Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 251135

Area Forecast Discussion
National Weather Service Mobile AL
635 AM CDT Mon Sep 25 2017

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


25/12Z issuance...Showers and thunderstorms will be moving in off
the Gulf and across much of the forecast area today, with most of
the stronger convection this morning remaining just offshore.
Ceilings and visibilities will generally remain VFR, but periods
of MVFR and possibly brief IFR conditions will be possible today
in and near stronger storms. Surface winds primarily easterly at 5
to 10 knots today, becoming slightly more east-northeast tonight.
Winds will likely be more variable with stronger gusts, at times,
near the stronger showers and storms. 12/DS


.PREV DISCUSSION... /issued 430 AM CDT Mon Sep 25 2017/

NEAR TERM /Now Through Monday night/...Water vapor imagery and Sunday
evening regional upper air observations indicate the mid-upper level
low pressure continues spinning just west of the forecast area this
morning, and models indicate this feature will drift south-southeast
over the Gulf and be just south of the forecast area tonight. As a
result, deep layer moisture is streaming north across the region
with the south to southeast flow aloft. At the surface, a high
pressure ridge continues to extend into the area from the northeast,
resulting in a predominant easterly low level flow. The more
southerly moist flow aloft is running up and over the more easterly
flow below, resulting in areas of light rain and embedded heavier
showers across portions of the forecast area this morning, with some
stronger convection noted offshore over the Gulf. With daytime
heating and instability, expect this trend to continue today with a
good to likely chance of rain, showers and some isolated
thunderstorms expected across much of the area. The highest PoPs
will be over the southern half of the forecast area. A few of the
stronger storms could produce gusty winds and small hail, but risk
of severe storms is very low. A low PoP will continue over coastal
zones tonight, where some weak overrunning will continue. Highs
today in the upper 80s over most of the interior and mid 80s
over some southern and all coastal locations. Lows tonight
expected to range from the mid to upper 60s over most of the
interior to the low 70s near and along the coast. 12/DS

SHORT TERM /Tuesday Through Wednesday night/...Upper level
low over the central Gulf coast Tuesday morning, opens up into a
trof axis which pushes southward over the Gulf Tuesday night as
upper ridge builds over the Lower MS River Valley. Highest deep
layer moisture lingers over the southwest half of the local area
Tuesday, where pwats range from 1.7 to 1.9 inches. Considering
moisture, ascent from the upper level low and daytime
instability, forecasters call for chances of showers and storms
generally along and southwest of a line from Waynesboro MS to Fort
Walton Beach FL. Some of the storms locally strong with brief
strong wind gusts, frequent lightning activity and locally heavy
rain being the main threat.

Eastern nose of upper ridge axis over the Lower MS River Valley
drops southward over AL/GA on Wednesday with drier air advecting
in from the northeast and a rain-free day.

Daytime highs in the upper 80s to lower 90s interior and upper
half of the 80s along the coast. Overnight lows, mid to upper 60s
interior to lower to mid 70s coast. /10

LONG TERM /Thursday Through Sunday/...Moving into the latter half
of the week, mid level ridge axis holds in place from TX into the
Lower MS River Valley with upper trof over the northeast Gulf
evolving into a new upper low. Between these two pressure systems
aloft, there is support for a surface frontal boundary to ease
southward to the coast by late in the day Thursday and meander
near the coast or just offshore thru Friday. Although a small
ribbon of moisture may accompany the front, little to no
precipitation is anticipated thru Saturday. North of the
boundary, surface high pressure from the upper Mid-West into the
southern High Plains by the close of the week is forecast to
expand eastward thru the weekend.

Latest gridded temperatures shows the warmest day in the outlook
occurring on Thursday with highs mostly in the lower 90s over the
interior and 87 to 91 coast. Thereafter, a lowering trend with
each day, settling closer to more seasonable numbers in the lower
to mid 80s area-wide into the weekend. Overnight lows to
gradually lower as well, trending closer to seasonal values as we
close out the month of September with the coolest mins (lower to
mid 60s) along and north of I-10 over the weekend. /10

MARINE...High pressure ridging into the marine area from
the northeast will continue through early Wednesday, but begin to
break down during the middle part of the week as a cold front
approaches from the northwest. This will continue to create a
light to occasionally moderate easterly flow through midweek. Mid
to late week, this front may move just offshore out over the
marine area, with a light to moderate offshore flow developing,
becoming more moderate offshore by late Friday. Seas initially 2
to 3 feet offshore, subsiding slightly through midweek, then
rebuilding to around 3 feet offshore by late Friday. Scattered to
numerous showers and a few thunderstorms over the marine area
today and tonight, decreasing in coverage mid week, before
increasing once again late in the week. 12/DS




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