FXUS64 KBMX 161129

Area Forecast Discussion
National Weather Service Birmingham AL
629 AM CDT Sun Jun 16 2019

For 12Z Aviation.


Today and tonight.

An upper-level trough is located over the Southern Plains and is
associated with ongoing convection from Kansas into Oklahoma and
Texas. The 500 mb trough will make slow eastward progress with
outflows from ongoing convection likely to serve as a focusing
mechanism for development this afternoon. Some of this activity
could reach our western counties tonight. Before that occurs,
isolated to scattered showers and storms are possible across the
western half of the area this afternoon. This will be supported by a
combination of daytime heating and weak low-level convergence
resulting in PWAT values increasing to 1.75 inches. Additional
activity moving in from Mississippi this evening and tonight should
mainly affect areas along and northwest of Interstate 59 as a ridge
remains in place across our southeastern counties.


/Issued at 340 AM CDT/

Monday through Saturday.

Long-term weather conditions across Central Alabama will be
relatively warm & humid, with daily chances of showers &
thunderstorms primarily driven by diurnal heating. High temperatures
should fall within a few degrees of 'normal' values for this time of
year with upper 80s to lower 90s the overall theme through next
weekend. Overnight lows in the upper 60s to lower 70s are expected
as temperatures cool to just above their respective dewpoints. A
couple days during the week will likely be wetter than others, with
current expectations that Tuesday & Thursday will be more active as
shortwave disturbances aid in forcing for ascent. As such, Central
Alabama can expect a variety of afternoon showers & thunderstorms as
tropical air encompasses the region.

By Monday, southerly surface flow and southwesterly weak mid-level
flow will be in place as a shortwave trough passes over the ArkLaTex
region. This is expected to continue east-northeastward amidst
relatively quasi-zonal flow overall, with enhancement to rain
chances expected primarily to our northwest by that afternoon.
Tropospheric PWs ~1.8" & modest instability suggests a decent
coverage of showers/thunderstorms across Central Alabama with PoPs
adjusted to 40-50%, with an increase to 50-70% for Tuesday afternoon
as better lift & moisture content (PWs ~2.0") is available just
downstream of the shortwave now generally over our area.

After somewhat of a lull in convective activity on Wednesday
afternoon (still have chances for diurnal convection), a more potent
shortwave is progged to enter from the northwest amidst a
strengthening Polar Jet by Thursday morning. This particular wave is
set to contain more substantial mid-level flow around its base (~40
kts at 500 mb), which yields a scenario such that a moist/buoyant
lower troposphere will have 30-40 kts of effective shear available.
This suggests a few storms could be strong/severe, though timing and
other unseen mesoscale considerations need to come together. Thus,
despite the synoptic signal, will need to get closer to Thursday for
enough confidence to mention in the HWO. A simple change in speed
and/or trajectory of this shortwave trough would result in a much
different scenario (ie. stronger/organized convection displaced out
of our forecast area). Regardless, rain chances remain in the
forecast through next weekend as the Gulf airmass remains situated
across the Southeast & diurnal convective remains possible.
Generally have kept 'chance' PoPs in for Fri/Sat afternoons to
account for available moisture with expected decreases in
coverage/intensity into the overnight hours. Forecast rain chances
hopefully brings good news to those needing rainfall to improve any
localized short-term drought conditions.



12Z TAF Discussion.

VFR conditions expected for much of the day across Central AL.
TCL is showing MVFR CIGs in the past couple of hours, but expect
the ceilings to rise by mid-morning to VFR. I can't rule out some
scattered thunderstorm development this afternoon into early
evening, but even the more aggressive of the high resolution
guidance keeps coverage scattered, so I don't have enough
confidence to add it to a particular site for now. Southerly winds
continue for much of the day, increasing slightly with daytime
mixing then becoming light to calm after 00-02z tonight.




Rain free conditions continue through the morning hours. Scattered
showers and thunderstorms possible in the afternoon, but will be
hit or miss. We will see a continued recovery in minimum relative
humidity values thanks to the southerly flow. KBDI values remain
high, but the increased low level moisture will keep us from
reaching critical fire weather criteria.


Gadsden 89 68 88 67 86 / 20 20 50 30 70
Anniston 89 69 89 69 87 / 20 20 50 30 60
Birmingham 91 72 90 71 87 / 30 20 50 30 70
Tuscaloosa 93 71 91 71 89 / 30 30 50 30 70
Calera 90 70 89 69 87 / 30 20 50 30 70
Auburn 89 70 89 70 87 / 10 10 40 20 60
Montgomery 92 71 92 71 91 / 20 10 40 20 60
Troy 92 70 91 69 90 / 10 10 40 20 50




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