673
FXUS64 KMRX 211919
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
319 PM EDT Fri Jun 21 2024

...New SHORT TERM, LONG TERM...

.SHORT TERM...
(This evening through Saturday)
Issued at 315 PM EDT Fri Jun 21 2024

Key Messages:

1. A slight chance of showers and storms higher elevations Saturday
afternoon into early evening.

2. Temperatures above normal tonight and Saturday.

Discussion:

Ridging aloft is now centered over the western Tennessee Valley and
lower Ohio Valley this afternoon. A dry airmass is keeping heat
index values in the lower 90s just above actual temperatures with
dew points in the mid 60s. There has been a little more Cu
development then yesterday but still no convection. An isolated
shower or storm could still form across the northeast forecast area
furthest from the upper ridge center where upper level heights are
lower but the chance is too small to put in forecast. A light
easterly flow continues but overall surface winds are light and
variable. For tonight and Saturday expect partly cloudy skies.
Tonight lows will be slightly warmer in the upper 60s to lower 70s.
A little more patchy fog is possible, especially in the Tennessee
River Valley. Saturday the upper ridge shifts southwestward or
flattens more and the airmass will still be very warm. Highs reach
into the low to mid 90s with heat index values again in the 90s
and a few locations in the central and southern valley could reach
around 100 heat index for a few hours. An increase of moisture
will be moving north from the south and southeast. This will be
enough with the instability during the afternoon to trigger
showers and storms across the higher elevations in NC, east TN, SW
VA and the Cumberland Plateau. Rainfall amounts are not expected
to be that significant. However it may drop temperatures a few
degrees giving some relief from the heat.

&&

.LONG TERM...
(Saturday night through next Friday)
Issued at 315 PM EDT Fri Jun 21 2024

Key Messages:

1. The heat continues.

2. Chances of showers and storms increase around Sunday evening into
Monday, and again for Wednesday/Thursday.

The hot 500 MB ridge of high pressure that has been parked over the
area will have begun to retrograde westward by Sunday, and will set
up shop over the Four Corners by Tuesday. This means that our area
will slowly but surely come under the influence of a northwesterly
steering flow, which will begin to push weather systems through the
area. The first and weaker one will occur on Sunday, with an
accompanying chance of POPs. A second system will focus in on
Wednesday-Thursday, with POPs bumping up into the likely category.
In the days between these events and beyond, there may still be
isolated diurnal showers or tstms possible.

With the passage of the Thursday system/front, the ridge to the west
will extend eastward again and keep precip to a minimum until late
in the weekend.

Afternoon max heat indices will flirt with 100 degrees in the
southern Valley from Sunday to Wednesday.

&&

.AVIATION...
(18Z TAFS)
Issued at 131 PM EDT Fri Jun 21 2024

VFR conditions will prevail through the period, along with light
winds. Late today CU field should dissipate with high clouds at
times tonight. Airmass to dry again today for afternoon showers
and storms to form. Patchy fog possible tonight in NE TN but not
confident enough to put in TRI forecast.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             73  95  74  96 /   0  10   0  10
Knoxville McGhee Tyson Airport, TN  72  93  73  93 /   0  10   0  20
Oak Ridge, TN                       72  92  71  93 /   0  10   0  20
Tri Cities Airport, TN              66  91  69  90 /   0  10   0  30

&&

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

$$

SHORT TERM...TD
LONG TERM....GC
AVIATION...TD