Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 260817
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
317 AM CDT Wed Jul 26 2017

.SHORT TERM...
Today and tonight.

Patches of low clouds and fog are present this morning in the wake
of rainfall on Tuesday. Dissipation is expected shortly after
daybreak. Aloft, an elongated deep-layer trough continues to move
slowly southward and is approaching the Gulf Coast. This should
result in somewhat lower PWAT values and rain chances a ridge moves
in behind the trough. The highest rain chances (30-40 POP) are
confined along and south of Interstate 85, where slightly higher
moisture content and weak low-level convergence may contribute to
scattered afternoon convection. Otherwise, only isolated activity is
expected for the majority of the forecast area.

87/Grantham


.LONG TERM...
Thursday through Wednesday.

Another hot/humid day in store for Thursday. Upper level ridging
slides slightly eastward as the low level high pressure sets up over
the Texas coast. A broad/weak low is still present over Southern GA
as we get into the afternoon, so could see some afternoon
showers/storms in the eastern half of Central AL. For the western
half, westerly flow brings in some drier air in the lower levels.
With the light winds aloft, expect that this drier air could mix
down in the afternoon, lowering the dewpoints. With 1000-850mb
thickness approaching 1440m, still expect afternoon highs to be in
the mid to upper 90s in the western counties and the low 90s for the
eastern counties. Heat indices are forecast to approach and
possibly hit 105 in some areas in the western portions of Central
AL, so will continue mentioning heat impacts in the HWO. The
question will be just how much afternoon mixing can occur to
decrease the surface moisture, limiting the heat index.

A surface low moves through the Ohio River Valley on Friday and
stretches a cold front down through the TN Valley. An upper level
trough helps push this cold front south through Central AL Friday
night into Saturday morning. The PWATs ahead of this system are near
or just above 2.5", so expect heavy rainfall with the storms that
form along the frontal boundary. Latest model runs have sped this
frontal passage up some, pushing it south of our area by Saturday
morning. Have kept some lower-end chance PoPs in the forecast for
our southeastern areas even after this front passes due to the
trough axis hanging around. Otherwise, drier and cooler weather
filters in with the northerly flow for the weekend and into early
next week.

25/Owen

&&

.AVIATION...
06Z TAF Discussion.

Conditions could deteriorate at any given TAF site overnight and
around daybreak with light winds, mostly clear skies, and high
moisture content in place. The most likely locations for IFR
cigs/vis will be KTOI and KMGM. Will closely monitor trends and
update other sites to prevailing IFR if/when it becomes necessary.
Conditions should rapidly improve after daybreak, and isolated
afternoon showers and storms are possible in the latter portion of
the TAF period.

87/Grantham


&&

.FIRE WEATHER...

Isolated to scattered rain chances today and tomorrow and ridging
builds in. Light winds at the surface and aloft will limit
dispersion for the next couple of days. Hot and humid weather, so
no fire weather concerns at this time.


&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     93  73  92  73  89 /  20  20  30  20  60
Anniston    92  73  92  73  90 /  20  20  30  10  40
Birmingham  93  76  94  76  91 /  20  20  20  10  50
Tuscaloosa  94  75  96  75  92 /  20  20  20  10  50
Calera      93  74  93  75  92 /  20  20  20  10  40
Auburn      90  73  90  74  91 /  30  20  30  10  30
Montgomery  94  75  94  76  94 /  30  20  30  10  30
Troy        91  72  93  73  93 /  40  20  30  10  30

&&

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

&&

$$



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