356
FXUS64 KHUN 171041
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
541 AM CDT Sat May 17 2025

...New AVIATION...

.NEAR TERM...
(Early this morning through this afternoon)
Issued at 258 AM CDT Sat May 17 2025

There have been no significant changes to near term forecast
reasoning since the update late yesterday evening. Clusters of
strong-severe thunderstorms will continue to spread east-
southeastward across the CWFA through the remainder of the early
morning hours, likely exiting the region between 10-12Z. Lingering
light rain will end across our southeastern counties between
12-15Z, with mostly sunny, warm and dry conditions anticipated for
the rest of the day (featuring highs in the m-u 80s).

Previous Discussion:
An occluding surface low (initially drifting westward across
west-central MN) will continue to weaken as it accelerates
eastward into the Upper Great Lakes overnight in conjunction with
a filling cyclone aloft that will spread east-southeastward into
the Central Great Lakes. As this occurs, a dryline (which
initiated cellular convection earlier today to our northwest) will
be overtaken by the synoptic cold front, with the effective
moisture gradient boundary predicted to extend from central OH
southwestward into the Arklatex vicinity by 12Z. Current radar
data suggests that earlier supercells have now congealed into a
squall line extending from the Upper OH Valley southwestward into
northwestern TN, with additional but more scattered thunderstorms
noted across central AR.

As both regions of convection travel further eastward and away
from the low-level forcing mechanism, there remains a good deal of
uncertainty regarding how much additional development will occur
in the intermediate region between the two convective regimes
(i.e. from east-central AR into western TN). However, should
additional thunderstorms form in this region, they would likely
adjoin the two regimes, resulting in a somewhat broken QLCS
spreading southeastward through our CWFA during the early morning
hours. Although storm coverage remains very uncertain, it is
becoming increasingly certain that any impacts will not begin
until the 12A-3A timeframe in the northwest. Regardless, both
deep-layer and low-level shear will remain favorable for storm
organization, even as MUCAPE (currently in the 2000-2500 J/kg
range) diminishes to 1500-2000 J/kg. The main threats from the
strongest cells will be locally damaging winds of 55-65 MPH and
hail of 1-1.5" diameter. However, with a WSW low-level jet of
30-35 knots in place, a brief tornado or two may occur as well.

As deeper convection exits the region around 12Z, lingering light
rain will be possible for a few hours across the southeastern
portion of the forecast area before ending by late tomorrow
morning. It still appears as if the lingering outflow boundary
will drift southward into central portions of MS/AL/GA before
reigniting afternoon convection, with mostly sunny and dry
conditions expected across our forecast area for the remainder of
the day. That said, the true cold front will lose definition to
our north, with highs once again predicted to reach the m-u 80s.

&&

.SHORT TERM...
(Saturday night through Monday night)
Issued at 1055 PM CDT Fri May 16 2025

In the wake of a departing mid/upper low and downstream from an
amplifying shortwave trough (predicted to eject from the
southwestern deserts into the central High Plains), ridging aloft
will build from the northwestern Gulf into south-central Canada
from Saturday night-Sunday night, resulting in WNW flow aloft of
40-50 knots across the TN Valley. Present indications are that a
lee cyclone will gradually become established across southeastern
CO/northeastern NM in response to the motion of the southwestern
CONUS shortwave trough, with the outflow boundary expected to
begin lifting slowly northeastward tomorrow night. Weak ascent
along and north of this feature will help to sustain an area of
elevated convection (that should initially develop across north-
central TX/southern OK tomorrow afternoon) as it advances
northeastward into northeastern MS/northwestern AL by 12Z Sunday,
with greatest spatial coverage of rain/storms in our CWFA expected
to occur late Sunday morning as this system may be overtaken by a
separate/elevated MCS spreading southeastward from the Ozarks.
With elevated CAPE of 1000-1500 J/kg and sufficient effective
shear, small hail and a few wind gusts up to 40-50 MPH may occur
with the strongest cells. A similar scenario may unfold once again
Sunday night as afternoon storms across OK/KS congeal into a
southeastward-propagating MCS. However, with the synoptic warm
front predicted to lift northward through the region during the
period as the lee cyclone begins to eject northeastward across
western KS, impacts from this system may largely remain to our
northwest.

The axis of the 500-mb ridge will translate eastward across the
TN Valley on Monday, and with the warm front predicted to reside
to our north, lingering impacts from nocturnal MCS activity may
largely miss our CWFA to the northeast. Highs will return to the
m-u 80s (after dropping into the l-m 80s Sunday), as our region
will be within the warm sector. From late Monday night into
Tuesday morning, redevelopment of convection is expected to occur
in the vicinity of the warm front, as a mid-level vort max
(peripheral to a developing closed low over the central High
Plains) ejects northeastward. However, this activity should be
most concentrated to the north of our region.

&&

.LONG TERM...
(Tuesday through Friday)
Issued at 1055 PM CDT Fri May 16 2025

Guidance from the latest suite of global models suggests that a
prominent mid-level shortwave disturbance will accelerate
northeastward from the TX Panhandle into the Lower Great Lakes/OH
Valley on Tuesday and Tuesday night, in the flow around a closed
low over the central Plains. As this occurs, a related surface low
will spread eastward through the OH Valley, with a trailing
trough expected to initiate convection as it tracks eastward and
through the local area Tuesday afternoon/evening. Mid-level WSW
flow of 55-60 knots will once again support organized convection
featuring a risk for severe wind/hail, and perhaps a few tornadoes
given a low-level jet of 30-35 knots. However, early day cloud
cover may have a minor impact on instability, and this trend will
need to be monitored.

Beyond Tuesday night, deep-layer flow will veer to NW as a new
closed upper cyclone evolves across the northeastern CONUS and the
OH Valley surface low ejects northeastward. Although some clouds
and perhaps a few light showers will be possible from Wednesday
into Thursday, the airmass in the wake of this system will be
notably cooler and drier.

&&

.AVIATION...
(12Z TAFS)
Issued at 540 AM CDT Sat May 17 2025

There is a small cluster of showers moving through both terminals
early this morning that should be through by the time the 12Z
package goes into effect. In the wake of storms, westerly winds
8-10 kts will prevail through the afternoon hours before becoming
light and variable overnight. There is a very low (10-20%) chance
that an additional storm or two impacts the terminals tonight.
Confidence is too low to include in the TAF at this time.

&&

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

$$

NEAR TERM...70
SHORT TERM....70
LONG TERM....70
AVIATION...30