Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 041837 AAB
AFDMOB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
1237 PM CST Sun Dec 4 2016

.DISCUSSION...Updated for latest marine discussion below.

&&

.MARINE...Have updated to include a marine dense fog advisory for
Mobile Bay where visibilities have been as low as a half mile.
Visibilities will improve late this afternoon into the early evening
hours as the light southerly flow turns northerly. /29

&&

.PREV DISCUSSION... /issued 1202 PM CST Sun Dec 4 2016/

DISCUSSION...See updated information for land areas and aviation
discussion below.

UPDATE...Will update to make downward adjustments generally west of
I-65 as the bulk of the convection east of I-65 moves slowly off to
the east with less coverage expected further to the west. Will make
additional adjustments to temperature trends and winds. /29

AVIATION...
18Z issuance...An area of showers located mostly along and east of
I-65, with an isolated stray thunderstorm or two, will shift eastward
through the day. Expect additional rains to advance into the area
from the west this evening and continue on and off through Monday
morning.  The frontal boundary, which is currently over the western
Florida panhandle, will be pushed back offshore late this afternoon
where the boundary remains through the end of the period. Ceilings
will tend to be IFR/MVFR through the period, except for IFR/MVFR near
the coast. /29

PREV DISCUSSION... /issued 607 AM CST Sun Dec 4 2016/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...
12Z issuance...MVFR to IFR ceilings will continue through the
morning with period of RA and BR. VCTS will be possible this
afternoon and evening with associated reductions in the ceilings and
visibilities. /13

PREV DISCUSSION... /issued 453 AM CST Sun Dec 4 2016/

NEAR TERM /Now Through Sunday night/...the large upper low
continues to move slowly east across Northern Mexico this morning
and will continue slowly eastward tonight as it begins to eject
northeast. Ahead of this feature, a large moisture plume stretches
from the eastern Pacific northeast across the eastern states. As the
upper low moves east, the moisture plume will also shift eastward
across the central Gulf Coast. Meanwhile, a sfc warm front over the
northern Gulf will move northward into southern portions of the area
this afternoon. To the west, a weak wave of low pressure will move
east along the front with a line of showers and embedded
thunderstorms through the afternoon hours. A strong low lvl jet will
bring low to mid 60s dewpoints back into the area south of the warm
front by this afternoon. This will support MLCAPE values of
500-1000J/KG along with deep layer shear values of 50-55 knots.
Therefore, some strong to severe thudnerstorms are possible with
straight line wind and isolated tornadoes a possibility. The tornado
potential will likely be maximized near the warm frontal boundary
where low lvl shear will be maximized. SPC has outlooked the southern
1/3 of the area in a marginal risk of severe thunderstorms. Locally
heavy rainfall amounts of 1-2 inches will be possible especially
across northern portions of the area. Patchy fog will be possible
near the coast as the warm front moves northward.

The severe threat ends by this evening as the low lvl jet weakens
and the wave moves east of the area. Meanwhile, the warm front is
shoved back to the south. Highs today will range from the upper 50
and low 60s across northern areas to low 70s across the south. lows
tonight range from the low 50s inland to mid 60s near the coast. /13

SHORT TERM /Monday Through Tuesday night/...The deep upper level low
pressure system pushes northeastward into Texas Monday driving a
surface frontal system towards us. A warm front over the Northern
Gulf will try to push inland but will be initially thwarted by the
strong surface high pressure over the Southeastern States ridging
southwestward into our area. Initially the warm front will likely get
hung up on the coast or just inland. However...upper level dynamics
continue to lift northeastward and the surface low moves off the Gulf
into Louisiana...expect some northward movement then of the warm
frontal boundary. Storms north of this boundary will remain elevated
but storms developing in the warm sector will be able to tap into
some low level instability...though marginal...as ML CAPEs appear to
only climb as high as 400 to 600 J/KG. During the afternoon and
evening hours deep layer bulk shear (0 to 6 KMs) climbs to 50 to 70
knots...with 0 to 1 KM helicities climbing to 200 to 300 m2/s2 as
the cold front approaches from the West Monday evening. Low Top
Supercells will be possible from the warm frontal bounday southward
and could generate strong to marginally severe wind gusts as well as
a short lived tornado or two Monday afternoon and evening. Wet Bulb
Zero heights look to remain too high to support severe hail criteria.

A band of showers and thunderstorms forming ahead of the cold front
and move through the region Monday evening and Monday night. Band
looks to be a little disorganized as upper level energy shears
somewhat north and south of us...but will still may produce some
strong to perhaps low end severe straight line winds. The cold front
should move through the area by late Monday night and early Tuesday
morning with skies slowly clearing in its wake. Mostly clear skies
and drier weather expected by late Tuesday afternoon through Tuesday
night. Total rainfall accumulations Monday through Tuesday night look
to range from around 1 to 2 inches

High temperatures will range from the mid 60s to mid 70s Monday with
lows following into the mid 50s and 60look to form outs. Tuesday`s
highs will range from the mid 60s to low 70s with overnight lows
ranging from the mid 40s to low 50s. /08

LONG TERM /Wednesday Through Saturday/...The next cold front is
forecast to move across the region Wednesday night with much cooler
air following in its wake. Overnight lows should fall below freezing
Thursday night and Friday night and daytime highs Friday will
struggle to get out of the 40s...a little warmer Saturday with highs
climbing into the 50s. /08

MARINE...A strong east to southeast wind flow will continue over
the marine area this morning becoming southerly today as a warm
front moves north of the marine area. Winds diminish some late
tonight into Monday before increasing again Monday night into
Tuesday as a cold front approaches from the west. The cold front
moves across the marine area early Tuesday, leading to moderate
offshore flow by midweek. Winds and seas will build later in the
week as a much colder airmass moves over the area. /13

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...High Rip Current Risk until 6 PM CST this evening for ALZ265-266.

FL...High Rip Current Risk until 6 PM CST this evening for FLZ202-204-
     206.

MS...None.
GM...Small Craft Advisory until 6 PM CST this evening for GMZ650-655-
     670-675.

     Dense Fog Advisory until 6 PM CST this evening for GMZ630-631.

&&

$$

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