223
FXUS64 KHUN 160856
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
356 AM CDT Fri Aug 16 2024

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

.NEAR TERM...
(Today)
Issued at 357 AM CDT Fri Aug 16 2024

A storm system continues to affect central and eastern portions
of the U.S. CONUS this morning. The parent low of this system is
centered over north central portions of Minnesota with frontal
boundaries extending into the Ohio Valley and Oklahoma/Texas.
Several disturbances have been producing areas of convection along
or ahead of these boundaries this evening. The most intense area
of convection currently is developing over southern Missouri. The
evolution of this disturbance and convection/cloud cover associated
with it will be the primary driver of conditions today.

Mainly westerly 0-6 km flow suggests that most of the energy
associated with this disturbance will move through northern
Tennessee and southern Kentucky than further south. However, by
the mid afternoon hours, plenty of instability will be in place
over northern Alabama and southern middle Tennessee. Also, 25 to
30 knots of shear (30 knots mainly in our southern middle TN
counties) does develop along/ahead of the convergence boundary
that extends SSW from this disturbance aloft. With DCAPE values
forecast to be between 1000 and 1400 J/KG and low level lapse
rates between 6.5 and 7.0 degrees, strong along with a few severe
storms look possible. Convection may be a bit more organized in
our southern middle Tennessee counties. The main threats with this
activity will be heavy rainfall, frequent lightning, and damaging
winds.

Timing though is tricky, but based on current radar and
observations given the expected mean flow, expect any stronger
convection to develop between 2 and 4 pm in southern middle
Tennessee. Further south, likely closer to between 4 PM and 6 PM.

Despite increasing cloud cover later this afternoon and the
convection expected, temperatures will likely climb into the mid
to upper 90s (925 mb temperatures 27 to 30 degrees depending on
the model) this afternoon, mainly in northern Alabama. Though
mixing of drier air aloft will occur this afternoon in northern
Alabama, dewpoints may remain between 71 and 76 degrees in
southern middle Tennessee and portions of NE Alabama. This will
likely keep apparent temperatures up just enough to warrant
continuing the current Heat Advisory that is in effect from 11 AM
through 5 PM CDT today.

&&

.SHORT TERM...
(Tonight through Saturday night)
Issued at 357 AM CDT Fri Aug 16 2024

This activity will likely push east of the area after 9 or 10 PM
and dissipate. The highest and better chance of showers and
strongest thunderstorms looks to be near and east of the I-65
corridor into southern middle Tennessee. Temperatures will still
be rather warm when you wake up on Saturday morning (68-73
degrees) given expected cloud cover. Highs look like they will be
hard pressed to climb above the 90 to 94 degree range. This
should keep heat index values at bay. They could briefly hit 105
degrees for an hour, but not long enough to entertain another
Heat Advisory yet.

The actual cold front associated with this storm system doesn`t
really move much on Saturday. Additional disturbances move either
ESE or SE along the front Saturday into Saturday night. Just how
they move will have a big impact on the forecast on Saturday. For
now, going with the clustering of most guidance, which moves
another disturbance east from southwestern Missouri into the area
on Saturday. This appears like it could be more widespread
coverage of showers and thunderstorms on Saturday afternoon into
Saturday night in northwestern Alabama. Shear will be strong with
more widespread shear of 35 to 40 knots shown in most models over
the area. However, due to more prevalent cloud cover with
showers/convection likely starting a bit sooner by the late
morning/early afternoon, instability and lapse rates don`t look as
good as on Friday. Despite this, there will still be enough
instability (1000-2000 J/KG) for at least marginally severe storms
to occur. Main threat again will be damaging winds, frequent
lighting, and heavy rainfall.

&&

.LONG TERM...
(Sunday through Thursday)
Issued at 357 AM CDT Fri Aug 16 2024

Consensus guidance from the 16/00Z suite of global models suggests
that a mid-level longwave trough will become established across
eastern North America early in the period, with moderately strong NNW
flow aloft predicted to remain in place across the TN Valley through
the middle of next week. At the surface, an area of low pressure
will shift east-northeastward across southern Quebec and into western
New England on Sunday/Sunday night, with the trailing cold front
expected to cross the CWFA at some point Sunday afternoon. Thus, a
low-medium (20-40%) chance for showers and a few thunderstorms has
been maintained in the grids through late Sunday morning. Although
some wrap-around stratus clouds may impact the northeastern portion
of the region on Sunday night/Monday (in the wake of the departing
cyclone), probabilities for any light rain showers or sprinkles
remain very low (5-10%). Light-moderate N-NE flow will advect a
cooler/drier continental airmass southward early next week, with
highs falling into the m-u 80s for most of the region beginning
Monday, and lows dropping into the u50s-l60s Tuesday morning (and
perhaps m-u 50s Wednesday morning). Present indications are that low-
level ESE flow will return Wednesday night as a subtle surface trough
retrogrades westward across the region, and this will allow for a
minor increase in both low-level moisture and chances for showers on
Thursday.

&&

.AVIATION...
(06Z TAFS)
Issued at 1226 AM CDT Fri Aug 16 2024

VFR conditions are expected at both terminals through much of the
TAF period. A low chance of -TSRA is possible after 16Z at both
terminals, however due to uncertainty at KMSL only included VCTS.
Winds will turn to the WSW around 10 knots with some gusts to
around 16 knots possible after 16Z at both terminals. At KHSV
though, expect enough coverage to warrant a tempo group for -TSRA
between 20Z and 24Z. During this period, MVFR VSBYS or CIGS could
occur.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Heat Advisory from 11 AM this morning to 5 PM CDT this afternoon
     for ALZ001>007-016.

TN...Heat Advisory from 11 AM this morning to 5 PM CDT this afternoon
     for TNZ096.

&&

$$

NEAR TERM...KTW
SHORT TERM....KTW
LONG TERM....70/DD
AVIATION...KTW