Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

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FXUS64 KMRX 221738
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
138 PM EDT Fri Mar 22 2024

...New AVIATION...

.UPDATE...
Issued at 1048 AM EDT Fri Mar 22 2024

Overall, the forecast remains on good track this morning. Some minor
discrepancies in hourly temperatures as the clouds held in heat
overnight and observations were about 3 degrees warmer as the sun
began to rise. However, it looks like temperatures are slowly coming
back around so minimal change was made to hourly temperatures. Did
blend in some 12Z hi-res/hand edits to help depict downslope
warming along the east Tennessee mountains more. Surface dewpoint
depressions have remained around 10 degrees F as some radar
returns moved south to north across the forecast area this morning
- no AWOS/ASOS stations reported any rain reaching the surface.
Warm and moist advection increases into the afternoon with rain
chances becoming more widespread late afternoon into the evening
hours. Lastly, the wind advisory appears to remain on track as
well. Camp Creek and Cove Mountain have both peaked at 42 mph
gusts so far.

&&

.SHORT TERM...
(Today and tonight)
Issued at 334 AM EDT Fri Mar 22 2024

Key Messages:

1. Low pressure to our south will bring a return of light to
moderate rain tonight.

2. Downslope flow keeps most of central and northeast Tennessee
through southwest Virginia mostly dry with light rain amounts.

Discussion:

Clouds increase today with southwest flow aloft and isentropic
ascent across the region. Light rain showers will be possible
today, mainly across southern portions of the forecast area where boundary
layer moisture is higher. Dry air across much of the region will
limit rain potential today and result in some observations of
virga this morning.

This evening and into tonight, the upper shortwave will move
across the Lower Mississippi Valley and eastward into southern
GA/AL. A mid-level deformation zone will bring some light to
moderate steady rain to the region tonight, mainly for southern
and eastern counties near the mountains. As the surface low begins
to move northeast into the Carolinas by 12z Saturday, the main
bulk of precipitation will begin to exit our region with some
limited rain showers remaining ahead of a surface cold front
pushing southeast across the region.

&&

.LONG TERM...
(Saturday through Friday)
Issued at 334 AM EDT Fri Mar 22 2024

Key Messages:

1. Rain will be exiting on Saturday, followed by drier conditions
for Sunday and Monday.

2. A system will approach the area early in the week, bringing
breezy conditions on Monday, followed by rain and mountain wave high
winds on Tuesday.

3. Drier and cooler conditions return on Wednesday, followed by a
warming trend through the rest of the week.

Saturday through Tuesday

At the start of the period, a system will be centered to our
southeast with the associated frontal boundary arriving from the
northwest. This will put the region in a northerly to northwesterly
flow pattern with lingering low-level moisture keeping PoPs early in
the day. While the flow is not ideal for orographic lift, the
northerly component will keep PoPs more focused along the terrain
later in the day after the better forcing shifting off to the south.
Based on the extent of low-level CAA, a brief mix of rain and snow
is possible in the highest elevations by the evening, but any
mentionable accumulations are unlikely. By Sunday morning, the
system will have pushed off well to the east with ridging and
surface high pressure building into the area. This will promote
subsidence and potential frost development before fire weather focus
returns during the day. Luckily, the MSLP gradient and low-level
flow will be fairly weak, but efficient mixing will promote a drop
in RH`s to below 30 percent in many places. Also during this time,
focus will turn towards a deepening low pressure system ejecting out
of the Rockies below upper-level divergence and troughing.

By Sunday night towards Monday morning, the consensus is for the
aforementioned system to track towards the upper Mississippi River
Valley with a low pressure center of 990mb or less. The tightening
of the MSLP gradient across much of the eastern U.S. will be
accompanied by 850mb flow of 60 kts or greater across a broad area.
Locally, these winds winds and continued mixing will increase fire
weather concerns on Monday, especially with initial mountain wave
enhancement of winds. The favorability for mountain wave winds will
only increase towards Tuesday morning with the 60+ kt 850mb flow
near a SSE direction and across much of Middle Tennessee. While
timing differences still exist, the overall consensus is for the
potentially occluded frontal boundary to bring rain through the day
on Tuesday. Based on the overall model consensus, the warm sector
still looks to remain far to our south, but elevated instability
will be sufficient for isolated thunder mention.

Wednesday and Thursday

The frontal boundary is likely to move through the area by Wednesday
morning, which will produce a more northwesterly flow pattern and
CAA. As high pressure expands from the west, this will lead to a
return of drier conditions into Thursday. Height rises will promote
the beginning of another warming trend with low-level flow likely
remaining fairly light during this time.

&&

.AVIATION...
(18Z TAFS)
Issued at 132 PM EDT Fri Mar 22 2024

Unsettled weather returns with rain chances increasing south to
north late this afternoon through tonight. Expect MFVR conditions
to settle in for all sites, but IFR conditions cannot be ruled
out(both cigs and vis). Have opted to include a scattered IFR
deck to cover the uncertainty at this time. In addition to the
rain, a wind shift is expected over the period. Gusts will settle
tonight as winds back, becoming more easterly. Winds will
continue to back and become more northerly for tomorrow afternoon,
in which breezy conditions will return. Turbulent low-level winds
near the mountains and western foothills will persist through the
evening.


&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             53  62  37  68 / 100  30   0   0
Knoxville McGhee Tyson Airport, TN  52  58  33  65 / 100  70   0   0
Oak Ridge, TN                       52  60  33  65 / 100  40   0   0
Tri Cities Airport, TN              49  56  28  65 / 100  80   0   0

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Wind Advisory until 2 AM EDT Saturday for Blount Smoky Mountains-
     Cocke Smoky Mountains-Johnson-Sevier Smoky Mountains-
     Southeast Carter-Southeast Greene-Southeast Monroe-Unicoi.

VA...NONE.
&&

$$

SHORT TERM...JB
LONG TERM....BW
AVIATION...KRS


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