017
FXUS64 KHUN 021926
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
226 PM CDT Tue Jul 2 2024

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

.NEAR TERM...
(Remainder of today and tonight)
Issued at 226 PM CDT Tue Jul 2 2024

Aside from making a slight downward adjustment to high
temperatures this afternoon, we have made no significant changes
to the forecast for the rest of the day since the previous update
this morning. Overnight, we expect a moderately strong SSE flow
regime in the lower troposphere to persist across the region, due
to a contracted pressure gradient between a ridge of high pressure
spanning much of the Eastern Seaboard and a decaying surface low
that will progress northeastward into the western Great Lakes in
conjunction with the motion of a northern stream shortwave trough
across Manitoba/Ontario. Although forecast soundings depict
partial clearing of the stratus layer this evening, low clouds
will likely return to much of the TN Valley prior to sunrise on
Wednesday, and this along with slightly elevated winds and a
gradual increase in dewpoints will support warmer lows ranging
from the u60s-l70s (E) to m70s (W).

&&

.SHORT TERM...
(Wednesday through Friday night)
Issued at 226 PM CDT Tue Jul 2 2024

During the period from Wednesday-Wednesday night, global models
depict a broad subtropical ridge in the mid-levels to extend from
the northwest Gulf Coast to the southeastern Atlantic Coast.
Although the amplitude of the ridge will likely begin to decrease
as early as tonight in response to the northeastward motion of the
shortwave trough (discussed above), synoptic scale subsidence
provided by the anticyclone will result in a pronounced capping
inversion that should remain intact for much of the period. In the
low-levels, a ridge axis is predicted to lie across the northern
Gulf of Mexico, which will translate to lighter S-SW flow across
our region to the south of a cold front that will drift
southeastward before stalling north of the OH River. A few showers
and thunderstorms will be possible (mainly across the
southwestern portion of the CWFA) tomorrow afternoon as strong
warming of the increasingly moist boundary layer is anticipated
after morning stratus clouds erode, with a low probability for
convection along and north of the AL-TN border on Wednesday night
(perhaps initiated by outflow from extensive frontal convection to
our northwest). High temperatures are expected to return to the
l-m 90s for most of the region tomorrow, and this coupled with
dewpoints in the l-m 70s (highest in the west) will yield apparent
temps near or slightly in excess of Heat Advisory criteria for
all but the higher terrain of northeast AL/southern Middle TN.

The general orientation and strength of the subtropical ridge is
not predicted to change much during the Thursday-Thursday night
timeframe. However, a lower-latitude shortwave trough digging
southeastward across the northern Plains will likely begin to
initiate subtle height falls across our region, which should erode
the subsidence inversion in conjunction with strong heating of
the surface layer. This alone will support a slightly higher
coverage of afternoon thunderstorms on Thursday, but northern
portions of the CWFA may also be clipped by the remnants of an MCS
that will initiate across NE/KS Wednesday evening and spread
east- southeastward reaching the southern Appalachians Thursday.
Although afternoon storms will diminish in coverage and intensity
during the evening, a second MCS is predicted to evolve across
eastern KS Thursday afternoon as another surface low begins to
lift northeastward through the central Plains, and this feature
may reach northwestern portions of the TN Valley prior to sunrise
Friday. The Heat Advisory will remain in effect on Thursday due to
similar temperatures/dewpoints and HI values once again in the
102-108F range for most of the region.

By Friday-Friday night, the subtropical ridge will become
suppressed to the south/east of the region (along the southeastern
Atlantic Coast), as the shortwave trough noted in the paragraph
above begins to lift northeastward into the Great Lakes. This will
support a more favorable environment for convection, with several
bands/clusters of showers and thunderstorms expected to spread
eastward across the warm/moist sector to the southeast of a slow-
moving cold front. West-southwesterly flow aloft will increase to
20-25 knots supporting faster storm motions, and POPs have been
increased to 70-80% on Friday and Friday night. Although the
current forecast depicts HI values that warrant continuation of
the Heat Advisory through Friday afternoon, this portion of the
forecast is highly uncertain due to potential impacts from
clouds/precipitation early in the day.

&&

.LONG TERM...
(Saturday through Monday)
Issued at 250 AM CDT Tue Jul 2 2024

The boundary will slowly sag south through the area into central
Alabama by Saturday. However, since it will remain in the vicinity
of the area medium chances for showers/storms (40-60%) will
remain in the forecast for Saturday. Cloud cover will help to keep
temperatures just a few degrees lower, likely keeping heat
indices below Advisory criteria. With the boundary to our south
Sunday and Monday, much lower chances for showers/storms are
forecast (10-20%) with highs remaining near normal in the lower
90s. The combination of these lower temperatures and dewpoints
should keep peak heat index values below 100 degrees through
Monday.

&&

.AVIATION...
(18Z TAFS)
Issued at 1154 AM CDT Tue Jul 2 2024

Low stratus clouds (within a moderately strong SSE flow regime)
persist across the eastern half of northern AL late this morning,
with latest satellite data indicating that the clouds are slowly
spreading west-northwestward toward MSL. Although cigs may remain
in the MVFR category for another 1-2 hours at HSV, deeper mixing
this aftn should promote scattering and gradual lifting of the
cloud layer, and we will advertise VFR conditions at the beginning
of the TAF. Forecast soundings suggest that skies will partially
clear around sunset, but that lower stratus will return between
Midnight and sunrise on Wednesday. Periods of MVFR cigs will be
possible at both terminals btwn 11-15Z, but this has not been
indicated in the official forecast attm. Sfc winds will remain
from SSE at 8G16 kts this aftn, but should weaken to 5-10 kts
around sunset and veer to SW after 12Z Wednesday.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...

AL...Heat Advisory from 1 PM Wednesday to 7 PM CDT Friday for
     ALZ001>010-016.

TN...Heat Advisory from 1 PM Wednesday to 7 PM CDT Friday for TNZ076-
     096-097.

&&

$$

NEAR TERM...70/DD
SHORT TERM...70/DD
LONG TERM...AMP.24
AVIATION...70/DD