Area Forecast Discussion
Issued by NWS Mobile, AL

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS64 KMOB 181216

Area Forecast Discussion
National Weather Service Mobile AL
716 AM CDT Sun Mar 18 2018

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


18/12Z issuance...Widespread IFR/LIFR ceilings and general IFR
visibilies early this morning due to low stratus clouds and areas
of fog. Both the very low ceiling and surface visibilty will
improve later this morning> Prevailing VFR conditions this
afternoon, with periods of IFR in and around scattered showers and
thunderstorms. Southerly surface winds around 10 knots expected,
but with stronger gusts and more variable in direction near
stronger thunderstorms this afternoon. 12/DS


.PREV DISCUSSION... /issued 456 AM CDT Sun Mar 18 2018/

NEAR TERM /Now Through Monday/...A nearly stationary surface
front extending east-west across central Mississippi and Alabama
today will remain in place through tonight, but lift back north as
a warm front on Monday as low pressure moves east across the
Tennessee Valley area and an associated cold front approaches our
area from the west. South of the stationary front to the north, a
very moist airmass remains in place across our area through
Monday, with dewpoints generally remaining in the mid 60s. This
abundant low level moisture, combined with daytime heating today,
will result in MUCAPES up to around 1200 J/KG over interior portions
of the forecast area this afternoon.

In the mid levels, a weak shortwave that has generated scattered
convection from western Texas across northern Louisiana and into
southern Arkansas early this morning is progged by most models to
continue east into central Alabama by this evening. This feature
should be enough to maintain scattered to occasionally numerous
showers and thunderstorms across the region, mainly this afternoon
and evening, and especially over interior northern sections of the
forecast area. The aforementioned instability, combined with modest
deep layer shear of 45 to 55 knots, should allow some of the storms
that do develop to become severe with damaging winds being the
primary threat, although some large hail and an isolated tornado is
not out of the question. The storms will continue into the late
evening hours before decreasing in coverage and intensity overnight.
Storm potential will primarily be over interior sections of the
forecast area, where the Storm Prediction Center has outlined a
slight risk of severe storms, roughly north of a Lucedale to Bay
Minette to Crestview line.

On Monday, another round of showers and storms is expected,
especially over eastern portions of the forecast area. Some of the
storms could again be severe on Monday, especially northeast of a
Camden to Andalusia line. A cold front with some mid level support
will be moving into the forecast area from the west on Monday as
surface low pressure moves east out of the plains states and into
Tennessee. Although instabilities will remain rather high across our
area on Monday (MUCAPES potentially up to around 2200 J/KG) and deep
layer Bulk shear will again be around 50 knots, there remains some
uncertainty regarding convective initiation across our area Monday
as much of the guidance continues to suggest warm 850 mb
temperatures maintaining a capping inversion over our area through
much of the day, especially over the western half of the forecast
area. The cap will be weaker to the east, and it is in that area
previously mentioned (northeast of a Camden to Andalusia line) that
the cap may be more easily broken and the chances for possible severe
storms will be greatest Monday afternoon. We will have to continue
to monitor trends for Monday.

SHORT TERM /Monday night Through Tuesday night/...A complex upper
air pattern for Monday night with lead mid level impulse (height
falls) ejecting eastward over the Appalachians and deamplifying.
On its heels, a more pronounced impulse (associated height falls)
is progged to expand eastward into the Lower MS River Valley by
daybreak Tuesday. This feature gives the lead surface front an
eastward push. Will start off Monday evening with the potential of
ongoing convection moving east across the area, and a gradual
reduction in PoPs late in the night, most notable west of I-65.
There may still be a small lingering threat of severe weather in
the evening mainly over the eastern half of the area where
guidance places the axis of better instability. Thereafter, severe
weather threat looks to end as instability wanes. By Tuesday, a
complex pattern in the surface features sets up initially over the
southeast with two frontal low pressure systems. The first
lifting off the Mid-Atlantic coast early in the day and the second
one strengthening over the southeast as the result of approach of
concentrated mid level height falls. Will likely see wrap around
cloudiness around the southeast US low coming in from the north on
Tuesday. Under these clouds, a small chance of rain or showers
possible. The southeast US low begins to lift quickly off the Mid-
Atlantic coast Tuesday night with drier and much cooler air
filtering in as high pressure begins to move in from the west. /10

LONG TERM /Wednesday Through Saturday/...Rain-free weather
expected mid to late week with high pressure moving east over the
area, then a small chance of showers and storms by Saturday.
Daytime highs Wednesday, below seasonal normals begin to moderate
by the end of next week. Overnight lows trend well below
climatology Wednesday thru Friday mornings. Lows moderate closer
to climatology by Saturday morning with high pressure more to the
east, resulting in a light southerly flow off the Gulf then. /10

MARINE...A predominantly light to occasionally moderate
onshore flow will continue over the coastal waters through late
Monday afternoon, then begin to increase Monday night and shift to
offshore by early Tuesday as a cold front moves east across the
marine area. A strong northwesterly offshore flow is expected
Tuesday through early Wednesday, and a Small Craft Advisory will
likely be required for increased winds and seas. The weaker offshore
flow will then continue through late week, with subsiding seas.


AL...High Rip Current Risk from Monday morning through Wednesday
     morning for ALZ265-266.

FL...High Rip Current Risk from Monday morning through Wednesday
     morning for FLZ202-204-206.



This product is also available on the web at: is the U.S. government's official web portal to all federal, state and local government web resources and services.