I think "Snow Squalls" are worse than blizzards.

Why? Because Blizzards come with warnings for a particular geographical area. Snow squalls are like severe storms and tornadoes in April. It's will be sunny one minute and then the clouds will  turn dark and then a storm is upon you. That's exactly what snow squalls are like. You never see them coming and once it happens, there's wind driven snow and blinding white-out condition for 15 minutes. After that, the sun is out and you think it's over except it's not. Blizzards allow you time to prepare. Snow squalls do not because they are random. Here is what the National Weather Service office from Indianapolis is saying:

.SHORT TERM /Friday and Friday Night/...
Issued at 314 PM EST Thu Jan 14 2021

Forecast challenges focus on a growing confidence in a potential
high impact convectively induced snow shower/squall setup for Friday
afternoon and evening as the upper low drifts across the region.

The upper low will track slowly east through the period from western
Illinois to eastern Indiana with a weakening surface reflection
following in tandem. The presence of both features will produce an
increase in forcing aloft over the region that is set to peak during
the afternoon and evening hours. The real story though is set to
unfold at the mesoscale level within the thermodynamic structure of
the low levels where parameters are set to align to provide
potentially the best convective setup for snow showers experienced
locally within the last 2 years or so. High confidence exists in
potential localized travel impacts throughout the afternoon and
evening hours Friday.

Scattered snow showers are possible through the morning and will
largely focus over northern counties. After 18Z though is when the
atmosphere will start to set up nicely for the convective threat as
the upper low moves into the area. Model soundings are extremely
impressive in the 18-00Z timeframe in support of heavier bursts and
snow rates within showers and developing squalls. Dry adiabatic flow
is set to peak at a level up to 700mb with weak instability present
through the boundary layer and steepening lapse rates that will peak
at 8C/km or greater below 800mb and potentially in the 9-9.5C/km
range in the lowest 2kft or so. Furthermore...the dry adiabatic
layer will coincide with the dendritic growth zone by mid to late
afternoon. This will result in an increasing coverage of snow
showers with locally brief heavy rates of snowfall that may approach
meeting snow squall criteria over a 3-5 hour period focused from mid
afternoon into the early evening.

Have increased pops substantially over guidance for the afternoon
and continued it through Friday night. While the convective
component will diminish Friday evening...the presence of the upper
low and surface wave over the region will maintain strong forcing
aloft to keep snow showers going most if not all of the night. CAMs
analysis is picking up on the localized...convective nature of the
showers and the very likely possibility that those locations that
get under any repeated bouts of brief heavy rates of snowfall will
likely cash on some light accumulations potentially up to an inch
or greater by Saturday morning.

The greatest concern with the upcoming snow showers for Friday
afternoon and evening is the potential impact to travel and roads
across the region due to the quick hit and miss nature of locally
heavy snow bursts. One potential saving grace which may mitigate
concerns to some degree is that surface temps during the afternoon
in particular are likely to fall in the 32-36F range but if it snows
hard enough even for a short time at these temperatures...expect
road to become snow covered and slick in spots. As temperatures fall
Friday night...this could cause an increase in icy conditions as
well. Will continue to message concerns via HWO and social media
platforms at this time.

Temps...undercut guidance across the board for highs Friday which
look far too warm. Expect highs to hold mainly in the mid to upper
30s. Lows will fall back into the upper 20s Friday night which will
end up above most guidance as well.

&&

.LONG TERM /Saturday through Thursday/...
Issued at 234 PM EST Thu Jan 14 2021

An active pattern continues into the long term period as we
transition into being along the backend of the exiting strong
upper level low pressure system. During the day Saturday, surface
winds will generally be westerly with some mid and upper level
advection of Lake Michigan air into the northern counties.
Isolated to scattered snow showers are expected through the day
with the best chances mid afternoon when soundings show good low
level lapse rates and a passing vort max. The best forcing will
have already exited so with meager moisture, only a few tenths of
an inch of snow are expected along with some locally higher
amounts where snow behaves more convectively.

Going into Saturday night, confidence in precipitation drops off
as a strong low level inversion builds. There are some signs that
there could be some freezing drizzle as moisture aloft drops off
and a lack of ice crystals is present in the cloud deck. The big
question will be if there is enough low level lift to lead to any
precipitation and confidence in that is too low at this time.
0
During the day Sunday, another upper level low will be arriving
from the west triggering another round of isolated to scattered
snow showers during the day and into the overnight hours. Upper
level forcing is strong with this system, but like the last the
low level moisture is lacking which will limit the overall
potential for snow accumulations. This pattern of isolated to
scattered snow showers will continue into much of early next week,
but confidence in timing for each of these and the impacts for
central Indiana wanes later in the period as differences in model
guidance increases along with the uncertainty with how each
system will interact with the next. A stronger system approaching
from the Gulf may bring some impacts to central Indiana as early
as Thursday, but confidence is higher that impacts won`t be seen
until Friday or Saturday and more likely closer to the Ohio River.

Overall, light snow accumulations are expected this weekend with
amounts between a half inch and an inch. With the convective
nature of the snow on both Saturday and Sunday, locally higher
accumulations with some areas of 2 inches certainly possible.
Going into next week, occasional shots for a rain/snow mix are
possible, but not as likely as the weekend system. Temperatures
will begin the period near normal with above normal temperatures
next week.

&&


1 comment:

  1. So... this afternoon is not a great time for a leisurely drive. Dang!

    ReplyDelete