Area Forecast Discussion
Issued by NWS Mobile, AL

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347
FXUS64 KMOB 280501
AFDMOB

Area Forecast Discussion
National Weather Service Mobile AL
1201 AM CDT Fri Jul 28 2017

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

&&

.AVIATION...
06Z issuance...VFR conditions with light and variable winds will
continue through sunrise. Isolated showers and storms are possible
by Friday afternoon, but not as widespread as past few days.
Storms that develop will contain frequent lightning and wind gusts
of 35 knots or greater. 07/MB


&&

.PREV DISCUSSION... /issued 949 PM CDT Thu Jul 27 2017/

DISCUSSION...See updated information for land areas below.

UPDATE...Nearly all of the showers and storms have dissipated
except for a small part of eastern Covington county, and this
portion will dissipate very soon. Have updated to remove pops for
the remainder of the night and made adjustments to temperature
trends and winds. /29

PREV DISCUSSION... /issued 709 PM CDT Thu Jul 27 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...
00Z issuance...Storms across south central Alabama and northwest
Florida will begin to dwindle over the next 2 to 3 hours with the
loss of daytime heating. Light and variable winds expected overnight.
Expect much of the same on Friday afternoon with scattered showers
and storms across the area bringing frequent lightning and wind
gusts of 35 knots or greater. 07/MB

PREV DISCUSSION... /issued 552 PM CDT Thu Jul 27 2017/

DISCUSSION...See updated information for land areas below.

UPDATE...Have updated to increase pops over much of the western
Florida panhandle through the early evening hours, and also to
include small pops over much of southeast Mississippi where a few
stray showers/storms may occur. Made additional adjustments to
temperature trends early in the period. /29

PREV DISCUSSION... /issued 410 PM CDT Thu Jul 27 2017/

NEAR TERM /Now Through Friday/...27.12Z upper air analysis shows
a deep layer ridge positioned from New Mexico, eastward into the
Mid-South. A weakness in the geo-potential height field is more
aligned over the southeast, where a weak trof/cyclonic circulation
was generating cloud cover over the southeast US along the
Georgia and southern South Carolina coast. At the surface, weak
high pressure was analyzed over the central Gulf coast. An
assessment of deep moisture has shown a continued lowering of pwat
values over the past 24 hrs with values now 1.4 to 1.7 inches
over the forecast area. Deepest moisture (pwat`s 1.8 to 2.2 inches
resides over the northern Florida Peninsula closer to the trof
position.

Isolated to lower end scattered coverages of storms is expected
thru the remainder of the afternoon mainly along and east of the
Tombigbee River. Drier conditions look to persist west of the
river which is dominated by the eastern nose of the deep layer
ridge/better compressional sinking there. Considering instability,
latest Mesoscale analysis shows surface based capes between 2000
to 4000 J/KG and along with drier air aloft, the collapse of any
stronger afternoon thunderstorm cores will be efficient in
producing the potential of brief strong gusty surface winds up to
near 50 mph and frequent lightning. A very isolated severe storm
cannot be ruled out, with main threat in these be damaging winds
in excess of 60 mph.

Away from storms, latest observations show afternoon heat index
values on track and ranging from 102 to 107 degrees for many
areas. Review heat safety tips at the following link:
www.nws.noaa.gov/om/heat/index.shtml

Given latest radar trends, will carry over a small chance of
showers and storms into the evening before decreasing. Overnight
lows in the mid 70s interior to mid to upper 70s coast. For
Friday, as eastern nose of mid level ridge retreats west as a
energy dives southeast across MS/AL, could see a complex of storms
begin making impacts over the interior by afternoon. Some of the
storms potentially strong with brief strong wind gusts and
frequent lightning being the main threats. A few severe storms
cannot be ruled out for Friday afternoon as well with a marginal
risk of these over the far northern zones generally along and
north of US Hwy 84. Daytime highs in the lower to mid 90s. Highest
heat index values 102 to 107. /10

SHORT TERM /Friday night Through Sunday night/...An upper level
trough will continue to deepen from the Ohio Valley to the Eastern
Seaboard Friday night into Saturday. A shortwave trough pushing
southeastward across the Ohio and Tennessee Valleys on the back
side of this feature will send a cold front southward across our
forecast area late Saturday afternoon into Saturday night. Another
axis of anomalously deep moisture will sink southward into our
area along the frontal zone Saturday, with precipitable water
values locally as high as 2.3 to 2.5 inches. We expect numerous
showers and thunderstorms to develop along and ahead of the front
as it approaches our region Saturday, and will maintain POPs
around 60% for now, but would not be surprised if these will need
to be increased further with later forecasts given the quality of
moisture that will likely be available to work with. Locally heavy
rainfall and localized flooding or isolated flash flooding may
become a concern with the stronger storms with locally very heavy
rainfall over the area Saturday. A few strong to marginally severe
storms with strong to locally damaging winds and frequent
lightning strikes will also be possible over the area Saturday,
with MLCAPE values between 1500-2500 J/KG. The front continues to
push south Saturday night, with a much drier airmass arriving in
its wake through late Sunday night. Highs Saturday trend a little
cooler in the upper 80s to around 90, rising slightly Sunday to
around 90 to the lower 90s. Lows Saturday and Sunday nights trend
a little cooler with drier air advecting into the area - readings
should range from the upper 60s to lower 70s inland to the mid 70s
along the beaches. /21

LONG TERM /Monday Through Thursday/...A dry northwesterly flow
looks to prevail over the area Monday and Tuesday on the back side
of the persistent upper trough over the eastern CONUS. POPs will
remain very limited and mainly confined over southern areas.
Deeper moisture may bring better coverage of showers and storms by
mid to late week as southwest flow aloft increases ahead of an
upper trough axis from the Tennessee or Mississippi Valley and
back toward TX. Temperatures otherwise remain near seasonal
levels. /21

MARINE...Weak high pressure over the north central Gulf begins to
break down to close out the week, allowing a weak frontal boundary
to move south to the central Gulf coast on Saturday. Showers and
thunderstorms will increase in coverage late in the week and over
the weekend with the approach of the frontal boundary. Winds and
seas will be higher near showers and thunderstorms. The front moves
south of the coastal waters by Monday and begins to stall. As this
occurs and with high pressure moving east over the deep south, more
of an easterly wind component is progged to set up Monday and
Tuesday. /10

&&

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

$$

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