199
FXUS63 KJKL 250144
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
844 PM EST Sun Nov 24 2024

.KEY MESSAGES...

- Monday will bring mild temperatures, but a series of cold fronts
  will then result in an overall downturn in temperatures for the
  rest of the week.

- The first cold front will bring rain Monday night. More rain is
  forecast Wednesday night into Thanksgiving day, possibly mixing
  with or changing to snow Thursday night.

&&

.UPDATE...
Issued at 844 PM EST SUN NOV 24 2024

Valley temps have dropped off quickly, especially in the eastern
portion of the forecast area. Low level flow will pick up during
the night, creating uncertainty around which valleys remain
decoupled and cold versus mixed and milder. As is usually the case
eastern valleys are most probable to remain decoupled and cold,
with western valleys standing the best chance to mix.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 351 PM EST SUN NOV 24 2024

After several cloudy and chilly days, a weak southwesterly breeze
combined with ample sunshine has sent temperatures surging into the
mid 50s north of I-64 up to the lower 60s on the floors of southern
broad valleys. At the surface, high pressure is centered south of
Bermuda to over the Florida Peninsula with a narrow axis of high
pressure extending poleward along the western slopes of the
Appalachians. Further upstream a 500H trough is passing over the
Central Rockies/Northern High Plains. Low pressure is developing
over eastern Kansas ahead of the upper level trough.

This surface low will rapidly lift northeast to near Chicago by
Monday morning and then slow to over Georgian Bay by Monday night.
An associated cold front will dive southeast on the back side of the
low and cross eastern Kentucky on Monday night. Ahead of that front,
low-level moisture will stream northeastward into the Ohio Valley
late tonight and especially on Monday. This will bring the
opportunity for sprinkles and perhaps a few spotty rain showers on
Monday. A more widespread rainfall is expected Monday evening/night
with the passage of the cold front.

In sensible terms, mostly clear skies for most of the night should
allow for the formation of a relatively strong nighttime inversion
with temperatures ranging from the mid 40s on the thermal belt
ridges down the lower 30s in the most sheltered northeastern
valleys. A few upper 20 degree readings cannot be ruled out in the
coldest hollows. A low cloud deck will rapidly increase from west to
east around around dawn leading to a mostly cloudy Monday. Rain
chances will gradually rise from the northwest through the day and
peak between 80 and 90 percent during the first half of Monday
night. Temperatures top out in the lower to middle 60s on Monday,
likely the warmest of the week, before dipping back into the
upper 30s to mid 40s Monday night behind the cold front. In
addition, winds will pick up from the southwest on ridges late
tonight and across the entire area on Monday with gusts of 10 to
20 mph expected during the daylight hours. Those winds shift
northwest and weaken Monday night.

.LONG TERM...(Tuesday through Sunday)
Issued at 237 PM EST SUN NOV 24 2024

The active pattern rolls on into the extended. The period does begin
with the break in the weather. This as surface high pressure builds
into the Ohio Valley Tuesday into Wednesday. However, quasi-zonal
flow aloft will move this across the area at a good pace. This will
keep it dry until later on Wednesday. Warm air advection does kick
in on Wednesday, with highs pushing back into the 50s and even upper
50s in some cases, but with increasing clouds through the day.

By the time we get to Wednesday night, we will see another upper
level wave push into the Middle Mississippi River Valley. This
feature will eventually help generate another surface low that will
generally track some where within Ohio and Tennessee Valley. However,
when diving more into the ensembles the variability within where
and how deep this low gets is quite different. The depth of this low
is likely tied to the jet stream structures at play and therefore
will have to be resolved more in later updates of the guidance. This
leads to many different surface reflections and therefore lower
predictability on specifics at this time. Either way, there is
enough to keep the PoPs in the categorical range Wednesday night, as
most outputs suggest the potential for rain showers to overspread
the region. This as the probability of greater than a quarter of an
inch of rain in a 12 hours period from Wednesday evening into
Thursday morning is around 60 percent.

Again the amount of left over moisture and lift that is in play on
Thursday is quite uncertain, with all the previous mentioned
features still at play. Given the faster and slower solutions all in
play in this case. That said, there remains a 40-50 percent chance
of seeing around a tenth of inch of precipitation on Thursday. The
speed of this system will play a role moving into Thursday night
into Friday, as well with colder air arriving. This will eventually
lead to a mix with or changing over to snow Thursday night into
Friday. We will also see a more northwest flow pattern develop in
the wake of this low pressure and this would allow parts of the Ohio
Valley to see some moisture from the Great Lakes come into play. The
NBM data combined with the overall trends seems to be a little over
done on snow potential when looking at the overall snowfall within
the dataset itself. The big news here is this could cause some
travel impacts for Thanksgiving even if we are just talking rainfall.

In the wake of this system, longer range guidance and
teleconnections point to the potential for a much colder pattern to
develop across the Ohio Valley. This could bring some of the coldest
air so far this season by next weekend into early next week. There
is also signal for additional fast moving waves to progress across
the Ohio Valley and this could bring in additional chances of wintry
weather.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 844 PM EST SUN NOV 24 2024

VFR conditions prevailed at TAF issuance. A low cloud deck will
begin to move in from the northwest before dawn and then
overspreadthe rest of the area early Monday morning. Ceilings
are forecast to initially be mostly low end VFR, but drop to MVFR
in most places during the course of the day.

LLWS is also a possibility overnight and early Monday (mainly over
the western portion of the forecast area) as southwesterly low
level flow increases significantly a little off the ground.

&&

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

$$

UPDATE...HAL
SHORT TERM...GEERTSON
LONG TERM...DJ
AVIATION...HAL