Area Forecast Discussion
Issued by NWS Mobile, AL

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225
FXUS64 KMOB 261127 AAA
AFDMOB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
627 AM CDT Wed Jul 26 2017

.DISCUSSION...Updated for latest aviation discussion below.

&&

.AVIATION...
12Z issuance...VFR conditions forecast over the next 24 hours.

&&

.PREV DISCUSSION... /issued 447 AM CDT Wed Jul 26 2017/

NEAR TERM /Now Through Wednesday night/...Mixed layer clouds cover
much of the forecast area early this morning, with patchy fog
continuing to develop under breaks in the coverage. The patchy fog
will dissipate by mid morning, while a light deep northerly wind
flow pushes much of the mid and upper level clouds south over the
Gulf of Mexico this morning. Surface heating will result in more
low level cumulus clouds between 4-5 thousand feet to develop
throughout the day, but all locations should see mostly sunny
skies by late morning through the afternoon hours.

An upper level trough extending from eastern South Carolina to
southeast Mississippi will gradually shift southeast through late
tonight, while an upper high pressure ridge extending east from a
closed upper high pressure area over the southern plains moves
slowly over much of the region. Meanwhile, a weak surface high
pressure ridge extending westward from the western Atlantic across
the northern Gulf of Mexico will remain intact, keeping winds
generally light from the northwest.

With the weakness aloft shifting southeast we will see a return to a
more diurnal driven pattern, with rainfree conditions throughout
the morning followed by isolated to low-end scattered coverage this
afternoon along and east of the Tombigbee River. Dry conditions will
persist west of the river. The shower and thunderstorm activity
inland areas will dissipate with loss of surface heating as sunset
nears, with isolated to scattered coverage redeveloping across the
northern gulf. A few showers may impinge along the coast throughout
the night.

Warmer temperatures are in store for today as we rebound a degree or
two above normal, with highs ranging from 90 to 94 degrees. Heat
indices this afternoon will range from 101 to 106 degrees. Low
temperatures tonight will be in the mid 70s, except for the upper
70s along the beaches. /22

SHORT TERM /Thursday Through Friday night/...An upper ridge
extending east from the Texas panhandle into the southeastern U.S.
begins to drift south over our area through the short term. This
should bring in drier air aloft and increase the amount of mid-
and upper-level subsidence over the region, leading to drier
weather and clearer skies. At the surface, high pressure building
over the northwestern Gulf of Mexico means a shift in boundary
layer winds over the central Gulf coast from westerly to north-
northwesterly. This pattern ultimately boils down (pun intended)
to a single term: HOT. Guidance continues to suggest high temps
across much of the area reaching the mid to upper 90`s. Even area
beaches are likely to reach the low to mid 90`s as the light
north to northwesterly winds act to impede the advancing sea
breeze. Relief from showers and storms will be hard to come by, as
strong subsidence beneath the upper ridge means only a slight
chance to chance of rain each afternoon. Plus, with the drier air
remaining largely aloft, surface dewpoints are expected to remain
in the low to mid 70`s across the area. This will lead to heat
indices each afternoon in the 102 to 107 degree range. A few
locations may even see indices peak a degree or two warmer,
though current expectations are for those occurrences to remain
too isolated to warrant issuing a heat advisory at this time. That
said, this level of heat can still be dangerous, and extra
precautions should be taken if making outdoor afternoon plans. Be
sure to pack plenty of sunscreen and water, and plan for regular
breaks in the shade or air conditioning. /49

LONG TERM /Saturday Through Tuesday/...Heading into Saturday, the
upper ridge continues to push south over the central Gulf as a
longwave trough deepens over the eastern CONUS. This pushes a weak
frontal boundary through our area Saturday evening, with
increasing chances for showers and storms setting up ahead of
that front Saturday morning and afternoon. Models are still
having some trouble in deciding where the front will ultimately
stall, with the GFS remaining more aggressive in pushing it out
into the central Gulf and the ECMWF essentially stalling it just
offshore. In both cases it appears Sunday remains a bit drier,
especially for inland areas west of I-65. Models then depict a
weak low developing over the northern Gulf as more shortwave
energy rotates around the base of the longwave trough, digging it
a bit farther south and west. This returns showers and storms to
the forecast Monday into midweek as we see winds shift back to
southerly and rebounding deep-layer moisture.

With the stormy pattern setting up this weekend, we get some relief
from the hot temperatures we`re seeing Thursday and Friday. Highs
should reach the upper 80`s Saturday and upper 80`s to low 90`s
Sunday through Tuesday. In the wake of the front, lows Saturday
and Sunday nights dip into the upper 60`s inland to mid 70`s along
the coast, before rebounding back to low to mid 70`s inland and
upper 70`s along the coast Monday and Tuesday nights as the
moisture returns. /49

MARINE...A ridge of high pressure over the northern Gulf of Mexico
will slowly move south throughout the week. A light offshore flow
this morning will shift to the west by noon, and then shift to the
northwest tonight. A more established westerly wind flow will occur
through the remainder of the week. Isolated to scattered showers and
thunderstorms are expected through Friday night, with better rain
chances occurring over the weekend as a surface boundary approaches
the coast from the north. /22

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...None.
&&

$$

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