Chris's Corner - Record for Latest First Flakes May Fall

Slight shift SE with advisories now as far as NW ARK

.SHORT TERM... (Through Late Tuesday Night)
Issued at 300 PM CST Mon Jan 8 2024

Latest regional radar mosaic widespread precipitation surging
north/northeast into parts of east central and northeast Missouri as
well as west-central Illinois as of 2000 UTC. This area of
precipitation is being forced by strong low-level warm/moist
advection along with increasing mid/upper level support ahead of the
approaching trough. Observations, including mPING, show more
rain/snow and pure snow further southeast than was forecast
initially this morning. In addition to wetbulb effects, it appears
that the high precipitation rates (>0.10"/hr) are helping cool the
surface via dynamic cooling. Latest SPC mesoanalysis continues to
show a pocket of 4-6+ degrees of cooling at the surface over the
past 3 hours heading toward parts of central Missouri. This is
occurring well after saturation and even in the face of persistent
southeasterly flow. Given the forecast for more snow further to the
southeast, amounts across central and northeast Missouri as well as
west-central Illinois have generally been raised by 1 to as much as
2". As a result, expanded the winter storm warning into Monroe and
Ralls counties and expanded advisory southeast as well into Osage,
Montgomery, Lincoln, Gasconade, and Warren counties in Missouri in
addition to Greene and Jersey counties in Illinois. Exactly how far
to the southeast the rain/snow line gets late this afternoon/early
this evening is still a bit uncertain, but the best guess is near I-
44/I-55 in Missouri/Illinois. Within the St. Louis metro area,
mostly rain is forecast for the city and metro east, with a brief
(~2-3 hour) changeover to snow expected in western St. Charles
county. There also probably will be some pings of sleet (more likely
within the first 1-2 hours of precipitation) as dual polarization
radar imagery shows high reflectivities near the St. Louis metro area
with low correlation coefficient values. Given the high
precipitation rates, there may be quite the gradient on the
southeastern edge of the accumulating snowfall through this evening,
with multiple inches and little/no accumulation only separated by a
matter of 5-10 miles or so.

The highest snowfall rates for the entire event are forecast to be
with the warm-air advection portion of the snowfall. The HREF from
1200 UTC this morning shows very high probabilities (60-90%) for
>0.5"/hr, with 30-50% probabilities for >1.0"/hr. These
probabilities are highest between roughly 2200 UTC late this
afternoon and 0300 UTC this evening. These high snowfall rates will
be falling during the evening rush hour in many areas (including
Columbia/Jefferson City) and will make the commute hazardous for
drivers.

The rain/snow line will surge northward tonight as the low-level
cyclone approaches from the southwest. The vast majority of the area
should be rain late tonight, with the exception of parts of
northeast Missouri. The precipitation also should shut off for a
time over much of the area as the dry slot works into the region. By
1200 UTC, the low-level cyclone should be approaching the
Mississippi River, with the southeastern edge of the deformation
zone entering northeast Missouri. Any rain should transition back to
snow from west/northwest to east/southeast through the day on
Tuesday as sufficiently cold air advects into the area. Snowfall
rates look to be on the lighter side on Tuesday, with only a weak
signal even for 0.25"/hr on the HREF. Lift within the TROWAL
airstream is modest looking at isentropic charts also supporting the
more modest snowfall rates. Light snow within the deformation zone
should reach eastern Missouri just after midday and then begin to
pull out of the area to the north and east by early evening.

In terms of snowfall totals, the highest totals (6-10") remain
across parts of northeast Missouri and west-central Illinois. Totals
gradually taper off as you go further southeast, with about 3-5"
from an axis near KCOU>>KPPQ. For areas near the I-44/I-70 corridors
in Missouri and Illinois respectively, generally less than 1" is
expected, though areas just to the northwest may see up to an
additional inch through this evening.

In addition to the light snow during the day on Tuesday, northwest
wind speeds and gusts will really increase as the surface low moves
into northern Illinois. While the strongest winds (sustained 20-30
mph, gusts 30-40+ mph) will be just after the snow ends. The winds
will help reduce visibility before the snow concludes, and also
cannot rule out some blowing and drifting overnight tonight in parts
of northeast Missouri. However, given the wet nature of the
snowfall, do not expect anything widespread.

18z Icon has a blizzard for those north of 70 on Friday.

What is this "Grand Ensemble" that they speak of?

Edit: It is the combined GEFS, GEPS, and EPS. See here.

WC IS icon north of st charles county for friday storm

Rain snow mix hwy k and mexico rd

all snow now. 28*. NW Pike Co IL

Gfs is still pretty for along and north of 70 friday, including St.charles County

Rain

Alright who replaced BRTN with 99

Sleet N snow driving from O’Fallon to wentzville. Starting to stick

HERE HERE

I was wondering what my issue was…that is it!

Snowing in Wentzville for the past half hour or so. Fat flake have a coating on the grass and slushy roads.