Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 250404

Area Forecast Discussion
National Weather Service Birmingham AL
1104 PM CDT Fri Mar 24 2017

For 06Z Aviation.


Tonight and Saturday.

A mild night tonight due to south to southeast winds staying up
around 10 mph. The air mass is still relatively dry across Alabama
with precipitable water values less than one inch. Models also
indicate the low levels will not moisten up much overnight, so
rain free conditions expected this evening, with only a slight
chance of showers in the far west towards sunrise. A pre-frontal
band of convection will be across western Mississippi early
Saturday morning. The line of strong to severe thunderstorms will
likely be near a Tupelo to Jackson Mississippi line by 10 am,
reaching Marion and Lamar counties in central Alabama by late
morning. Best low level speed and directional shear across west
Alabama will be before 18z, before main convective line moves
across west Alabama, so tornado threat still looks minimal at this
time. 0-6km Bulk Shear still looks favorable for organized
convection along squall line. Hi-res models also show surface
based CAPE values approaching 1000 j/kg across west Alabama
Saturday afternoon, so slight risk of severe storms for areas west
of I-65 still looks valid. With loss of daytime heating and a
weakening low level wind field, expect convective activity to
diminish in intensity once it shifts east of I-65. The convective
line`s speed will also slow down in the afternoon as the mid level
closed upper low over the Plains States takes a more northward
component. With the closed upper low over the Plains States
lifting northward and filling, the surface cold front never
reaches Alabama and low level winds stay south southwest Saturday
night. Although the threat of severe storms and heavier rainfall
will end Saturday evening, there will be enough residual moisture
hanging around Saturday night for a chance of showers and a few
storms throughout the night.


Sunday through Thursday.

Moist southwesterly low-level flow is expected to continue into
Sunday, and isolated showers/storms cannot be ruled out. Another
upper trough will move toward the area on Monday and has trended
more impressive in terms of the severe weather threat. SBCAPE is
now expected to reach 1000-2000 J/kg with steep lapse rates
spreading eastward across MS into West AL. Lift/forcing with the
upper trough appears to be subtle which would allow higher CAPE to
build before convective initiation occurs. Moderate 500mb
westerlies of 30-40 kt could yield clusters and supercells capable
of producing hail possibly larger than quarter size and damaging
winds. The tornado threat appears very low at this time due to
marginal surface to 700mb shear. The upper trough will be slow to
move through, and convection could linger into Tuesday morning
across the north with a moist southwesterly fetch remaining in

Yet another system will move into the Plains on Wednesday with
drier and warmer conditions across Alabama as a 500 mb ridge
amplifies over the region. It is too early for specifics, but
another severe weather threat could be on the table for Thursday
especially if the trough trends toward more of an open wave than
currently indicated.



06Z TAF Discussion.

--VFR cloudiness tonight into Saturday morning; increasing threat
of thunderstorms west-to-east through Saturday with sub-VFR impacts;
instances of breeziness--

Broken to overcast cloudiness continues overnight. Based on progged
low-level winds either side of 35-knots and RH values, ceilings are
expected to remain comfortably within VFR range.

A weather system will affect all terminals Saturday, tracking west-
to-east across the state. We should begin with spotty/VCSH showers
before a line of thunderstorms moves through. Sub-VFR conditions are
expected with the convection (visibility and/or ceilings). Given the
surface front hanging upstream, areas of lingering showers/storms
are possible beyond the end of the TAF period as well. Added an
addition line to show TSRA transitioning to SHRA. Latest model
trends have been slower with the eastward progression/development of
storm/shower activity. Adjusted timing slightly where needed.

Light to modest breezes continue tonight thanks to the pressure
gradient between upstream low pressure and ridging off the Carolina
coastline. Gusty winds are expected Saturday, with gusts to around
20kts outside of strong TS.




Rain free conditions expected overnight with south to southeast
winds staying up overnight. Low level moisture will gradually
increase on Saturday as a line of strong to possibly severe
storms moves across central Alabama during the day Saturday. Rain
chances will continue Saturday night and into Sunday due to a
moist southwest flow holding over the area. An active weather
pattern will continue into next week. Critical fire weather
conditions are not expected through the next 7 days.


Gadsden     57  77  58  76  57 /  10  80  80  50  20
Anniston    58  76  58  77  58 /   0  70  80  50  20
Birmingham  61  76  60  78  59 /  10  80  80  40  20
Tuscaloosa  61  73  61  81  61 /  10  80  60  30  10
Calera      60  77  60  79  60 /  10  80  70  40  10
Auburn      58  76  58  78  59 /   0  60  70  40  10
Montgomery  61  79  60  84  61 /  10  70  60  30  10
Troy        58  78  60  82  61 /   0  60  50  30  10




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