-- Discussion containing changed information from previous version are highlighted. --
261
FXUS64 KHUN 220448
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1148 PM CDT Tue May 21 2024

...New AVIATION...

.NEAR TERM...
(Rest of tonight)
Issued at 946 PM CDT Tue May 21 2024

A 500-mb ridge (which was aligned across the TN Valley earlier
this evening) will progress southeastward overnight, with WSW flow
aloft predicted to increase into the 30-40 knot range by sunrise.
A gradual increase in the coverage/density of convective debris
clouds (originating from thunderstorms to our west) is expected in
this regime, and this coupled with light southerly winds at the
surface should result in a rather warm night featuring lows
ranging from the m60s (NE) to u60s (NW).

Current thinking is that the cold front (responsible for
convection to our west) will decelerate as it shifts southeastward
through the Mid-MS Valley during the early morning hours, likely
in response to the eastward motion of a trailing shortwave trough
across the central Rockies/High Plains and subsequent development
of a secondary frontal wave across northwest TX. However, due to
the increase in deep-layer steering flow, it would certainly be
possible for weakening clusters of thunderstorms to move off the
front, perhaps grazing the northwestern portion of our CWFA around
or shortly before 12Z Wednesday. Thus, we have maintained a low
(20-30%) POP for portions of northwest AL/southern TN during this
timeframe. In spite of strengthening flow aloft, weak instability
will limit storm intensity should any convection survive as far
east as our region, with occasional lightning the primary concern.

&&

.SHORT TERM...
(Wednesday through Friday)
Issued at 228 PM CDT Tue May 21 2024

Moisture will continue to increase across the region as an upper
trough axis shifts east across the Great Lakes, pushing the ridge
axis farther east. Wednesday will be another dry day with
afternoon temperatures nearing 90 degrees despite the increasing
cloud cover. As broad upper troughing becomes more dominant, this
will result in increasing chances (20-50%) for showers and
thunderstorms by Thursday. These storms will be primarily
diurnally driven as a sfc cold front is held up to our north and
west. By Friday, a shortwave trough axis will swing across the
area, and combined with rich moisture will result in medium
(40-60%) chances of showers and thunderstorms. Given that this is
more typical of a summer-time pattern, some of these storms could
be on the strong side and could produce gusty winds and small
hail, but the chance for widespread severe storms looks very low
and confined to areas farther west. Daily highs will remain in the
mid to upper 80s with lows near 70 degrees.

&&

.LONG TERM...
(Friday night through Monday)
Issued at 320 AM CDT Tue May 21 2024

This impulse along the front swings east Friday night and south of
the area Saturday night. This subsequently bring medium to high
(40-70%) chance for showers and storms to the area. General view
of the storm environment would favor plenty of CAPE with
sufficient shear to support at least a few organized strong
storms, with gusty winds and hail (along with locally heavy
downpours) being the main threats on Friday night into Saturday
night. We`ll remain in a fairly active pattern through the the
upcoming Memorial Day holiday weekend, with zonal low aloft
allowing for additional shortwaves to traverse the region.
Subsequently, medium chances (40-60%)for showers/storms will be
present in the forecast both Sunday and Monday.

&&

.AVIATION...
-- Changed Discussion --
(06Z TAFS)
Issued at 1148 PM CDT Tue May 21 2024

There have been no significant changes to previous aviation
forecast reasoning, as convective debris clouds will continue to
provide bkn-ovc VFR cigs overnight. With the most recent forecast
update, we have included TEMPO group for lgt RA (remnants of
convection to our west) which may impact the MSL terminal btwn
10-14Z, and although the close proximity of a stalled front to our
northwest may indeed result in additional SHRA/TSRA across NW
AL/southern TN tomorrow, anticipated storm coverage does not
warrant inclusion of VCTS or PROB30 groups for KMSL at the current
time. Sfc winds will remain from SSE overnight and SSW during the
day tomorrow, with sustained speeds of 5-10 kts.
-- End Changed Discussion --

&&

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

&&

$$

NEAR TERM...70/DD
SHORT TERM...25
LONG TERM...KTW
AVIATION...70/DD