Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/29/22

Area Forecast Discussion

National Weather Service Louisville KY

 822 PM EST Fri Jan 28 2022

.Forecast Update...
Issued at 822 PM EST Friday Jan 28 2022

Snow will begin winding down over the next 1 to 3 hours from NW to
SE across the area. We`ve steadily seen a decrease in the intensity
of the snow showers since the sun has gone down, and low level lapse
rates have slackened. However, there are still pockets of moderate
snow embedded in the overall light precip shield, and some
additional light accums can be expected through 10 or 11 PM EST. The
Winter Weather Advisory is set to expire at 10 PM EST, however may
need to contemplate a 1 or 2 hour extension for SE portions of the
headline until snow has fully stopped. Will make that decision in
another hour or so.

We`ve seen some pretty impressive snow totals along a corridor from
the Louisville metro, southeastward through Bardstown, and down
toward Somerset. In a corridor from Bardstown to Springfield,
localized amounts between 3.5 and 4.5 inches have been noted!
Overall, most folks will end up with 1 to 3".

Once the snow ends, expect a quiet but cold overnight. Temperatures
are expected to drop into the low and mid teens by dawn on Saturday,
with wind chills in the single digits for many. Even after the WSW
expiration, slick roads will continue to be a problem for the
overnight.

Issued at 530 PM EST Friday Jan 28 2022

Intense snow showers have developed ahead of an strong mid level
vort max this afternoon. Meanwhile, an arctic surface boundary is
quickly advancing southeastward through the most intense
reflectivities. We are seeing evidence of 1 to 2" per hour rates
along with gusty winds up between 25 and 35 mph behind the boundary.
Temperatures quickly fall off into the mid and upper 20s along with
visibilities below 1/4 SM, making the perfect setup for heavily
impacted roads.

Issued a Snow Squall Warning for the Louisville metro (thanks PAH!)
and have been handling the other intense bands with Snow Squall SPS
due to lesser impacts to significant roadways. The main area of
focus for the next few hours will be the Louisville Metro, down
through Bardstown, and over toward Somerset, KY.

&&

.Short Term...(This evening through Saturday)
Issued at 255 PM EST Fri Jan 28 2022

...Locally Intense Snow Showers Possible Through Early Evening...

Key Points:
- Convective snow showers possible across southern Indiana and
mainly between I-65 and I-75.
- Additional snow amounts around 1 inch for most, but localized 3"
snowfall is possible.
- Localized snowfall rates could exceed 1" per hour, resulting in
low visibility and deteriorating road conditions during the PM
commute.

Increasingly convective snow shield is continuing to press SSE
into the Ohio Valley ahead of a deepening upper wave that is still
diving through Illinois. BMG has had vis as low as 1/4 mile but
other sites have been bottoming out just above 1 mile in the heavier
snow. Lapse rates from the sfc to 700mb already approaching 8C/km
based on AMDAR soundings, and progged to continue to steepen, so the
more intense snowfall rates are yet to come.

As the upper disturbance dives southeast across Kentucky into
eastern Tennessee, the corridor for the most intense snow will run
either side of a line from roughly Louisville to Somerset. This will
be the favored area for additional snowfall exceeding 1 inch. Hi-res
models are showing narrow tracks with the potential for 4+ inch
snowfall amounts, but am not about to jump on that, especially given
that most of the area will not even approach those totals. Will
mention localized 3" amounts possible, but even then we can`t pin
down where that will be. Snowfall rates with these intense bursts
will briefly exceed 1 inch per hour.

Current Winter Weather Advisory strategy looks to be in good shape.
One saving grace, especially west of the advisory area, is that
temps remain just a couple degrees either side of freezing, which
will at least slow the onset of travel impacts. Snow should diminish
after 0Z as sfc temperatures drop, but will carry the advisory
through 3Z as the cooler temps could allow impacts to continue even
with lesser snowfall rates.

Breezy north winds will continue for much of the night, only really
decoupling just before sunrise. Min temps in the lower/mid teens
will still feel like single digits early Sat morning. High pressure
builds quickly, so expect a tranquil but cool Saturday, with temps
struggling to crack 30.

.Long Term...(Saturday night through Friday)
Issued at 325 PM EST Fri Jan 28 2022

SYNOPSIS...Temperatures gradually warm from a cold start on Sunday
through Monday and Tuesday with highs returning to above normal for
the middle part of next week. Dry weather is expected through
Tuesday morning, with Sunday and Monday only containing a mix of sun
and clouds. Rain chances will return Tuesday afternoon ahead of a
strong cold front and are expected to last through at least Thursday
evening, with some mixed precipitation possible on Thursday as cold
air tries to enter the region before the moisture clears out. Rain
totals of between 1-2" are still expected with the event, with
isolated higher totals possible. After the cold front passes
through, another shot of arctic air will move through the region for
the end of next week.

DISCUSSION...The extended period begins with a strong, nearly-
stacked surface cyclone moving through the Canadian Maritimes with
synoptic scale troughing located over the eastern CONUS. Across the
Ohio and Tennessee Valleys, NW flow will provide dry and cold
conditions for Sunday. A weak upper shortwave disturbance will move
from the upper Great Lakes down into the mid-Atlantic region but
will be moisture starved and will not impact our region outside of a
few additional clouds on Sunday. As the trough over the eastern
CONUS flattens out on Monday, temperatures will begin to rebound as
thickness values increase over the central U.S. with low-level flow
becoming more southerly.

Deep SW flow will begin to set up across the region on Tuesday as an
upper trough across the western half of North America begins to
amplify. A cold front will descend into the area from the NW but
will likely stall out before passing through. Along with broad
isentropic lifting and rich moisture advection associated with the
return flow, this front could serve as an axis for initial
precipitation Tuesday afternoon, with areas along and north of the
Ohio River most likely to see rain at this time. Waves of
precipitation will continue throughout the day on Wednesday and
Thursday until the upper trough and associated surface cold front
finally kicks it into gear and passes through on Friday. At this
time, it doesn`t look like there will be too much moisture that will
stick around and overrun the cold air; however, if there was to be
any mixing of precipitation, it would be most likely north of the
Ohio River. Total QPF for Tuesday through Thursday is still
generally in the 1-2" range, although isolated pockets of up to 3"
are possible where heavier bands persist.

After the moisture ends, arctic air returns to the Ohio and
Tennessee Valleys for Friday morning as the upper-level eastern
CONUS trough re-establishes itself.

&&

.Aviation...(00Z TAF Issuance)
Issued at 633 PM EST Fri Jan 28 2022

Snow is still affecting the SDF/LEX/BWG terminals at this hour,
however expect HNB to be dry by the time this TAF issuance goes
valid. For SDF, expect light snow and IFR/MVFR vis through about 10
PM EST. For LEX, expect light snow and IFR/MVFR vis through about 11
PM or Midnight EST. BWG will see light snow ending around 930 PM
CST.

Any lingering MVFR ceilings will quickly erode as drier air works in
behind the arctic cold front. In addition, gusty N winds will
slacken to a steady NW wind overnight. Look for VFR and light and
variable winds going into Saturday.


&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...Winter Weather Advisory until 10 PM EST this evening for INZ084-
     090>092.

KY...Winter Weather Advisory until 10 PM EST /9 PM CST/ this evening
     for KYZ025-028>043-045>049-053>057-063>067-074>078-081-082.

&&

$$

Update...BJS
Short Term...RAS
Long Term...CSG
Aviation...BJS