Area Forecast Discussion
Issued by NWS Mobile, AL

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752
FXUS64 KMOB 251136 AAA
AFDMOB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
636 AM CDT MON JUL 25 2016

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

&&

.AVIATION...
12Z issuance...VFR conditions will prevail through this evening.
Seeing some coastal showers this morning. The best coverage of
scattered storms later today will be confined to coastal AL/NW FL and
portions of inland SE MS. Winds also become breezy (10-15 kt) out of
the east and southeast by late morning into the afternoon. Convection
fades this evening, but will redevelop along coastal areas after
midnight and may become numerous from Gulf Shores east to Destin by
sunrise. Pockets of MVFR ceilings are also likely prior to daybreak
Tuesday. 34/JFB

&&

.PREV DISCUSSION... /issued 422 AM CDT MON JUL 25 2016/

NEAR TERM /Now Through Monday night/...A tropical upper tropospheric
trough (TUTT) currently over the far eastern Gulf will retrograde
west today toward the north central Gulf. Meanwhile, a deep layer
moisture gradient persists across our region with the highest
moisture values over the southern and western zones. This gradient
will stay in place through the day with precip waters hovering near
or just under 1.5 inches in the far NE zones with values around
1.8-1.9 inches across the coastal zones west into inland SE MS.
Therefore, the best chance for scattered convection will be across
the south and west forecast area with only a slight chance well
inland north of Highway 84. Highs very similar to the last few days
with upper 80s to near 90 along the immediate coast and mid 90s well
inland. Heat indices topping out in the 100-105 degree range.

The TUTT will continue its westward progression across the Gulf
tonight. Regarding convection, the evening hours will generally be
diurnally driven with most convection over land fading away.
However, as the TUTT moves west of the area overnight, southerly
deep layer winds with send a surge of tropical moisture into the
marine and coastal areas (precip waters 2 to 2.2 inches). Therefore,
scattered to numerous showers and thunderstorms are expected to
develop over the coastal waters after midnight and affect coastal
areas as the activity moves northwest. Have increased rain chances
into the likely category from roughly Gulf Shores over to Destin.
These storms will produce torrential downpours. 34/JFB

SHORT TERM /Tuesday Through Wednesday night/...Tuesday into Tuesday
night continues to be a worrisome period in the forecast. As a
system moves over and west of the fa late tonight through Tuesday as
an upper ridge builds west over the southeastern states, a very humid
airmass returns to the fa (precip h20 values rising to around 2.3").
Combined with decent instability (1000-1500j/kg) for strong
thunderstorms and decent 15-20kt southerly flow, some localities may
see several thunderstorms pass over. With the increasing moisture
levels comes better rainfall efficiencies and a better chance of
localized water problems. At this point, it does not look like the
coverage of any flooding problems will be extensive enough for a
watch, though. With the increased rain coverage and cloud cover over
mainly the southern half to two thirds of the fa, temps below
seasonal expected, with coolest temps along the coast, warmest well
inland. Highs for Tuesday range from the mid to upper 80s along the
coast to low to mid 90s inland. with warming southerly flow off the
Gulf continuing, lows ranging from around 80 along the coast to low
70s north of the Highway 84 corridor expected.

Wednesday through Wednesday night...the upper ridge over the
southeastern states becomes dominant. How strong the ridge and
ultimately where an upper trough develops over the Lower Mississippi
River Valley end up varies in the guidance. The NAM is advertising
the strongest upper trough, the GFS the weakest. Have blended the
guidance, with numbers more inline with the ECMWF resulting. With
eastern portions of the fa seeing the better subsidence from the
upper ridge, temps above seasonal (low to mid 90s) expected, with a
chance of rain. The temps will drop (mid to upper 80s) as one moves
west over the fa, with the chance of rain increasing. Lows in the low
to mid 70s expected Wednesday night over most of the fa, warmer along
the coast.

/16

LONG TERM /Thursday Through Sunday/...Shortwave energy moving into
the upper trough over the Mississippi River weakens and shifts east
the upper ridge over the southeast. The GFS is most aggressive with
this shift, resulting in a cooler/wetter forecast than the ECMWF.
Have went with a blend, resulting in temps/pops around seasonal.

/16

Marine...An upper level disturbance moving west across the Gulf
and an associated surface trough over the northern Gulf results in
an increase in onshore flow today through midweek. Winds near 15 kt
are likely at times over the open Gulf waters. Seas will build to 2
to 4 ft as a result this afternoon through Wednesday. Winds and seas
diminish Thursday and Friday as high pressure builds back over the
central and eastern Gulf.

Isolated to scattered showers and storms are expected today, with
storms becoming numerous at times after midnight tonight through
Wednesday. The storms will produce frequent lightning, locally
higher winds/waves, and torrential downpours. Waterspouts are also
possible. 34/JFB

&&

.MOB Watches/Warnings/Advisories...
AL...None.
FL...None.
MS...None.
GM...None.
&&

$$

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