Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 191735 AAC
AFDMOB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
1135 AM CST Sun Feb 19 2017

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

&&

.AVIATION...
18Z issuance...VFR conditions thru the afternoon with winds light.
Conditions support the re-development of nighttime fog with
restrictions to vsby lowering to LIFR/VLIFR categories by and
after 20.03Z. Overnight winds continue light. /10


&&

.PREV DISCUSSION... /issued 911 AM CST Sun Feb 19 2017/

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

UPDATE...Widespread dense fog has decreased in areal coverage and
the dense fog advisory has been allowed to expire at 9 AM. Zones
updated to remove headlines. Latest satellite and surface
observations indicate that there is lingering fog near river
valleys and along portions of the coast near area bays. Overall
trends observed in satellite animations, though, indicate that
fog is shrinking in these areas. With that in mind, anticipate
lingering fog to completely mix out by the noon hour. /10

PREV DISCUSSION... /issued 537 AM CST Sun Feb 19 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...
12Z issuance...LIFR to IFR cigs and visibilities through about
19.15z followed by MVFR to VFR cigs and visibilities through
19.17z followed by VFR conditions through 20.03z then MVFR to IFR
cigs and visibilities through 20.12z. Widespread dense fog will
begin to lift around 9 am CST this morning then redevelop by 9 pm
CST tonight. Winds will be light and variable early today
becoming east to southeast at 5 to 8 knots late this morning
through early this evening then becoming light and variable
through 20.12z. 32/ee

PREV DISCUSSION... /issued 453 AM CST Sun Feb 19 2017/

NEAR TERM /Now Through Sunday night/...High amplitude mid to
upper ridge just west of the MS river valley early this morning
will shift east across the forecast area today and tonight with
ridge axis situated along the AL/GA line and central FL panhandle
by 12z Sun. At the surface high pressure becomes reestablished
over the SE conus and central Gulf states early today becoming
reinforced from the north by early Mon morning. With this pattern
expect mostly sunny skies and increase subsidence today possibly
leading to afternoon high temps reaching or just exceeding record
levels today. See the climate section below for record high
temperature information. Through mid morning today widespread fog
will continue...likely dense in many areas leading to a dense fog
advisory for all areas through 9 am CST this morning. Dense fog
will likely redevelop late this evening and overnight due to the
increase subsidence aloft...a light southerly wind flow developing
along the coast in the afternoon helping to push better moisture
near the surface inland followed by light winds at the surface for
most inland areas late this evening and overnight. High temps
today will range from the mid 70s to near 80 for most inland areas
and the mid 70s near the immediate coast...followed by lows
ranging from the lower to middle 50s for most inland areas and the
middle 50s to to near 60 along the immediate coast. 32/ee

SHORT TERM /Monday Through Tuesday night/...The upper level
ridge axis will continue to shift eastward and extend from the
Ohio Valley to the FL Peninsula by late Monday afternoon, as the
next upper level trough translates across the Plains states. A
southwesterly mid level flow pattern will develop across our
forecast area between these two features, but a very dry deep
layer airmass with plenty of subsidence will still hold strong
across our region, so mostly sunny skies and no precipitation is
expected through Monday afternoon. A southeasterly surface flow
pattern will take shape Monday as the surface ridge axis also
shifts eastward, and with the influence of the deep layer ridge
still in place over our area, we anticipate another day of much
above normal temperatures, possibly near record warmth again.
Highs Monday afternoon are expected to range from the upper 70s
to around 80 over inland areas with lower to mid 70s near the
immediate coast.

Short range model guidance is in agreement that an upper level
low will pinch from the trough axis and deepen somewhere in the
vicinity of south or southeast TX late Monday night into early
Tuesday morning, then farther south over the northwest or north
central Gulf Tuesday into Tuesday night. There continues to be
differences in timing on short range model solutions regarding the
location and eastward progression of the upper level low and the
subsequent deep moist/southerly mid level flow in advance of this
feature late Monday night through Tuesday night. Interesting to
note that the 00Z NAM and 06Z GFS are actually in pretty good
agreement on location of the upper air features Monday night and
early Tuesday morning, while the ECMWF remains consistent in its
solution with a more progressive and little farther eastward
movement with its depiction of this system through Tuesday night,
thus bringing potential for heavier rainfall over a good portion
of our area. We have enough confidence that the zone of deep layer
moisture/lift will arrive into our western zones and bring an
increasing chance of rain showers to southeast MS late Monday
night into Tuesday and will continue to carry the highest POPs
over southeast MS and adjacent southwest AL, with lower
probabilities farther east. Some weak instability could also favor
a few isolated thunderstorms over western portions of the area
Tuesday into Tuesday night. We will continue to monitor trends
over the next couple of days, but for now the rainfall forecast
remains in line with WPC guidance, with forecast rainfall amounts
averaging between 0.5" to 1" over our southeast MS counties, and
amounts generally between 0.10" to 0.50" over the rest of the
region.

Lows Monday and Tuesday nights are forecast to range in the mid
50s inland to around 60 near the coast. Highs Tuesday afternoon
will remain quite warm in the lower to mid 70s over most places,
except upper 70s in the typically warmer spots. /21

LONG TERM /Wednesday Through Saturday/...The upper level low
should continue to move east and southeast across the central Gulf
of Mexico Wednesday, before approaching the Florida Straits
Wednesday night into Thursday. Moisture on the northern fringe of
this system will keep a low chance of showers in the forecast
Wednesday. A drier northwest to zonal flow will bring an end to
rain chances with dry weather subsequently anticipated through
late Thursday. A shortwave trough lifting northeastward within
developing southwest flow aloft may interact with available
instability ahead of an approaching cold front to result in the
development of isolated to scattered showers and thunderstorms
around the region Friday through Friday evening. The cold front
should move through the area late Friday, with cooler and drier
conditions then expected Saturday following frontal passage. /21

MARINE...High pressure will build over the north central Gulf
through Mon afternoon then begin to shift east in response to a
deep area of low pressure moving eastward from tx to the central
and SE Gulf through Wed evening. A light north to northeast flow
early this morning will quickly shift east then southeast this
afternoon then back to the east overnight and early tue morning. A
better flow from the southeast develops by Tue afternoon. This
diurnal pattern to the winds along the coast and offshore will
continue through mid week building also by mid week as a deep area
of low pressure moves from the northwest gulf to the southeast
gulf late tue through late in the week. Seas will likely build to
4 to 5 feet by midweek and continue through late week. Areas of
dense fog will also be likely early today reforming again late
this evening and early mon morning. Currently a dense fog advisory
is in effect for the near shore waters of AL and NWFL including
all inland bays and sounds through 9 am cst this morning and will
likely be reissued this evening and early Mon morning. 32/ee

CLIMATE...The February 19 record high for Mobile is 80 set in
2011 and 77 for Pensacola set in 2011. The February 20 record high
for Mobile is 79 set in 1981, and for Pensacola is 80 set in 1981.

&&

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

$$

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