Area Forecast Discussion
Issued by NWS Mobile, AL

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998
FXUS64 KMOB 230519
AFDMOB

Area Forecast Discussion
National Weather Service Mobile AL
1119 PM CST Wed Nov 22 2017

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

&&

.AVIATION...
06Z issuance...VFR conditions and north winds around 10 knots
expected to prevail through the forecast period. /49

&&

.PREV DISCUSSION... /issued 156 PM CST Wed Nov 22 2017/

NEAR TERM /Now Through Thursday/...Morning water vapor imagery and
most recent 500 mb height analysis continue to show a sharp upper
level trough axis moving east out of the Great Lakes region, with a
weaker upper level trough in the vicinity of the northwestern Gulf
of Mexico. The northern, stronger upper level trough axis will
gradually pivot eastward and be off the New England Atlantic coast
this evening and weaken while lifting rapidly northeast from there.
The weaker, southern upper trough axis will slowly drift east across
the central and into the eastern Gulf of Mexico tonight through
Thursday. Dynamics associated with the Gulf upper trough will result
in gradual cyclogenesis along an old surface frontal boundary over
the eastern Gulf during the near term period. Deep layer moisture
and ascent in advance of this developing system will spread
northeastward across the northeastern Gulf of Mexico and toward
northern portions of Florida tonight and Thursday. Short range
models still indicate that the northwestern fringe of this moisture
and lift may skirt far southeastern portions of our area (i.e. the
NW Fl Panhandle) tonight, so will continue to carry a low chance of
rain roughly southeast of a Crestview-Navarre line, but the best
chance of rain showers should remain focused over our offshore
eastern marine zones and into the Florida Big Bend region east of
our forecast area. Moderate to occasionally strong northerly winds
(gusting into the 20 to 25 mph range at times) today decrease to
around 10 mph overnight, then remain relatively light on Thursday,
except near the coast, especially along the beaches where they will
continue to be a bit gusty. Cooler temperatures are anticipated in
the near term as the upper trough axis moves east. Lows tonight
expected to range from the low and mid 30s to around 40 generally
along and northwest of I-65 (potentially reaching near freezing over
far interior southeast Mississippi and southwest Alabama) and in the
mid 40s to around 50 farther east and closer to the coast/beaches.
Highs on Thursday ranging from the upper 50s and near 60 over far
northwestern zones of our MS and AL counties, to the upper 60s far
southeastern zones (parts of Covington AL and the western FL
panhandle counties). 12/DS

SHORT TERM /Thursday night Through Saturday night/...While the
northern portion of an upper trof over the eastern states moves
off into the western Atlantic Thursday night, the remaining
portion remains in place over the extreme southeast states and
eastern Gulf. A powerful system meanwhile advances across the
Plains, then moves into the eastern states through Saturday, and
phases with the remaining trof pattern over the southeast states
to form a longwave trof over the eastern states. A surface low
over the northern Florida peninsula Thursday evening moves off
into the western Atlantic through Friday while a surface ridge
over the southeast states gradually weakens. A deep surface low
well to the north meanwhile brings a cold front across the Plains
which is expected to move through the forecast area Saturday into
Saturday night. Deep layer moisture remains limited over the area
during much of the period, and given that cold front will be
fairly weak, am not expecting precipitation through the period or
even much in the way of cloud cover. Lows Thursday night range
from the mid to upper 30s generally west of I-65 and in the 40s
further to the east. Lows on Friday night and Saturday night will
be in the lower 40s over interior areas with mid 40s at the coast.
Highs on Friday will be mostly in the mid to upper 60s except for
around 70 over interior portions of the western Florida panhandle.
Saturday will be a bit warmer and generally near 70. /29

LONG TERM /Sunday Through Wednesday/...A longwave trof over the
easternmost states moves off into the western Atlantic through
Monday as upper ridging builds into the eastern states. Another
upper trof advances across the central states early next week then
moves into the eastern states during midweek. A large surface
high builds into the southeastern states through Sunday night then
shifts off into the western Atlantic through Tuesday as another
cold front approaches from the west. This next front is expected
to move through the forecast area on Wednesday or Wednesday night.
Dry conditions continue ahead of the approaching front, then a
chance for rain returns mainly Wednesday night. Highs on Sunday
range from the lower 60s well inland to the upper 60s at the coast
then trends a warmer to around 70 by Tuesday with similar highs
for Wednesday, except a bit cooler well inland. Lows Sunday night
range from the mid to upper 30s inland to the lower 40s closer to
the coast, then overnight lows trend warmer with Tuesday night
ranging from the upper 40s inland to the lower 50s closer to the
coast. /29

MARINE...A moderate to strong northerly flow will prevail over the
Gulf zones of the marine area through most of tonight, and Small
Craft Advisory`s are in effect through 3 AM Thursday for those
zones. Most mesoscale model data suggest that winds will diminish
below SCA thereafter, but there is a possibility the Advsy may need
to be extended to around daybreak Thursday, and this will be
monitored. Wind speeds will be at cautionary levels over most bays
and sounds tonight. Cautionary level winds will then continue over
most of the marine area through late Thursday, with a light to
occasionally moderate offshore flow then expected for the remainder
of the forecast period. 12/DS

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...Small Craft Advisory until 3 AM CST Thursday for GMZ650-655-670-
     675.

&&

$$

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