Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 160600 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
200 AM EDT Sat Mar 16 2024

.KEY MESSAGES...

- Temperatures will remain about 5 to 10 degrees above normal
  through tonight.

- A deep trough passing aloft brings a threat of some rain/snow
  showers on Monday.

- Hard freeze conditions Monday night could kill any cold
  sensitive vegetation that has emerged prematurely due to early
  season warmth.

&&

.UPDATE...
Issued at 145 AM EDT SAT MAR 16 2024

Seeing the fog develop in our northwest counties - am preparing
an SPS to address this. Otherwise, the forecast is on track so
have mainly just added in the latest obs and trends for the
T/Td/Sky grids along with a touch up to the extent of the fog
through the rest of the night. These minor adjustments have been
sent to the NDFD and web servers along with a freshening of the
zones and SAFs.

UPDATE Issued at 1047 PM EDT FRI MAR 15 2024

There are no changes with the late evening update except to blend
in latest hourly observations. Satellite shows clearing skies
moving into the area from the northwest, which lends higher
confidence to fairly widespread fog formation after midnight.

UPDATE Issued at 827 PM EDT FRI MAR 15 2024

The NBM has trended a degree or two higher with dew point
temperature forecasts late tonight into Saturday morning, while
also trending toward at least partial clearing toward the pre-dawn
hours. Given these two trends, expanded the duration and areal
extent of fog for the morning hours Saturday. Otherwise, the only
other change was to remove any further mention of thunderstorms
from the grids and text forecasts for the remainder of this
evening. Hourly observed trends were blended into the forecast as
well.

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 435 PM EDT FRI MAR 15 2024

Late this afternoon, the axis of a shortwave trough extended from
near the Ontario and Quebec border to the Central Great Lakes
while a more southern shortwave was moving across the Lower OH
Valley region. Further northwest an upper level low was working
across Manitoba with an associated shortwave trough to the south
toward the US/Canadian border. A sfc low associated with this
system was tracking from Manitoba into portions of Ontario with a
cold front trialing southwest to near the ND and MT border with
Canada. Closer to home, a surface cold front continues to sag
south and southeast across eastern KY and was located from near
Charleston WV to JKL to Rockcastle County. Showers were most
prevalent near and south of this boundary although some showers
were located near the front aloft further to the north. Meanwhile,
a sfc ridge of high pressure was centered over the Central Plains
and extended toward portions of the MS Valley.

This evening and tonight, the shortwave moving across the OH
Valley will cross eastern KY through tis evening, moving east of
the area by late this evening followed by a more moisture starved
shortwave overnight. In advance of this, the cold front that is
sagging south and southeast across eastern KY should sag into VA
and TN by mid to late this evening with the sfc ridge of high
pressure building east into the OH Valley behind it. The axis of
this ridge of high pressure will sag south of eastern KY through
the day on Saturday. This will occur in advance of the upper low
moving from Manitoba into Ontario and the trailing shortwave
trough working across the upper MS Valley and into the Great Lakes
region and the associated cold front that should drop southeast
of the western and central Great Lakes through the day on
Saturday. The upper low is progged to move to Quebec through the
end of the period while the trailing shortwave trough rotates
across the Great Lakes and into the OH Valley. This will help push
the cold front across the Commonwealth on Saturday night. A much
colder airmass than what has been experienced recently will arrive
behind the front as the period end with 850 mb temperatures
forecast to drop to the 0C to 5C range at that point with further
cooling and cold air advection continuing into the start of the
long term period.

Limited instability remains across the region at present with
MUCAPE analyzed in the the 100 to 250 J/kg range with effective
shear in the 20 to 25 KT range though these values will be
diminishing over the next few hours. Lighting has not been
detected across the region so far this afternoon, however, with
the limited instability remaining, an isolated storm or too
cannot be ruled out ahead of the boundary. However, mainly just
showers are expected with chances diminishing from northwest to
southeast through this evening. Precipitation free weather will
follow for the balance of the near term period.

Although the airmass behind the front crossing the region at this
time will cooler than what was experienced earlier this week,
temperatures will remain a few degrees above normal, by about five
degrees through Saturday. Mild weather will above normal
temperatures will persist into Saturday night ahead of the
secondary boundary.

