damage.

- Dry weather will extend through the middle of next week.

&&

.DISCUSSION...(through next Friday)
Issued at 130 PM CDT Fri Mar 15 2024

An area of elongated surface high pressure currently extends from
southeast Colorado to the Great Lakes to the Hudson Bay, and is
responsible for abundant sunshine and diminishing wind. Fair
weather conditions will remain in place overnight, but the pattern
quickly changes by Saturday morning as a swift-moving disturbance
digs toward the Great Lakes region and drags a cold front across
the Upper Midwest.

Surface winds will steadily increase Saturday morning across the
region as the pressure gradient tightens ahead of the approaching
cold front. Sporadic 30 mph gusts may develop in areas north of
I-72 just after sunrise as the boundary layer begins mixing into a
receding low- level jet. More frequent 30-35 mph gusts will then
occur by early afternoon in all areas north of I-70 as the
boundary layer mixes deeper to 750mb. Confidence in achieving
30-35 mph gusts is high, with both blended and ensemble guidance
exhibiting mean values within that range, though there is
semblance among both suites of guidance for occasional gusts over
40 mph, mainly across east central Illinois where the probability
of exceeding such gusts is over 50%. With the breezy return flow,
afternoon temperatures ahead of the front will reach into the
low-to-mid 60s.

Cooler weather filters in Saturday night behind the departing
front. Temperatures will fall near freezing, but a reinforcing
shot of cold air will move in Sunday evening as an embedded
disturbance forces a secondary cold front through the region.
Deterministic NBM guidance exhibits temperatures in the mid 20s
Sunday night in all areas north of I-70, and we see no reason to
stray. Seasonably cold temperatures then linger into Monday night
with lows in the mid 20s in areas east of I-57.

If the current forecast verifies, we will achieve hard freeze
conditions across much of our area. And while it`s not unusual for
us to receive overnight temperatures in the 20s this time of
year, vegetation does appear to be a little further along given
our recent spells of warm weather. Nevertheless, we`re unlikely to
issue hard freeze headlines with this brief cold snap since the
growing season has yet to begin in earnest.

Moderating temperatures and continued dry weather will extend
through the middle of next week as a longwave ridge sets up across
the West. Our next chance for widespread measurable rainfall
arrives Thursday afternoon or Thursday evening as a pair of
shortwaves lift across the Plains, effectively breaking down the
ridge. Both LREF/NBM mean guidance are in agreement that it is
likely to rain (> 70% chance) between Thursday and Friday, though
mean QPF amounts are generally low (0.1"- 0.3").

MJA

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1227 PM CDT Fri Mar 15 2024

The main aviation concern is for gusty winds to return within the
last 6 hours of this TAF period. Surface winds will back
southwesterly overnight ahead of a cold front. Sporadic gusts
exceeding 25 kts may begin as early as daybreak Saturday as the
boundary layer mixes into a receding low-level jet. Gusts will
then increase and become more widespread by late Saturday morning
as the boundary layer achieves deeper mixing. Occasional gusts up
to 35 kts is possible by the end of the TAF period.

MJA

&&

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

$$


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