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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS64 KMRX 211414 AAA
AFDMRX

Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
1014 AM EDT Sun Apr 21 2024

...New UPDATE...

.UPDATE...
-- Changed Discussion --
Issued at 925 AM EDT Sun Apr 21 2024

An area of showers will move across mainly southeast Tennessee,
southwest North Carolina, and far east Tennessee mountains. An
upper jet moving across the area associated with a positive tiled
upper trough passage late today/early tonight. This jet is
producing weak isentropic lift and elevated fronto-genesis.

This forcing moves quickly east by early/mid afternoon with drying
clearing sky cover later today and evening.
-- End Changed Discussion --

&&

.SHORT TERM...
(Today and tonight)
Issued at 325 AM EDT Sun Apr 21 2024

Key Messages:

1. Light rain showers through late morning/early afternoon, mainly
along and south of I-40 and east of I-81.

2. Frost Advisory tonight for the northern Cumberland Plateau,
northern TN Valley, northeast Tennessee, southwest Virginia, and
southwest North Carolina.

As of 07Z this morning, radar shows light returns across most of the
forecast area. However, the temp/dewpoint depressions range between
10 and 20 degrees across most areas. This means that rainfall is not
reaching the surface. The only exception is across southwest NC
where light rainfall has been reported at RHP.

Now through early afternoon, an area of low pressure will track from
southwest to northeast, just south of our area. Models are in good
agreement that most of the precip will mainly be along and south of
I-40 and east of I-81 with Less than 0.1 inches of QPF expected.
However, slightly higher QPF may occur across the east TN mountains
and southwest NC, where up to 0.25 inches is possible. Showers come
to end around 16Z. Then, skies will begin to gradually clear by mid
to late afternoon for most areas as drier air pushes in from the
northwest. Areas along and west of I-75 will be the first to clear
out. The east Tn mountains, northeast TN, and southwest NC may hang
onto cloud cover through most of the afternoon and not see clearing
until early evening.

Tonight, patchy/areas of frost are likely across any sheltered
valleys across northeast Tennessee, southwest Virginia, southwest
North Carolina, portions of the east TN mountains, and the northern
Cumberland Plateau. A Frost Advisory has been issued for these
areas.

&&

.LONG TERM...
(Monday through Saturday)
Issued at 325 AM EDT Sun Apr 21 2024

Key Messages:

1. Patchy frost possible Tuesday morning, especially in northeast
Tennessee, southwest Virginia, and southwest North Carolina.

2. Warmer temperatures expected Tuesday onward, with low-end rain
chances early Wednesday and again Friday and Saturday.

Discussion:

A series of shortwaves will impact the region through the first half
of the upcoming work week. For Monday and Tuesday, shortwave ridging
will lead to mostly dry conditions. Light northerly winds and below
normal temperatures Monday will transition to southwesterly flow and
near to just slightly below normal temperatures Tuesday. For Monday
night / Tuesday morning, favorable radiational cooling conditions
will lead to additional frost in portions of the northeast Tennessee
Valley, East Tennessee mountains, southwest Virginia, and southwest
North Carolina. Additionally, latest NAM soundings and high-
resolution guidance suggest that favorable afternoon mixing among a
dry airmass will result in low afternoon RHs Monday. Winds will be
light and not of concern. Have added low RH wording to the FWF.

By Tuesday night into Wednesday morning an upper level disturbance
will result in a shortwave trough digging into the Ohio Valley and
surface low pressure sliding across the Great Lakes region. An
approaching cold front will bring the chance for light rain across
the forecast area. The progressive nature and rather unimpressive
dynamics of the system will hold QPF to just a few hundredths of an
inch, coming to an end by Wednesday evening.

A more amplified upper level pattern begins to take shape by the end
of the work week. Deep cyclogenesis will occur on the lee side of
the Rockies as upper level troughing settles in atop the western
half of the CONUS. A boundary draped along the southeast United
States and southerly flow suggest the chance for some showers and
perhaps thunderstorms possible Friday into the weekend, though the
weather will not be unsettled the whole time. Thursday should remain
dry under the influence of surface high pressure. Given the
uncertainty this far out, PoPs have generally been restricted to no
more than chance at this time. Indications continue to suggest no
impactful weather from this system through the current 7-day
forecast period.

&&

.AVIATION...
(12Z TAFS)
Issued at 724 AM EDT Sun Apr 21 2024

Trends suggest that CHA will remain VFR for the period, thus, have
removed the previous MVFR mention. Vicinity showers with the
potential for occasional rain to impact terminals through early
afternoon, but then clearing out for the remainder of the period.
North winds gusting up to 20kts at CHA this afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
Chattanooga Airport, TN             62  43  67  42 /  60   0   0   0
Knoxville McGhee Tyson Airport, TN  58  40  64  39 /  40   0   0   0
Oak Ridge, TN                       61  40  66  40 /  20   0   0   0
Tri Cities Airport, TN              56  35  61  37 /  40   0   0   0
-- End Changed Discussion --

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...Frost Advisory from 2 AM to 9 AM EDT Monday for Cherokee-Clay.

TN...Frost Advisory from 2 AM to 9 AM EDT Monday for Campbell-
     Claiborne-Cocke Smoky Mountains-Hancock-Hawkins-Johnson-
     Morgan-Northwest Carter-Northwest Cocke-Northwest Greene-
     Scott TN-Southeast Carter-Southeast Greene-Sullivan-Unicoi-
     Washington TN.

VA...Frost Advisory from 2 AM to 9 AM EDT Monday for Lee-Russell-
     Scott VA-Washington VA-Wise.

&&

$$

SHORT TERM...DH
LONG TERM....KRS
AVIATION...KRS