-- Discussion containing changed information from previous version are highlighted. --
129
FXUS64 KMRX 180604
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
204 AM EDT Wed Sep 18 2024

...New AVIATION...

.UPDATE...
Issued at 808 PM EDT Tue Sep 17 2024

Currently showers and storms are continuing across the southern
Appalachians as the center of the remnants of the topical system
continue to sit right over our region. We have a generally
easterly to northeasterly direction to the storms which is keeping
the majority of the heavy precipitation to the east of the
Appalachians. Across northeast TN and southwest VA we`ve seen a
moderate amount of rain spill over the mountains with
radar/satellite estimating around an inch or more in some spots of
southwest VA. Expect the trend of weakening showers to continue
the rest of the evening, but not all of the storms will completely
go away. This rainfall will likely lead to fog across many
locations north of Interstate 40 before sunrise tomorrow.

&&

.SHORT TERM...
(This evening through Wednesday)
Issued at 330 PM EDT Tue Sep 17 2024

Today was a cloudy to mostly cloudy day as the remnants of the
tropical system spread clouds and moisture across east Tennessee
and vicinity with steady rain in the morning and scattered light
rain showers in the late morning and early afternoon. The center
of this system at mid afternoon was near the northern SC/NC
border. Bands of light showers were moving from east to west
across east TN and more concentrated over southwest Virginia. Only
light amounts of rain were falling and this will continue into
the evening before ending outside of the eastern mountains. Some
brief clearing occurred during the afternoon in the valley areas.
Temperatures were in the upper 60s to mid 70s at mid afternoon. A
few showers could continue along the TN/NC border overnight. Also
patchy dense fog may form with some clearing overnight. The near
tropical low will move little tonight and Wednesday but weaken
over time. Still expect increasing showers and a chance for a few
storms with limited instability Wednesday northeast half of the
region but only a few hundredths of an inch of precipitation
expected. Temperatures will be warmer. Low clouds will break up by
afternoon. Highs will be closer to average in the upper 70s to mid
80s.

&&

.LONG TERM...
(Wednesday night through next Tuesday)
Issued at 330 PM EDT Tue Sep 17 2024

Key Messages:

1. Other than showers and an isolated rumble of thunder in the east
on Thursday, dry and progressively warmer conditions are expected
Friday through the weekend.

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

Wednesday Night through Saturday

At the start of the period, a closed low will be centered to our
east with ridging to our west. This low will slowly lift
northeastward on Thursday with drier air approaching from the west.
Weak northwesterly flow will provide some lift along the terrain
through Thursday. With moisture limited to eastern areas, this is
where PoPs will be contained.

By Friday, ridging will continue to expand from the west with
surface high pressure taking shape across much of the eastern U.S.
This will promote dry and warmer conditions compared to Thursday. By
Saturday, ridging will expand even further across the area with high
pressure continuing to strengthen. 850mb temperatures will rise to
above 18 Celsius, at or above the 90th percentile for this time of
year. As such, many places in the southern Valley will likely rise
into the 90s with similar heat further north in the Valley. Deep
mixing will likely promote low RH`s Friday and Saturday but with
fairly light winds.

Sunday through Tuesday

On Sunday, similarly strong ridging will remain in place, keeping
the area very warm and dry. By early next week, the main question
will be how troughing to our northwest will evolve. Some solutions
suggest a strong system to develop and progress to our north with
others showing more zonal evolution. If a more dynamic system
develops, this could produce our first mountain wave high wind
event. However, many ensemble members are split on if this will
transpire. In any case, some moderation in temperatures and a return
of low-end rain chances can be expected.

&&

.AVIATION...
-- Changed Discussion --
(06Z TAFS)
Issued at 146 AM EDT Wed Sep 18 2024

BLUF: a complicated overnight aviation forecast. TYS has gone
down harder/faster than originally thought, while TRI is still
VFR. Current HREF guidance shows CIGS and VSBY will impact TYS the
most overnight. Still some indication TRI will go down too, but
not too overly confident on timing and extent. Wouldn`t be
surprised if TYS remains LIFR much of the night, but will keep a
close eye. Given the current wind direction, TRI may also escape
lower flight categories if they become downsloped. CHA recently
reached MVFR CIGS, so would expect that to persist through the
morning. Guidance wants to throw in some fog there, but not too
sure that`s possible given how dry they have been, although
climate earlier reported a Trace of rainfall.

CIGS and VSBY overall will improve into Wednesday with chances for
afternoon and evening showers returning for TYS and TRI. TRI I
believe may have the better chance of thunder, so that was left
and TYS removed.
-- End Changed Discussion --

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
Chattanooga Airport, TN             85  65  89  64 /  10   0   0  10
Knoxville McGhee Tyson Airport, TN  82  63  86  61 /  20  10  10  10
Oak Ridge, TN                       83  63  86  61 /  10   0  10  10
Tri Cities Airport, TN              78  61  80  60 /  30  10  30  10
-- End Changed Discussion --

&&

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

$$

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