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

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS64 KMRX 291929
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
329 PM EDT Fri Mar 29 2024

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

.SHORT TERM...
(This evening through Saturday)
Issued at 325 PM EDT Fri Mar 29 2024

A warmer and mostly sunny day across the forecast area. Winds
have been strongest in the northeast, closest to upper trough
that is exiting to the east and where pressure difference is
greatest between trough to the northeast and surface high over the
inland southeast US. Relative humidity values are mostly 25 to 30
percent with winds westerly 10 to 15 mph and gusts to 25 mph and
up to 30 mph in a few locations. Temperatures are warmer than
Thursday in the mid 60s to lower 70s at mid afternoon.

For tonight and Friday expect a gradual decrease in winds this
evening and then some clouds tonight as a weak shortwave moves
through the Ohio Valley tonight and early Friday which will
increase moisture over the Tennessee Valley tonight. This and
ridging aloft moving into the region will keep some southwest to
west wind flow going overnight and combined with some cloud cover
and warmer temperatures today lows will be mostly in the 40s with
a few sheltered valleys in the upper 30s. Do not expect any frost
early Friday. During the day Friday the weak system to the north
will move to the east coast by evening. Ridging aloft will keep
the region warmer with variable cloud cover north and mostly sunny
conditions south. Expect gusty west to southwest winds to occur
again like today but over more of the region and gusts up to 30
mph in the afternoon. High temperatures will be near 70 northeast
to mid and possibly upper 70s southwest.

&&

.LONG TERM...
(Saturday night through next Friday)
Issued at 325 PM EDT Fri Mar 29 2024

|Key Messages:

1. Above normal temperatures Sunday and Monday, with low rain
chances in SW VA near a stalled front.

2. A strong low pressure system will bring numerous showers and
possibly some strong to severe thunderstorms on Tuesday, mainly
afternoon/evening.

3. Cooler temperatures behind a cold front for Wednesday and
Thursday, with higher elevations potentially having a light
rain/snow mix.

Discussion:

A large high pressure ridge will extend from the Bahamas across FL
and the GoM, putting our area in a generally zonal flow pattern. A
front will be stalled E-W in the OH Valley region to our north, and
this will be the focus of precip with isentropic lift and weak
midlevel disturbances embedded in the zonal flow. Most activity
will stay north of our area, but the forecast will have just a low
to slight chance in SW VA on Sunday as the models have that area
on the southern edge of their QPF signals. As a low pressure
system develops in the lee of the Rockies on Monday, the pattern
becomes more amplified, and a southerly flow strengthens across
the region. The warm advection pattern will push highs into the
upper 70s to lower 80s Monday afternoon despite increasing cloud
cover.

Rain chances start to rise on Monday night ahead of the approaching
system, associated with upper divergence in the jet exit region and
a strengthening LLJ. Some elevated instability could bring a few
thunderstorms Monday night, but the instability ramps up and becomes
surface-based on Tuesday. This will be a very dynamic system, with
the GFS showing a 45-50 kt LLJ producing strong shear in the late
afternoon, along with decent instability from steep midlevel lapse
rates around 7.5 C/km and SBCAPE of 1500-2000 J/kg. The pattern
suggests a potential for severe storms, but much can change this far
out. Confidence is low on the details of what the main severe
threats might be, but hail/wind/tornado threats are all on the
table. Details of location of the greatest threat are also
uncertain, and much will depend on where upstream convection
develops on Monday and where it tracks as it moves east. There does
seem to be reasonably good model agreement on Tuesday
afternoon/evening timing for the best thunderstorm potential.

The pattern evolves into a cutoff low over New England and the Mid
Atlantic region on Wednesday, which will usher in a much colder air
mass into our area. Highs on Wednesday will only be in the 50s, with
a return of 30s for lows Wednesday night. A strong NW flow pattern
will continue into Thursday as the low is slow to progress east once
it moves offshore. Steep lapse rates under the low will result in
scattered showers Wednesday night and Thursday, mainly in the
northern sections where moisture depth will be better. Temperatures
in the higher elevations may support snow at times, with light
accumulations possible due to the upslope enhancement.

&&

.AVIATION...
(18Z TAFS)
Issued at 125 PM EDT Fri Mar 29 2024

Winds have increased at TRI with gusts to around 20 to 25 kts
expected next few hours. Elsewhere winds around 10kt at TYS and
KCHA being light and variable this afternoon. Clouds do not
increase until Saturday and they will be only high level type.
Saturday expect winds to increase again by late morning or
afternoon from the SW at 10 to 15 kt and gusts to 25 kts. CHA
winds will be slightly less than TRI and TYS.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             49  77  54  80 /   0   0   0   0
Knoxville McGhee Tyson Airport, TN  47  74  55  79 /   0   0   0   0
Oak Ridge, TN                       46  75  53  79 /   0   0   0   0
Tri Cities Airport, TN              38  71  53  76 /   0   0  10  10

&&

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

$$

SHORT TERM...TD
LONG TERM....DGS
AVIATION...TD


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.