Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 180006 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
806 PM EDT Sun Mar 17 2024

.KEY MESSAGES...

- A deep trough passing aloft brings a threat of light snow
  showers and flurries on Monday afternoon.

- Freezing conditions tonight and a hard freeze Monday night
  could kill any cold sensitive vegetation that has emerged
  prematurely due to early season warmth.

- Gusty southwest winds transport warmer air into the region on
  Tuesday, but dewpoints are slower to rise leading to low
  afternoon relative humidity and Fire Weather concerns.

- Temperatures rebound back to near normal for Wed and into next
  weekend, with lower confidence in the next potential chance of
  precipitation moving in towards the end of the work week.

&&

.UPDATE...
Issued at 806 PM EDT SUN MAR 17 2024

Thicker high clouds will exit off to our east early this evening,
with some higher-based cumulus also generally drying up to our
north with sunset. Gustier west winds will also gradually
diminish through the evening, hanging on the longest on ridgetops
and more open areas north. The forecast remains on track early
this evening, and have only freshened up the sky cover through
midnight, as well as adjusted some of the hourly temperatures to
better match the trend in the observations.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 357 PM EDT SUN MAR 17 2024

As of mid afternoon, an upper level low was centered near the
Ontario and Quebec border with an associated upper level trough
extending into the Great Lakes, Upper and mid MS Valley regions, and
much of the eastern Conus. Further west, an upper level ridge
extended from the eastern Pacific into the Northwest, portions of
western Canada, and into portions of the Northern Rockies. A closed
low was centered southwest of the Four Corners region in AZ with
a series of weaker shortwaves in west to southwest flow from
Mexico across the Southern Plains to the Gulf Coast states. At the
sfc, an area of low pressure associated with the upper level low
near the Ontario and Quebec border with a triple point low over
northern ME and a trailing cold front near the eastern seaboard to
the Delmarva and then southwest to northern portions of the Gulf
Coast states to TX. Another boundary was further south from east
of the coast of the Carolinas across the Gulf Coast region to the
lower portions of the Rio Grande valley and then into Mexico.
Meanwhile, a ridge of sfc high pressure was centered near the
Saskatchewan and Manitoba border and extended through the Northern
to Central Plains and also extends east into the Lower OH Valley.

This evening through Monday, the upper level low is progged to track
east and northeast toward the Maritimes while the axis of the 500 mb
trough is expected to rotate across the St Lawrence valley and Great
Lakes to the Northeast Conus to Mid Atlantic states and portions of
the OH Valley and to the southern Appalachians through sunset on
Monday evening. The axis of this trough will shift east of the
area to end the period while mid level height rises occur across
the OH Valley including the Commonwealth. At the same time, the
sfc ridge of high pressure is expected to build south across the
Plains and into the Lower OH Valley and TN Valley as well as the
Lower MS Valley to end the period.

As the 500 mb trough axis/shortwave approaches on Monday and Monday
evening, moisture is expected to increase generally in the 850 mb to
700 mb layer. At the same time, cold air advection that is ongoing
at present will have continued through tonight and through the day
on Monday as well. Daytime heating combined with the gradual cooling
aloft will lead to development of rather high based cumulus and
stratocumulus. Saturation to the DGZ is anticipated with much of
the cloud depth potentially residing within it Monday afternoon
to early Monday evening. A dry subcloud layer and dry adiabatic
lapse rates should support what precipitation that falls from the
rather high based cumulus either sublimating or reaching the
ground as snow flurries despite temperatures that may be near 40
or in the lower 40s in locations below 2500 feet elevation.
Overall, based on the trends in coverage from the 12Z HRRR and 12Z
Namnest, the coverage of potential for flurries was expanded to
include most of the area on Monday afternoon, especially from near
Interstate 75 and points east.

The main forecast concern of the period is anticipated scattering
of clouds and clearing as winds slacken on Monday night. This
should lead to lows well down into the 20s, which ordinarily is
not impactful. However, recent mild weather has led to some
vegetation prematurely emerging and any such vegetation will be
susceptible to the below freezing temperatures. Although the
official start of the growing season has yet to begin, in
consideration of this this threat has been added to the HWO. Some
locations will also experience sub freezing temperatures for the
upcoming night as well. With the cold airmass and 850 mb
temperatures falling from the -5C to around -10C range to about
-7C to -9C on Monday evening, highs Monday will be below normal
and more typical of mid January highs. Normal highs for this time
of year are in the mid to upper 50s.

.LONG TERM...(Tuesday through Sunday)
Issued at 332 PM EDT SUN MAR 17 2024

The primary forecast concerns in the extended will be the potential
for low dewpoints and very dry conditions across the area on Tuesday
and generally above normal temperatures. With winds still expected
to be blustery and perhaps a bit gusty to begin the period, there
could be some fire weather concerns for eastern Kentucky. This
threat has been highlighted in the HWO. A ridge of high pressure
will be the dominant weather system to start, but a weak area of
low pressure passing by to our south, will bring rain chances back
into the picture late in the week and into the upcoming weekend.

The overall large scale upper level pattern to begin the period will
feature a trough of low pressure moving slowly into and across the
Desert Southwest and across the southern CONUS over time. This will
be the system that brings rain to our area toward the end of the
period. High pressure will dominate the weather of the southeastern
CONUS initially, but another expansive trough of low pressure is
forecast to dive southward out of Canada Wednesday and Wednesday
night. Since it appears this system will be moisture starved, we
should see nothing more than scattered clouds across the area as
this system moves through aloft to our north and northeast. The
southern stream trough mentioned earlier, will be our next weather
maker Thursday night through Sunday. Another weak northern stream
system might also be moving through during this time, and could
influence our weather as well, but the southern stream low still
looks like the main show.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 806 PM EDT SUN MAR 17 2024

VFR conditions are expected to prevail through the period. Some
higher-based cumulus will diminish through this evening across the
norther portion of our area, affecting mainly KSYM. The rest of
the area will see a general diminishment in the high clouds
through early Monday. A passing deeper upper level disturbance will
move through the region during the day on Monday. This will bring
scattered to broken clouds ranging from 4-6k feet agl, with
perhaps a fleeting sprinkle or flurry possible. Winds will
continue to be the main aviation concern at the terminals. West
winds of 5 to 10 kts, with gusts of 15 to 20 kts, will diminish at
most locations early this evening. The gusts will hang on longer
at KJKL and especially KSYM. Winds will become more northwesterly
with time. Northwest winds will increase to around 10 kts, with
gusts of 15 to 20 kts by mid to late morning, as deeper mixing
commences across the area.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GEOGERIAN
SHORT TERM...JP
LONG TERM...AR
AVIATION...GEOGERIAN


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