Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 281145

Area Forecast Discussion
National Weather Service Mobile AL
645 AM CDT WED SEP 28 2016

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


12Z issuance...Aside from patchy MVFR fog across interior south
central AL and northwest FL early this morning, VFR will prevail
through the forecast period. Isolated SHRA or TSRA will be possible
east of I-65 today. Calm to light NW winds early this morning should
become west to southwest 5-10 knots by this afternoon. /21


.PREV DISCUSSION... /issued 439 AM CDT WED SEP 28 2016/

NEAR TERM /Now Through Wednesday night/...Water vapor satellite
imagery shows a deep upper level low spinning over the vicinity of
the Great Lakes early this morning, and our forecast area remains on
the base of the associated deep upper level trough encompassing much
of the eastern CONUS. Surface analysis shows a cold front extending
from far southeast LA into southeast MS and northeastward across
southwest and central AL early this morning. Surface dewpoints have
fallen into the upper 50s to mid 60s behind this feature, along with
very light northwest winds. Surface observations reveal some patchy
fog development across a few spots in southwest and south central AL
and the interior northwest FL panhandle again early this morning and
have added mention to the weather grids over these locations through
around 12Z.

The upper level low over the Great Lakes region will continue to dig
southward across the IL/IN/OH/KY vicinity through tonight, while the
associated broad upper level trough encompasses the Ohio/Tennessee
Valley regions and central Gulf Coast/Southeast states. The surface
frontal boundary will continue to slowly sag southeastward today and
should be oriented from coastal southwest AL and northeastward
through south central and southeast AL by late this afternoon.
Precipitable water values will average between 1.4-1.6 inches along
and ahead of the boundary, which could aid in the development of a
few showers and thunderstorms late this morning and this afternoon.
Looking at short range and high resolution model trends, have kept
POPs conservative in the 20% chance range generally along and east
of a Dauphin Island, Brewton, Luverne line today. Drier air will
filter into northwestern portions of the forecast area behind the
front today, with dewpoints looking to drop into the 50s to lower
60s, allowing for much lower and more comfortable relative humidity
values in the 30-40% range. High temperatures today are forecast to
range in the upper 80s to around 90 over most locations, except mid
to upper 80s near the immediate coast and beaches. The cold front
will push offshore tonight, and a much drier deep layer airmass will
spread across our forecast area in its wake overnight, with clearing
skies and cooler temperatures. Overnight lows will certainly feel
more autumn-like over the interior with readings in the upper 50s to
lower 60s. Lows near the immediate coast and beaches will range from
the upper 60s to lower 70s. /21

SHORT TERM /Thursday Through Friday night/... A large upper low
dominates the eastern states through the period, with a deep layer
dry northwesterly flow over the area. A reinforcing front moves
through the area on Thursday bringing another shot of cool and dry
air to the Gulf Coast. This will maintain dry conditions through the
forecast period with temps dropping a few to several degrees below
normal, especially at night, where lows in the 50s can be expected
over much of the region. Highs will generally be in the upper 70s to
low and mid 80s with much lower humidity levels. /13

LONG TERM /Saturday Through Tuesday/...The large upper low over the
eastern states shifts northward slowly through the weekend before
ejecting northeast early next week. A deep layer northerly flow
continues over the area through the period as a surface ridge builds
into the eastern states. This will maintain dry conditions through
Monday. Moisture levels increase enough for rain chances to increase
on Tuesday. Highs on Saturday will be mostly in the lower 80s and
trend gradually warmer to mostly in the upper 80s by Tuesday. Lows
Saturday night range from the upper 50s inland to the mid 60s near
the coast, and likewise trend warmer to the lower/mid 60s inland and
near 70 at the coast by Monday night. /13

MARINE...A light to moderate westerly flow will develop over the
marine area today in advance of a weak frontal boundary approaching
the coast. This boundary will move offshore tonight, with light to
moderate northwest flow expected in its wake. A reinforcing cold
front is expected to move across the marine area late Thursday, and
will bring an increasing northerly flow late Thursday evening
through early Friday morning when wind speeds could range within
cautionary levels. High pressure will build across the Tennessee
Valley and Gulf Coast states this weekend, which should allow for a
generally light offshore flow over the marine area through Sunday.


.MOB Watches/Warnings/Advisories...


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