Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 051140

Area Forecast Discussion
National Weather Service Mobile AL
640 AM CDT Wed Aug 5 2020

05/12Z issuance...VFR conditions will prevail through the period.
Very isolated showers and thunderstorms are possible during the
afternoon and early evening hours today, however the probability
is too low to include in the TAF. Mostly only high thin clouds,
but a few mid level cumulus clouds from late morning through the
afternoon hours. /12


.PREV DISCUSSION... /issued 405 AM CDT Wed Aug 5 2020/

NEAR TERM UPDATE /Now Through Thursday/...An upper trof over the
eastern states will remain in place through Wednesday before
gradually weakening on Thursday. A very dry mid and upper level
atmospheric profile will continue with precipitable water values
generally from 1.3 to 1.5 inches. Meanwhile, a very diffuse surface
trough will remain draped across southern portions of the forecast
area. The boundary will move offshore overnight and return onshore
with the seabreeze circulation during the day. While an isolated
shower or storm cannot be ruled out each afternoon with the boundary
in the area, the dry mid and upper level air will be hard to
overcome. Pops will generally be no more than 15 to 20 percent each
day, and mainly over inland areas (especially northeast interior)
during the afternoon and early evening hours. Hot temps will
continue with highs mainly in the low to mid 90s, heat indices
generally remaining in the upper 90s due to lower dewpoints mixing
down during the afternoon hours with the drier air continuing aloft.
Lows tonight in the low 70s inland to mid/upper 70s along the coast.

SHORT TERM /Thursday night Through Friday night/...The upper
trough that had settled over the eastern CONUS the past few days
finally begins to lift northeast and flatten through the short
term. This ceases the persistent deep-layer northwest flow across
the region and thus, the constant influx of dry air in the mid and
upper levels. At the surface, high pressure remains firmly
planted across the western Atlantic, ridging into the Southeast
and Deep South states. This maintains light and variable winds
across the region, with the land/sea circulation dominating wind
direction along the coast (onshore flow during the day and
offshore flow at night). Wouldn`t be surprised to see some
isolated shower and thunderstorm activity along the sea breeze
during afternoon hours Friday given the weakening northwest flow
and subsequent increase in deep-layer moisture content. Thus,
opted to keep slight chance PoPs in the forecast along the coast
and over portions of interior south-central AL east of I-65, where
PWATs will have rebounded back into the 1.6 to 1.8 inch range and dry
air entrainment won`t be as big of an issue for aspiring updrafts.
Kept rain chances at or below 10% across interior SW AL and SE MS
since those will be the last places to see deep-layer moisture return
and PWATs remain under 1.5 inches. Any convection will be driven by
daytime heating, so left out mention of rain during overnight hours
Thursday and Friday nights.

Temperatures continue to trend on the warm side of normal,
reaching the mid to upper 90s inland and low 90s along the coast
Friday afternoon. Little change expected with low temps Thursday
and Friday nights as they hold steady in the low/mid 70s inland
and upper 70s along the coast.

A LOW rip current risk continues along area beaches through
Friday night. /49

EXTENDED TERM /Saturday Through Tuesday/...Looking ahead there
appears to be signs to at least a return to the normal afternoon
shower and thunderstorms. You know the ones that you can almost
set your watch to since they occur around 4 pm almost every day.
The upper trough that has brought us the drier weather for most of
the weak will finally breakdown and flatten out to our north as a
mid-level ridge of high pressure begins to develop over western
Texas. Upper level flow will almost become non-existent. The main
thing will be PWATS will be allowed to slowly climb to around 1.8
to 2.0 inches. The better deep layer moisture will likely lead to
a few more storms than what we will se during this week. Storms
will likely follow the typical diurnal pattern with storms
beginning offshore during the morning before more storms develop
along the seabreeze during the afternoon. Since it is summer a
strong to severe storm cannot be ruled out especially earlier in
the period when there might be just enough dry air lingering
around. Luckily deep layer flow is expected to be so weak that no
organized storms would be expected and the storms will be of the
popcorn variety. Temperatures will remain high with highs in the
low to mid 90s. The hottest days appear to be on Saturday and
Sunday where there is enough dry air aloft to promote vertical
mixing and temperatures to climb. By the middle of the week, the
increased moisture will keep temperatures more in the low 90s.
Unfortunately, increased moisture will mean it will be a little
more humid each afternoon and heat index values will likely creep
up into the triple digits. BB/03

MARINE...A mostly light south to southwest flow expected to
continue over the coastal waters through the period with little
change in seas expected. The only marine impacts expected will be
locally higher winds, waves, and seas near isolated to scattered
showers and storms late this week, through the weekend and into the
early part of next week. /12




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