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

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FXUS64 KMRX 281726
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
126 PM EDT Thu Mar 28 2024

...New AVIATION...

.UPDATE...
Issued at 1050 AM EDT Thu Mar 28 2024

A drier and sunnier day today than Wednesday. Behind the cold
front from yesterday higher pressure was building in from the west
and northwest with the center just to the northwest and extending
through the lower Mississippi Valley and southwest into east
Texas late this morning. The colder air was advecting in from
north to northeast winds. Wind gusts possible today of around 25
mph and somewhat higher in the higher elevations. Relative
humidity values still look to drop into the 25 to 30 percent range
this afternoon, lowest in the valley areas. High temperatures
will be 5 to 10 degrees cooler today than Wednesday mostly lower
to mid 60s. Updated the winds, temperatures and dew points in the
hourly grids. Zone update changed winds and wind gusts slightly
and removed frost from early morning wording.

&&

.SHORT TERM...
(Today and tonight)
Issued at 354 AM EDT Thu Mar 28 2024

Key Messages:

1. Cooler and drier conditions are expected today with breezy
northerly winds.

2. Tonight, temperatures will drop into the 30s across much of the
area with patchy frost development.

Today

Currently early this morning, deep troughing is centered just to the
west with surface high pressure centered to the west. A cold front
has also moved off to our east, which has continued a northerly flow
pattern when combined with the MSLP gradient. Recent CAA, height
falls, and subsidence will make for a drier and cooler day today.
Deep mixing and 20 or more kts of 850mb flow will allow for
increased focus on fire conditions. Many places can expect RH`s to
drop into the 20s with a persistent breeze and higher gusts.
Luckily, many places have seen recent rainfall with fuel moistures
near and above 20 percent.

Tonight

Tonight, mid/upper troughing will be east of the area with surface
high pressure to our south. Overall, the pattern will support a
cooler night than this past night. Regarding the development of
frost, the main inhibiting factor will be continued winds due to the
MSLP gradient and continued low-level flow. Patchy development is
expected at a minimum, but additional products will be held off due
to the current one in effect for the northern Plateau.

&&

.LONG TERM...
(Friday through Wednesday)
Issued at 354 AM EDT Thu Mar 28 2024

Key Messages:

1. Frost/freeze potential into Friday morning. Dry air and low RH on
Friday afternoon.

2. An upper level system will bring unsettled weather and warmer
temperatures for next week, especially thunderstorm potential on
Tuesday.

Discussion:

The extended begins under the influence of surface high pressure and
areas of patchy frost on Friday morning. The highest probability of
frost will be across sheltered valleys where winds will be lightest.
Upper ridging begins to build back into the Tennessee Valley on
Friday afternoon which will kick off a warming trend. As high
pressure shifts east over the weekend, southerly flow returns with
warmer temperatures and increasing moisture. Due to the amplified
pattern, temperatures will be much above normal on Sunday through
Tuesday.

A potent upper shortwave will begin to amplify upper-level troughing
across the Great Plains early next week. Increased southwest flow
and isentropic lift will produce chances of rain showers north of
our area across the Ohio Valley. As a surface low intensifies across
the Great Plains and moves northeast towards the Ohio Valley and
Great Lakes, a cold front will move eastward towards our area on
Tuesday or Tuesday night. There is still a lot of uncertainty with
the exact location of the surface low and the evolution of the upper-
level trough early next week. However, the 0z deterministic GFS and
ECMWF, as well as their respective ensembles, are showing an
increasing potential of active weather possible on Tuesday. The 0z
GEFS probabilities of SBCAPE greater than 500 J/Kg are between 30 to
40 percent across the area, and the mean sfc-500mb bulk shear is
between 60 to 70 kt. Just based on the synoptic pattern and time of
year, this system will need to be monitored closely for severe
weather potential early next week across the region. In addition, as
PW values increase near and above 1.4 inch, near the max of
climatology for this time of year, heavy rainfall rates will be
possible which could result in flash flooding. As emphasized in
previous forecast cycles, there is still a lot of uncertainty, but
this system bears close watching over the next few days.

Longwave trough amplification is expected behind the departing
system with much cooler weather, and possible continued orographic
precipitation, on Wednesday into Thursday.

&&

.AVIATION...
(18Z TAFS)
Issued at 120 PM EDT Thu Mar 28 2024

A quiet period expected at all sites next 24 hours with the main
focus being gusty northerly winds this afternoon, especially at
CHA. This will continue until around sunset tonight. Only
scattered higher level clouds today through Friday morning and no
fog with dry airmass. Light north to northwest winds tonight will
shift to the southwest Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             40  71  48  76 /   0   0   0   0
Knoxville McGhee Tyson Airport, TN  38  68  47  74 /   0   0   0   0
Oak Ridge, TN                       37  70  44  75 /   0   0   0   0
Tri Cities Airport, TN              35  65  42  70 /   0   0   0  10

&&

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

$$

SHORT TERM...TD
LONG TERM....JB
AVIATION...TD


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