Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 210543

Area Forecast Discussion
National Weather Service Birmingham AL
1243 AM CDT Sun Jul 21 2019

For 06Z Aviation.


Through Sunday.

Widespread showers and storms have developed this afternoon in
response to the lift associated with the upper level low pressure
centered just off the Gulf Coast. With PWATs well over 2 inches
for most of Central Alabama, these storms have been efficient
rainfall producers. One storm that popped up over the Bessemer
Airport dropped 1.74 inches in just over an hour. A wind gust to
31 knots was also reported in Bessemer, but gusty winds haven`t
been very prevalent with these storms today due to the saturated
air mass that`s in place. Fortunately, we haven`t had any storms
last long enough to cause any flood concerns like we had during
the day on Friday. Even with the widespread showers and storms
there have still been a few spots that remain bone dry. One of
those spots is our office here at the Shelby County Airport.
That`s certainly the nature of summer convection here across
Central Alabama. We can expect at least numerous showers and
storms to continue through the early evening hours, and we`re
watching some fairly strong outflow boundaries pushing northward
out of southern Alabama. Those boundaries have triggered showers
and a few storms in Troy and will be capable of keeping convection
going through at least the next 3 to 4 hours farther north.

Convective activity and coverage will diminish with the loss of
daytime heating this evening. However, with the upper low still in
the vicinity as a lifting mechanism on the synoptic scale there
have been some indications in guidance of showers and storms
continuing to persist during the overnight hours. That would
especially be the case across the western and northern counties,
and have left mention of chance and slight chance PoPs in the
forecast through the overnight hours.

Sunday should feature less coverage of showers and storms, as was
covered in the previous discussion. Drier air, as can be clearly
seen in WV Satellite this afternoon over much of Georgia and South
Carolina, will start pushing into eastern Alabama by Sunday
afternoon. Only isolated to scattered PoPs can be expected, with
highest coverage expected across the western and northwest


/Updated at 0337 AM CDT Sat Jul 20 2019/

Sunday through Friday.

Moisture quality should decrease on Sunday as a weak 500 mb low
continues to move westward away from the forecast area. A ridge
to our east is expected to provide weak subsidence across our
central and eastern counties, where PWAT values may fall to around
1.7 inches. This will support POPs ranging from 30 percent in the
southeastern counties to 50 percent in the northwestern counties,
and a further reduction in rain chances may be needed. A similar
setup is likely for Monday as 2 inch PWAT values remain confined
to the northwest of I-59.

On Monday night, the first cold front in quite some time will be
approaching from the northwest, providing a focus for showers and
storms. Rain chances should increase during the evening and
overnight hours from the northwest, with rain chances of 60 to 70
percent along and north of I-20 through daybreak on Tuesday.
While the southern half of the forecast area appears to be in line
for widespread showers and storms on Tuesday afternoon, rainfall
amounts near I-20 will depend on the timing of the cold front. If
the front passes through during the early morning hours, a lack
of daytime heating could lead to a relative lull in convection and
rainfall intensity.

Much drier air will be advected in behind the front for Wednesday
and Thursday, leading to rain chances being confined to our
southeastern counties near the stalled front. Moisture recovery
and higher rain chances are expected on Friday with the onset of
moist southerly flow.



06Z TAF Discussion.

A very moist air mass in place across central Alabama. Several
sites already reporting fog and IFR cigs. Forecast thru 13z will
be difficult due to variations of low clouds and fog, but expect
widespread IFR conds between 09z and 13z. Fog will be more of an
issue at KMGM and KTOI with cigs more prevalent at other sites.
Conds will improve rapidly after 14z with VFR conds by 16z. Sct to
numerous showers and tstms will develop by 17z, with highest rain
chances along the I-59 corridor. Expect heavy downpours with vsbys
blo 2 miles in rain. Areal coverage of convection will decrease
rapidly after 00z.




Following numerous showers and storms today, some reduction in
rain chances appear likely for Sunday and Monday across the
central and eastern counties of Central Alabama. A cold front
should bring more widespread rain for Monday night into Tuesday.
With a moist airmass in place, there are no fire weather concerns
at this time.


Gadsden     88  71  88  70  82 /  40  20  60  70  80
Anniston    88  72  89  71  82 /  30  20  60  70  80
Birmingham  89  73  89  72  83 /  40  20  60  70  80
Tuscaloosa  90  73  90  72  84 /  50  30  60  70  80
Calera      88  71  89  71  83 /  40  20  50  60  80
Auburn      89  72  89  72  84 /  20  20  30  50  80
Montgomery  91  73  92  73  87 /  30  20  30  50  80
Troy        90  71  91  71  87 /  30  20  30  30  80




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