Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 211123

Area Forecast Discussion
National Weather Service Mobile AL
623 AM CDT Fri Jul 21 2017

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


12Z issuance...Scattered showers and thunderstorms develop across
the area today amidst a typical hot and humid summertime airmass
and light southerly winds. Expecting cigs/vis to remain at VFR
levels, with the exception being locally lower cigs/vis in and
around heavier showers and storms. Stronger storms will also be
capable of producing gusty downburst winds and frequent lightning.
Convective activity tapers after sunset, with VFR conditions and
light and variable winds settling in once again tonight. /49


.PREV DISCUSSION... /issued 331 AM CDT Fri Jul 21 2017/

NEAR TERM /Now Through Friday night/...A weak cutoff low in the mid
levels currently over the Florida-Georgia state line will continue
to retrograde towards the west through the near term before
beginning to fill in as it settles over the northern Gulf. This low
will act to increase thunderstorm coverage over the area today, with
storms initiating along the coast and over eastern portions of the
area this morning and gradually spreading westward and inland
throughout the afternoon. Ample instability coupled with improving
lapse rates and a layer of relatively drier air aloft could result
in a few storms becoming strong enough to produce gusty downburst
winds and frequent cloud-to-ground lightning. With PWATs expected to
remain around 2.00 inches, locally heavy downpours will also be
possible. However, given the decent storm motion and scattered
coverage, not foreseeing any sizable flooding threat, with the
exception of some minor nuisance flooding of urban areas unfortunate
enough to see training or backbuilding of storms. Activity should
then taper over inland areas after sunset, with some lingering
showers and storms possible tonight along the immediate coast and

In terms of temperature, not expecting today to get quite as hot as
Thursday afternoon, given the increased cloud cover and convective
activity. That said, will still likely see temps reach the low 90`s
in most places, with some spots reaching the mid 90`s inland.
Dewpoints in the low to mid 70`s will maintain heat indices in the
100 to 105 degree range across the area this afternoon. Lows tonight
range from mid 70`s inland to upper 70`s along the coast. /49

SHORT TERM /Saturday Through Sunday night/...A weak upper trof
oriented along the northern Gulf coast persists through Saturday
night then loses definition during the remainder of the period as
a larger scale upper trof evolves over the interior eastern
states. A surface ridge remains over the northern/central Gulf
through the period and maintains a light south to southwest flow
over the forecast area. Continue to expect a diurnal convective
pattern through the period, with scattered convection developing
with daytime heating and the sea breeze, then lingering into the
evening hours. Some strong storms will be possible, producing gusty
winds, frequent lightning and heavy downpours. Highs will be in
the lower 90s each day except for near 90 at the coast, resulting
in heat indices of 100 to 105. Lows continue to range from the
lower 70s inland to the mid 70s at the coast. /29

LONG TERM /Monday Through Thursday/...An upper trof over the
interior eastern states moves off into the western Atlantic
Tuesday night, but leaves a weak upper trof over the southeast
states that lingers through much of the remainder of the period. A
surface low (well to the north) associated with the upper trof
brings a surface trof into Tennessee early in the period which may
make it into the interior southeast states on Tuesday, but
looks to remain well north of the forecast area. A surface ridge
over the northern and central Gulf will continue to promote a
light southerly flow over the forecast area, and expect a
continued pattern of scattered convection developing each day and
lingering into the evening hours. Highs through the period will be
mostly in the lower 90s with lows ranging from the lower 70s
inland to the mid 70s at the coast. /29

MARINE...Surface high pressure continues over the central Gulf,
albeit weakening slightly over the weekend as a mid-level low
retrogrades to the west and over northern Gulf today and Saturday.
Thus, light south to southwest winds persist through Saturday,
before increasing to a light to moderate westerly flow Sunday
through early next week as the surface high over the central Gulf is
once again reinforced. Rain chances increase today through the
weekend as that aforementioned low moves overhead and better
moisture and lift come together. General thunderstorm motion will be
towards the southwest, with stronger storms capable of producing
gusty downburst winds and frequent cloud-to-water lightning. With
the increase in winds, seas likewise build to around 2 to 3 feet
Sunday into early next week. /49




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