Bloomington, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

889
FXUS63 KILX 031700
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
1100 AM CST Tue Dec 3 2024

.KEY MESSAGES...

- Near and east of the I-57 corridor, there is a 20% chance for
  freezing drizzle during the Wednesday morning commute. Drivers
  should leave extra time to deice their vehicles and exercise
  caution while on the roads.

- There is an 80% chance minimum wind chills Thursday morning will
  fall somewhere between roughly -12 and 0 degrees north of I-72,
  and between -8 and 5 degrees further south. In addition, west-
  northwest winds will gust 35 to 45 mph Wednesday evening,
  creating difficult travel for high profile vehicles.

&&

.UPDATE...
Issued at 1059 AM CST Tue Dec 3 2024

Lower clouds are moving in from the southwest with higher clouds
moving in from the northwest. Clouds will control the temps across
the area this afternoon. Following satellite trends, clouds should
move east through the afternoon and into the evening, so should
not last much into the night. Updates planned will just be for
high temps slightly cooler this afternoon due to cloud cover and
also increasing cloud cover over parts of the area. Update will be
out shortly.

Auten

&&

.DISCUSSION...
Issued at 210 AM CST Tue Dec 3 2024

Mid level water vapor satellite shows northwest flow aloft across
the Northern Plains and Midwest behind an upper trough slowly
shifting into the Northeast. Under the influence of the sfc high,
currently situated in central/eastern MO, light winds and gradually
diminishing stratus have allowed temps to take a plunge into the
teens. As the axis of the sfc ridge shifts east today, winds will
back to southwesterly, bringing forth a brief thaw for most of the
roadways that remain icy this morning as 2m temps approach freezing
and abundant sunshine warms road surfaces.

Temps should hold steady or even begin to gradually warm after
around midnight tonight as westerly warm advection strengthens,
culminating in low to mid 40s degF highs around lunchtime tomorrow.
Cannot completely rule out freezing drizzle across areas along and
east of roughly the I-57 corridor for a couple hours in the morning
tomorrow, but conditions are looking pretty marginal; the NAM
continues to advertise the three ingredients (0-1km RH > 85%, lack
of cloud ice, and 0-1km negative omega) being met in this area
between roughly 4 and 8am, but it continues to be the most moist
model and the only one with any precip output, and its visibility
and ceilings have come up compared to previous iterations. Since
it`s already been added to the forecast, we kept it this forecast
package, but if the trend continues to be less favorable for
freezing drizzle there we`ll pull it out.

Conditions will turn breezy tomorrow afternoon as winds, gradually
veering but generally westerly, gust 25 to 35 mph - unfortunately
making our one seasonably warm day of the work week feel
considerably cooler. As the upper trough digs into the Great Lakes
region, a tight geopotential height gradient on its southwest
periphery will position itself across the Midwest, with the
deterministic ECMWF suggesting 500mb winds in the core of that jet
streak exceed 130 kt over our area tomorrow evening! Mixing should
be limited ahead of the cold front, but behind it subsidence in the
strong cold air advection regime would favor mixing between the sfc
and around 850mb if you believe the GFS and NAM whose forecast
soundings suggest winds at the top of that layer reach 45+ kt for a
few hours. At this point, the strongest west-northwest gusts are
expected north of I-70 between roughly 4 and 10 pm. The 00z and
06z HRRR depict gusts to 50 mph during that time frame, though
the fact that (1) these are just two runs of one model and (2) the
global ensembles are running closer to 40 mph, we`re going to cap
gusts in the deterministic forecast around 40 or slightly higher
and will message 35 to 45 mph peak gusts for now.

While the area is accustomed to gusty winds during the cool season,
the concern is that the combination of these winds with temps
plummeting into the teens will result in wind chills of 5 to -15
degF - something we haven`t yet experienced this winter season. LREF
continues to advertise an 80% chance minimum wind chills Thursday
morning will lie somewhere between -12 and 0 north of I-72, and
between -8 and 5 degF or so further south. We`d encourage folks to
bundle up when venturing out Thursday morning, and to ensure kids
are dressed appropriately for the cold.

The coldest temps aloft (around -15 to -20 degC at 850mb) shift east
Thursday into Friday, but given 10-20 mph northwest winds on
Thursday and a lack of clouds Thursday night, both will be much
colder than normal. Thursday`s highs will struggle to reach the
mid 20s across most of central and southeast IL, while Friday
morning low temps will once again reach the 10-15 degF range -
which won`t feel as cold as Thursday morning given light-calm
winds, but is still around 15 degrees below climatological normal
for early December. As the upper trough shifts east and zonal flow
or weak ridging expands into the region from the southwest, temps
will return to near or even above normal by Saturday and
especially Sunday when NBM gives a 40-60% chance high temps reach
50 degrees.

Bumgardner

&&

.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 457 AM CST Tue Dec 3 2024

Nighttime satellite reveals an area of MVFR ceilings extends
along the Mississippi River across the IA/IL border, and also
across southern IL. Considerable uncertainty surrounds their
evolution given no model has correctly depicted them thus far this
morning, but given their gradual southeastward shift we`ve added
those to the forecast at SPI and DEC and hinted at them with SCT
groups at the other three sites mid morning into early afternoon.
As a surface high shifts east, winds will back to south-
southwesterly today and increase overnight ahead of the next storm
system. Southwest winds between FL020 and FL025 will increase to
45 to 50 kt by the end of the forecast period, so a few hours of
LLWS was added.

Bumgardner

&&

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

$$