656
FXUS64 KMRX 101434
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
1034 AM EDT Fri May 10 2024

...New UPDATE...

.UPDATE...
Issued at 1033 AM EDT Fri May 10 2024

No changes made to the forecast for the morning update, and the
previous short term discussion still applies.

&&

.SHORT TERM...
(Today and tonight)
Issued at 255 AM EDT Fri May 10 2024

Key Messages:

1. Scattered showers, and some embedded thunderstorms, expected in
the mainly the northern half of the forecast area this afternoon.

2. Cooler with less humidity through the short term. Temperatures
should run around 5 degrees below normal.

Discussion:

A northern stream upper shortwave will swing southeast across the
forecast area today. Some phasing of this feature with the
subtropical jet will result in an area of enhanced H3 winds across
the central Appalachians into the mid-Atlantic seaboard, leaving
our CWA beneath the right entrance region. Lift associated with
this, combined with cooling throughout the column and subsequent
increase in lapse rates aloft as the trough approaches, should
lead to some development of showers by this afternoon. Confidence
is high in them occurring, but I`m not sold on what the coverage
will be. Raw NBM guidance had some likely PoPs in the north, but
chose to cap it at high-end chance values which seems reasonable.
The greatest coverage should be north of the Knoxville metro area,
primarily in the Tri-Cities area and southwest Virginia. We`ll
also have persistent upslope flow into the higher terrain so I
wouldn`t be surprised to see some isolated to scattered coverage
as far south as the Smokies. The trough axis shifts east of us
by early this evening, which will coincide with loss of daytime
heating. Expect to see a rapid loss of whatever showers there are
as this occurs, and have rain chances going to zero by 00z.

Otherwise, the only other thing to really talk about is the drier
air moving in today/tonight and resulting below normal
temperatures. Should see temps running around 5 degrees below
normal, with dewpoints mixing out into the low 50s. With highs in
the low 70s and afternoon RH values below 60 percent, it will be a
very pleasant day.

&&

.LONG TERM...
(Saturday through Thursday)
Issued at 255 AM EDT Fri May 10 2024

Key Messages:

1. Cool temperatures through the weekend, with a chance of showers
in northern sections Saturday.

2. An active pattern sets up by late Monday, with rain and
thunderstorm chances Tuesday through Friday.

Discussion:

On Saturday, a trough and associated frontal system swinging SE from
the Great Lakes, will bring a chance of showers and perhaps a
thunderstorm or two to the northern sections of the forecast area;
Mainly around north of I-40. CAPE values are rather pretty low for
anything more than isolated thunderstorms, or anything at all. The
southern valley, plateau, and the Appalachians south of around the
Smokys should remain dry.

Mother`s Day is shaping up to be a nice day for the entire forecast
area, as ridging and surface high pressure build in from the west.
High temperatures will either be around normal or just a couple
degrees below normal. Should be a great day for outdoor plans with
dry weather expected and comfortable dew points.

The first part of Monday should be dry as ridging edges eastward,
but later Monday into the end of the forecast period, we will return
to an active pattern. A low pressure center that will track eastward
from the central part of the country, will increase precipitation
chances late Monday from the west and southwest. Tuesday looks to be
a pretty wet and at times stormy day, as a warm front from the
aforementioned low lifts north. Precip from this system appears will
stick around through Wednesday, although chances will be lower.

Possibly a brief break late Wednesday into early Thursday before the
next system develops over the Plains, possibly tracking towards the
Great Lakes increasing chances for showers and thunderstorms into
Friday.

&&

.AVIATION...
(12Z TAFS)
Issued at 735 AM EDT Fri May 10 2024

An area of RADZ has formed across the central TN valley but this
is falling from a mid level deck so impacts at KTYS should be
minimal if any. Continue to believe there will be SCT SHRA across
areas of east TN this afternoon, mostly north of I-40. But also
continue to think coverage is uncertain, so will stick with VCSH
mention at KTRI only for now. High pressure builds in from the
west tonight. Given recent rains and expected light winds and cool
temperatures tonight, fog seems like a distinct possibility. MOS
guidance isn`t sold but other visibility guidance shows it.
Confidence is therefore a little lower than I`d like and since
it`s late in the period, will leave out of the TAFs for the 12z
package.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             78  53  77  54 /  10   0   0   0
Knoxville McGhee Tyson Airport, TN  73  49  72  50 /  20   0  10   0
Oak Ridge, TN                       73  49  74  50 /  20   0  20   0
Tri Cities Airport, TN              70  45  68  47 /  40   0  40  10

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&

$$

SHORT TERM...
LONG TERM....KS
AVIATION...CD