265
FXUS64 KMRX 050535
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
135 AM EDT Sat Oct 5 2024

...New AVIATION...

.UPDATE...
Issued at 910 PM EDT Fri Oct 4 2024

Showers and storms dissipated shortly after sunset tonight. Fog
looks possible in the central and northeast sections where clouds
lingered, isolated showers and storms developed and not as much
drying occurred before sunset. Updated hourly grids to reflect
current temperatures and dew points. Removed afternoon wording
with update. Updated forecast sent.

&&

.SHORT TERM...
(This evening through Saturday)
Issued at 329 PM EDT Fri Oct 4 2024

Key Messages:

1. Lingering showers and storms will diminish this evening with
clearing and potential for fog late tonight into Saturday morning.

2. During the day on Saturday, dry and mostly sunny conditions are
expected with most places rising into the 80s.

This Evening/Tonight

Currently this afternoon, a near 90kt upper jet is located over the
area with a shortwave moving to our north and east. At the surface,
a weak frontal boundary is also centered over the area with high
pressure to our north. This pattern has continued to promote
isolated to scattered showers and a few storms with overall
instability having been limited to 1,000 J/kg or less because of
early cloud cover. Ultimately, this activity is expected to diminish
quickly through the evening hours with clearing skies anticipated
overnight as high pressure expands southward. Because of the surface
moisture in place and potential clearing, patchy dense fog is likely
to develop by the early morning hours. This will, however, depend on
the rate of clearing from the evening and will also likely be more
notable further northeast where more rain potential exists.

Saturday

On Saturday, aforementioned high pressure will be centered over the
eastern Great Lakes with northeasterly winds and dry conditions
promoted by the subsidence. As such, morning fog and low clouds will
dissipate pretty early in the day, followed by mostly clear skies.
Temperatures will be fairly warm due to the more abundant sunshine
and CAA staying far to our northeast. Far into the Northern Plains
towards Canada, another shortwave/system will also become more
apparent.

&&

.LONG TERM...
(Saturday night through next Friday)
Issued at 329 PM EDT Fri Oct 4 2024

Key Message:

1. Other than limited northern rain chances Sunday night, dry
weather is expected through the extended period.

2. Cooler conditions are expected Tuesday onward, especially
overnight with lows forecast to drop into the 40s or even lower in
some isolated locations.

Saturday Night through Tuesday

The northern system will likely progress even further north towards
the Canadian Shield Saturday night to Sunday. Its associated frontal
boundary will also be noted to our northwest with increased
southerly flow out ahead, keeping temperatures very warm on Sunday.
By Sunday night, the frontal boundary will approach the area from
the north and west. With much of the upper level winds and dynamics
staying to our north, rain chances will also follow this same trend.
However, overall moisture and the frontal boundary itself will be
sufficient for at least low-end rain chances in the north. There are
still some model differences as to when the front will move through
the area, but most solutions suggest anytime from Monday morning to
Monday night. During this time, 1,020 to 1,025 mb high pressure will
be expanding from the west, keeping moisture and any rain chances
to our south or east. By Tuesday, the front will have passed
through our area with cooler air arriving from the northwest.

Wednesday through Friday

Mid to late week, model guidance does show another tropical system
strengthening and progressing through the Gulf. Thankfully for our
area, high pressure will remain in control over this timeframe.
Models still differ on the location and strengthening of the surface
high throughout the week. Solutions that show progression and
strengthening over the area would support stronger subsidence and
better potential for radiational cooling. Based on the overall
trend, most of the area can expect to see highs remaining in the
70s with many locations dropping into the 40s, perhaps every
night. If stronger subsidence is achieved, these values could even
reach into the 30s for far eastern places of southwest Virginia
and the Tennessee mountains. This will still depend on how the
exact pattern evolves, but drier and notably cooler conditions can
ultimately be expected mid to late week.

&&

.AVIATION...
(06Z TAFS)
Issued at 114 AM EDT Sat Oct 5 2024

Main flight conditions are the development of LIFR fog and low-
clouds early this morning mainly at TRI and TYS. MVFR conditions
at CHA.

Fog will remain until 13-15Z, then VFR conditions. Pressure
gradient remains weak so winds will be light throughout the
forecast period.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             85  62  87  63 /   0   0   0   0
Knoxville McGhee Tyson Airport, TN  83  59  84  61 /   0   0   0  10
Oak Ridge, TN                       83  58  85  58 /   0   0   0   0
Tri Cities Airport, TN              79  56  80  58 /   0   0   0  20

&&

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

$$

SHORT TERM...TD
LONG TERM....BW
AVIATION...DH