Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 031633 AAA
AFDMOB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
1033 AM CST Sat Dec 3 2016

.DISCUSSION...See updated information below.

&&

.UPDATE...Adjusted sfc temps up just a degree or 2 for most
locations in the forecast area for the remainder of this morning.
Also kept the chance of rain the same for all location mentioning
mostly light rain for the rest of today. 32/ee

&&

.MARINE...Went ahead and increased winds mostly along the immediate
coast including inland bays and sounds mainly to reflect current
conditions. As a result a small craft advisory is now in effect for
the lower end of Mobile Bay and the Mississippi Sound east of
Pascagoula through this afternoon. 32/ee

&&

.AVIATION...
18Z issuance...Expect mostly VFR cigs and visibilities through this
afternoon followed by MVFR to IFR cigs and visibilities late tonight
through sun morning. Lower ceilings and visibilities mostly in and
around scattered areas of light rain and showers later this afternoon
and early tonight followed by heavier showers with maybe an embedded
thunderstorm during the morning hours on sun. 32/ee

&&

.PREV DISCUSSION... /issued 624 AM CST Sat Dec 3 2016/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...
12Z issuance...VFR ceilings will lower through the day as moisture
levels increase. VCSH can be expected near all terminals through
today with better chances of rain coming tonight. /13

PREV DISCUSSION... /issued 454 AM CST Sat Dec 3 2016/

NEAR TERM /Now Through Saturday night/...A large upper level trough
continues to dig across northern Mexico, resulting in strong
southwest upper level flow across the Gulf Coast. Mid and high level
moisture within the southwest flow is helping to moisten the
atmosphere from the top down. However, the lowest layers of the
atmosphere remain fairly dry. Radar indicates some returns across
the area this morning with only small amounts observed at the ground
due to the dry air. Surface high pressure will continue to move
eastward through tonight allowing a more east to southeast flow to
develop by late tonight as a warm front approaches the coast. A high
risk of rip currents will develop along the Gulf beaches of Alabama
and Northwest Florida tonight. The approaching warm front will allow
better deep layer moisture to return to the area through the day with
gradual moistening of the low levels by evaporation allowing some
higher rainfall amounts this afternoon and tonight. The higher rain
chances will be across western and northern zones through tonight as
that is where the highest axis of moisture looks to setup. Not
expecting any thunder today and tonight as a stable atmosphere
continues over the region.

Highs today will climb into the mid and upper 50s across
northwestern portions of the area. To the south and east of I-65
highs will climb into the mid and upper 60s. Lows tonight will fall
into the upper 40s and low 50s inland to around 60 along the coast. /13

SHORT TERM /Sunday Through Monday night/...Sunday looks to be a very
wet and cloudy day with southerly winds creating breezy conditions
near the coast. A high risk of rip currents will continue along the
Gulf coasts of AL and FL Sunday...not exactly swimming weather,
anyway. The anomalously deep upper low pressure system which has
been digging southward over Mexico the past couple of days finally
begins to propagate eastward. As a result, a warm front will move
northward out of the Gulf to perhaps over the coastal counties during
the day on Sunday and then stall close to the I-65 corridor. Looks
like the front will have trouble proceeding much further northward
due to the influence of the strong surface high pressure system
ridging southeastward from the Virginia/North Carolina region.
Deepening southerly flow then creates a warm and very moist conveyor
belt over the area creating optimal deep layer isentropic ascent
leading to widespread rainfall...occasionally enhanced as elevated
convection is generated by minor shortwave troughs rippling through
the moist south to southwesterly flow aloft.

The warm front pushes further inland on Monday as the surface low
moves northeastward out of the Gulf over the Lower Mississippi River
Valley. As a result...at least a slightly unstable warm sector will
exist across the area. Widespread cloud cover and rain should keep
instability somewhat in check. However, as the day progresses and
the cold front approaches deep layer shear over the area increases, a
low level jet of 40 to 50 knots develops by Monday evening with 0-1
KM helicity values climbing to 200 to 300 m2/s2. We could see some
rotation develop in some of the discrete cells ahead of the front
Monday evening and possibly produce an isolated tornado or two. As
well...marginally severe straightline winds will be possible with the
main line of storms moving through in advance of the cold front
Sunday night. Total rainfall of 2 to 4 inches with locally higher
amounts are possible through the period.

Temperatures will trend well above climatological normals through the
short term.

LONG TERM /Tuesday Through Friday/...A few lingering showers may
linger across the area early Tuesday as the cold front exits the
region. A dry southwest to west flow will follow in the fronts wake.
Temperatures will trend a little cooler but remain above normal. Cold
air will not arrive here until the next cold frontal passage expected
sometime Wednesday night through Thursday. A band of light to
moderate rainshowers will likely arrive with the boundary. But
cool...dry...modified arctic air will follow in its wake dropping
temperatures well below what is typical for this time of year and
sending most of the forecast below freezing Thursday night and even
colder going into the weekend./ 08

MARINE...A strong easterly flow will continue through tonight ahead
of storm system approaching from the west. A strong southerly flow
develop on Sunday as a warm front moves northward over the marine
area. Winds and seas decrease late Sunday into Monday before
increasing Monday night into Tuesday as a cold front approaches from
the west. The front moves across the marine area Tuesday morning
with moderate offshore winds in the wake of the front. /13

&&

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

FL...High Rip Current Risk from 6 PM CST this evening through Sunday
     afternoon for FLZ202-204-206.

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

     Small Craft Advisory until 6 PM CST this evening for GMZ631-632.

&&

$$

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