Special Weather Statement, NWS Mobile, AL

Area Forecast Discussion
National Weather Service Mobile AL
339 PM CDT Fri Sep 22 2017

.NEAR TERM /Now Through Saturday/...An upper trough visible in water
vapor satellite imagery currently extends roughly from post-tropical
cyclone Jose off the New England coast southwest into the
northeastern Gulf. Ongoing scattered thunderstorms over the
southeastern states are being supported by strong daytime heating,
weakened static stability across the region, and upper level
divergence associated with a jet streak rotating around the western
side of the trough. Despite the dynamic support aloft, storms should
remain largely driven by heating and are thus expected to gradually
dissipate after sunset this evening. Until then, coverage will
increase into the late afternoon hours as storms drift from
northeast to southwest, with frequent cloud-to-ground lightning and
brief heavy downpours being the primary threats in the stronger
cells. Skies then clear out and light patchy fog will be possible
late tonight through sunrise Saturday. Low temps will range from the
upper 60's to around 70 inland and the low to mid 70's along the
immediate coast.

The aforementioned upper trough is bisected by a narrow ridge
building ahead of a very deep longwave trough over the western
CONUS. The northern half of the former trough, including the
remnants of Jose, are caught up and swept east over the Atlantic by
an embedded shortwave in the mid-latitude jet (currently situated
over southern Canada). The southern half is pinched off, forming a
cutoff low which then begins to push south over the southeastern
U.S. late tonight into Saturday morning. Our local area remains on
the "dry" side of this upper low Saturday afternoon and evening as
it retrogrades over southeastern Alabama and the Florida panhandle,
with only a slight chance for some isolated showers and storms
during that time. High temps reach the low 90's over southeast
Mississippi and far southwest Alabama, where less cloud cover will
allow for plenty of daytime heating. Over south central Alabama and
the western Florida panhandle, expect highs to stay a couple degrees
cooler (upper 80's to around 90) due to greater cloud cover
associated with the retrograding upper low. Look for convective
activity to increase over our area later in the weekend as the low
continues to drift to our west. /49

.SHORT TERM /Saturday night Through Monday night/...Period begins
with the aforementioned FL Panhandle mid-level upper low moving
westward. Clouds and the chance of rain both increase Saturday
night and into Sunday as the feature moves further west to be
located over coastal MS by dark on Sunday. On the east side of the
upper system is where our greatest rain chances will be. So,
Sunday expect a fairly good coverage of showers with scattered
thunderstorms from late morning on (and spreading in from the
southeast). Some of the most intense storms may produce localized
heavy rainfall given both higher absolute values of low level
moisture and moisture flux convergence (especially south of
Highway 84 and closer to the coast and also across interior SE
MS)convergence. Relatively higher rain chances continue into
Monday afternoon as regional static stabilities remain low due to
the presence of that feature. Shower and thunderstorm coverage
decreases Monday Night as the upper low moved further westward.
Temperatures will average a few degrees cooler than normal on
Sunday afternoon, but it will be muggy.

The rip current risk may climb on Sunday, as the day begins with an
increasing easterly wind. It becomes more southeasterly as the upper
low moves further west.  Eventually slightly longer period swell
will begin and there is a pronounced spring tide early next week.
The risk will remain elevated into early next week. The Surf Zone
Forecast will likely be updated later today for Sunday. /23 JMM

.LONG TERM /Tuesday Through Friday/...On Tuesday, the upper low
fills and is advected back to the east, away from the region, in the
deep-layer mean flow as the pronounced deep-layer U.S. Western
Trough advances slightly eastward into the Plains. Scattered
showers and thunderstorms linger, but coverage should be a little
less each day this period. For the remainder of the period, back
to drier conditions as ridge builds over the Gulf of Mexico
through Friday. Will have to watch exactly how the western U.S.
trough advances, forecast could change slightly for Friday. /23
JMM

&&

.MARINE...Winds and seas build slightly over the weekend as the
local pressure gradient tightens between a building ridge to the
north and Hurricane Maria east of the Bahamas. Expect east to
southeast winds of 10 to 15 knots with gusts to around 20 knots
Saturday through Sunday night. Seas build to around 2 to 3 feet over
the weekend. The gradient relaxes again heading into next week, with
easterly winds around 5 to 10 knots and seas returning to around 1
to 2 feet Monday through midweek. Showers and thunderstorms will
remain possible through the forecast period, with the greatest
coverage currently expected Saturday night through Sunday. /49

&&

.PRELIMINARY POINT TEMPS/POPS...
Mobile      70  89  70  85 /  10  20  20  60
Pensacola   73  88  72  83 /  10  20  30  50
Destin      74  88  75  84 /  10  20  30  50
Evergreen   69  88  68  86 /  10  20  10  40
Waynesboro  68  90  67  86 /  20  20  10  50
Camden      69  88  68  87 /  20  20  10  40
Crestview   70  88  70  85 /  10  20  20  50

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...None.
&&

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