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000
FXUS63 KJKL 210729
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
329 AM EDT Sun Apr 21 2024

.KEY MESSAGES...

- Fair weather lasts through early in the new workweek.

- Frost will be possible in some sheltered valley locations Sunday
  morning, but is expected to be most widespread Sunday
  night/Monday morning and again Monday night/Tuesday morning,
  especially through the valleys.

- Another moisture-starved cold front is forecast to pass Tuesday
  night into Wednesday morning, bringing a round of light rain
  for northern locations.

- Confidence in weather forecast late next week is lower than
  normal at this range due to significant weather model differences.

&&

.UPDATE...
Issued at 728 PM EDT SAT APR 20 2024

Minor adjustments were made to hourly grids based on recent
observations and trends. This led to no substantial changes at
this time.

&&

.SHORT TERM...(tonight through Sunday night)
Issued at 423 PM EDT SAT APR 20 2024

Sprawling surface high pressure was over the Great Plains late
today, ridging eastward to the lower Great Lakes and central
Appalachians. A nearly stalled frontal boundary was near the gulf
coast and southeast coast. The high is supplying us with a cool
and dry air surface air mass. However, moisture overriding the
frontal boundary has produced some clouds at times, with one batch
exiting to the southeast this morning, and some more high clouds
starting to show up late this afternoon.

Our flow aloft is fairly zonal, but a highly positively tilted
trough is dropping south from the north central CONUS, while at
the same time a weak shortwave trough over TX is zipping eastward.
The southern wave will progress eastward ahead of the northern
trough and is expected to send more moisture/clouds northward,
overriding our surface air mass tonight and early Sunday.
Deterministic models are generally keeping precip to our south,
and our POP has been held below 20 percent in the forecast.
However, can not completely rule out some very light precip in our
far southern counties should virga make enough headway into
moistening our low level air mass before the wave aloft departs.
The other consideration with the southern system is its impact on
our temperatures. Initially scant cloud cover should allow decent
radiating to start the night, but thickening clouds will cut into
the temperature descent during the night. The current forecast has
some patchy frost developing late tonight, mainly in our northern
valleys. This could end up less in coverage should clouds be
thicker than currently forecast, or greater should clouds be
thinner.

The northern trough will swing southeast toward us Sunday and
Sunday night, while the southern wave departs to the east with the
moisture. At the surface, high pressure ridging eastward will
continue supplying us with cool and dry air. Despite sunshine
returning on Sunday, temperatures will struggle to get out of the
50s. That will set us up for a more favorable night for frost on
Sunday night. If the current outlook persists, a Frost Advisory
will need to be considered on an upcoming shift.

.LONG TERM...(Monday night through Saturday)
Issued at 328 AM EDT SUN APR 21 2024

The period begins with surface high pressure in place across the
area. This will continue to keep the forecast area dry with clear
skies. This coupled with continued northwesterly flow, areas of
frost will be possible again late Monday night through early Tuesday
morning mainly in the more sheltered eastern valleys.

Models continue to remain in agreement with a system moving across
southern Canada. While this occurs, a surface low and associated
cold front will cross across the northern CONUS. Ahead of the
approaching front, flow turns southwesterly and increasing
temperatures are forecast before the front crosses through the
Commonwealth late Tuesday night through early Wednesday morning.
Showers and thunderstorms are forecast along and ahead of the front
but due a widespread lack of instability due to the timing of the
front, severe weather looks to be limited. Also, recent model runs
have continue to weaken the front. Total QPF for the front ranges
from 0.20" for the northern half of the CWA with decreasing amounts
going south approaching the TN/KY state line.

High pressure builds back into the region for late Wednesday and
persists through early Friday morning. However, models remain in
agreement for the end of the week, with another system moving out of
the Central Plains with another cold front bringing shower and
thunderstorms chances for the end of the week. Long-term
deterministic models keep shower and thunderstorm chances through
the end of the period with what appears to be a constant train of
ridge-riding MCSs.

Overall, frost chances will exist Tuesday morning before warming
temperatures are expected ahead of a surface cold front for
Wednesday. Temperatures drop a little bit for Thursday but begin to
rebound Friday and Saturday. Also, an active period is expected as
multiple rounds of showers and thunderstorms are forecast.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
ISSUED AT 135 AM EDT SUN APR 21 2024

Sfc high pressure will bring VFR conditions through the period
though some few to scattered low and mid clouds are anticipated
at times particularly during the day Sunday. Sustained winds are
generally expected to be 10 KT or less and through the period
averaging from the north to northwest.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 1 AM to 9 AM EDT Monday for KYZ044-050>052-
058>060-068-069-079-080-083>088-104-106>120.

&&

$$

UPDATE...JP
SHORT TERM...HAL
LONG TERM...VORST
AVIATION...CMC