Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 251119

Area Forecast Discussion
National Weather Service Birmingham AL
619 AM CDT Fri May 25 2018

For 12Z Aviation.


Today and Tonight.

Some subtle changes in the overall flow pattern across central
Alabama today and tonight. Very moist near surface conditions and
calm winds will result in areas of dense fog this morning. Several
locations already reporting visibilities at one-half or less, and
expect the fog coverage to increase through sunrise. The lowest
visibilities will likely be across the southern portions of Central
Alabama due to fewer mid level clouds. A dense fog advisory has
already been issued for the southern half of Central Alabama, but
may be expanded northward if clouds erode. Models still show a weak
zone of low level convergence across the southern portions of the
area, with another zone across west Alabama this afternoon, so
highest pops will be generally along and west of Troy to Birmingham
line. Models still show weak steering level winds, generally 7 mph
or less, so convection will be slow moving and dominated by
outflows. This will result in a threat of localized flash flooding
due to slow moving storms. Scattered convection will continue into
the evening hours, but gradually diminish throughout the night.



Saturday through Thursday.

For the extended period all eyes will be on the Gulf of Mexico and
the prospects of Invest 90L. According to the Hurricane center,
environmental conditions are forecast to become more conducive for
development, and a subtropical or tropical depression or storm is
likely to form during the weekend over the eastern or central Gulf
of Mexico. There is a flight scheduled to investigate this

The system has quite a bit of distance to travel over the next 3
days, so there is plenty of time to get some better agreement
amongst models. One thing to note is that while the models are still
very divergent on the track scenarios, there is some agreement on
the timing and overall track. The NAM takes the system close to
Florida and then swings the center of the system toward New Orleans
and strengthens it quite a bit as it would remain over water a
little longer. The GFS remains the further east and further north
with the system track. With these two scenarios the GFS would be the
wetter solution, while the NAM would be the drier solution as it
would actually bring an area of subsidence over the area for the
weekend. The EURO is right in the smack dab middle of both scenarios
and brings the system in between Mobile and New Orleans. This
scenario would be a wetter scenario as well, but would also place
Central Alabama into a zone where isolated tornadoes would be

Once the system is inland the path would still be to the west then
north, then northeast. So while the NAM would be further west of the
area initially one could decipher that it would move into the area
and increase rain chances a little later. So in a nutshell, the
forecast for the entire period is highly dependent on 90L and the
development and movement over the weekend. Overall, confidence
overall is higher on Monday through Wednesday as all solutions have
Central Alabama wet, while the confidence for the weekend forecast
remains fairly low in regards to impacts and placement. Stay tuned
for the updated forecast.



12Z TAF Discussion.

LIFR conds will impact KMGM and KTOI thru 14z due to low cigs and
fog. Vsbys have been variable at KTCL and there vsbys may briefly
fall below 3 miles thru 14z. Sct-bkn clouds with cigs 4-5k feet
agl will prevail at all TAF sites thru the day, along with sct
TSRA, and handled with VCTS. Convection will gradually diminish
after 00z, with only isold shwrs/TSRA after 05z. Low cigs and fog
likely to impact KMGM and KTOI after 09z.




A moist pattern is expected over the next seven days and should
result in daily rain chances. Patchy fog and low clouds will be
possible each morning particularly where rainfall occurs during
the prior afternoon and evening.


Gadsden     86  67  85  67  81 /  60  40  70  40  70
Anniston    84  67  84  67  80 /  60  40  70  40  70
Birmingham  86  68  87  69  83 /  70  40  70  40  70
Tuscaloosa  86  69  87  69  85 /  70  40  70  40  60
Calera      85  67  85  67  81 /  70  40  70  40  70
Auburn      83  68  83  67  77 /  60  40  60  50  80
Montgomery  85  69  85  68  80 /  70  40  60  50  80
Troy        85  68  84  67  77 /  70  40  60  60  80


Dense Fog Advisory until 9 AM CDT this morning for the following
counties: Autauga...Barbour...Bibb...Bullock...Chambers...


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