.LONG TERM...(Sunday through Friday)
Issued at 447 PM EDT FRI MAR 15 2024

The 15/12z model suite is in reasonably good synoptic agreement
Sunday morning but does show some deterioration, especially after
Wednesday. On Sunday morning, a broad and deep upper level low
will be found over Eastern Canada, dipping down into the Great
Lakes. A moisture-starved cold front front, originating from an
~995 surface low over southern Quebec, is seeping southeastward
along the periphery of the aforementioned upper level trough into
the Ohio Valley where there is near zonal flow aloft.
Additionally, a prominent 500H vorticity lobe extends from the
vicinity of the surface low over Southern Quebec through the
southern Great Lakes to the Upper Midwest/Manitoba where a potent
shortwave trough will be traversing the periphery of the parent
upper level trough. Meanwhile, an ~556 dam closed low is spinning
atop Arizona.

The cold front will slip south of eastern Kentucky during the day on
Sunday, while heights aloft start to subside in advance of the
shortwave trough diving southeast from the Upper Midwest. A busy
west northwest breeze will advect drier air in through the day,
leading to falling dew points (values in the 20s can be expected
for many by Sunday evening). BUFKIT GFS mixed-layer momentum
transfer values support gusts in the 15 to 20 mph range around
peak heating. Meanwhile, cold air advection will keep the day`s
highs muted, primarily in the mid 50s north of I-64 to the mid 60s
in the deepest valleys near the Virginia border. No measurable
precipitation is expected with the front; rather, just anticipate
a period of more abundant cloud cover.

The upper level shortwave trough (and attendant vort lobe) will
carve deeply into the Ohio Valley on Sunday night through Monday
Night as it rides around the base of its parent trough.
Uncertainty remains as to how much moisture will be available to
this system, which may be dependent, at least in part, on how
much moistening of the air mass occurs over the Great Lakes. The
12z NAM12 solution falls on the moist side of guidance with more
than ample moisture for deep convection and equilibrium levels
above -20C. Such a scenario combined with 850 mb temperatures
falling to around -10C would lead to the potential for squally
snow showers with the possibility for lightning. Conversely, the
Canadian and ECWMF soundings are much drier and would support
little more than some patchy cloud cover and perhaps some light
flurries. A 20 to 30 PoP was maintained across most of eastern
Kentucky to account for this potential and can be trended up or
down depending upon whether the moister or drier solutions
prevail. Regardless, Monday`s temperatures will be cold with
highs ranging in the upper 30s to lower 40s for most locations --
a far cry from what we have experienced this week. Those chilly
temperatures will be compounded by a cold northwesterly breeze
which could gusts to between 20 and 25 mph. Monday night is
shaping up to be the coldest night of the period with lows easily
in the 20s. Lows in the teens cannot be ruled out for colder
locations if skies are able to clear early in the night.

Looking ahead to Tuesday, the low level flow will quickly turn
more westerly ahead of a second, albeit weaker, upper level
shortwave trough riding around the parent upper level trough. This
system tracks slightly further to the east than the previous
shortwave, but will drop another cold front into eastern Kentucky
from the north or northeast on Tuesday night or Wednesday morning.
While a sprinkle or flurry cannot be ruled out with the boundary,
no measurable precipitation is forecast. Ahead of the front,
temperatures will make a quick rebound on Tuesday back to between
50 and 55 for most locations. The core of the chillier air with
the second front will only brush our area and will likely be felt
more as a reinforcing shot of drier air rather than the return of
a colder air mass (due to modification by the strong spring
sunshine). Thus expect temperatures to to warm several degrees
further in the mid 50s to lower 60s on Wednesday with a subsequent
ridge-valley split of 27 to 40 on Wednesday night.

Later in the week, forecaster confidence drops as model solutions
diverge with respect to the closed low initially over the Desert
Southwest and possible interaction with a northern stream
shortwave trough coming ashore the Pacific Coast. In most cases,
a low pressure system is depicted to develop and pass through the
eastern CONUS, though the track remains highly uncertain.
Therefore, the NBM forecast was retained for Thursday and Friday
and shows PoPs increasing to likely levels while temperatures
rise back to near or above normal levels.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
ISSUED AT 200 AM EDT SAT MAR 16 2024

A mix of VFR, MVFR, and IFR conditions are found from northwest to
southeast through the area as the low clouds are slowly eroding
from the northwest. Partial clearing will continue through
sunrise, leading to fog development with a deterioration to LIFR
or lower for the valleys and at least IFR conditions, for a time,
at most TAF sites. The fog will clear off by 14Z Saturday, with
VFR conditions prevailing thereafter. Light winds through the
night will become west to southwest by Saturday afternoon at 5 to
10 kts.

&&

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

$$

UPDATE...GREIF
SHORT TERM...JP
LONG TERM...GEERTSON
AVIATION...CMC/GREIF


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