Hollytree, Alabama Weather Forecast Discussion

984
FXUS64 KHUN 211946
AFDHUN
Area Forecast Discussion
National Weather Service Huntsville AL
246 PM CDT Sun Sep 21 2025
...New NEAR TERM...
.NEAR TERM...
(Tonight)
Issued at 246 PM CDT Sun Sep 21 2025
The previous forecast mostly remains on track except
showers/thunderstorms have formed earlier than anticipated and
PoPs have been updated to reflect that. Lightning and moderately
heavy rainfall continue to be the primary threats, however, gusty
winds up to 30-40 mph will still be possible. If you have outdoor
plans this evening, be sure to remain weather aware and if thunder
roars, go indoors!
Previous Discussion:
Patchy fog that was impacting some portions of NW AL this morning
has since dissipated as sunshine has increased. Dry conditions are
forecast to continue this morning before rain chances increase
this afternoon under the influence of an upper level shortwave
pushing in from the west. The latest CAM solutions agree on
thunderstorm activity forming between 21-22Z throughout primarily
the I-65 corridor. Instability throughout the Tennessee Valley is
forecast to be in the 800-1200 J/kg range with meager shear
(around 10-15 kts) in addition to steep low level lapse rates (8-9
C/km). Threats with storms will include frequent lightning,
moderately heavy rainfall, and gusty winds up to 40-50 mph. If a
storm over performs, there is a low chance that a severe warning
could be issued. However, widespread severe weather is not
anticipated. These storms should progress ENE into the evening
hours, gradually decreasing in coverage and strength around
sunset.
While a few showers could linger overnight, thunderstorms are not
expected. Mostly dry weather will resume across the area with
cloudy skies. Cloud cover should dissuade widespread fog
formation. Low temperatures are forecast to drop into the mid 60s.
&&
.SHORT TERM...
(Monday through Tuesday night)
Issued at 1022 AM CDT Sun Sep 21 2025
Starting the work week, an upper level trough stretches from the
Great Lakes region southward into the lower Mississippi Valley.
Ahead of this trough, southerly winds will allow an increase in
moisture throughout the Tennessee Valley- fueling additional
chances (20-50%) of showers and thunderstorms, with the greatest
chances remaining north of the Tennessee River. Similar to recent
events, instability and steep low level lapse rates continue to
look favorable for potential strong storms with gusty winds and
frequent lightning as the primary threats. Weak shear should
prevent widespread severe thunderstorms. However, as we`ve seen
the past few days with the assistance of diurnal heating, a
couple storms may be capable of over performing to produce severe,
damaging winds (~60mph). The Storm Prediction Center has clipped
portions of the area both Monday and Tuesday in a Marginal risk
(level 1 of 5) for severe thunderstorm development. Storms should
primarily impact the area during the afternoon into evening
hours, with mostly dry conditions forecast overnight as storms
decrease in coverage around sunset. Highs during this time are
forecast to reach the upper 80s to lower 90s, which is 5-10
degrees above normal for this time of year. Overnight lows are
forecast to drop into the mid 60s.
&&
.LONG TERM...
(Wednesday through Saturday)
Issued at 959 PM CDT Sat Sep 20 2025
Global models are in agreement in depicting a strengthening mid-
level trough (with an increasing negative-tilt) to track across the
east-central Plains and into the Mid-MS Valley on Wednesday/Wednesday
night. As this occurs, a deepening surface low will shift from the
Ozarks into the Lower OH Valley, with potential development of a
secondary wave to the south of the primary cyclone (across
southeastern AR/northwestern MS). As a 20-30 knot southwesterly low-
level jet (ahead of this system) gradually becomes more established
across the TN Valley throughout the day, scattered convection is
likely to develop within the increasingly moist airmass (highlighted
by a plume of dewpoints in the u60s-l70s).
Coverage of showers and thunderstorms within the open warm sector
across our region will begin to increase early Wednesday evening and
should remain rather high through Thursday morning. With CAPE
expected to remain sufficiently high overnight to support
thunderstorms, we will need to watch this timeframe very closely for
a risk of severe weather, as WSW flow in the mid-levels will
progressively strengthen into the 40-50 knot range creating a
favorable kinematic environment for organized multicell clusters and
perhaps even a few supercells. At the present time, the magnitude of
the low-level jet appears only marginally conducive for weak
mesocyclone development, but trends in this parameter will need to be
monitored as any increase would yield at least a low-end risk for
tornadoes in addition to damaging winds. With a moist/tropical
airmass expected to be in place (featuring PWAT values in the 1.8-2"
range), locally heavy rainfall and flash flooding will also be a
concern as indicated in the Day 5 ERO from the NWS Weather Prediction
Center.
During the period from Thursday-Saturday, the surface low is
predicted to advance northeastward through the OH Valley before
slowly decaying over the central Appalachians. A surface trough and
cold front attached to the low may initiate additional showers and
storms on Thursday as they track across our forecast area, and
although shear profiles will remain favorable for storm organization,
instability will be uncertain in the wake of nocturnal
precipitation. Light-moderate NNW flow in the low-levels will begin
to advect a slightly drier continental airmass into the region
following frontal passage, but due to the slow movement of the mid-
level low, periods of low clouds and showers may occur from Thursday
nigt-Saturday (mainly across the northeastern portion of the CWFA).
Highs will fall back into the u70s-l80s, with lows likewise dropping
into the u50s-l60s.
&&
.AVIATION...
(18Z TAFS)
Issued at 1159 AM CDT Sun Sep 21 2025
While VFR conditions are forecast to prevail through most of the
forecast period, afternoon showers and thunderstorms will
potentially cause MVFR conditions today. There is higher
confidence in this occurring at KHSV rather than KMSL as coverage
looks to be limited primarily to the I-65 corridor and eastward.
However, amendments may be needed if thunderstorms begin to form
in NW AL to add a vicinity group to KMSL.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...None.
TN...None.
&&
$$
NEAR TERM...HC
SHORT TERM....HC
LONG TERM....70
AVIATION...HC

NWS HUN Office Area Forecast Discussion