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419
FXUS64 KBMX 060858
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
358 AM CDT Mon May 6 2024

...New SHORT TERM, LONG TERM...

.SHORT TERM...
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(Today through Tuesday)
Issued at 330 AM CDT MON MAY 6 2024

A cluster of strong thunderstorms over northeast Mississippi was
tracking east and will clip northern Marion and Winston early this
morning. Expect frequent lightning and wind gusts up to 30 mph.
For today, upper heights will rise slightly and cap convective
development for areas south of I-20, with better chance for storms
near the southern flank of the storms coming out of Mississippi.
A slight chance of early evening storms north of I-20, with rain
free conditions likely overnight and into early Tuesday morning.
Instability really ramps up on Tuesday with forecast soundings from
a majority of the CAMS showing surface based CAPE near 3000 J/kg and
DCAPE 1200-1500 J/kg. A weak upper level trough will move across
Mississippi and into west Alabama Tuesday afternoon. This will help
initiate strong to severe storms for areas along and north of the
Interstate 20/59 corridor.

58/rose
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&&

.LONG TERM...
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(Tuesday night through next Sunday)
Issued at 358 AM CDT MON MAY 6 2024

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
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&&

.AVIATION...
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(06Z TAFS)
Issued at 117 AM CDT MON MAY 6 2024

A few showers will persist across north Alabama thru 09Z. The
upper ridge will build slightly northward today and keep
convective activity mostly isolated, and no inclusion of TSRA
this forecast period. Widespread MVFR cigs expected between 10Z
and 14Z across the northern TAF sites, with lcl IFR cigs. VFR
conds return by 16Z to all TAF sites.

58/rose
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&&

.FIRE WEATHER...

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Isolated to scattered showers and storms are possible each day
through Wednesday. Rainfall amounts will average 0.5-1.0 inch
under heavier storms. Afternoon minimum RH values will be above
40-45 percent each afternoon. 20-foot winds should average less
than 10 mph from the south to southwest, though gusts to around 25
mph will be possible at times.
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&&

.PRELIMINARY POINT TEMPS/POPS...
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Gadsden     86  66  86  67 /  30  20  40  30
Anniston    86  67  88  67 /  20  20  30  30
Birmingham  87  69  87  70 /  20  20  40  30
Tuscaloosa  86  70  88  70 /  20  10  50  30
Calera      86  69  87  69 /  20  10  30  30
Auburn      86  68  88  69 /  20  10  10  10
Montgomery  89  69  90  71 /  20  10  10  10
Troy        89  68  90  69 /  20  10  10  10
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&&

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

$$

SHORT TERM...58/rose
LONG TERM....32/Davis
AVIATION...58