-- Discussion containing changed information from previous version are highlighted. --
330
FXUS64 KMRX 141756
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
156 PM EDT Fri Jun 14 2024

...New AVIATION...

.UPDATE...
Issued at 1118 AM EDT Fri Jun 14 2024

For the afternoon and evening today we will see if scattered
thunderstorms moving in the northwest flow can sustain updrafts
against the suppressive effect of the ridge subsidence. HRRR is not
enthusiastic about convection today, with just a thin CAPE profile
against the warm environmental temperature. Other guidance is
similarly wimpy. Still, added very low PoPs a little further south
to near Knoxville for later this afternoon into early evening for
an isolated shower or storm. SPC has southwest Virginia in a
marginal risk for a severe downburst, if a storm were to be tall
enough, modeled DCAPEs are supportive of a severe wind gust.
Apart from questions on convection, the forecast is on track for a
hot and muggy day today.

&&

.SHORT TERM...
(Today and tonight)
Issued at 440 AM EDT Fri Jun 14 2024

Key Messages:

1. Warmer today with continued mostly dry conditions.

2. Heat indices will top out near 100F near Chattanooga this
afternoon.

Discussion:

Continued mostly dry weather continues today with northwest flow
aloft and upper ridging intensifying across the central CONUS.
Subsidence along the eastern periphery of the ridge will continue
to limit afternoon convection for our area with subsidence aloft.
With slightly warmer 850mb temperatures this afternoon, max
temperatures are forecast to be 2 to 4 deg warmer than on
Thursday. A few showers could develop along the higher elevations,
but PoPs are not expected to be above 10 to 20 percent. Tonight,
we remain clear and warm with high pressure in control.

&&

.LONG TERM...
(Saturday through Friday)
Issued at 440 AM EDT Fri Jun 14 2024

Key Messages:

1. Hot and humid conditions are expected with highs in the 90s most
days and heat indices near 100.

2. Many places will likely stay dry, but isolated to scattered
thunderstorms are possible Sunday and Monday, especially over the
higher terrain. Chances are very minimal other days.

Saturday through Monday

At the start of the period, strong upper ridging will be centered to
our west with surface high pressure over the Great Lakes. Locally, a
frontal boundary will be near to just south of our area. While this
will provide northerly flow, 500mb heights near 5,900m will keep the
region very warm with the main result being an overall drier
airmass. By Sunday, ridging will continue to strengthen with a near
5,920m high at 500mb and surface high pressure moving off towards
New England. Height rises and a shift in the frontal boundary will
lead to even hotter conditions and more southerly flow at the
surface. A 500mb high this strong and 850mb temperatures to near 20
Celsius are near record high values per BNA sounding climatology.
This strongly suggests temperatures to rise well into the 90s with
heat indices near 100 degrees across most of the lower elevations.
This will also promote moisture advection sufficient for diurnal
convection focused mainly on the higher terrain.

By Monday, the 500mb high will reach very close to record-high
values of 5,940m and be centered just to our east. This will
continue to promote very hot conditions. A difference for Monday,
however, will be increased moisture throughout the column in
comparison to the days prior. Weak embedded shortwaves aloft and
local terrain will support better chances for diurnal convection,
centered on the higher terrain. Depending on coverage, this could
lessen overall high temperatures. In any case, here are the record
highs and their most recent year of occurrence:

Date    Chattanooga    Knoxville      Tri-Cities     Oak Ridge
06-15   98(1952)       96(2022)       95(2022)       96(2022)
06-16   99(1936)       98(1936)       94(2022)       97(2022)
06-17   98(1952)       99(1936)       95(1944)       96(2015)

Tuesday through Thursday

Throughout the week, the 500mb high will strengthen to near a record
6,000m as it remains fairly stationary over New England. Locally,
the airmass will be drier than on Monday with PWATs generally just
above 1 inch. Some moister return is possible by Thursday, but this
pattern will continue very hot and mostly dry conditions with
Tuesday and Wednesday more likely to remain dry. Any convection
these days would be very isolated and focused over the higher
terrain. By Thursday, chances may begin to increase, but model
guidance is expectedly more divergent.

&&

.AVIATION...
-- Changed Discussion --
(18Z TAFS)
Issued at 152 PM EDT Fri Jun 14 2024

VFR to continue at all TAF sites through the period. Light winds
should be predominant, with any afternoon gust limited in time. A
nonzero chance (10%) of a shower or thunderstorm exists through
03z tonight across northeastern TN into VA, however coverage is
too isolated to mention in the TAF at KTRI. Dry weather will
dominate through the period otherwise.
-- End Changed Discussion --

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
Chattanooga Airport, TN             71  94  70  95 /   0   0   0  10
Knoxville McGhee Tyson Airport, TN  70  90  68  93 /  10   0   0  10
Oak Ridge, TN                       69  90  67  93 /   0   0   0  10
Tri Cities Airport, TN              64  86  64  90 /  10   0   0  10
-- End Changed Discussion --

&&

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

$$

SHORT TERM...Wellington
LONG TERM....BW
AVIATION...Wellington