437
FXUS64 KBMX 062044
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
344 PM CDT Mon May 6 2024

...New LONG TERM...

.SHORT TERM...
(This afternoon through Tuesday)
Issued at 103 PM CDT MON MAY 6 2024

Central Alabama will be under a persistent warm air advection regime
over the next few days with broad scale troughing over the Central
CONUS and a deep ridge over the western Atlantic. This pattern is
favoring above average temperatures with highs in the upper 80s.
Some spots in the south will reach 90 degrees leading to some
heat risk for vulnerable individuals due to the lack of
acclimation this early in the season. There will be a mix of sun
and clouds this afternoon with isolated showers or thunderstorms
possible. Mild and humid conditions are expected overnight. Some
patchy fog may develop before sunrise.

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...
(18Z TAFS)
Issued at 103 PM CDT MON MAY 6 2024

A scattering of cu is present across Central Alabama this afternoon,
but VFR conditions are expected through most of tonight. Convection
should be more isolated this afternoon with the ridge in control, so
did not include any TS mention in the TAFs at this time. Low
ceilings are expected to redevelop early tomorrow morning amidst the
moist southerly flow, and some patchy fog may develop for a few
hours, especially at TOI.

86/Martin

&&

.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 Tuesday,
increasing to 8-12 mph Wednesday. Wind gusts to around 25 mph are
possible near convection.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     64  86  67  89 /  20  50  30  30
Anniston    66  86  68  88 /  20  40  20  20
Birmingham  68  86  70  89 /  20  50  20  20
Tuscaloosa  68  87  70  90 /  20  50  20  20
Calera      67  86  69  88 /  20  40  20  20
Auburn      66  86  70  88 /  20  10  10  10
Montgomery  67  90  70  92 /  20  20  10  10
Troy        66  90  69  91 /  20  10   0  10

&&

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

$$

SHORT TERM...86
LONG TERM....32/14
AVIATION...86