998
FXUS64 KBMX 070550
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
1250 AM CDT Tue May 7 2024

...New AVIATION...

.SHORT TERM...
(Tonight through Wednesday)
Issued at 720 PM CDT MON MAY 6 2024

Clouds will form late tonight as southerly, moist flow continues.
Additionally, a brief period of patchy fog is also possible
around sunrise. The best chances for fog will be south. The lower
clouds will increase in height and thin somewhat by afternoon.
Scattered thunderstorms will develop mainly during the maximum
heating of the day. The discussion below still applies for Tuesday
afternoon.

75

Previous short-term discussion:
(This afternoon through Tuesday)
Issued at 103 PM CDT MON MAY 6 2024

A cold front moves into the Mid-South region tomorrow, and a very
subtle weakness in the low to mid-level flow will move across the
Lower MS River Valley and towards the Tennessee Valley during the
afternoon. Although forcing will be very weak, the airmass will
quickly destabilize during peak heating. MUCAPE is progged to rise
to around 3000 J/kg across the west where dewpoints will stay
near 70F, and eff. shear of 40 kts will support some scattered
strong to severe thunderstorm potential. Stronger storms will be
capable of producing damaging winds up to 60 mph and quarter size
hail with highest thunderstorm coverage expected along and north
of I-20.

86/Martin

&&

.LONG TERM...
(Tuesday night through next Sunday)
Issued at 326 PM CDT MON MAY 6 2024

Not many changes needed in the extended this afternoon, other than
minor changes rain chances. Will have more details for the Wed
night/Thu system once we are in the time range of CAM models. For
now, will continue to highlight the key messages below.

Key messages:

- The warmest day of the spring so far is expected Wednesday with
  heat indices in the mid 90s.

- One or more rounds of showers and storms will result in a threat
  of damaging winds, large hail, and localized minor flooding
  Wednesday night possibly into Thursday, especially across the
  northern half of Central Alabama. However, confidence on details
  remains low at this time.

Isolated to scattered showers and storms may linger into the evening
hours on Tuesday before weakening, though some activity could
persist across the far northern counties in closer proximity to a
stalled cold front and lingering boundaries.

A rex block will be in place to start the period with an upper low
over the Northern Plains and an anticyclone over the Canadian
Prairies. The upper low will eventually split with the majority of
its vorticity going into a trough over the Great Lakes by Thursday
and a lesser portion going to an upper low over the Southwest
CONUS as part of a developing omega block over the eastern
Pacific/West Coast. Meanwhile a strong subtropical ridge will be
centered over the Bay of Campeche. At the surface the stalled
frontal boundary will lift northward as a warm front across the
Ohio Valley in response to a broad but sub-1000mb area of low
pressure moving from Missouri to the southern Great Lakes. A
fairly strong late spring cold front will eventually move through
Central Alabama Thursday and Thursday night.

Dry air aloft and weak ridging should keep any diurnal convection
isolated to widely scattered Wednesday while strong low-level
southwesterly flow results in the warmest day of the spring so
far. Those that are especially sensitive to heat impacts may need
to take precautions given the lack of acclimation to the heat this
early in the season. Robust convection should develop to our
northwest ahead of the cold front Wednesday afternoon and evening
in a very unstable and sheared air mass, aided by a vort max
moving through the Mid-Mississippi Valley. This convection will
probably eventually grow upscale into one or more MCSs potentially
moving towards our northern counties Wednesday night aided by a
modest LLJ. With weak forcing there is quite a bit of model
spread regarding timing as is typical in this setup. The ECMWF and
its ensembles bring convection in during the evening hours while
other guidance holds off until after midnight. An earlier timing
would coincide with more instability and a greater threat for
severe storms, but given mild overnight lows and steep mid-level
lapse rates with an EML there would still be at least an isolated
severe threat with the later overnight timing. Damaging winds and
large hail will be the main threat. The tornado threat while very
low may be non-zero. Some guidance does indicate some marginal SRH
developing depending on whether a secondary surface low forms.
Given the uncertainty over timing, convective mode, and whether
storms will be surface-based, will hold off on any brief tornado
mention at this time.

Fast zonal flow will be in place Thursday as the cold front moves
in, with little in the way of height falls until evening when
troughing begins to deepen over the eastern CONUS. An impressive
overlap of CAPE and shear may be present, but this will be
highly dependent on how much convection occurs Wednesday night
and Thursday morning and any leftover cold pools. Additionally,
low-level flow will be veering and weakening, limiting
convergence, while moisture dries up aloft. There will probably
end up being at least an isolated threat of severe storms, but
will hold off on messaging past Wednesday night given the limiting
factors mentioned above. There is also the possibility for an MCS
to move along the Gulf Coast Thursday night which could cause
locally heavy rainfall and some stronger storms across our
southern counties.

Behind the front, a welcomed relief from the heat is expected
going into the weekend with highs in the 70s to lower 80s and lows
in the 50s. There are some model disagreements regarding potential
shortwave activity by Sunday, but ensembles support keeping PoPs
at 10 percent or less on Sunday.

32/Davis/14

&&

.AVIATION...
(06Z TAFS)
Issued at 1244 AM CDT TUE MAY 7 2024

Southerly low level flow is quite moist and will become saturated
toward daybreak. There is some isentropic lift that will occur
and expect MVFR ceilings after 08-10z at all terminals. Several
locations will also see IFR ceilings which should be rather brief,
4 hours or less. The MVFR ceilings will rise and become VFR by
15-17z. Scattered thunderstorms will be possible in the afternoon
for the northern terminals. Starting off with a PROB30 mention.
Winds will be south southwest 5-10 kts.

16

&&

.FIRE WEATHER...

Isolated to scattered showers and storms are possible each day
through Wednesday, with greater rain chances Wednesday night and
Thursday. Rainfall amounts will average 0.5-1.0 inch under
heavier storms. Afternoon minimum RH values will be above 40-45
percent each afternoon through mid week. 20-foot winds will
average less than 10 mph from the south to southwest today,
increasing to 8-12 mph Wednesday. Wind gusts to around 25 mph are
possible near convection.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     86  67  88  66 /  40  50  50  60
Anniston    87  69  88  69 /  40  40  40  40
Birmingham  88  70  88  69 /  50  30  40  50
Tuscaloosa  87  70  89  70 /  50  30  20  50
Calera      87  69  88  70 /  50  30  30  40
Auburn      87  69  88  70 /  20  20  40  20
Montgomery  90  71  92  72 /  30  10  20  20
Troy        90  69  91  71 /  20  10  20  10

&&

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

$$

SHORT TERM...75
LONG TERM....14
AVIATION...16