-- Discussion containing changed information from previous version are highlighted. --
132
FXUS64 KMRX 190543
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
143 AM EDT Thu Sep 19 2024

...New AVIATION...

.UPDATE...
-- Changed Discussion --
Issued at 923 PM EDT Wed Sep 18 2024

The main adjustment this evening will be to extend PoPs in NE TN a
few more hours, as an isolated showers has developed over Scott
Co. VA and is drifting slowly SW. PoPs in that area will be
extended to around midnight. After midnight, fog is expected to
develop in many locations, mainly in northern sections that have
had more rain recently. Cloud cover currently in that area may be
a limiting factor to fog development, so confidence that the
clouds will clear out is not high enough yet to issue a DFA or
SPS.
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&&

.SHORT TERM...
(This evening through Thursday)
Issued at 311 PM EDT Wed Sep 18 2024

Key Messages:

1. A few showers and maybe a thunderstorm or two are possible
through this evening and again tomorrow afternoon.

2. Fog is likely again tonight, followed by clearing and warmer
temperatures on Thursday.

This Evening/Tonight

Currently this afternoon, tropical remnants from the Carolinas have
continued to weaken and are centered over northeast Tennessee to
southwest Virginia. A closed upper-low remains centered just to our
east. This has continued fairly weak northerly to northeasterly flow
and widespread cloud cover. Additional light showers remain
possible, along with an isolated thunderstorm as current data
indicates at least 250 J/kg of instability. This will be focused
further east closer to the better height falls. Otherwise, activity
will decrease overnight as diurnal heating is lost. With clearing
also expected, fog development is likely, especially in places that
see the better clearing and any rainfall.

Thursday

During the day on Thursday, the tropical remnants, including the
upper low, will shift further east. This will change the flow to be
more northwesterly throughout the column. In addition to some
orographic considerations, this system will continue to provide
broad but weak lift across the area. However, drier air will also be
filtering in from the northwest. Based on these considerations, rain
chances will be contained further north and east closer to the
better moisture, in addition to along the terrain. Overall, the
thermodynamics will be limited similar to today, but there is still
enough support for maintaining slight chance of thunder. The drier
air and eastward shift of this system will also allow for less cloud
cover and notably warmer temperatures than today.

&&

.LONG TERM...
(Thursday night through next Wednesday)
Issued at 311 PM EDT Wed Sep 18 2024

Key Messages:

1. Ridging will make conditions very warm and dry Friday to Monday.

2. Early next week, temperatures moderate closer to normal with some
low-end rain chances returning Tuesday.

3. Tropics might become a player during the latter half of next week.

Discussion:

Ridge of high pressure at 500 MB will be squeezed between an east
coast trough and a Rockies trough for days two-five Fri-Mon. This
means predominantly dry and very warm days during and surrounding
the weekend. This won`t be much help to the drought conditions.

The pattern will very slowly progress however, such that the ridge
will flatten along the northeast Gulf coast Mon and Tues, allowing
troughing to graze our area with some chance of precip Tues and Wed.

Late period questions will include whether troughing sharpens enough
to give us a drying NWly flow during midweek, which would also usher
in cooler air again. One of the complications is a potential
tropical system in the Gulf during Wed/Thur, and how it and the
trough interact with each other`s timing. The future track of said
tropical system may or may not be an influence on area precip come
late week -- i.e., does it dodge us through Tampa or moisten
us through Mobile?

&&

.AVIATION...
-- Changed Discussion --
(06Z TAFS)
Issued at 133 AM EDT Thu Sep 19 2024

CHA will likely keep VFR status through the newest TAF period. The
question again this morning, becomes fog - when and how dense?
Kept persistence from the 00Z TAF issuance with down to LIFR at
TRI and MVFR at TYS. Fog currently not as widespread as it was
this time early Wednesday. Also didn`t record the rainfall amounts
yesterday that we received Tuesday. All three TAF sites up until
the evening, did not record any rainfall. Confidence isn`t all
that high in how this will play out. Fog does surround our
forecast area in middle Tennessee, northern Georgia, western North
Carolina, and Kentucky into Virginia, but nothing in our area as
of this time.
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&&

.PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN             89  65  92  65 /   0   0   0   0
Knoxville McGhee Tyson Airport, TN  86  63  89  62 /   0   0   0   0
Oak Ridge, TN                       86  62  89  62 /   0   0   0   0
Tri Cities Airport, TN              81  60  83  60 /  20   0  10   0
-- End Changed Discussion --

&&

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

$$

SHORT TERM...DGS
LONG TERM....GC
AVIATION...KS