027
FXUS64 KHUN 240451
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1151 PM CDT Thu May 23 2024

...New AVIATION...

.NEAR TERM...
(Rest of tonight)
Issued at 953 PM CDT Thu May 23 2024

Regional doppler radar data this evening indicates a broad region
of showers and thunderstorms moving slowly northeastward into the
southern/central Appalachians, with this activity related to the
MCV that brought convection to our region earlier this afternoon.
Although there is currently a dearth of precipitation across
northern AL/southern TN, a mesoscale boundary trailing
southwestward from this feature into our CWFA could result in
occasional development of light-moderate showers (generally north
of the TN River) from the present time through 8-9Z, and we will
leave a low (15%) POP in the grids to account for this
possibility.

Beyond 9Z, the general expectation is for gradual redevelopment
of thunderstorms (particularly across the western half of the
forecast area), as another convectively-induced vort max lifts
east-northeastward into western portions of the TN Valley,
enhancing deep-layer vertical motions to the north of a marine
warm front extending from southern AR/northern LA eastward into
central AL. Guidance from the 12Z HREF suggests that elevated CAPE
will begin to increase (perhaps to 1000-1250 J/kg) in the 9-12Z
timeframe, which could support a few stronger cells in conjunction
with WSW flow aloft of 25-35 knots. Although we have increased
POPs during this period (especially west of I-65), the majority of
this activity will likely occur after 12Z. Aside from changes to
POP/weather grids mentioned above, other elements of the forecast
are on track, with abundant mid/high-level clouds and light SSE
winds promoting lows in the m-u 60s.

&&

.SHORT TERM...
(Friday through Sunday)
Issued at 336 PM CDT Thu May 23 2024

An unsettled weather pattern will continue as we go into the
Memorial Day weekend. A southerly lower level flow and passing
upper level systems from the west will keep chances of more
showers and thunderstorms continuing. With minimal large scale
forcing, coverage of this activity is expected to occur on a
diurnal basis (with better chances in the afternoon and evening).
Going more with blended output, an upper system approaching the
area should bring scattered to numerous showers/thunderstorms
forming late tonight, and continuing into Fri afternoon. With more
clouds than sun, high temperatures to close out the workweek
should warm into the lower 80s.

More of a diurnal trend is expected over the weekend, with mainly
afternoon convection. Highs on Saturday should warm into the
mid/upper 80s, and in the upper 80s/near 90 on Sunday. Because
of the warmth and resultant instability (CAPES rising into the
1000 to +2000 J/kg and mainly weak shear), some of the storms
could become strong to severe in intensity, with strong to
damaging wind gusts the main threat.

&&

.LONG TERM...
(Sunday night through Wednesday)
Issued at 441 AM CDT Thu May 23 2024

A stronger synoptic storm system moving from the eastern Plains to
the Great Lakes will bring another round of more organized
convection Sunday and into Sunday night. Model trends seemed to
take a more northern track with the parent low. But it will be
close enough, to bring a risk of severe storms to the Tennessee
Valley. Most of the area is within a Slight Risk for severe
weather on the Storm Prediction Center Day-4 forecast.

A strong cold front is forecast to move across the area Sunday
night. Very steep lapse rates, strong shear, high DCAPE values,
and strong instability (3000 to 4000 J/KG) will provide the
impetus for a MCS that develops along this front as it pushes into
and through the area overnight into Monday morning. Saturated
soils by then could produce a more enhanced threat for flash
flooding or river flooding from this rainfall.

Models differ on how quickly this system pushes through the area
though, so activity cloud linger into the afternoon on Monday.
However, the atmosphere will likely be worked over from earlier
convection earlier in the day, so severe weather should not be
much of an issue if that occurs.

Finally northwest flow aloft and dry weather builds back into the
area Tuesday into Wednesday. Highs will drop back into the upper
70s to lower 80s again thankfully with lows dropping back into
the mid 50s to lower 60s.

&&

.AVIATION...
(06Z TAFS)
Issued at 1151 PM CDT Thu May 23 2024

A few SHRA or perhaps a TSRA will be possible thru 9Z in the
vicinity of a subtle outflow boundary positioned north of the TN
River, but confidence in coverage is too low to include
precipitation in the TAFs initially. However, an approaching upper
air disturbance will likely begin to initiate additional
convection to our west around or shortly after 9Z, which should
spread eastward, warranting TEMPO groups for MVFR cig/vsby
reductions from 11-15Z/MSL and 12-16Z/HSV. AWWs for lightning and
brief strong wind gusts may be issued during this period, as well.
In the wake of morning precipitation, additional SHRA/TSRA will
be possible along a trailing outflow boundary late tomorrow aftn,
with a broader cluster of storms potentially spreading
southeastward thru at least the western portion of northern AL
tomorrow evening. Due to this, we have included PROB30 groups btwn
22-04Z, although timing will likely need to be adjusted as we
move forward in time. Prevailing conditions outside of convection
will remain VFR, with sfc winds from SSE-SSW at speeds of 5-10
kts.

&&

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

&&

$$

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