Flash Flood Warning 55, NWS Mobile, AL

Area Forecast Discussion
National Weather Service Mobile AL
346 PM CDT Fri Aug 26 2022

.NEAR TERM UPDATE /Now Through Saturday/...The longwave trough
situated near the Great Lakes region finally begins to shift
eastward as weak upper ridging begins to build over the south
central US. One or two weak shortwaves will continue to slowly
progress over, or just south of, the local area through Saturday
morning before the upper ridge pushes overhead. At the surface,
the frontal boundary stretched across the Southeast US continues
to wash out as the low over the ArkLaTex region broadens out and
weakens. With this occurring, some weak surface ridging from the
Western Atlantic will attempt to build into the Southeast US.
Abundant deep moisture, however, will remain in place across the
region for both today and tomorrow, as seen by the saturated
profiles observed in the latest 12Z soundings at LIX and JAN, and
in modeled soundings. PWAT values will generally range from 2.0 to
2.3 inches for both days.

Showers and thunderstorms continue to pop up across the area this
afternoon as a result of outflow boundary collisions. We will
maintain the Flash Flood Watch for counties south of Highway 84
through its expiration time at 6pm CDT this evening due to the
already saturated/near-saturated antecedent conditions in place and
the slow-moving nature of these efficient rain-producing storms.
Coverage will decrease during the evening hours due to the loss of
daytime heating. Similar to today, convection on Saturday will once
again follow a diurnal cycle, with scattered showers and storms
developing offshore/along the coast in the morning and spreading
inland during the day due to sea breeze and outflow boundary
collisions. Coverage should not be as widespread as previous days,
thanks to the ridge building overhead, however, with abundant
moisture still in place, maintained elevated PoPs of around 50-70
percent during the afternoon. Localized flooding will once again be
the primary hazard for Saturday.

Lows tonight will be in the low 70s, with mid to upper 70s along the
coast. Highs on Saturday will be in the mid to upper 80s. Lastly, a
LOW risk of rip currents continues through the period. /96

&&

.SHORT TERM /Saturday night Through Monday night/...To open up the
latter end of the weekend, the forecast area remains between the
western extension of southwest Atlantic upper ridge and a broad
upper trof positioned just west of the MS Valley Sunday. There
are indications though that H50 geopotential heights may build
west over the southeast Monday. Even so, the weaker portion of the
heights aloft look to linger over the Lower MS River Valley. At
the surface, a weak pressure pattern exists following the
dissipation of a quasi-stationary front. Little change noted in
environmental moisture in the near term, with soupy precipitable
water (pwat) values holding firm from 1.9 to 2.1 inches. From a
climatological perspective these pwat value ranges are close to ~1
standard deviation above the means. With the stronger portion of
the ridge aloft to our east, availability of abundant deep
environmental moisture profiles, daytime heating, and convergence
along afternoon sea breeze/other mesoscale boundaries, convective
coverage will remain generally high (supportive of scattered to
numerous coverages). A typical diurnal late summer-time cycle of
storms is expected with morning activity along the coast,
transitioning inland each afternoon. A few storms could also
linger into the early evening hours. The typical hazards in and
near storms are expected, that being locally heavy rain, frequent
lightning and brief strong, gusty winds.

Overnight lows on the muggy side, in the lower/mid 70s. Highs
ranging 85 to 90. /10

&&

.EXTENDED TERM /Tuesday Through Friday/...26.12Z weather model
runs in the medium range show long-wave upper trof axis pivoting
east across the Great Lakes and northeast US Tuesday and sharpens
southward across the OH River Valley and central Appalachians
Wednesday. The upper trof holds over the Mid-Atlantic at various
degrees of amplitude Thursday and Friday. To the southwest of the
mean trof position, the local area looks to see fluctuation in
position of weaker heights or flat ridging at high levels
depending on which spectral model one chooses.

At the surface, a weak pressure trof looks to set-up from the
Mid-Atlantic to the central Gulf coast by mid-week with some
indications of a front slipping southward over the southeast
Thursday and Friday. Forecasters anticipate a diurnally driven
convective pattern to continue with scattered to numerous showers
and storms each day. As for temps through the period, highs are
expected to range generally in the upper half of the 80s/perhaps a
few lower 90's. Lows remaining mostly in the lower/mid 70s. /10

&&

.MARINE... light south to southeasterly flow will continue through
early next week, with winds becoming variable at times. Otherwise,
no impacts are expected for the marine area other than higher winds
and waves in and around showers and thunderstorms. /96

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Flood Watch until 6 PM CDT this evening for ALZ052-059-261>266.

FL...Flood Watch until 6 PM CDT this evening for FLZ201>204.

MS...Flood Watch until 6 PM CDT this evening for MSZ067-075-076-078-
     079.

GM...None.
&&

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