Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 190454 AAC

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
1154 PM CDT Fri Aug 18 2017

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


06Z issuance...General VFR conditions expected through most of the
night, with favored locations seeing VISBY drops into MVFR levels
closer to sunrise. Another round of shra/tsra are expected to
develop offshore, then develop inland during the day. Local drops
to MVFr levels likely in the storms, along with possible winds
gusts to 30 knots in the stronger storms are possible during the
afternoon/early evening hours.



.PREV DISCUSSION... /issued 1019 PM CDT Fri Aug 18 2017/

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

UPDATE...Afternoon package cleaned up to remove evening precip,
with nothing showing on radar attm. Am still expecting shra/tsra
to develop after midnight, so have left in. everything out


PREV DISCUSSION... /issued 624 PM CDT Fri Aug 18 2017/

DISCUSSION...Updated for latest aviation discussion below.

00Z issuance...Early evening activity will bring local drops and
cigs to MVFR levels. Strong thunderstorm outflow of 30kts+ have
been in evidence with the stronger storms. These storms have been
isolated as they move SSE at around 15 knots. With the setting
sun, coverage and intesity will decrease, with patchy fog
developing over preferred areas inland overnight. Another round
of TSRA development is expected Saturday afternoon, with scattered
coverage and a few strong storms.


PREV DISCUSSION... /issued 333 PM CDT Fri Aug 18 2017/

NEAR TERM /Now Through Saturday/...Current radar and satellite
observations indicate isolated to scattered showers and
thunderstorms developing across southeast Mississippi and the
immediate coast this afternoon amidst a healthy summertime cu
field. This activity is expected to continue into the early
evening hours before tapering off after sunset, with storm motion
remaining slow and generally from northwest to southeast. The
heavier cells could be capable of producing locally heavy
rainfall, gusty winds, and frequent lightning. Outside of showers
and storms, surface obs are showing temps a few degrees above
expected this afternoon, particularly along the coast where weak
northwest flow is inhibiting the inland sea breeze propagation.
Heat indices are generally running in the 100 to 105 degree range.
Remember to bring water and sunscreen if working or planning
activities outdoors, and take frequent breaks in shade or A/C.

A weak upper-level trough extending from the central Caribbean north
over the Florida peninsula pushes northwest into the southern and
central Gulf through the remainder of the near term. In response to
this shift, the area of high pressure currently over the northern
Gulf pushes west over Texas, though ridging over the western
Atlantic will continue to nose west over the northeastern fringe of
our local area. Meanwhile at the surface, weak high pressure
persists over the northern Gulf, maintaining the current pattern of
northwesterly flow Saturday morning shifting to more southwesterly
during the afternoon. Precipitable water remains below seasonal
during this time over interior southern Alabama, where models
indicate PWATs down around 1.5 inches. This, coupled with weak
subsidence beneath the aforementioned upper ridge nosing in from the
east, should limit convective activity over these areas Saturday,
with only a slight chance in place for a few isolated cells to form.
That said, have kept higher (chance) PoPs along the coast and over
the southwestern third of the forecast area during the day Saturday,
where PWATs are expected to remain closer to 2.00 inches and the
approaching inverted trough over the central Gulf will lend a
supportive hand in getting more scattered thunderstorm activity

In terms of temperature, expect more of the same tonight and
tomorrow. Lows will range from low to mid 70`s inland to upper 70`s
along the immediate coast. Highs reach the low to mid 90`s areawide,
with heat indices once again reaching around 100 to 105 degrees.

SHORT TERM /Saturday night Through Monday night/...An upper
trough will move westward across the central Gulf through the
weekend. Meanwhile, a weak front will gradually wash out across
the region through the weekend. As the upper trough moves into
the western Gulf on Monday, moisture levels will increase across
the area with precipitable water values climbing back above 2
inches. This will maintain scattered showers and thunderstorms
over the weekend with slightly higher chances on Monday as
moisture levels increase. Highs remain in the low to mid 90s with
heat index values between 102-107 in most areas. /13

LONG TERM /Tuesday Through Friday/...An upper trough will move
from the upper midwest on Tuesday through the northeast by
Friday. This will send another front southward toward the area by
the end of the week. A typical August pattern of daily, mostly
afternoon and early evening, scattered showers and thunderstorms
can be expected through midweek with chances increasing late in
the period as the frontal boundary sinks southward. Heavy rain and
frequent lightning will be the main threats. A few isolated
storms could become strong and produce gusty winds. Highs will
continue in the low 90s with lows in the mid and upper 70s. /13

MARINE...Weak surface high pressure persists over the northern Gulf
into the weekend, continuing the pattern of northwesterly flow
during morning hours and southwesterly flow during afternoon hours
today through late Saturday. Heading into Sunday, high pressure
begins to ridge westward from the western Atlantic into the
southeastern U.S., leading to a shift in surface flow to more east
to southeasterly Sunday into early next week. Seas remain around a
foot over the weekend before increasing to around 2 feet early to
mid next week. Locally higher winds and seas can be expected in and
around showers and thunderstorms through the period, as well as
frequent lightning and reduced visibilities due to heavy rainfall in
stronger cells. /49




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