686
FXUS64 KBMX 170601
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
101 AM CDT Fri May 17 2024

...New AVIATION...

.SHORT TERM...
(Tonight through Saturday)
Issued at 845 PM CDT THU MAY 16 2024

The 00z Raob from BMX indicates that we have gained about a
quarter inch of precipitable water since this morning. Winds
through the atmospheric column increase slightly and become
southerly all the way up by midnight or so. The model soundings
have some dry air that we need to overcome and this will occur
from top down moistening. Sped up the arrival pops slightly
overnight as we should have a chance of light rain a bit earlier
west, and then the rain/storms spread quickly west to east and
cover much of the area by Friday morning. The evolution/strength
of storms through early Saturday will largely be mesoscale
dominated. The forecast discussion below is still largely valid.
Several waves will have the potential of kicking off showers and
storms. Each wave will have an impact on how the atmosphere
responds and how much instability will be available. It appears
there will be plenty of shear for organized storm development. We
will monitor the areas of storms and their placement as we move
through the overnight hours. Additionally, it still appears the
best axis for heavier rainfall remains over the southern half of
the area. Overall, some changes to temp, dew points, rain chances,
but the message remains the same.

75

Previous short-term discussion:
(This evening through Friday)
Issued at 1255 PM CDT THU MAY 16 2024

A tranquil but warm day is ongoing across the region with a brief
period of upper level ridging at 500mb. A weak surface ridge is
also just off to our northwest, producing light northerly winds in
the lower levels. We`ve rapidly warmed at the surface early this
afternoon into the 80s in most locations, with 1000-850mb
thicknesses supportive of highs in the upper 80s, perhaps close to
90 degrees across the far south. Our weather will quickly
deteriorate overnight tonight as a shortwave trough begins to
develop and eject eastward out of the four corners states.
Northwesterly flow aloft will become southwesterly after midnight,
with rapidly moistening conditions aloft. The first of several
upper level shortwave impulses will advance eastward during the
morning hours on Friday, with shower and storm activity expected
to be ongoing across southern and Central Mississippi. These
storms are expected to move across southern Alabama and the Gulf
Coast region, with some uncertainty in terms of the northward
extent of the storms. Following that round of convection,
confidence decreases in terms of what our environment will look
like behind it. Guidance trends are currently depicting a break in
the action by the afternoon hours, with potential re-development
of scattered to numerous showers and storms during the afternoon.
Another more potent shortwave is expected to arrive Friday night,
which will bring the best chance for severe storms as well as
flash flood potential. Storms will likely train over the same
areas as the flow becomes southwesterly across the atmospheric
profile with PWATs progged to rise over 2 inches. The latest
trends with the CAMs this afternoon depict the highest rain
chances a little more to the south, and the Moderate Risk of
Excessive Rainfall was also adjusted accordingly. Based on
mesoscale trends that occur tomorrow, we certainly can`t rule out
being "cut off" from the greatest moisture due to MCS development
and the risk areas going even further south when all is said and
done. Although further updates will be needed, 2-4 inches of rain
remain in the forecast across our southern counties with isolated
higher amounts.

The severe weather risk has also shifted farther south as a
result, with the best moisture and instability across the southern
half of Central Alabama. With all that said, the setup will be
very messy and conditional based on where MCS activity develops
and moves through the next 36 hours. Large hail and isolated
damaging winds will be the main hazards, with an isolated tornado
threat possible across our far southern counties in the Slight
Risk area. More isolated severe storms are still possible
elsewhere, but much less of a chance as you go northward.

56/GDG

&&

.LONG TERM...
(Friday night through next Wednesday)
Issued at 345 PM CDT THU MAY 16 2024

We will continue the trend from the short term. The main changes
to the extended are with the latest guidance shifting the best
instability and moisture/rainfall amounts overall further to the
south. Will continue to mention severe for Fri/Fri evening for the
SRN half of the area. We will also continue to mention the threat
for heavy rain, especially in the SRN portions of C AL. However,
with the trends of lower rainfall amounts expected over the
Fri/Sat timeframe and the fact that the areas with the highest
expected amounts have not had a great deal of qpf over the past
week will forgo a flood watch at this time. Will reassess with the
next set of guidance over the mid shift to determine which counties
if any may need a watch.

Sunday evening through Tuesday evening shows a return to rain free
but warming conditions each day. Another system approaches by the
end of the extended with low pops returning by next Wednesday.

08

Previous long-term discussion:
(Friday night through next Wednesday)
Issued at 255 AM CDT THU MAY 16 2024

Friday night through Saturday.

A second wave of southerly moisture works into the area Friday night
into Saturday morning. As the morning progresses rainfall becomes
more widespread ahead of the upper low that will move through early
Sunday morning. The consensus of the models indicate another 1 to
1.5 inches of rain with this swath of rain from generally north of
Birmingham and to the the east. If this heavier band does develop
and falls over the areas that receive the most rainfall on Friday
then flooding may once again be a threat for much of the area on
Saturday. Watches will likely be needed with the afternoon forecast
update.

Sunday through Wednesday.

The upper level low exits most of the area by Sunday morning,
however a few models tries to warp some additional rainfall along
the backside of the low. Will keep in PoPs through the afternoon on
Sunday. Deep-layer ridging is depicted in medium-range & ensembles
thereafter, which supports a period of dry, warm weather that
appears to extend into early next week. Highs in the 90s could be
possible by then. On Wednesday we will begin to see the next system
take shape to our west. A shortwave will ride along that boundary
and clip our northern areas, with generally isolated to scattered
showers/storms. A wetter pattern looks to be shaping up for the end
of next week, but will be discussed over the next few days.

16

&&

.AVIATION...
(06Z TAFS)
Issued at 101 AM CDT FRI MAY 17 2024

Unsettled weather is expected for this forecast period as a couple
waves of rain and thunderstorms impact the area. Terminals start
off VFR with the potential of MVFR/SHRA/TSRA by 12-14z. The rain
and storms will move west to east through the day on Friday, with
a few waves of activity possible at each terminal. Predominant
ceilings will be MVFR with lowering to IFR during the afternoon.
Winds will be light and variable through early Friday morning,
then veer from southeast to south through the day at 5-10kts.

14

&&

.FIRE WEATHER...

Widespread rainfall and thunderstorms return to the area tonight
through Saturday, along with some lingering scattered activity
hanging around through Sunday. Minimum relative humidity values
remain well elevated through Saturday. 20 foot winds become
southeast to south on Friday and increase to 8 to 10 mph, and
then become southwesterly on Saturday. Drier conditions return by
Sunday evening.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     75  64  80  62 /  70  70  80  50
Anniston    77  67  79  64 /  80  70  80  50
Birmingham  78  68  80  64 /  80  70  80  40
Tuscaloosa  78  67  81  64 /  80  60  70  30
Calera      77  68  80  65 /  80  70  80  40
Auburn      78  69  78  66 /  80  70  90  40
Montgomery  81  69  80  66 /  80  70  80  40
Troy        81  69  79  66 /  80  70  90  40

&&

.BMX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...75
LONG TERM....08
AVIATION...14