Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 181955
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
355 PM EDT Mon Mar 18 2024

.KEY MESSAGES...

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

- A hard freeze later tonight 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.

- A passing dry cold front brings another day of Fire Weather
  concerns on Wednesday.

- 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 150 PM EDT MON MAR 18 2024

Forecast still in good shape, other than the clouds continuing to
spread across the state faster than originally anticipated.
Updated the grids to account for this. Will also confirm if any
sprinkles are hitting the ground in our far northern counties, in
case the weather grids need to be increased for an hour or so.
Other tweaks, including temperature and winds, were made based on
the ongoing conditions and resulted in only very minor changes.
All updates have been published and sent to NDFD/web. The new
forecast package was also sent out to remove morning wording.

UPDATE Issued at 1103 AM EDT MON MAR 18 2024

|Forecast still seems on track so far through the morning. The
only real change was to increase the cloud cover across our
northern counties, speeding up it`s onset over the next few hours.
ILN`s radar does show some low returns across Fleming and Rowan
County. That being said, their radar beam is quite high in these
locations, and despite the cloud cover, it is still very dry at
the low levels. Called the EM in Fleming County and confirmed the
cloud cover but nothing (flurries or sprinkles) were occurring.
Therefore did not update the pops or weather grids at this time,
only the cloud cover. All updates have been published and sent to
NDFD/web. Went to update the zones/SAF, but it wanted to use late
morning wording, which will then require another update at noon to
remove the morning wording. Since the updates were very minor,
going to wait until noon to send out the zone updates.

UPDATE Issued at 730 AM EDT MON MAR 18 2024

Current forecast remains on track so have just added in the latest
obs and trends for the T/Td/Sky grids. These minor adjustments
have been sent to the NDFD and web servers.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 450 AM EDT MON MAR 18 2024

08Z sfc analysis shows high pressure attempting to build into
eastern Kentucky from the west. However, a passing trough aloft
will help to maintain cyclonic sfc flow over the area into the
evening. This flow is responsible for the chilly temperatures this
morning on northwest winds of 10 mph or less. Accordingly,
readings are running in the low to mid 30s most places with a few
sheltered spots able to cool into the upper 20s. Meanwhile,
dewpoints are lower than temperatures, generally in the upper
teens to lower 20s under a smattering of mainly high clouds.

The models, and their individual ensemble suites, continue to be
in pretty good agreement aloft through the short term portion of
the forecast. They all depict a deep trough tilting through the
southern Ohio Valley and across the Tennessee Valley today. This
brings strong height falls, steep lapse rates, and a cluster of
mid level energy through our moisture starved area this
afternoon. This trough bottoms out to our south this evening and
slips quickly east of the Appalachians leaving lower heights and
northwest flow at 5h behind. The now very small model spread
supports using the NBM as the starting point for the forecast
grids with most adjustments related to terrain distinctions in
temperatures tonight as well as extra mix down drying on Tuesday
afternoon.

Sensible weather will feature a cold day after our warmth of late
with a northwest breeze adding to the chill. Dry conditions in
the boundary layer should keep any light pcpn in the form of
flurries and sprinkles, though an influx of moisture from the
Great Lakes may be enough for a stray shower of light rain or
snow (10 percent threat or less) - but more probable northeast of
the JKL CWA. The clouds and light pcpn associated with the
passing trough aloft will move off to the east tonight. These
conditions, when combined with diminishing winds, will allow for
better for better radiational cooling and a ridge to valley
temperature difference to set up overnight and into Tuesday
morning - enhancing the widespread hard freeze in the valleys
especially. The recent warmth has encouraged many buds and
blossoms to develop on the vegetation throughout the area and
these are seriously threatened by tonight`s cold. For this reason
(as the growing season has not been declared started, yet) an SPS
has been issued giving heads up to those with agricultural and
fruit tree interests. For Wednesday, the dry conditions combined
with rebounding temperatures on breezy southwest winds will lead
to humidity values well below 25 percent, for most. Combined with
the winds pushing 15 mph sustained, at times, from mid morning
into the afternoon there will be heightened fire weather concerns
and a Red Flag Warning may be needed for at least portions of the
forecast area for the latter part of the day. This concern will be
addressed in the narrative portion of the forthcoming Fire
Weather Forecast product.

