-- Discussion containing changed information from previous version are highlighted. --
521
FXUS64 KMRX 250530
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
130 AM EDT Sat May 25 2024

...New AVIATION...

.UPDATE...
Issued at 1055 PM EDT Fri May 24 2024

No major updates tonight with low PoPs expected overnight as a
weak shortwave/MCV near the Cumberland Plateau moves eastward. A
few scattered showers and thunderstorms will be possible, but most
areas remain dry tonight.

The complex of showers and thunderstorms across MO/IL/IN is
expected to move southeastward tonight and arrive in our area
early Saturday morning around 12-14z. At this time, no severe
convection is expected with less instability overnight, but some
gusty winds, heavy rain, and frequent lightning will be possible.

JB

&&

.SHORT TERM...
(This evening through Saturday)
Issued at 314 PM EDT Fri May 24 2024

Key Messages:

1. Some showers and thunderstorms in the southern TN Valley and SW
NC through the evening.

2. Upstream MCS remnants may affect the area Saturday morning, but
confidence is low.

Discussion:

Storms have begun to develop in N GA where surface heating has been
occurring, near the outflow boundary from morning convection and
ahead of a weak shortwave trough. This activity will slowly track
E- NE, mainly affecting the TN border counties and SW NC. Outflow
from these storm may initiate new storms farther north into the
central Valley through the evening. Severe storms are unlikely as
shear decreases north of GA and cirrus has been limiting
instability. The shortwave trough exits to the east by 06Z, and
storms should dissipate by that time.

Convection over MO/IL this afternoon is expected to merge into a MCS
that will propagate SE through the evening. Models differ on how
well it will hold together during this journey, with the HRRR being
the strongest as it enters our area around 09-12Z. A severe threat
seems unlikely given this overnight timing and the weak wind profile
ahead of it - the stronger storms with it may stay well to our west.
The forecast will bring increasing PoPs to the Plateau around
sunrise, spreading eastward through the morning, but only in the
chance range for now as CAMS do not agree. The chance of convective
development in the afternoon is uncertain as any morning precip will
likely work over the environment and suppress afternoon development.
Will keep some low/slight chance PoPs in the afternoon due to the
uncertainties with the morning system.

&&

.LONG TERM...
(Saturday night through next Friday)
Issued at 314 PM EDT Fri May 24 2024

Key Messages:

1. Evening showers and storms Saturday then scattered activity
Sunday. Another round of showers and thunderstorms late Sunday
night into Memorial Day.

2. Some of the storms may be strong to severe Sunday night into
Monday morning. Localized flooding will also be possible Sunday
into Monday afternoon.

3. Drier and cooler weather expected to begin Tuesday night through
the end of next week. Only slight rain chances Tuesday during the
day and Wednesday afternoon into the evening northeast part of
the forecast area.

Discussion:

Saturday night after anticipated afternoon showers and storms
continue to dissipate skies will be partly cloudy with some patchy
fog and there will be a brief lull in convection. A weak cold front
will become nearly stationary to the north over the Ohio Valley.

Sunday with a front to the north and a deep low pressure area over
the central plains, the atmosphere will be moist and unstable out
ahead of the cold front. Shortwave energy also out ahead of this
front, south of the warm front and to the west and northwest of
the eastern Tennessee Valley will be triggering more convective
development overnight Saturday night and into the day Sunday. GFS
and European models showing scattered showers and storms
developing or moving in either in the morning or by early
afternoon. Right now storms don`t look to be severe and rainfall
amounts look to be lighter than the last couple days. Later Sunday
as the deep low moves northeast from the central Plains to Lake
Michigan and the Canadian border severe storms are likely to
develop across the western Great Lakes into the Ohio Valley Sunday
evening and then move southeast into Tennessee by around 06 to
12Z. The storms should weaken through time but pose a risk for
damaging winds and heavy rainfall. Rainfall amounts late Sunday
night and Monday morning could reach well over 1 inch and possibly
2 inches in a few spots. The northern plateau would
likely see the most rainfall. An isolated tornado or two could
occur within the anticipated line of storms. The timing of he
storms development to the northwest will affect the strength of
the system and the later development takes place the less intense
it might be as it approaches east Tennesse.

The showers and thunderstorms with the complex or line moving down
from the northwest should continue through at least Monday morning
and weaken as it moves far enough ahead of the main front in the
Ohio Valley. The frontal passage associated with this system will
still be over the Ohio Valley Monday morning. The front should
cross the forecast area Monday afternoon or early evening. NAM
model is also showing additional convection Monday afternoon and
early evening along the front so expect some more storms that
could be strong if the atmosphere can recover from the morning
storms. High temperatures Sunday and Monday will stay above normal
in the 80s each day but may reach 90 in the southern Valley
Sunday. Temperatures slightly cooler Monday.

From Tuesday onward as the upper trough settles over the region
there will be only a slight chance of showers early Tuesday in the
northeast and again Wednesday afternoon to early evening as
shortwaves move south through the NW flow. The deep upper trough may
even close off by the end of the week. From Tuesday through Friday
temperatures will be several degrees cooler with highs Wednesday and
Thursday only in the 70s to near 80 during the day and 50s at night
Wednesday through Friday mornings. Some locations in the northeast
will drop into the upper 40s. Skies will be partly cloudy to mostly
sunny during the day and mostly clear at night.

&&

.AVIATION...
-- Changed Discussion --
(06Z TAFS)
Issued at 119 AM EDT Sat May 25 2024

VFR conditions are expected this TAF cycle with the exception of
some possible fog near TRI this morning. A batch of rain may
develop or move into CHA this morning. Confidence is medium on
rain development and even lower on thunder, so left thunder out.
Showers may develop across the region at anytime today but
confidence is low on timing and activity if any will likely be
more isolated. So, showers/storms were left out for this afternoon
and evening.
-- End Changed Discussion --

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
Chattanooga Airport, TN             86  69  91  71 /  50  20  30  50
Knoxville McGhee Tyson Airport, TN  85  66  88  70 /  40  20  40  60
Oak Ridge, TN                       84  66  87  69 /  50  20  40  70
Tri Cities Airport, TN              85  62  85  66 /  30  20  40  50
-- End Changed Discussion --

&&

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

$$

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