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fxus64 kmob 131520 

Area forecast discussion
National Weather Service Mobile Alabama
issued by National Weather Service Tallahassee Florida
920 am CST Wed Nov 13 2019

Discussion...see updated information for land areas below.


new model guidance is suggesting slightly warmer temps (2-3
degress) over the water this afternoon. The forecast has been
adjusted to account for this. Precip is not expected until
tomorrow afternoon.


Previous discussion... /issued 718 am CST Wed Nov 13 2019/

Discussion...updated for latest marine discussion below.

Marine...reports and observations after sunrise from the Alabama
and western Florida Panhandle beaches are reporting dense steam
fog just off the coast over the Gulf of Mexico as result of sub-
freezing temperatures moving south over the warm Gulf waters.
Camera images from the offshore bouy 12 miles south of Orange
Beach Alabama are also showing dense steam fog. Visibilities then
improve out to 60 nm as as camera images from the bouy 63 miles
south of Dauphin Beach Alabama are showing a low status cloud
deck. Have updated the coastal waters forecast (cwf) and issued a
marine weather message (mww) product for the dense fog conditions
for all four of our Gulf zones through noon CST. /22

Previous discussion... /issued 608 am CST Wed Nov 13 2019/

Discussion...see updated information for marine areas and aviation
discussion below.

Marine...latest bouy data over the north central Gulf of Mexico
are reporting that the sustained winds have diminished to 18 knots
with occasional higher gusts to 23 knots 12 miles south of Orange
Beach al, and to 16 knots with occasional gusts to 23 knots 63
miles south of Dauphin Beach Alabama. Seas have also subsided to 3 to 6
feet, respectively. Therefore, have cancelled the Small Craft
Advisory 3 hours before its original expiration time of 9 am.
Small craft should still exercise caution throughout the morning
hours. /22

12z issuance...VFR conditions will occur through 14.12z. North-
northeast winds 8 to 12 knots with occasional higher gusts to 18
knots early this morning will diminish and become east around 6
knots by 13.18z. A cirrus canopy moving in from the west will
thicken throughout the day, becoming broken by early afternoon.
Winds around 5 knots overnight will shift back to the northeast,
while an overcast mid level cloud deck moves in from the west. /22

Previous discussion... /issued 405 am CST Wed Nov 13 2019/

Near term /now through Wednesday night/...a 1032mb surface high
pressure area centered over the eastern portion of the Ohio River
valley, that also encompasses much of the southeast conus, will
reach the eastern Seaboard by late this afternoon. A surface ridge
however will remain from New England to the southeast states
through the overnight hours, while a weak inverted surface trough
developing over the central Gulf of Mexico this evening moves
eastward over the eastern Gulf by daybreak Thursday. A cutoff
upper low pressure area over northwest Mexico will gradually fill
as it advances eastward in the southern jet stream, reaching the
Red River valley by late tonight. A 100 knot northern jet streak
over southwest Canada and the northern rockies will dive southeast
and weaken slightly, carving out an upper level shortwave over
the north central conus that will shift eastward, and extend form
the Great Lakes to the Central Plains by late tonight. Strong low
to mid layer subsidence ahead of these two systems will keep dry
conditions across the area through the near term. However, high
level clouds associated with upper closed low pressure area will
quickly move in the west, and thicken substantially later today
and this evening, resulting in cloudy skies area-wide by midnight.

Plenty of sunshine early in the day will allow this mornings record
low temperatures to warm into the low to mid 50s today, but will
still be 16 to 19 degrees below normal. Low temperatures tonight
will fall into the mid to upper 30s inland areas, lower 40s along
the coastal sections, with mid 40s at the beaches. /22

Short term /Thursday through Friday night/...a southern stream
upper trough over northern Mexico will slowly drift east-northeast
over the western Gulf. At the same time, a deep trough over the
Central Plains will dig into the mid-Mississippi Valley and begin
to phase with the upper trough over the Gulf. Ahead of these two
features, isentropic upglide over the remnant cold airmass
leftover from the previous system will allow for light to moderate
rain to develop across the area Thursday afternoon into Friday
night. However, rain will likely be limited Thursday night into
Friday by two factors.

Factor one is the relatively dry air already in place over the
area. Given the short return period between systems, deep moisture
will struggle to return to the area. This will lead to rain
struggling to reach the ground especially during the day Thursday.
The second caveat will be the potential to be dry slotted as the
upper lows phase over our area. Current water vapor imagery shows
the southern stream system already has some drier air wrapped up
in it and models are hinting at a solid mid-level dry punch as
the northern stream shortwave amplifies. If the dry slot moves
over our area, this will lead to rain ending sooner. This will be
significantly dependent on the track of the upper system. Given
this uncertainty and still some model divergence, I kept pops
similar to previous forecasts. If it appears that the dry slot
doesn't develop or a little more moisture is able to make its
way over the area, pops may need to be increased as coverage would
likely increase.

By Friday night, the upper low will be directly overhead leading
to drier air moving in and cooler northerly flow returning.
Temperatures will be a slightly warmer friday; however, cloud
cover will likely keep the area in the mid 50s inland to upper 50s
at the coast. Bb/03

Long term /Saturday through Tuesday/...Saturday and Sunday
will be rather nice compared to the few days prior. The deepening
upper low will move east off the mid-Atlantic coast leading to
drier air over the area. A shortwave trough will dig into the
central Great Plains leading to weak ridging over the area.
Temperatures will remain below normal; however, they will warm
into the low to mid 60s for highs and 40s for lows. With sunny
skies, this will likely feel a lot better than the 20s and low
50s we saw earlier in the week.

By late Sunday night into Monday, the upper trough over the
Central Plains will move over the area. It will likely bring the
chance of rain; however, the return period will be short between
systems leading to drier air in place of the area. Most of the
rain chances will likely remain along and south of the coast where
moisture is maximized. Temperatures will likely remain moderated
in the mid 60s Monday due to clouds. By Tuesday, skies should
clear and temperatures will continue to slowly creep into the
upper 60s. Bb/03

Marine...moderate to strong northerly winds early this morning will
shift to the northeast and diminish throughout the day as a high
pressure ridge over the southeast states weakens and shifts
eastward. Seas will gradually subside as well. A moderate to strong
northerly flow will redevelop Thursday through Friday between a
surface ridge of high pressure over the Southern Plains and a
developing low pressure area just east of the Georgia and
South Carolina coastline. /22


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