-- Discussion containing changed information from previous version are highlighted. --
046
FXUS64 KMRX 191510
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
1110 AM EDT Wed Jun 19 2024

...New UPDATE...

.UPDATE...
-- Changed Discussion --
Issued at 1110 AM EDT Wed Jun 19 2024

A warm day today but expecting dew points to be lower as upper
ridge has strengthened over the area. Also considerable mid and
high level clouds are streaming northeast from the Gulf of Mexico
ahead of now named Tropical Storm Alberto. This may hold
temperatures down a degree or two depending on how much sun can
filter through them. The easterly flow around the upper ridge
centered to the northeast across the mid Atlantic should keep
skies a little sunnier in the northeast third of the forecast area
than the central and southern sections. Temperatures were warmer
in northeast TN at late morning mainly due to less cloud cover.
Updated hourly temperatures and dew points and changed cloud cover
slightly with forecast update. Expect highs to be around 90 to
the lower 90s most locations...similar to Tuesday but slightly
lower Heat Index values.
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&&

.SHORT TERM...
-- Changed Discussion --
(Today and tonight)
Issued at 249 AM EDT Wed Jun 19 2024

Key Messages:

1. Hot and dry conditions continue with strong ridging in place.

Discussion:

NAFES anomalies depicts a strong upper ridge persists across the
mid-Atlantic states into the Tennessee valley and Appalachians.
Model soundings show PWs in the bottom quartile with a subsidence
inversion between the 850-700mb layer.

A strong dry lapse rate becomes evident this afternoon up to this
layer which will mix drier air to the surface. Blended the NBM and
NBM 10th percentile dewpoints to better reflect this dry airmass.
The easterly flow around the surface ridge across the region will
produce some weak downslope into the valley as well lowering
dewpoints.

Even though a good deal of ci/cs high level cloudiness is expected
today, the dry air will allow temperatures to warm into the lower
90s most locations in the valley. The heat and dry conditions
will increase the threat of flash drought conditions for much of
the area.

The dry air will allow temperatures to cool into the 60s area-wide
tonight under mostly clear sky.
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&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 249 AM EDT Wed Jun 19 2024

.LONG TERM...(Thursday night through Tuesday)

Key Messages:

1. Above average temperatures continue with strong ridging in place.

2. Diurnal convection probabilities increasing Sunday into early
next week.

Discussion:

Anomalously strong ridging continues across the Eastern CONUS late
week through the weekend with 500mb heights of 594 dam across the
Tennessee and Ohio Valleys. NAEFS anomalies show this near the max
of climatology. The 850mb ridge also remains directly over the Ohio
Valley with weak easterly flow resulting in subsidence and limited
moisture transport across the region. This will keep LFC heights
higher each afternoon with limited probabilities for diurnal
convection on Friday and Saturday.

The upper ridge retrogrades and flattens across the Ohio Valley on
Sunday as a shortwave trough and associated surface frontal features
moves eastward across the Great Lakes. The 850mb ridge shifts east
with southerly flow bringing increasing moisture beginning Sunday.
This increased moisture and lower upper heights will increase
instability with higher probabilities for diurnal convection into
early next week.

&&

.AVIATION...
(12Z TAFS)
Issued at 641 AM EDT Wed Jun 19 2024

VFR conditions expected at all TAF sites through the forecast.
Scattered/broken 3500-4kft area of cloud is moving into the CHA
airport early this morning. Overall, the will be plenty of high
level cloudiness today.

Surface ridging into the southern Appalachians will produce mainly
light winds today and mainly easterly.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             91  70  92  71 /   0   0   0   0
Knoxville McGhee Tyson Airport, TN  91  67  92  69 /   0   0   0   0
Oak Ridge, TN                       90  67  92  70 /   0   0   0   0
Tri Cities Airport, TN              91  63  90  64 /   0   0   0   0

&&

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

$$

SHORT TERM...TD
AVIATION...DH