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

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FXUS64 KMRX 241103
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
703 AM EDT Sun Mar 24 2024

...New AVIATION...

.SHORT TERM...
(Today and tonight)
Issued at 337 AM EDT Sun Mar 24 2024

Key Messages:

1. Sunny and warmer today with high pressure in control.

2. Southerly flow begins late today and tonight with a warming
trend.

3. Low RH values expected today with the warmer temperatures and
dry air.

Discussion:

Surface high pressure and ridging across the region will result in
subsidence, dry air, and sunshine today. With mid-level heights on
the rise this afternoon, temperatures will be back on the rise
with afternoon max temperatures near seasonal normals. With these
warmer temperatures and the dry airmass, low RH values are
expected area-wide.

The surface high moves east of the area this evening with
increasing southerly flow late this afternoon and tonight due to
the tightening pressure gradient. In addition, increasing high
clouds are expected due to the isentropic lift within the deep
southwesterly flow aloft. Southerly flow and increased cloud cover
will keep temperatures more mild tonight into Monday morning.

&&

.LONG TERM...
(Monday through Sunday)
Issued at 337 AM EDT Sun Mar 24 2024

Key Messages:

1. Breezy and dry conditions are expected area-wide on Monday with a
high-end mountain wave event increasingly likely Monday night into
Tuesday.

2. Showers and isolated thunderstorms are expected off and on
Tuesday through Tuesday night with shower coverage decreasing on
Wednesday.

3. Cooler conditions will return on Thursday with a widespread
frost/freeze event possible Thursday night into Friday morning.

Monday through Wednesday

At the start of the period, deep troughing will be centered over the
Rockies with a broad upper jet in excess of 150 kts at its base.
During this time, a deep low pressure system will be progressing
into Kansas with a center of near 990mb MSLP. Recent subsidence and
receding surface high pressure will keep dry air in place to start
the period. As the MSLP gradient and low-level jet strengthen, this
will make for a breezy day, which combined with the dry air, will
elevate fire weather concerns, especially in the higher elevations.
Based on the latest model guidance, a very anomalous 850mb jet of
over 70 kts will be centered over the Mississippi River with values
of 40 to 50 kts reaching western portions of the area before the
evening. Overnight on Monday into Tuesday morning, model guidance
suggests these 70+ kt values to be across Middle Tennessee with a
strong MSLP gradient along the mountains and foothills. Per the
NAEFS percentiles and sounding climatology, the 850mb jet will be
near record-high values to our west, sufficient for a high-end
mountain wave event. Outside of these areas, the flow below 850mb
will be supportive of Wind Advisory criteria across much of the
area. This will all be before rain ahead of the associated frontal
boundary will reach the area. Based on the temporal scale, wind
products will be held off for now but will be needed during future
updates.

Based on the model consensus, most of the rain is likely to fall
during the day on Tuesday with elevated instability sufficient for
low-end thunder mention. With how high the low-level winds will be,
a transfer of locally higher gusts will be possible, but the overall
thermodynamics are not conducive for severe convection this far
north. The passage of the actual front also appears to be later,
towards Wednesday, meaning rain chances will continue through the
day with temperatures remaining mild.

Thursday through Saturday

The front is expected to move through the area by Thursday morning
with fairly deep troughing aloft. This will lead to persistent
northwesterly flow and CAA, which will make for a cooler day
overall. Thursday night into Friday morning, high pressure will be
centered near to just south of the area. During this time,
conditions for radiational cooling will be fairly ideal for a
widespread frost/freeze event. During the day, height rises will
begin a warming trend back to normal temperatures with high pressure
keeping the region dry. A similar pattern is expected by Saturday
with the flow gradually becoming more zonal.

&&

.AVIATION...
(12Z TAFS)
Issued at 702 AM EDT Sun Mar 24 2024

VFR conditions are forecast today and tonight with generally light
winds as high pressure sets up over the region.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             66  45  62  52 /   0   0   0  60
Knoxville McGhee Tyson Airport, TN  64  40  67  50 /   0   0   0  30
Oak Ridge, TN                       65  40  66  49 /   0   0   0  40
Tri Cities Airport, TN              65  37  65  45 /   0   0   0  10

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...Freeze Warning until 9 AM EDT this morning for Cherokee-Clay.

TN...Freeze Warning until 9 AM EDT this morning for East Polk.

VA...NONE.
&&

$$

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


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