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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS64 KMRX 161939
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
339 PM EDT Tue Apr 16 2024

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

.SHORT TERM...
-- Changed Discussion --
(This evening through Wednesday)
Issued at 251 PM EDT Tue Apr 16 2024

Key Messages:

1. Warm temperatures this afternoon with isolated storms through
the afternoon.

2. Chance for stronger showers and thunderstorms Cumberland
plateau counties Wednesday afternoon.

Discussion:

This afternoon scattered showers and thunderstorms developed the
last couple hours along the crest of the Appalachians of northeast
Tennessee. They back built into Johnson and Carter counties and
produced some gusty winds and heavy rainfall. At mid afternoon a
weak front was located from the eastern part of West Virginia to
the northeast Tennessee border with North Carolina. Skies were
mostly cloudy in the northeast and partly cloudy in the southwest
part. Temperatures were in the upper 70s to the mid 80s. This
evening expect the front to slowly shift north. The convection
should end early this evening with skies partly cloudy this
evening. Later tonight clouds will increase ahead of another cold
front moving into the western Tennessee Valley and Ohio Valley.
Lows will again be mild. Some light rain showers are possible
before 12Z in the west but the most of the precipitation will come
in after 12Z.

Overnight tonight an upper-level wave and attendant surface low
the is over the central Plains/Midwest is forecast to weaken over
the next 24-48 hours as it gradually lifts to the northeast. A
trailing surface cold front associated with the low is forecast to
push east across the Great Lakes region through the day
Wednesday.

A residual outflow boundary from Tuesday night`s convection is
expected to push east through the morning hours, reaching the
eastern TN Valley into northern AL/MS by peak heating. More
thunderstorm development is possible during peak heating across
parts of the TN Valley as the residual outflow boundary moves
east. The best time for strong to severe storms is late afternoon.
Thunderstorm development and/or re-intensification is possible
where latest CAMs show CAPE Values increasing to around 1500 J/kg.
Low-level flow is forecast to be weak with 30-40 knot westerly
aloft and combined with steepening low-level lapse rates by late
afternoon and could support a few stronger cells or clusters with
large hail and high winds. The forecast area is only the marginal
risk area. Highs Wednesday will be cooler with extensive cloud
cover in the mid to upper 70s.
-- End Changed Discussion --

&&

.LONG TERM...
-- Changed Discussion --
(Wednesday night through next Tuesday)
Issued at 251 PM EDT Tue Apr 16 2024

Key Messages:

1. Showers and thunderstorms return for Thursday night and Friday.
There is a low chance of strong storms with strong and gusty winds
and hail possible Friday.

2. Turning much cooler this weekend. Low confidence of lingering
showers across mainly southeast Tennessee, southwest North Carolina,
and far east Tennessee Mountains this weekend through early next
week. This is due to potential slowing of the front and southern
stream system moving across the Gulf Coast states.

Discussion:

For Thursday, upper ridge building over the region with weak surface
ridging as well. End result will be an unseasonably warm and day
across the region.  Highs will only be a couple of degrees below
daily records at CHA and TYS.

Records for April 18th
CHA  90/2002   TYS  90/1896   TRI  87/2002

For Thursday night and Friday, an upper level jet will move across
the mid-west into the Ohio valley with broad divergence expected
over the Tennessee valley. This upper jet Thursday night will
strengthen a low level jet over the region increasing the isentropic
lift producing an area of showers and thunderstorms.

For Friday, a frontal boundary will move into the area.
Deterministic models show quite a difference in degree of
instability with the NAM the highest. NBM SBCAPE probabilities are
more in line with the weaker GFS with values of 500-1000. However,
models do agree with decent mid-level lapse rates of 6.5 to 7.0
degrees. Will monitor the potential of strong storms Friday with
main concern being strong and gusty winds and small hail.

For Saturday and Sunday, frontal boundary moves through the area but
some disagreements on how far south and potential of showers
lingering across the far east and southern areas. Most locations
will be dry with cooler temperatures.

For Sunday, the southern stream becomes active with a jet moving
across the Gulf Coast states. Low confidence of any showers moving
into the southern Appalachians.

For Monday and Tuesday, a good deal of discrepancy between models
on evolution of systems. Currently mainly dry with moderating
temperatures.
-- End Changed Discussion --

&&

.AVIATION...
(18Z TAFS)
Issued at 118 PM EDT Tue Apr 16 2024

VFR conditions with some increased winds at CHA this afternoon.
At KTRI a chance of an afternoon thunderstorm developing next few
hours but still VFR. Overnight tonight lighter winds and some
lowering of clouds. Wednesday generally expect VFR conditions
early but MVFR conditions possible with showers before 18Z so
inserted a prob30 group at CHA. At TYS expect VFR conditions with
showers possible after 18Z so not included in current forecast.

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
Chattanooga Airport, TN             64  76  62  87 /  20  60  10  10
Knoxville McGhee Tyson Airport, TN  65  77  62  84 /  10  40  20   0
Oak Ridge, TN                       65  76  61  85 /  10  40  20  10
Tri Cities Airport, TN              61  78  59  81 /  10  30  20  10
-- End Changed Discussion --

&&

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

$$

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