770
FXUS64 KMRX 061438
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
1038 AM EDT Sun Apr 6 2025

...New UPDATE...

.UPDATE...
Issued at 1014 AM EDT Sun Apr 6 2025

This morning a convergence boundary draped through portions of
KY/TN southward along the AL/MS border continues to promote a
fairly broad stratiform precip shield along the Cumberland Plateau
and southern valley into portions of the central valley. Made
some minor adjustments to the hourly PoP trends with the morning
update, most notably in our northeastern zones where radar returns
are lackluster due to downslope drying. Also made sure that
thunder wording was limited to slight chance but even that may be
generous as the persistent cloud cover and rain chances have
really worked over the atmosphere and instability will be very
limited this afternoon. As such, this mornings update from SPC has
omitted the marginal risk and left us with just general thunder.
Of course we will continue to monitor for isolated hydro concerns
as the rain continues today, however, the threat continues to
remain on the low side with the Plateau and southern valley the
most likely to have some isolated issues occur. Expect it to be
mostly nuisance ponding in low-lying or poor drainage areas at
this time.

&&

.SHORT TERM...
(Today and tonight)
Issued at 214 AM EDT Sun Apr 6 2025

Key Messages:

1. A line of storms will move through the region early this morning,
bringing a threat for damaging winds. A low-end tornado risk exists,
especially in southeast Tennessee and southwest North Carolina.

2. Additional storms are likely this afternoon, but they will be
less robust and present a lower risk for strong winds.

Discussion:

At the time of this forecast issuance, broad troughing is centered
to our west with an impressive 190 kt jet streak to our north. A
frontal boundary extends from central Kentucky into West Tennessee
with linear convection moving into our region. Broad southerly flow
has generated impressive surface heating with much of the region
still into the 70s. 850mb winds are generally around 40 kts area-
wide with effective bulk shear in excess of 50 kts. Instability is
fairly limited further north but is currently increasing south to
north with MLCAPE and SBCAPE to reach 250 to 500 J/kg. This is
especially south of an outflow boundary north of Chattanooga. These
indications support the linear convection to maintain its strength
through much of the area, especially further south, presenting a
risk for marginally severe damaging winds. Regarding the tornado
potential, 0-1km bulk shear is generally near 20 kts along I-40 to
near 30 kts in southeast Tennessee to southwest North Carolina. It
should also be noted that the better 0-3km CAPE of 75 to 100 J/kg is
focused further south. Based on these considerations, a low-end
tornado risk exists for southern portions of the area. This is
further illustrated with 0-1km SRH of 250 m2/s2 and STP values of
around 1, especially along the southern Cumberland Plateau.

This line of convection is likely to be east of the region by late
morning with stratiform rain having continued for at least a couple
of hours. There will be at least some window for destabilization
again during the afternoon with the frontal boundary expected to be
just west of the region. A lot of the CAMs are showing additional
development during the afternoon. However, by this time, the flow in
the lower levels will be weakened and unidirectional. Deep-layer
shear will be similarly strong and supportive of a low-end damaging
wind risk.

Late tonight, the frontal boundary will begin to move through the
region. As moisture will still be present, chances for rain will
continue. However, any instability will be well east of the region,
meaning showers will be the main result.

&&

.LONG TERM...
(Monday through Saturday)
Issued at 214 AM EDT Sun Apr 6 2025

Key Messages:

1. Rain will linger along the mountains on Monday, followed by drier
and much colder temperatures. A widespread frost is likely Tuesday
morning, and a widespread freeze is likely Wednesday morning.

2. Another system will bring chances for rain late Thursday into
Friday morning. Isolated thunderstorms are possible, but these
chances are very limited.

Monday through Wednesday

At the start of the period, the frontal boundary that is bringing
strong to severe storms in the short term period will be east of the
region. Deep upper troughing and high pressure will be centered to
our west and moving into the region. Northwesterly flow will usher
in much colder air with lingering low-level moisture keeping some
rain chances along the mountains. Based on 850mb temperatures
falling below freezing and lingering moisture, a brief transition to
snow is possible along the highest elevations. However, this is not
expected to amount to amount to anything. The surface high will
gradually settle in from the west with subsidence leading to drier
and notably cold temperatures by Tuesday morning. Much of the area
can expect lows in the mid 30s to upper 20s, producing a widespread
frost/freeze. Similarly cold air will linger on Tuesday, keeping
temperatures far below normal through the day. By Wednesday morning,
even better radiational cooling will allow for most of the region to
see freezing temperatures. As the surface high shifts eastward,
southerly flow will recover temperatures further. Another shortwave
and developing system will come into view in the Midwest.

Thursday through Saturday

On Thursday, the aforementioned system will track towards the Great
Lakes with strengthening of southerly flow expected ahead of its
associated frontal boundary. This will bring another chance for rain
to the area by later Thursday into Friday. However, overall moisture
and surface heating will be limited, so mostly showers are expected.
There may be enough instability for embedded thunder, but this would
be very isolated. Behind the front, another notable cooldown is
expected heading into next weekend, which may bring another chance
for frost Saturday morning.

&&

.AVIATION...
(12Z TAFS)
Issued at 720 AM EDT Sun Apr 6 2025

The heavier rain from this morning has largely pushed off to the
east with a persistent light to moderate rain expected to continue
for the next several hours. Conditions will likely bounce between
VFR and MVFR. By the afternoon, rain is expected to decrease,
which may allow development of additional storms. If a storm
impacts one of the airports, further reductions and erratic winds
are possible. By the evening, rain may linger with aviation
conditions likely to drop to IFR across the region. Winds will
shift to be from the northwest as a frontal boundary moves through
from the west.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             71  52  59  40 / 100  50  20   0
Knoxville McGhee Tyson Airport, TN  72  49  57  36 / 100  70  30   0
Oak Ridge, TN                       70  48  58  35 / 100  60  20   0
Tri Cities Airport, TN              71  48  58  33 /  90  80  40  10

&&

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

$$

SHORT TERM...BW
LONG TERM....BW
AVIATION...BW