405
FXUS64 KHUN 130921
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
421 AM CDT Thu Jun 13 2024

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

.NEAR TERM...
(Today)
Issued at 421 AM CDT Thu Jun 13 2024

A mid-level trough (initially centered across the Lower MS
Valley) will spread southeastward into the northern Gulf of Mexico
today, with northerly flow aloft across our region expected to
strengthen due to increasing influence from a strong subtropical
high over northern Mexico and the southern Rockies. At the
surface, a weak area of low pressure along the northeast Gulf
Coast (related to the mid-level trough) will retrograde slowly
westward over the course of the day, with lift in the vicinity of
a subtle trough extending northeastward from the low currently
supporting the development of mid-level stratus clouds across
northwestern GA/northeastern AL. Strong diurnal warming of the
boundary layer and dewpoints recovering into the l-m 60s may be
sufficient to initiate a few showers and perhaps a thunderstorm or
two in the vicinity of the surface trough in the 16-22Z
timeframe, and for this reason we have included a slight chance
POP across portions of northeast AL. The remainder of the CWFA
should experience mostly sunny and dry conditions, with afternoon
temps in the u80s-l90s.

&&

.SHORT TERM...
(Tonight through Saturday night)
Issued at 421 AM CDT Thu Jun 13 2024

NWP model consensus indicates that the strong 500-mb subtropical
ridge (discussed above) will build progressively eastward,
becoming centered directly across the TN Valley by Saturday night,
and providing an increasingly favorable environment for hot/dry
conditions. At the surface, a cold front (attached to an area of
low pressure ejecting northeastward across Quebec) will shift
southeastward into the OH Valley by 12Z Friday accompanied by a
weakening band of convection that may result in an increase in
cirrus debris clouds prior to sunrise. Although diurnal
redevelopment of showers and thunderstorms will be possible along
the length of the front on Friday afternoon/evening, present
indications are that this activity will remain north of the I-40
corridor in Middle TN. A frontal wind shift to NE will arrive in
our CWFA Friday evening as the center of a modified Canadian
airmass spreads eastward through the Great Lakes, and should lie
to our immediate southwest on Saturday/Saturday night. However,
cooler/drier air will remain displaced well to our north/east, and
with a narrow axis of dewpoints in the u60s-l70s expected to pool
in the vicinity of the boundary, heat index readings will climb
above 100F across the southwestern half of the region Saturday
afternoon as temps warm into the m-u 90s. As a result of the
increase in low-level moisture, lows will also warm into the lower
70s for most locations Friday and Saturday nights.

&&

.LONG TERM...
(Sunday through Wednesday)
Issued at 421 AM CDT Thu Jun 13 2024

The center of the subtropical ridge is predicted to begin
shifting slowly northeastward and away from the TN Valley on
Sunday, becoming centered across western portions of VA/NC by
Monday. This (along with a surface ridge migrating eastward off
the coast of New England) will result in a gradual increase in
deep-layer SSE flow and atmospheric moisture content, which should
support a minor increase in the coverage of diurnal showers and
thunderstorms early next week. Although some deterministic and
ensemble guidance indicates that this could occur as early as
Sunday afternoon/evening, it currently appears as if our best
opportunity for rainfall will be Monday afternoon/evening.
Afternoon temperatures will peak in the upper 90s for many
locations on Sunday (with a 100F reading or two possible), but it
still appears as if heat index readings will be slightly below
advisory criteria. Highs are currently expected to be several
degrees cooler on Monday due to clouds and precip, but if this
does not materialize, temps will need to be increased.

During the period from Tuesday-Wednesday, global models suggest
that our deep-layer SSE flow regime will be disrupted by a
developing area of low pressure over the southwestern Gulf/Bay of
Campeche, and with more of an influence from the Bermuda ridge to
our east, we expect hot/dry conditions to return. Fortunately, it
appears as if the westward advection of a drier airmass into the
region will limit heat index readings in this regime. Strong
warming of lower-levels from Wednesday onward will likely support
development of afternoon thunderstorms in regions of enhanced
orographic ascent across the central/southern Appalachians on a
daily basis, and with deep easterly flow predicted to the south of
the subtropical high, some of this activity may eventually spill
into northeast AL. However, we have maintained a dry forecast at
this point.

&&

.AVIATION...
(06Z TAFS)
Issued at 1237 AM CDT Thu Jun 13 2024

VFR conditions are expected through much of the TAF period at
KMSL. Some fog could develop at KMSL between 10Z and 12Z dropping
VSBYS at times during that period into the MVFR realm. A bit more
cloud cover (VFR) should keep fog from forming at KHSV given
current dewpoint depression.

&&

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

&&

$$

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