The main adjustments to the NBM starting point were to include
more terrain distinction for temperatures tonight and also favor
the 10 percent or lower version of the NBM for dewpoints on
Tuesday afternoon.

.LONG TERM...(Wednesday through Monday)
Issued at 355 PM EDT MON MAR 18 2024

The large scale upper scale pattern across the CONUS to begin the
extended will feature ridging aloft along the west coast with a
developing small scale wave of low pressure aloft to the east of the
ridge. The northeastern quarter of the country looks to start off
under the influence of a broad trough of low pressure aloft,
especially the Great Lakes and New England. An elongated and flat
ridge of high pressure might also be in place along the Gulf Coast
to start things off. The southwestern CONUS trough will be our
initial weather maker in the extended, and should be moving through
our neck of the woods Thursday night through Saturday. Our highest
rain chances during that time should be from late Friday morning
through late Friday night, as the trough moves by to our south and
merges with a fast moving northern stream system that will be moving
through the Great Lakes and into New England. The GFS Ensembles did
a good job depicting the southern stream trough, while the GFS and
ECMWF operational runs contained more details on the northern stream
system and its evolution. High pressure will bring dry weather to
the area both Wednesday and Thursday, with Wednesday being the
warmer of the two days as strong sunshine and subsidence aloft will
be in place. Thursday should be a bit cooler, as winds shift to the
north and then northeast, as high pressure moves off to our east
ahead of the next incoming trough.

Clouds will be on the increase Thursday into Thursday evening, as
low pressure moves our way, and we should see the first rain moving
into our southern counties sometime late Thursday evening from the
southwest. We should see another breif period of dry weather from
late Saturday through early Monday morning, as we await the arrival
of another area of low pressure, that is forecast to bring another
round of rain to the area by Monday afternoon.

Regarding temperatures in the extended, readings should be above
normal on average, with most days seeing readings ranging from the
upper 50s to lower 60s Wednesday, Friday, and Saturday. We could see
highs reaching the low to mid 60s on Sunday, and the upper 60s to
lower 70s on Monday, as strong warm air advection occurs ahead of
the incoming storm system that day. We will also likely see very low
dewpoints again on Wednesday. With winds again expected to marginal,
and afternoon RHs also low, we will continue to monitor critical
fire danger thresholds across the area through mid-week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 201 PM EDT MON MAR 18 2024

A deep upper level disturbance is currently passing through the
Ohio Valley. While high pressure and generally low RH is present
at the surface, the upper level disturbance is resulting in a
mid-level cloud deck which has overspread much of the TAF sites
and will remain through much of the afternoon. While no
measureable precip is expected from this system, especially given
the dry low levels, can`t rule out a sprinkle or flurry making it
to the surface this afternoon. This should have no impact on the
VIS. Winds are predominately out of the NW between 5 and 15 kts,
with gusts between 15 and 20 kts this afternoon thanks to deep
mixing in place. Skies will finally clear heading into the
overnight, as the upper level system exits east of region. Winds
will also slowly dissipate throughout the overnight, but should
remain fairly mixed at the TAF sites, so kept predominate wind
conditions. High pressure will be the main weather driver
overnight and during the day Tuesday, with VFR conditions on tap.
Predominate winds will be more SWrly and breezy during the day
Tuesday as mixing increases again, but otherwise expect clear and
dry conditions to finish out the forecast period.

&&

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

$$

UPDATE...JMW
SHORT TERM...GREIF
LONG TERM...AR
AVIATION...JMW


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