743
FXUS64 KMRX 031120
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
720 AM EDT Mon Jun 3 2024

...New AVIATION...

.SHORT TERM...
(Today and tonight)
Issued at 338 AM EDT Mon Jun 3 2024

Key Messages:

1. While most areas are fog free this morning, some locations do
have patchy dense fog. Expect reduced visibilities down to 1 mile or
less across these areas.

2. Most areas will be dry but there will be a few isolated showers
and storms around through the day, non-severe.

Discussion:

A very unorganized pattern in place through the short term. We have
very weak ridging in place as we are sandwiched in between two
shortwaves. One wave is to our west across the Great Plains and the
other just off the southeast coast. This puts our area in a quasi-
zonal flow/weak ridging pattern. Within this pattern, there is just
enough vorticity moving through to spark a few isolated showers and
storms throughout the day. However, NAM soundings show a mid-level
inversion across most areas this afternoon. This means most of the
isolated showers or storms should mainly be focused across the
terrain, such as the Cumberland Plateau, the southwest NC, VA, and
east TN mountains. However, an isolated shower or storm in the
valley is still possible.

For any areas that do see storms, lapse rates are weak and shear is
pretty non-existent so there isn`t a severe threat today. However,
with dry air at the surface and in the mid-levels, DCAPE is elevated
at around 1000 J/Kg this afternoon. So there could be a storm that
reaches SPS criteria for gusty winds. But again, coverage will be
very isolated and most places dry.

Otherwise, near normal highs and lows today and tonight along with
more overnight patchy fog.

&&

.LONG TERM...
(Tuesday through Sunday)
Issued at 338 AM EDT Mon Jun 3 2024

Key Messages:

1. Multiple rounds of showers and storms are expected Tuesday into
Thursday. A few strong to marginally severe storms cannot be ruled
out Wednesday, with damaging winds the primary threat. Isolated
flash flooding is also possible.

2. Relatively drier conditions and mild temperatures are expected
Friday through the majority of the weekend. Given the occurrence of
any rain, it would likely be very light.

Discussion:

Shortwave energy will shift upper-level ridging eastward, leading to
an upward trend in the chances of showers and thunderstorms Tuesday.
Recent model derived soundings from the HRRR and NAM3km suggest
MLCAPE around 1000-1500J/kg with effective shear less than 10kts.
Believe activity will remain general thunderstorms but if peak
heating coincides with the upper disturbance, perhaps a stronger
storm with locally gusty winds and heavy rainfall will be possible.

As we head into Wednesday, a vertically stacked system will track
into southern Canada, with amplified H3 flow of ~100kts atop
portions of the northern Plains and northern Mississippi River
Valley. The combination of an upper level disturbance an approaching
surface front will lead to additional showers and storms Wednesday
and Thursday. Wednesday continues to look like the most favorable
day for strong to marginally severe storms with MLCAPEs between 1000-
2000J/kg and effective shear between 10-20kts. Worth noting that
DCAPE is generally in the range of 500-1000J/kg as well. As we
approach further into the warm season, freezing levels have started
to creep upwards. Soundings suggest the level will be near 13kft
Wednesday. PWAT values are still expected to remain around the 1.5-
1.8in mark. Given the above parameters, it is expected that damaging
winds and localized flash flooding will remain the primary concerns
with any strong to severe storm. With a worked over environment,
both instability and strong/severe chances trend lower Thursday.

Upper low becomes cutoff across the eastern Great Lakes region into
the weekend, and will result in lingering PoPs into the weekend.
However, based off soundings and ensemble guidance believe that if
any rain occurs it will be quite light. Have omitted slight chance
thunder that populated with NBM due to a notable mid level
inversion. Cooler temperatures are also expected as H5 heights fall
to near 570dam.

&&

.AVIATION...
(12Z TAFS)
Issued at 632 AM EDT Mon Jun 3 2024

VFR conditions expected through the period except for a TEMPO
MVFR at TRI late in the period for fog. There will likely be few
isolated showers and storms around through the day but not enough
coverage to include VCTS. Winds will remain light and less than
10kts, generally out of the south at CHA and southwest at TYS and
TRI.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             87  67  85  69 /  10  10  50  40
Knoxville McGhee Tyson Airport, TN  84  64  85  67 /  20  10  50  40
Oak Ridge, TN                       84  64  85  67 /  10  10  50  30
Tri Cities Airport, TN              82  61  85  64 /  20  10  30  30

&&

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

$$

SHORT TERM...
LONG TERM....KRS
AVIATION...