599
FXUS64 KHUN 151648
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1148 AM CDT Wed May 15 2024

...New AVIATION...

.NEAR TERM...
(Rest of Today)
Issued at 857 AM CDT Wed May 15 2024

As a trailing sfc low moves through the TN Valley, lingering
instability may result in a low chance of showers/storms (30% or
less) through NE AL and southern middle TN during the late morning
hours into the afternoon. No severe weather is expected, however,
a low chance of lightning exists. Any rain that forms should
subside by the evening hours as upper level ridging moves in from
the west, bringing dry air to the area. Otherwise, temperatures
today are forecast to reach the upper 70s under broken to
scattered cloud cover this afternoon with WNW winds around 10-15
mph.

&&

.SHORT TERM...
(Tonight through Friday night)
Issued at 348 AM CDT Wed May 15 2024

Under mostly clear to partly cloudy skies tonight, a break from
showers is expected. Lows should cool to around 60. W-NW winds of
5-10 mph should keep the lower atmosphere sufficiently mixed to
hamper fog formation. The "dry" spell continues Thu, with highs
rising into the mid 80s with light winds.

The dry period will come to an end Thu night, as yet another storm
system nears, and clouds increase from west to east. Shower and
thunderstorm chances also return mainly after midnight. This next
system will bring high chances of showers with isolated to
scattered thunderstorms on Fri. A bit cooler with highs in the
upper 70s. Of interest is a strong return of lower level moisture
to the region. The 00Z NAM in particular brings higher levels of
moisture and instability in a rather highly sheared environment.
Forecast soundings from this model look somewhat ominous far as
strong convection is concerned. The other models had decent winds
but lesser lower moisture return, with the ECMWF and Canadian
suggesting this moisture could be intercepted by convection to our
south (like with the system that just departed). This said, some
storms in this sheared environment could become strong to severe,
with damaging wind gusts the main threat. Storm relative helicity
values on Fri time range in the 200-300 m/sec, while CAPE values
were from the single digits to around 300 J/kg from the ECMWF and
Canadian. The NAM was showing CAPES over 2000 in comparison.
Shower and storm chances should continue Fri night with lows in
the mid 60s.

&&

.LONG TERM...
(Saturday through Tuesday)
Issued at 348 AM CDT Wed May 15 2024

To start the long term, an upper shortwave trough is expected to
traverse the Mississippi and Tennessee Valleys on Saturday. However,
there remains disagreement in the model guidance with regards to
timing and evolution of the trough. Once this feature moves east of
the area (Sunday morning), upper ridging looks to take hold and
persist through early next week. Although, a shortwave may sweep over
the Midwest and over the Ohio Valley on Monday. At the surface, a
low pressure system is shown to move over the lower Ohio Valley and
Tennessee Valley Saturday morning, with northern Alabama and southern
middle Tennessee in the warm sector. Anticipating this low to
continue eastward and move over Virginia and North Carolina by Sunday
morning, with high pressure building in behind it over our area for
Monday. This high pressure will then begin to shift east on Tuesday,
ushering moisture into the region with return flow.

Looking at thunderstorm potential, guidance varies a bit with bulk
shear and instability Saturday morning. But, values look to be at
least 40 knots with around 500-700 J/kg. 0-3 km SRH values also range
between 100-150 m2/s2 in the morning and into the afternoon. This,
the trajectory of the surface low, and potentially a LLJ around 40-50
knots moving over the Tennessee Valley Saturday morning increases
confidence in the potential for strong to possibly severe storms
Saturday morning and into Saturday afternoon. The main question is
with the timing of this system through the area. If it`s later
(afternoon hours), then there will be more time for warming which
would lead to more instability and high potential for severe. If it`s
earlier (morning hours), there may not be as much instability for
storms to tap into (especially with showers/storms possible Friday
night) and perhaps less of a severe threat. Although, that`s not to
say we can`t have strong to severe storms in the morning. Ultimately,
we`ll be monitoring this system and trends closely over the coming
days with subsequent model runs to better determine any severe
potential.

For sensible weather, expect medium to high chances (50-70%) of
showers and storms on Saturday. These could at least bring gusty
winds, frequent lightning, and heavy downpours. As was mentioned
previously, we`ll continue to analyze trends for the potential for
any severe weather. At this point, chances of showers and storms
dwindle from west to east in the evening, but timing could change a
bit in subsequent forecast updates. Sunday will then be mostly dry,
but some spots over the far northeastern portion of Alabama and
southern middle Tennessee could see a few showers/storms in the
afternoon. With an upper level shortwave moving over the Ohio Valley
on Monday (mentioned above), low chances (15-20%) of showers and
possibly a storm are forecast Monday evening and overnight. Low
chances (15-20%) of showers/storms are then possible on Tuesday.

Temperatures will be on the rise through Tuesday. Highs Saturday
afternoon are expected to top out in the upper 70s to lower 80s due
to the higher coverage of clouds and precipitation. Highs Tuesday are
then slated to reach the mid to upper 80s! As for low temperatures,
values will generally remain in the lower to mid 60s each night.

&&

.AVIATION...
(18Z TAFS)
Issued at 1148 AM CDT Wed May 15 2024

Current MVFR conditions are forecast to become VFR as broken
cloud cover becomes scattered into the afternoon hours. Winds are
forecast to continue gusting from the WNW around 15-17 kts this
afternoon, but should subside this evening. Overnight, as winds
calm and skies clear, a low chance of patchy fog is possible. This
has not been officially added to the TAF package at this time due
to low confidence, however, it may be added in future updates.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...None.
TN...None.
&&

$$

NEAR TERM...HC
SHORT TERM....RSB
LONG TERM....26
AVIATION...HC