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

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FXUS64 KMRX 020135

Area Forecast Discussion
National Weather Service Morristown TN
935 PM EDT Sat Oct 1 2022

...New UPDATE...

Issued at 932 PM EDT Sat Oct 1 2022

A forecast update will be issued to remove the chance of rain
across northeastern portions of the area through tonight. The
chance of rain will be replaced with sprinkles/drizzle for parts
of SW VA, as LNP has shown -DZ for a few hours despite the lack of
radar-indicated precip. All other forecast parameters are on


(This evening through Sunday)
Issued at 339 PM EDT Sat Oct 1 2022

Key Messages:

1. Light off and on rain will continue to be focused along and near
higher terrain places of northeast Tennessee and southwest Virginia.
Any additional rainfall will be very light.

2. Temperatures overnight will be seasonal in the upper 40s to low
50s with a large southwest to northeast gradient of high
temperatures on Sunday. Southern portions of the area will reach the
70s with many northeastern areas barely reaching above 60.

This Evening/Tonight

Currently, TC Ian`s remnants are merely a weak post-tropical
cyclone, moving into central Virginia. Aloft, this is also seen by a
shortwave/closed low further to the north. This will keep the region
in a fairly weak northerly flow pattern with overall moisture
remaining pretty close to normal for this time of year. Synoptically
forced vertical ascent continues to weaken with much of the forcing
being achieved by orographic means due to 20-25kts of 850mb flow.
However, with a non-NW direction and fairly weak magnitude, forcing
still remains fairly weak. This will keep a focus of PoPs in and
near the higher elevations in northeastern portions of the area with
most places likely remaining dry into tonight. With recent rainfall
and expectations of weaker low-level flow, northeastern portions of
the region are also likely to see fog development by the morning,
especially in low-lying areas.


By Sunday, the system will mainly just be seen as a mid/upper-level
feature moving towards the Mid-Atlantic coast. With the southward
progression of high pressure from Ontario and dissipation of the
surface feature, the low-level flow will likely become more
easterly. This will also reduce the orographic lift in many of the
higher terrain places with notable low-level moisture expected to
remain. As such, this will keep any PoPs in these areas with
additional rainfall totals expected to be very light. This will also
keep cloud cover focused in the northeastern half of the region,
keeping a large temperature gradient similar to what was seen today.


(Sunday night through next Saturday)
Issued at 339 PM EDT Sat Oct 1 2022

Key Messages:

1. Remnants from Ian will gradually depart through late Sunday. Dry
weather Monday through Thursday.

2. A gradual warm up through Thursday, then cooler for the weekend.

3. Cold front will arrive Thursday into Friday, but there is
uncertainty that any precipitation will accompany it at this time.

A weak remnant Ian will have only moved it`s center over Tidewater
Virginia at the start of the long term period. The upper level low
with northwesterly flow will continue to send moisture on the
backside of the system, prolonging cloudy and showery conditions
mostly for SW VA, the northern TN Valley, and upslope areas of the
Appalachians through late Sunday/early Monday.

Thereafter from Monday until early Thursday, the entire forecast
area will be under the influence of surface high pressure centered
over the Great Lakes region and an upper level ridge over the
Midwest. The upper level low to our east will persist until midweek,
but we will be on the good side or dry side of the upper level low
where we will remain mostly sunny and clear. Northwesterly flow
aloft will begin at the start, eventually turning westerly and then
southwesterly by Thursday, which will warm temperatures into the
upper 70s to low 80s in the Valley.

A pattern change will occur later Thursday into Friday with the
passage of a cold front. Models have trended drier the past few runs
as far as a dry cold front that will decrease high temperatures into
the upper 60s Saturday, but most recent runs and ensembles ping at
the possibility of a chance of precipitation, so will go with a
slight chance for now. This will change and adjust with subsequent
forecast packages, being so far in the long term period.


(00Z TAFS)
Issued at 726 PM EDT Sat Oct 1 2022

The main aviation impact this period will be ceilings at TYS and
TRI as a NW flow keeps moisture dammed against the mountains.
Current MVFR cigs at TRI are expected to gradually drop to IFR
around midnight-06Z, and some light MVFR fog may also develop.
Cigs may lift to MVFR during the day tomorrow. At TYS, current VFR
cigs will drop to MVFR through the night and tomorrow morning,
then are expected to return to VFR tomorrow afternoon.


Chattanooga Airport, TN             53  74  55  76 /   0   0   0   0
Knoxville McGhee Tyson Airport, TN  53  67  52  72 /  10  10  10   0
Oak Ridge, TN                       51  68  51  72 /  10  10   0   0
Tri Cities Airport, TN              49  60  50  66 /  30  30  20  10




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