689
FXUS64 KHUN 152356
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
656 PM CDT Wed May 15 2024

...New AVIATION...

.NEAR TERM...
(Tonight)
Issued at 115 PM CDT Wed May 15 2024

The mid/upper low will continue to shift eastward into the
Southern Appalachians and eventually the Carolinas this evening
and overnight as light showers taper off with the setting sun. The
end result will be clearing conditions from west to east as a
drier air mass filters into the region in wake of this system.
Subsequently, there will be a clearing sky and a decent setup for
radiational cooling as temperatures fall back into the mid/upper
50s. The clear/calm conditions and moist boundary layer from
earlier rainfall will create conditions favorable for patchy fog
late tonight into early Thursday morning -- especially in
sheltered valleys.

&&

.SHORT TERM...
(Thursday through Friday night)
Issued at 115 PM CDT Wed May 15 2024

A brief bout of ridging will take place on Thursday just prior to
the arrival of the next storm system. This will promote a mostly
sunny and very warm day as southerly winds help to reinforce this
air mass -- as highs will climb into the mid to upper 80s by the
afternoon. Although we will not be in the ballpark of heat related
products, those that are very sensitive/vulnerable to heat should
take an extra precaution if attending an outdoor event such as
graduations, sporting events, etc on Thursday afternoon/evening.

Things will change quickly by Friday and Friday night as the next
storm system swings into the Deep South, bringing very high
(70-90%) chances for showers/storms -- and potential for a few
strong to marginally severe storms depending on how the
environment evolves. Guidance continues to indicate a fairly
robust MCS along the northern Gulf Coast of MS/AL/FL during the
morning hours -- which will likely keep us "cut-off" from the more
favorable instability and air mass well to our south. However,
later in the afternoon and evening, this activity along the AL/FL
coast should have shifted well east into the Big Bend/Peninsula
region of Florida. As a result, southerly flow may help to recover
our air mass from earlier showers/elevated storms in the morning.
An additional round of showers and storms may develop along the
cold front sometime during the late afternoon/evening or even into
portions of the overnight hours Friday night. If morning
convection can wane quickly and air mass recovery can be realized,
a severe threat (mainly damaging winds and small hail) may evolve
during the afternoon/evening. However, there is still a decent
amount of spread between the solutions and for now the threat
remains at Marginal (1/5) per the latest SPC Day 3 Outlook.
Additionally, locally heavy rainfall and a low chance for
localized flooding concerns may also be a threat, especially if
training occurs.

&&

.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...
(00Z TAFS)
Issued at 656 PM CDT Wed May 15 2024

Wrap-around showers within the circulation around a decaying area
of low pressure across the central Appalachians will continue to
spread northeastward this evening, with a sct Cu field across the
local area expected to dissipate by 3Z. Aside from a few mid and
high-lvl clouds, mostly clear skies overnight will promote the
development of BR/FG as the boundary layer remains moist and winds
will be nearly calm with a ridge of sfc high pressure nosing into
our region from the north. Although we have included a TEMPO
group for MVFR vsby reductions at both terminals btwn 9-13Z, fog
may develop earlier than indicated and could become locally dense
(producing LIFR vsby) within the timeframe of the TEMPO. VFR conds
will return by 15Z (if not sooner), with lgt/vrbl flow
transitioning to a lgt SE wind by mid-afternoon.

&&

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

&&

$$

NEAR TERM...AMP
SHORT TERM...AMP
LONG TERM...26
AVIATION...70/DD