-- Discussion containing changed information from previous version are highlighted. --
950
FXUS64 KMRX 100006
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
806 PM EDT Thu May 9 2024

...New UPDATE, AVIATION...

.UPDATE...
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Issued at 739 PM EDT Thu May 9 2024

I am updating the current zone forecast to remove rain chances
for the rest of the night. Weak broad cold front is moving across
east Tennessee this evening with some drier air moving in from
the northwest. Temperatures are in the mid 70s to lower 80s early
this evening with skies partly cloudy to mostly clear. Longwave
trough approaching from the northwest has most precipitation far
to the north and northeast through the Ohio Valley and central
Appalachians tonight so removed the rain across the northeast.
Southwest winds are stronger in the northeast where drier airmass
is moving in so do not expect fog there. Clouds will also increase
from the southeast as high level clouds from storms to the south
spread towards our region after midnight. Then more clouds into
the northeast late with trough over the east. Some patchy fog is
possible in the southeast where winds will be lighter and more
low level moisture remains from the showers and storms that moved
across this area this morning. Updated the hourly temperatures
and dew points and cloud cover with tonight`s forecast. Will send
update in a few minutes.
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&&

.SHORT TERM...
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(This evening through Friday)
Issued at 229 PM EDT Thu May 9 2024

Key Messages:

1. A few isolated showers possible tonight across extreme northeast
TN and southwest VA. An isolated thunderstorm is also possible.
No severe threats expected.

2. Patchy fog across the southern TN valley overnight.

3. Slight chance to chance POPs Friday, with breezy winds.

Discussion...

Tonight, a few isolated showers and possibly a thunderstorm across
extreme northeast TN and southwest VA, out ahead of a longwave
trough approaching from the northwest. Winds stay up enough
overnight to prevent fog across most areas. However, calmer winds
are expected across the southern TN valley and patchy fog is
anticipated.

Tomorrow will be cooler with northwest flow, clouds, and isolated
showers. High temps will be around 5 to 8 degrees below
normal. NBM also wants to put a slight chance thunder in the
forecast but NAM soundings show a pretty significant midlevel
cap. Will leave NBM slight chance thunder in forecast but very low
confidence. If we do see a storm, it will be isolated with no
severe threats. POP chances are due to the aforementioned upper
level trough and associated shortwave rotating through the area.
The exception is the southern TN valley, where conditions should
remain dry. Breezy west to northwest winds expected tomorrow
afternoon due to a tight pressure gradient across the area. Winds
will gusts up to 25 mph in valley locations and up to 30 mph
across the east TN mountains.
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&&

.LONG TERM...
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(Friday night through next Thursday)
Issued at 229 PM EDT Thu May 9 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 midweek, with rain chances Tuesday
through Thursday.

Discussion...

On Saturday, a trough will be dropping SE from the Great Lakes to
the central Appalachians and Mid Atlantic region. Mid and upper
level forcing with the channeled vort max on the southern end of
this trough will cross our SW VA counties, and bring a chance of
showers in the afternoon. Forecast soundings show some low level
instability below 700 mb with stable conditions above, so it will
mainly be scattered showers and little to no thunderstorms. The
NBM PoPs in the chance range down to Knoxville appear overdone
for this system and will be scaled back a bit.

High pressure will build over the area and provide dry weather for
Sunday into part of Monday. Sunday`s temperatures will be a little
below normal in a N-NW flow pattern on the east side of the ridge,
with highs in the lower to mid 70s. The ridge axis move east of the
area on Monday, which should bring highs back into the mid and upper
70s, with increasing moisture and cloud cover. Showers may begin to
spread into southern sections Monday afternoon and evening as a low
pressure system tracks east across the MO Valley and Ozarks. Rain
chances will ramp up to categorical and likely for Tuesday as this
low tracks along the OH River. Instability and dynamic forcing look
limited at this time, so no severe threat is expected.

A weak ridge may bring a brief dry period from Wednesday into
Wednesday night, but an amplifying trough over the Plains will
result in PoPs increasing again on Thursday. Models differ on the
amplification of this trough and the dynamic forcing associated with
it, but if the GFS pattern is correct, it may be a system to watch
for potentially strong to severe storms.
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&&

.AVIATION...
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(00Z TAFS)
Issued at 739 PM EDT Thu May 9 2024

VFR conditions at all sites to start the evening. Gusty west to
southwest winds at TRI will decrease this hour. Expect some MVFR
fog at CHA to develop overnight due to left over moisture from the
heavy rainfall today in combination with lighter winds and clear
skies. TRI and TYS continued VFR through the entire period as
drier airmass moves in. Winds increase again Friday 15 to 18Z
from the northwest behind a cold front that is slowly moving
through this evening to about 20 KTS all sites.
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&&

.PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN             63  78  52  76 /  10  10   0   0
Knoxville McGhee Tyson Airport, TN  59  73  48  71 /  10  30   0  10
Oak Ridge, TN                       58  73  48  73 /   0  30   0  20
Tri Cities Airport, TN              56  70  45  66 /  10  40  10  40
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&&

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

$$

SHORT TERM...TD
LONG TERM....DGS
AVIATION...TD