Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 220447

Area Forecast Discussion
National Weather Service Mobile AL
1147 PM CDT Mon May 21 2018

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


06Z issuance...Convection has dissipated over much of the area
this evening, with only a few showers and storms currently
lingering along the coast and offshore. This activity should
remain offshore through the overnight hours. Low stratus and fog
currently settled in over inland portions of the Florida panhandle
and south-central Alabama will linger through tonight, with
cigs/vis dipping as low as LIFR levels at times. Elsewhere, patchy
low-end VFR/MVFR clouds and light fog will be possible, especially
in areas that received rain the previous day. Any visibility
issues should clear up after sunrise, with more scattered showers
and thunderstorms developing across the area Tuesday. Stronger
cells will once again be capable of producing heavy downpours,
frequent lightning and gusty outflow winds. Outside of storms,
VFR conditions and light south winds prevail. /49


.PREV DISCUSSION... /issued 1003 PM CDT Mon May 21 2018/

DISCUSSION...See updated information for land areas below.

UPDATE...22.00Z map analysis shows a weak pressure trof, surface
and aloft over the central Gulf coast. Lingering convection that
has held over into the evening from the afternoon has been
decreasing. Isolated evening storms that formed over Escambia co.
FL have been efficient rainfall producers with very localized
amounts of 3 to 4 inches being observed in several rain gauges
from Cantonment, southward to downtown Pensacola. Storms have
been showing a rapid weakening trend in these areas. Despite
little in the way of remaining precipitation, will adjust PoPs to
low end scattered coverages for the remainder of the evening out
of respect for the deep pressure trof over the area and abundant
Gulf moisture. No changes to late in the night when there is a
chance of storms interior to likely along the coastal zones
considering the potential for nocturnal redevelopment. /10

PREV DISCUSSION... /issued 414 PM CDT Mon May 21 2018/

NEAR TERM /Now Through Tuesday/...A weak upper level closed low
over the western Florida panhandle and south Alabama will lift
slowly northward and evolve into an open wave through Tuesday
afternoon. Meanwhile, a weak surface trough along the north
central gulf coast, roughly just north of the I-10 corridor, will
remain nearly stationary over the next 24 hours.

One primary cluster of showers and thunderstorms currently observed
on radar is located over portions of south central Alabama and the
western Florida panhandle, while convection continues to diminish
over the Mobile metro area. However, the high resolution models are
developing isolated to low-end scattered showers and thunderstorms
in the currently observed precipitation-free areas through early
evening, so will carry some level of POPs for the entire forecast
area to start off the evening. Much of the precipitation is expected
to dissipate by 10 pm, but redevelop east of I-65 after midnight.

Numerous to definite showers and thunderstorms will redevelop
Tuesday across the entire forecast area, especially along the west-
east surface trough axis. Both of the GFS and NAM have MLCapes
ranging from 1200-1700 J/kg by early Tuesday afternoon, so a few of
the storms could become strong with winds up to 45 mph possible.

SHORT TERM /Tuesday night Through Thursday night/...As an upper
ridge slowly advances from the eastern Pains and into the eastern
states through Thursday, a modest upper trof over the northwest
Gulf into eastern Texas/Louisiana evolves into a broad and weak
upper low centered over the central Gulf. A weak surface trof
lingers over the forecast area Wednesday into Thursday, during
which time a surface low is anticipated to develop near the south
central Gulf. Contribution from the sea breeze and also from the
periphery of a surface trof extending northward from the southern
Gulf surface low will contribute to low level convergence along
the weak trof each day. With a favorable convective environment
remaining over the forecast area during the period, this pattern
will support scattered to numerous showers and storms developing
each day. Strong storm development is possible. It is important to
note that despite the presence of the broad upper low over the
central Gulf, the surface low development near the southern Gulf
would be organized with a tropical structure - not as an
extratropical system.  A moderate risk of rip currents is
expected through the period. /29

LONG TERM /Friday Through Monday/...There is much to discuss
during the period and all centers on the potential movement of the
surface low in the southern Gulf. As alluded to in the previous
section, the surface low will likely be organized as a purely
tropical (warm-core) system. There is still uncertainty with the
forecast movement of this system, but it is noted that the
Weather Prediction Centers Surface Fronts and Sea-Level Pressures
forecast maps reflect the guidance consensus of moving the
surface low northward this weekend to somewhere along the northern
Gulf coast, probably the north central or northeast Gulf coast.
At this point, it is too early to discuss much more than rain
chances for the area, but this pattern supports going with at
least likely pops through the period. For other impacts, such as
potential flooding concerns, coastal flooding potential and rip
current risk levels, these will be assessed as confidence
increases in the overall evolution and pattern during the period.

MARINE...A light onshore will persist through midweek as a weak
surface ridge remains across the northeast Gulf of Mexico. Easterly
winds and seas will build later in the week and over weekend as the
next system moves northward over the central gulf. Scattered to
numerous thunderstorms will develop over the marine area both day
and night through midweek, followed by better coverage late in the
week and over the weekend. /22




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