Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 180529 AAD

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
1129 PM CST Sun Dec 17 2017

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


06Z issuance...VLIFR to LIFR ceilings will affect most of the
area during the period including corresponding low visibilities
during the overnight hours and into early Monday morning. Light
winds are expected tonight then become light northwesterly on
Monday. Another round of showers develops late tonight into early
Monday morning and shifts eastward across the area during the
remainder of the day. /29


.PREV DISCUSSION... /issued 900 PM CST Sun Dec 17 2017/

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

UPDATE...Am wrestling with a difficult fog forecast tonight which
is a combination of advection type dense fog for the coastal
areas combined with patchy to areas of dense fog associated with
a frontal boundary which is affecting the western and much of the
northern portion of the forecast area. With the advection fog
continuing overnight while the frontal boundary remains nearly in
the same position, this leaves generally south central Alabama
caught between these two fog production areas, where low ceilings
will be favored with at best patchy dense fog development later
tonight. Based on the latest trends and observations, have opted
to include Clarke and Wilcox counties into the Dense Fog Advisory
and will continue to monitor. /29

PREV DISCUSSION... /issued 737 PM CST Sun Dec 17 2017/

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

UPDATE...The area of showers has diminished significantly and
shifted eastward, so have updated the remainder of the evening
hours to go with good chance pops over the easternmost portion
tapering to dry conditions further to the west. Made other minor
adjustments. /29

PREV DISCUSSION... /issued 555 PM CST Sun Dec 17 2017/

DISCUSSION...See updated information for land areas and aviation
discussion below.

UPDATE...Have expanded the Dense Fog Advisory to include the
remainder of southeast Mississippi and interior southwest Alabama
based on observations and guidance showing dense fog likely to
affect these areas. Also increases pops for much of the area this
evening as an area of rain with a few possible storms has been
decreasing more slowly than earlier thought. Made additional
minor adjustments. /29

00Z issuance...LIFR to VLIFR conditions in a mix of dense fog and
low ceilings will continue to develop across the area tonight.
Visibilities improve during the morning on Sunday, although will
be slowest to improve near the coast. Ceilings are expected to
only improve to IFR at best on Sunday. /29

PREV DISCUSSION... /issued 426 PM CST Sun Dec 17 2017/

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

UPDATE...Have updated to issue a Dense Fog Advisory for the
western Florida panhandle, extreme southwest Alabama and extreme
southeast Mississippi which will be in effect until 9 am Monday.
Dense fog has developed over the Mobile Bay area and is in the
process of developing across other bays further to the east as
well as adjacent land areas, and will spread further inland to
affect the advisory area. Will need to continue to monitor to see
if areas further inland will need to be included in the advisory.
No other major changes. /29

MARINE...Have updated to issue a Dense Fog Advisory for the
Alabama and western Florida bay waters, including the adjacent
near shore waters.  Dense fog has developed over the Mobile Bay
area and is in the process of developing across other bays further
to the east. The advisory will be in effect until 9 am Monday and
may need to be extended in time to later in the day on Monday.

PREV DISCUSSION... /issued 342 PM CST Sun Dec 17 2017/

NEAR TERM /Now Through Monday/...Areas of rain, showers and
isolated thunderstorms has been moving east across the area today
as expected, and is not gradually weakening. Look for weakening
trend to continue this evening as tail end of upper shortwave
continues to lift northeast away from the area. Rains will taper
off this evening, but likely increase in coverage once again
(especially near the coast) late tonight and on Monday as yet
another weak upper level impulse approaches from the southwest.
Not expecting any widespread heavy rainfall, nor are we expecting
any severe weather with the embedded isolated thunderstorms that
are expected to remain a possibility. Widespread areas of fog have
yet to develop across much of the area, but models still indicate
areas of fog, dense in some locations near the coast, will
develop tonight. This still seems reasonable as a warm and moist
southerly flow moves ashore over the relatively cool near shore
waters. Late tonight at least patchy fog may develop well inland,
and we will have to monitor for the possibility of a Dense Fog
Advisory for at least portions of the area late tonight. Some fog
likely persisting near the coast well into the day on Monday. Much
warmer than normal temperatures for this time of the year
expected in the near term, especially tonight when overnight lows
will be 20-25 degrees above normal. 12/DS

SHORT TERM /Monday night Through Wednesday night/...A break in
the rain is expected Monday night as rain focuses along the warm
front over the Tennessee Valley and along the cold front
associated with the approaching system to the west. Rain chances
increase again Tuesday and Tuesday night as the upper low
approaches the region. Rain along with embedded thunderstorms
will increase after midnight Tuesday night as the sfc low moves
into the Tennessee Valley and a trailing cold front approaches.
Rain will end from west to east late Wednesday morning into the
afternoon as the front moves east of the area. Temps will be well
above normal through the period.

Advection fog will continue through much of the period as
dewpoints in the mid and upper 60s move northward over the cool
Gulf and bay waters. Light southerly winds will allow the sea fog
to advect far inland at times. While the inland areas will see the
fog dissipate during the daytime hours, some of our coastal zones
could see extended periods of dense fog lasting throughout the
daytime hours. /13

LONG TERM /Thursday Through Sunday/...The forecast late in the
week into the weekend remains very uncertain as now global models
are stalling a cold front to our west. This would keep the area
dryer and much warmer than what is currently forecast. Will
continue with the current blended approach and see if future runs
continue to flip-flop or come into better agreement. /13

MARINE...A light to moderate southerly wind flow is expected over
the coastal waters through most of this week as a high pressure
ridge persists near and to the north of the marine area. Only
exception will be on Wednesday, when a weak front may drift south
into the marine area, creating a brief period of northwesterly flow,
especially near shore. Showers and thunderstorms can be expected at
times through the forecast period. Little change in waves/seas
expected. Areas of fog, likely becoming dense at times, can be
expected into the middle part of this week as well, especially over
nearshore Gulf waters, area bays and sounds. 12/DS


AL...Dense Fog Advisory until 9 AM CST Monday for ALZ051>054-261>266.

FL...Dense Fog Advisory until 9 AM CST Monday for FLZ201>206.

MS...Dense Fog Advisory until 9 AM CST Monday for MSZ067-075-076-078-

GM...Dense Fog Advisory until 9 AM CST Monday for GMZ630>636-650-655.



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