Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 111142 AAA
AFDMOB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
542 AM CST Wed Dec 11 2019

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

&&

.AVIATION...
12Z issuance...Main impacts today for approaches and departures
will be moderate to strong north to northeast winds containing
gusts to between 25 and 30 kts at times. An area of mainly -RA
spreads east of I-65 but latest observations show precipitation
doing very little to lower vsby. Lowest cigs early at lower end MVFR
categories. Cig bases look to lift to above 6 kft going into the
afternoon. /10

&&

.PREV DISCUSSION... /issued 427 AM CST Wed Dec 11 2019/

NEAR TERM /Now Through Wednesday night/...Southern stream mid-
level trof axis was translating eastward over east TX this morning.
Ahead of this feature, a steady eastward advance of moisture was
occurring over the local area with radar and observations showing a
light cold rain pushing over the heart of the forecast area. The
physical solutions and high resolution weather model output shows a
steady eastward advance of moisture/rain to along and east of the I-
65 corridor this morning with the back edge of precipitation pushing
across the coastal counties and offshore the remainder of the day. A
large 1030 to 1035 MB surface ridge expands across the upper Mid-
West and Tennessee River Valley today. This supports a well defined
north to northeast flow. Current radar vad wind profiles (VWP) shows
30 to 40 kts of northeast flow encompassing the 1-3 kft layer off
the surface. This favors a brisk day with the higher wind gusts
mixing down to perhaps upwards of around 30 to 35 mph over the
coastal sections this morning, where forecasters will maintain the
wind advisory thru the noon hour.

Highs today, cool at around 55. Overnight lows in the mid 30s
northwest zones to mid to upper 40s coast. /10

SHORT TERM /Thursday Through Friday night/...A series of southern
stream shortwaves move across the forecast area on Thursday while
a shortwave trof advances across Texas/Oklahoma. The shortwave
trof continues eastward across the region Thursday night while a
larger scale upper trof evolves over the central states, then
advances into the eastern states through Friday night. In response
to the shortwave trof and evolving larger scale upper trof, an
inverted surface trof will have developed over the western Gulf by
Thursday morning and advances eastward, with a surface low
forming over the north central Gulf Thursday night. The surface
low moves into the extreme southeast states on Friday, then
strengthens while heading towards the New England area Friday
night. While the forecast area remains primarily in an
overrunning flow regime through the period, elevated instability
will occasionally allow for some embedded storms near the coast
Thursday night and over the southern portion of the area Friday
evening. Will have mainly chance pops developing over the
forecast area on Thursday as the southern stream shortwaves move
across the area then likely to categorical pops follow for
Thursday night as the surface low develops. Pops decrease to
chance to likely on Friday then slight chance to chance Friday
night as the surface low moves into the extreme southeast states
then turns northward. Highs on Thursday range from the mid 50s to
around 60 then highs on Friday range from around 60 well inland to
the mid 60s closer to the coast. Lows Thursday night mainly range
from the mid 40s inland to near 50 at the coast, then lows Friday
night will generally be near 50 except a bit cooler well inland
and a bit warmer at the immediate coast. /29

LONG TERM /Saturday Through Tuesday/...An upper trof over the
eastern states moves off into the western Atlantic through Sunday
leaving a fairly zonal flow pattern over the forecast area.
Another upper trof meanwhile advances into the western states then
amplifies substantially while advancing across the central states
early next week. A surface low is expected to develop over Texas
or the southern Plains by Sunday then moves off to the northeast,
bringing a strong cold front through the forecast area Monday
night. The 850 mb flow increases to 40 to possibly 50 knots
immediately ahead of the front, resulting in high shear values.
While the nocturnal timing results in limited instability, given
the elevated shear values will need to monitor this next system.
Have continued with a dry forecast Saturday into Sunday, then pops
increase to likely by Monday night as the front approaches then
moves through the area. Have stayed with chance pops on Tuesday
for patches of rain lingering in the wake of the front before the
precipitation comes to an end. /29

MARINE...A strong surface ridge of high pressure, expanding over
the Tennessee River Valley and Upper Midwest today, lifts
northeast up across the northeast United States Thursday. A
moderate to strong offshore flow today becomes more east to
northeast Thursday. Latest data collection platforms indicate that
the duration and strength of the offshore fetch has resulted in
seas building upwards of around 10 feet well offshore. High seas
over the open Gulf waters will persist the next couple days as a
long northeast to easterly fetch holds, resulting in hazardous
conditions for operators of smaller marine craft. As the influence
of the high lifts away Friday, winds decrease. Seas show a
subsiding trend into the weekend. /10

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Wind Advisory until noon CST today for ALZ263>266.

FL...Wind Advisory until noon CST today for FLZ202-204-206.

MS...None.
GM...Small Craft Advisory until noon CST today for GMZ630-633-634.

     Small Craft Advisory until 6 AM CST Friday for GMZ631-632-650-
     655-670-675.

&&

$$

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