-- Discussion containing changed information from previous version are highlighted. --
954
FXUS64 KMRX 010127 AAB
AFDMRX

Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
927 PM EDT Fri May 31 2024

...New UPDATE...

.UPDATE...
-- Changed Discussion --
Issued at 917 PM EDT Fri May 31 2024

No changes for the evening update. There`s a possibility that
overnight lows are a touch too warm in the north. This seems
reasonable given the slow spread of cirrus that direction.
However, clouds will indeed be increasing which lessens the
radiational cooling aspect, and the cooler guidance is lower by a
couple of degrees or so. Confidence is low for an insignificant
change in the grand scheme of things so will leave the forecast as
is. PoPs look to be in good shape still with respect to timing
tomorrow morning. All in all, no changes necessary.
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&&

.SHORT TERM...
(This evening through Saturday)
Issued at 319 PM EDT Fri May 31 2024

Key Messages:

1. Dry and mild conditions will continue through tonight.

2. Showers and isolated thunderstorms will arrive from the west by
mid-day Saturday.

This Evening/Tonight

Currently this afternoon, mid/upper-level ridging is overhead with a
shortwave located just west of the Mississippi River Valley. At the
surface, high pressure is centered to the north with a surface low
centered in Texas. High-level cirrus clouds have remained over the
area today, which has limited surface heating. Tonight, these clouds
will shift further east, along with upper-level ridging. As the
aforementioned shortwave approaches, additional clouds will arrive
from the west. Overall, this will lead to a fairly mild night with
little to no fog development.

Saturday

During the day on Saturday, high pressure will recede to the
northeast with fairly strong (35 to 40 kts) 850mb flow, especially
in western portions of the area. This will allow better moisture to
arrive from the west. Models differ on the timing, but the shortwave
to our west will arrive into the area by Saturday afternoon to
evening. This shortwave will provide lift for a return of rain
chances focused further west. Instability will be very limited to
250 J/kg or less, which may only be sufficient for isolated thunder,
especially if timing is earlier in the day. The increased activity
and cloud cover will keep temperatures fairly mild again.

&&

.LONG TERM...
(Saturday night through next Friday)
Issued at 319 PM EDT Fri May 31 2024

Key Messages:

1. Slightly below normal temperatures Sunday, with near to slightly
above normal temperatures next week.

2. There will be daily chances for showers and thunderstorms Monday
through Friday.  Best chances for thunderstorms will be Wednesday
and Thursday.

Discussion:

Saturday night, an upper level cutoff low will be off the northeast
Atlantic coast with short-wave ridging in place over the Mid
Atlantic states. A disturbance moving across the northern
states/southern Canada will induce development of a weak surface low
and shift across the Ohio Valley Saturday night and Sunday into
early next week.

A cold front crossing the Ohio Valley Monday Saturday night and
Sunday will result in higher chances of showers and perhaps a few
thunderstorms Saturday night into Sunday. Sunday night into Monday
there will still be a slight chance of showers and storms but the
front is expected to dissipate or weaken as it moves into the
forecast area. Higher pressure will stay off the southeast coast
with a southerly flow of moisture increasing and a more diurnal
trend in showers and thunderstorms. The same trend continues Tuesday.

The thermodynamic profiles and little upper level forcing will
develop general showers and thunderstorms. The NAM, which is often
times the most aggressive with instability has surface CAPE values
at around 500 to 1500 J/kg. Sunday and Monday between 18Z and 00Z.
On Tuesday through through Thursday a front will be to the west and
with the southerly flow and shortwave energy moving east there will
be a chance of showers and thunderstorms. The strongest shortwave
looks to move through on Wednesday so it may have the highest
chances afternoon and early evening. Thursday night into early
Friday another weak front pushes through so rain chances will still
be high Thursday afternoon into the evening. Friday still have a
chance of showers and storms. High temperatures will be in the lower
to mid 80s Monday and warm to the mid to upper 80s Tuesday to
Thursday cooling slightly behind the cold front Friday. Rainfall
amounts do not look that excessive now but will have to watch trends
in the last few days

&&

.AVIATION...
(00Z TAFS)
Issued at 754 PM EDT Fri May 31 2024

VFR conditions prevail at all terminals through daybreak or so.
Afterwards, SHRA will be moving northeast out of Alabama towards
the KCHA vicinity. Guidance shows those showers slowing as the
morning progresses, but expect prevailing SHRA with MVFR CIGS by
the early to mid afternoon hours there. Not confident enough in
how much thunder there will be so kept that out for now. Further
north, it`s unlikely that KTRI will see any rain or lowering CIGS
before the end of the 00z period, and it`s possible KTYS doesn`t
either so will stick with VCSH there. There will be some downslope
flow off the mountains tomorrow, so winds at KTYS may be variable
in direction from mid morning through the mid afternoon hours
before they pick up a steady southwesterly flow up the valley.

&&

.PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN             82  64  77  64 /   0  10  40  60
Knoxville McGhee Tyson Airport, TN  75  58  78  62 /   0   0  20  50
Oak Ridge, TN                       76  57  76  60 /   0   0  30  50
Tri Cities Airport, TN              79  51  78  59 /   0   0  10  30
-- End Changed Discussion --

&&

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

$$

SHORT TERM...BW
LONG TERM....TD
AVIATION...CD