Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 210544

Area Forecast Discussion
National Weather Service Mobile AL
1144 PM CST Mon Nov 20 2017

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


06Z issuance...
VFR Conditions will continue tonight with light and variable winds
overnight and into the day tomorrow. DJ/17


.PREV DISCUSSION... /issued 943 PM CST Mon Nov 20 2017/

DISCUSSION...Updated for latest marine discussion below.

Opted to remove POPs in the offshore waters for tonight as there
only appears to be increased low level cloudiness over the marine
zones. The dry air over head and subsequent inversion is
restricting the development of showers. Winds are easterly for now
but are expected to become more northerly throughout the night
and early morning. DJ/17

PREV DISCUSSION... /issued 609 PM CST Mon Nov 20 2017/

DISCUSSION...Updated for latest aviation discussion below.

00Z issuance...
VFR Conditions expected through the forecast period with variable
to light northerly winds overnight and into tomorrow. DJ/17

PREV DISCUSSION... /issued 252 PM CST Mon Nov 20 2017/

NEAR TERM /Now Through Tuesday/...Next short wave trof that has
moved east over the central plains early today will continue to
shift east reaching the lower Mississippi river valley and the north
central gulf states during the day on Tue. Near the sfc high
pressure generally over the se conus and western Atlantic will
continue to shift east through Tue afternoon. To the southeast most
of the model guidance continues to show a weak sfc trof/low forming
over the ne gulf generally south of Apalachicola progged to become
better developed and gradually shift east through late Tue, then
weaken further to the east over the Fl Penisula as the next surge of
colder air moves south out over the northern gulf waters. With this
pattern expect a mix of sun and clouds during the daylight hours
through Tue with a slight chance of showers occurring mostly east of
the I-65 corridor stretching offshore south of the Western Fl
panhandle occurring mostly during the day on Tue.

Temps will continue to be on the cool side tonight, generally 2 to 4
degrees below seasonal averages, with lows ranging from the mid to
upper 30s for most locations generally north of the I-10 corridor
and the lower to mid 40s further south to the immediate coast. Highs
Tue will run 2 to 3 degrees above seasonal averages, ranging from
the mid to upper 60s for areas generally north of the I-10 corridor
and the upper 60s to lower 70s further south to the immediate coast.

SHORT TERM /Tuesday night Through Thursday night/...The large
"5-Wave" pattern shows an upper trof amplifying over the eastern
states during the period, and while several strong shortwaves move
through this larger scale pattern, a persistent deep layer
northerly flow is maintained over the forecast area during the
period. A cold front approaching from the west (associated with a
surface low well to the north) moves through the forecast area
Tuesday night followed by a surface ridge building into the
southeast states. The deep layer northerly flow results in
steadily decreasing deep layer moisture, and have gone with a dry
forecast through the period except for slight chance pops near
Destin, Florida Tuesday night when the frontal passage combined
with the best deep layer moisture could combine to produce
isolated patches of rain. It should be noted that during this
period an inverted surface trof will be located over the
easternmost portion of the Gulf and later evolves into a surface
low centered over the east central Gulf. Based on the
progressively drier deep layer air flowing into the region, no
precipitation is expected to be able to develop which will affect
the forecast area in response to this system. Lows Tuesday night
will be in the lower to mid 40s along and west of I-65, with mid
40s to lower 50s further to the east. Cooler temperatures follow
for Wednesday night and Thursday night in the wake of the cold
front. Wednesday night will see mid 30s to lower 40s along and
west of I-65 with lower to mid 40s further to the east, then
Thursday night will be a bit cooler with mid to upper 30s along
and west of I-65 and upper 30s to lower 40s further to the east.
Highs on Wednesday will be mostly in the mid 60s, then Thursday
will range from upper 50s well inland to the mid 60s closer to the
coast. /29

LONG TERM /Friday Through Monday/...A longwave upper trof over the
eastern states moves very slowly eastward off the east coast and
into the far western Atlantic during the period, maintaining a
dry, deep layer northerly flow over the forecast area. Another
cold front approaches from the Plains on Friday and moves through
the area on Saturday, but no precipitation is expected given
limited deep layer moisture and also that the front is not
particularly strong. Highs on Friday will be mostly in the mid 60s
then warm to upper 60s/near 70 for Saturday ahead of the front.
Progressively cooler daytime highs follow for the remainder of the
period with highs on Monday mostly in the lower 60s. Lows Friday
night range from around 40 well inland to the upper 40s at the
coast, then trend cooler by Sunday night when mid to upper 30s are
expected over interior areas with lower 40s closer to the coast. /29

MARINE...A light easterly wind will continue through early this
evening then shift northeast overnight and on Tue mostly in response
to a weak sfc trof/low forming over the northeast gulf generally
south of Apalachicola Fl. To the north another surge of cold air
will move south to the northern and central gulf waters by late Tue
night into Wed leading to a moderate to occasionally strong offshore
flow late Wed through early Fri morning. Better rain chances are
also expected with this pattern with bulk of the precip remaining
east of Pensacola Fl throughout the week. Seas will subside to
around 2 feet through early Tue then gradually build to 4 to 5 feet
by early Thu, then slowly subside to 2 to 3 feet by early Fri
afternoon. Small craft will have to exercise caution with the better
offshore flow by midweek with possible Small Craft Advisories mostly
over the open gulf waters Wed night into early Thu. 32/ee




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