084 
FXUS64 KBMX 161801
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
101 PM CDT Mon Jul 16 2018

.UPDATE...
For 18Z Aviation.

&&

.SHORT TERM...

The western half of our forecast area remains busy this Monday
morning as a complex of showers with a few thunderstorms continues
to affect our southwest counties with a flood advisory in effect
until 10:30 am due to continued rainfall over this area as the
activity slowly moves south-southeast. More recently convection
has developed across much of Tuscaloosa County and this activity
is drifting southeast and starting to affect western Jefferson
County.

A convective complex over northwest Alabama is also sliding
southeast and is affecting portions of Marion/Winston/Walker
counties. We expect this activity to continue to move southeast
and likely affect the Birmingham metro area by early this
afternoon.

An upper level shortwave is depicted by most numerical models
across the Mid South region and this will move southeast across
the area through tonight. Toward the surface, high pressure is
near the Virginia/West Virginia border and is weakly influencing
the local area while a surface front extended from northwest Texas
east across Oklahoma and northeast into Missouri and Illinois.

The 16/12Z BMX sounding contains a moist airmass through much of
the vertical profile yielding a precipitable water (PWAT) value of
2.01 inches. Relatively light and variable winds are prevalent
through the vertical column with weak flow aloft. The modified
sounding for a forecast high of 92 degrees yields just over 3,000
J/kg of surface-based convective available potential energy 
(CAPE) but the moist vertical profile only produces downdraft CAPE
(DCAPE) values just over 600 J/kg.

Overall, expect heavy rain to be the primary concern today as is
already ongoing across our southwest counties. Localized flooding
will be possible in urban and poor drainage/low lying areas with
slow storm motions and high PWAT values. CAPE values will be high
enough to support stronger storm updrafts and gusty winds can not
be ruled out with the more robust convection.

Activity is expected to weaken after sunset tonight but shower
activity will likely linger with highest potential over our
south and central counties tonight.

05

.LONG TERM...
Tuesday through Sunday.

On Tuesday, we are looking at a low pressure system over Quebec
moving eastward and dragging a front across the northern half of 
Eastern Conus. However, across the southern half of Eastern Conus,
the upper flow will be much weaker and not favorable for pushing 
a front completely through Alabama. This is not surprising since 
it is July, but the front could make it into the northern half of 
the state before stalling. Rain chances will be well above normal 
for Tuesday with warm temperatures, lots of available moisture, 
and a front nearby. 

For Wednesday, we should see a north/south orientation for 
precipitation chances and dew points with a lingering stalled 
boundary somewhere likely across Central Alabama and high 
pressure building in from the north. For overnight lows on 
Thursday morning, readings should not be quite as warm and not as
muggy with a surface ridge across much of Eastern Conus and a 
stalled boundary remaining across the southern part of Central 
Alabama with weak flow aloft. Rain chances will be somewhat lower
for Thursday with not as much focus and more diurnally driven
activity.

By Friday, we move into a tricky upper northwest flow pattern. Our
previous surface front should be taken back northward as a warm
front with low level moisture increasing behind it and higher dew
points returning to the state. Going with mainly chance pops as we
head into next weekend. Confidence is low with extended guidance 
not agreeing on how deep upper troughing will become over Eastern
Conus along with the resulting intensity of any disturbances that
may be flowing through this upper troughing ahead of another 
approaching surface front by the end of next weekend. 

08


&&

.AVIATION...
18Z TAF Discussion.

The bulk of shower/t-storm activity is currently concentrated to 
the central counties impacting KBHM & KEET. This cluster is slowly
progressing eastward with lightning & heavy rainfall as the 
biggest threat. Have included a TEMPO TSRA for KEET, KBHM & KASN 
until 21Z, however this has been delayed for KANB until 19Z due 
to the slow storm progression. Only included VCTS for KMGM and 
KTOI for this afternoon, however this will have to be monitored 
for any development later as boundaries have the potential to
interact. Did continue the VCTS for KTCL due to development to 
the west that is progressing eastward.

Again, any areas that do receive rain will likely see fog/low 
cloud development this evening and into the morning. Currently 
have sites at MVFR ceilings for this time period. Timing may have 
to be altered at a later TAF issuance.


07

&&

.FIRE WEATHER...

Above normal coverage of mainly afternoon and early evening 
showers and thunderstorms is expected through at least Tuesday as
a weak front moves towards the area. Localized fog will be 
possible each morning where rainfall occurs during the previous 
afternoon and evening. There are no fire weather concerns.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     72  90  71  90  69 /  50  70  40  30  10 
Anniston    72  89  72  90  70 /  50  70  50  30  20 
Birmingham  74  90  73  91  71 /  60  70  50  30  10 
Tuscaloosa  73  92  74  92  72 /  60  70  40  40  10 
Calera      72  90  73  91  72 /  70  80  50  40  20 
Auburn      72  88  73  90  72 /  70  80  50  60  20 
Montgomery  74  91  75  92  74 /  60  80  50  60  20 
Troy        74  89  73  91  73 /  40  80  50  70  30 

&&

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

&&

$$