Normal, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

266
FXUS63 KILX 061419
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
919 AM CDT Sun Oct 6 2024

.KEY MESSAGES...

- Breezy and very dry conditions will develop behind a cold front
  this afternoon, bringing elevated fire danger to areas north of
  Interstate 70 where there is a 20-50% joint probability for
  gusts greater than 25 mph and RH values less than 25 percent.
  Rapid fire spread is a concern with any field or brush fires.

- Patchy frost is a possibility (30-50% chance) tonight in
  sheltered areas north of the Illinois River.

- The stretch of dry weather is very likely to continue through
  next Saturday, at least. There is currently less than a 15%
  chance for rain all week, with drought conditions sure to
  expand. A weak signal for rain has emerged for late next weekend.

&&

.UPDATE...
Issued at 918 AM CDT Sun Oct 6 2024

Temps and dewpoints were updated this morning to account for a
slightly slower frontal passage than what guidance was originally
suggesting. Given the better forcing with this system is displaced
to our north, this doesn`t come as a surprise. Dewpoints have been
running a little less cool than what some high res guidance, most
notably the HRRR, has been suggesting both in our neck of the woods
and upstream, but time will tell how these behave this afternoon as
mixing ensues. Mixing should be pretty efficient given the CAA
behind the cold front, but it`s possible that it doesn`t end up
being as aggressive as some of the more bullish highres guidance
advertises. Freshened up afternoon temps and dewpoints with a blend
of the CAMs and NBM to yield minimum afternoon RH values in the low
to mid 20s (locally upper teens). Concerns remain for conditions
favoring rapid fire spread this afternoon given both the low RHs and
blustery northwest winds gusting to 25 mph. High temps should be
confined to mainly the low to mid 70s north of I-72 and upper 70s to
low 80s south, but the drier airmass and breeziness will prevent it
from feeling hot for most.

Bumgardner

&&

.DISCUSSION...
Issued at 1203 AM CDT Sun Oct 6 2024

A robust 500-mb trough and its attendant cold front will push
across the region this morning. Upstream obs already indicate much
drier air spilling in behind the front, with Td values generally
between 25-35 degF. As this airmass advects into central Illinois
this afternoon, RH values are expected to fall below 25 percent
in areas along and north of I-70. In addition, breezy gradient
winds and deep PBL mixing will support occasional gusts exceeding
25 mph. This combination of dry air and breezy winds will elevate
the fire weather concern for today, with rapid spread becoming a
possibility for any field or brush fires that might ignite.
Fortunately, the 10-hour dead fuel moisture forecast for today is
around 15%, which is high enough to preclude a Red Flag Warning
in our area.

Aside from the fire weather concerns, another forecast challenge
for today is temperatures. With the cold front pushing through
this morning, we anticipate there being a notable temp gradient
in- between locations north of the IL River (upper 60s) and south
of I-70 (low 80s). For tonight, it`s quite possible that our
forecast lows are not cold enough. With such a dry airmass in
place, overnight temperatures should drop like a rock amid clear
skies and calmer winds. While we`re forecasting uniform low-40s,
there could be a few pockets of mid 30s (50% chance of 36 degF or
cooler), mainly in areas north of the IL River. This would
introduce a risk for patchy frost.

The stretch of dry weather will very likely extend through
Saturday, with both multi-model ensemble (LREF) and blended (NBM)
guidance supporting less than a 15% chance for rain. This is due
to strong upper-level ridging out west, but also a very active
Gulf. These circumstances will combine to provide very little
moisture return and few, if any, frontal passages this week.
Nevertheless, mid-range ensemble guidance seems to be picking-up
on some noise by late next weekend, meaning rain could return by
mid-October.

Otherwise, temperatures this week are trending about 4-6 degF
warmer than normal for early October.

MJA

&&

.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 453 AM CDT Sun Oct 6 2024

VFR conditions will persist through this TAF period as skies
remain clear behind a departing cold front. West winds will
gradually veer northwest this afternoon, occasionally gusting near
25 kts before diminishing overnight.

MJA

&&

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

$$