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

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FXUS64 KMRX 231139
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
739 AM EDT Sat Mar 23 2024

...New AVIATION...

.SHORT TERM...
(Today and tonight)
Issued at 345 AM EDT Sat Mar 23 2024

Key Messages:

1. Rain moves out his morning with gradual clearing from west to
east through the afternoon.

2. Cold tonight with a Freeze Watch for SW NC and eastern Polk.
Frost potential is questionable with continued northerly winds.

Discussion:

Surface low pressure will move northeast through the Carolinas
this morning with rain associated with a deformation zone shifting
east of the mountains by this afternoon. Northerly flow behind the
surface cold front will bring cooler, drier air to the region
later this afternoon and into tonight. Expect additional sunshine
from west to east across the area late today.

A clearing sky and cold, dry airmass will bring a return of cold
temperatures tonight with some areas near or below freezing. A
Freeze Watch has been issued for portions of SW NC and eastern
Polk County in SE TN. The biggest question, and current mitigating
factor for frost formation, is the brisk northerly winds tonight
which should remain at 5 to 10 kt through tonight and into Sunday
morning for most of the region. This will limit frost in areas
that have surface temperatures near or just above freezing;
however, some sheltered valleys could see localized calm winds
that result in frost formation.

&&

.LONG TERM...
(Sunday through Saturday)
Issued at 345 AM EDT Sat Mar 23 2024

Key Messages:

1. Very dry conditions are expected on Sunday with a breezier
southeasterly wind on Monday, which will increase the focus on fire
conditions.

2. A mountain wave high wind event is increasingly likely Monday
night into Tuesday, followed by arrival of showers and isolated
thunder.

3. Cooler conditions arrive late in the week with potential for
morning frost/freeze by Friday morning.

Sunday through Tuesday

At the start of the period, shortwave ridging will be building into
the area with high pressure centered to the north. A system will be
developing across the central U.S. that will be a focus into next
week. Initially, this pattern will promote subsidence and easterly
to northeasterly flow in the low-levels on Sunday, which will bring
fire weather to the forefront. Thankfully, the MSLP gradient and
850mb flow will be fairly light, but many places will likely see
RH`s drop to less than 30 percent in this pattern.

Heading towards Monday, the upper jet will be in excess of 150 kts
as it ejects into the southern Plains with an increasingly
negatively tilted shortwave to the north. During this time, the
surface low associated with this system will be near 990mb as it
progresses towards Iowa to Minnesota. In addition to a strengthening
MSLP gradient, the southerly 850mb jet will exceed 60 kts near the
Mississippi River Valley on Monday with a magnitude of near 40 kts
in our area. This will make for increasing fire weather concerns
with low RH`s due to efficient mixing and fairly breezy conditions
expected. By Monday night into Tuesday morning, the associated
frontal boundary will be approaching the area. The MSLP gradient
along the mountains will be very strong with 850mb flow in excess of
60 kts, making for a likely high wind event in the mountains. This
will continue the concern for any ongoing fires during this
timeframe. Regarding the precipitation, the warm sector will remain
far to our south. However, elevated instability will be sufficient
for low-end thunder mention.

Wednesday through Friday

By Wednesday, it is unclear how quickly the frontal boundary will
move through the area, but in any case, PoPs will remain higher
further to the east. Cooler temperatures would likely arrive by the
evening hours following northerly flow behind the frontal boundary.
By the end of the week, high pressure will arrive from the west,
promoting subsidence and a return of drier conditions. Based on the
overall consensus, a frost/freeze event is possible by Friday
morning.

&&

.AVIATION...
(12Z TAFS)
Issued at 734 AM EDT Sat Mar 23 2024

MVFR cigs continue this morning with gradually improving
conditions this afternoon. Northerly post-frontal winds will be
gusty at times this afternoon. Clearer conditions tonight across
the region with northerly winds decreasing to 10 kt or less.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             62  37  67  46 /  10   0   0   0
Knoxville McGhee Tyson Airport, TN  58  34  64  40 /  30   0   0   0
Oak Ridge, TN                       59  34  65  40 /  20   0   0   0
Tri Cities Airport, TN              55  29  65  36 /  60   0   0   0

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...Freeze Watch from late tonight through Sunday morning for
     Cherokee-Clay.

TN...Freeze Watch from late tonight through Sunday morning for East
     Polk.

VA...NONE.
&&

$$

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


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