Bloomington, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

737
FXUS63 KILX 040811
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
211 AM CST Wed Dec 4 2024

.KEY MESSAGES...

- There is a low (20%) chance that a band of briefly moderate-
  heavy snow accompanies a cold front this evening north of a
  roughly Macomb to Robinson line. The combination of gusty winds
  and snow would result in diminished visibilities and slick
  roads.

- There is a 60% chance west-northwest winds gust over 45 mph
  this evening, resulting in difficult travel conditions for high
  profile vehicles. A Wind Advisory is in effect for areas along
  and north of roughly I-70.

- There is an 80% chance minimum wind chills tonight are between
  roughly -11 and -3 north of I-70 and between -5 and 3 further
  south. This would increase the risk of hypothermia and frostbite
  to those outdoors who are inadequately dressed.


&&

.DISCUSSION...
Issued at 204 AM CST Wed Dec 4 2024

Nighttime microphysics satellite imagery shows an area of clouds
around 3-5 kft AGL shifting across eastern IL with a warm front,
which has resulted in gradually rising temps and dewpoints.
Highres guidance suggests temps will continue to rise through
early to mid afternoon when highs will surpass 40 degF in most
places along and south of a roughly Macomb to Paris line; in fact,
HREF suggests a 20-40% chance highs will reach 50 south of the
I-70 corridor. This reprieve from largely below normal temps will
be short-lived, however, as a potent storm system across the Great
Lakes pushes a cold front southeast across the region this
afternoon and evening. This system will be responsible for our
three forecast concerns: (1) Snow squall potential this afternoon
and evening, (2) gusty northwest winds this evening, and (3)
bitterly cold wind chills tonight into tomorrow.

***Snow Squall Potential***
Timing: 4-8pm This Evening
Confidence: Low

Along and immediately ahead of the aforementioned cold front, there
will be around a 30% chance for a line of rain/snow showers to
develop north of a Macomb to Robinson line. If (big if) this
develops, the precip (while brief) could become moderate-heavy given
strong frontal forcing and the presence of instability; in fact,
HREF mean/max for SBCAPE is 10/50 J/kg, and in the same area the
RAP`s snow squall parameter exceeds 2. This briefly heavy precip
would lead to a quick changeover from rain (or rain/snow mix) to
snow due to evaporational cooling in an initially mid 30s degF
airmass, and could also aid in mixing strong winds aloft to the sfc.
While a low confidence scenario, the potential for sudden visibility
reduction in a burst of moderate-heavy snow and wind gusts
surpassing 40 mph around or just after the evening commute time is
something we want to bring attention to. We`ll continue to monitor
forecast trends from highres guidance and sfc obs to see how the
potential shifts today.

***Gusty Northwest Winds***
Timing: 5-10pm This Evening
Confidence: High

Along and immediately behind the cold front, pressure rises of ~6mb
in 3h will favor efficient mixing of strong winds aloft to the
surface. Bufkit soundings from the NAM and GFS continue to advertise
winds at the top of the mixed layer (nearly 850mb) around 40-45 kt,
while both HREF and NBM suggest a 40-60% chance gusts surpass 45 mph
(Wind Advisory criteria). We generally try to wait until confidence
is nearer 80% to issue an Advisory, however given the meteorological
factors (tight pressure gradient, strong CAA favoring efficient
mixing, etc.) and in collaboration with adjacent offices we decided
to go ahead and issue one. Whether we hit criteria or not,
confidence is high it will be windy this evening with a 95+% chance
for gusts over 35 mph.

***Bitterly Cold Wind Chills***
Timing: Tonight-Thursday Morning
Confidence: High

While the timing of strongest winds and coldest temps will be
offset, there will be some overlap tonight into early tomorrow
morning as sustained winds even by sunrise have an 80% chance of
falling somewhere between 14 and 20 mph according to HREF. At that
time, forecast temps range from around 10 degF in Galesburg to 15 in
Lawrenceville. This combination would result in wind chills between
roughly -10 and -3 north of I-70 and -5 and 3 further south. This
isn`t quite hitting Cold Weather Advisory criteria, however it is
dangerously cold to anyone inadequately dressed. We`d encourage
folks to make sure they`re bundled up, carry an extra layer in the
car, and ensure kids are appropriately dressed (especially if they
have to wait at the bus stop).

Temps will rebound over the weekend as heights rise across the Ohio
Valley and Great Lakes behind the departing trough. The
deterministic models also depict a cut off low getting swept up by
the jet stream and lifted across the Midwest at some point late
Sunday-Tuesday, which could further increase warm advection across
the area. While there`s considerable spread between the GFS, EC, and
CMC on the evolution of this wave, precip chances come up with its
approach late Sunday, by which time NBM gives the region a 50-80%
chance for highs over 50 degF. Fortunately temps should be warm
enough to keep this all rain, even overnight into Monday morning
given forecast lows in the low to mid 40s. NBM/LREF mean suggest
temps start to trend cooler Tuesday into Wednesday, though there is
considerable spread on when the next deep trough encroaches on the
area; for example, the 04.00z EC has the aforementioned cut off low
deepening over the Great Lakes and blasting the Midwest with cool
advection late Monday-early Tuesday, while the GFS maintains more
of an open wave-type pattern and has the stronger trough/cold air
push arriving mid week. For what it`s worth, NBM has a 40-70%
chance morning lows are back in the teens Wednesday morning. In
addition, a subset of about 20-30% of LREF membership has
measurable snow falling sometime Tuesday-Wednesday - something
we`ll keep one eye on over the next several days.

Bumgardner

&&

.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1122 PM CST Tue Dec 3 2024

Strengthening southerly winds and VFR conditions are expected
overnight ahead of a an area of low pressure. A prefrontal trough
will move across central Illinois late morning and afternoon
turning winds southwesterly to westerly with gusts increasing into
the 25-30kt range. MVFR ceilings may accompany this trough,
especially along the I-74 corridor. A cold front will sweep
across the region Wednesday evening with winds turning
northwesterly and gusts further increasing above 30kt. A band of
snow showers may briefly move across the terminals. Confidence in
snow on station is low but if it does occur could briefly produce
very low visibility under a half mile.

Deubelbeiss

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 3 PM this afternoon to midnight CST tonight
for ILZ027>031-036>038-040>057-061>063.

&&

$$