Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 182354 AAA
AFDMOB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
554 PM CST Sat Nov 18 2017

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

&&

.AVIATION...
00Z issuance...VFR conditions will precede a narrow band of
showers along a strong cold front approaching the northern gulf
coast region from the northwest. MVFR visibilities due to light
to moderate rain will occur with the passage of the line between
19.03z thru 19.05z for MOB and BFM, and between 19.04z thru 19.06z
for PNS. Southwest winds 9 to 14 knots will shift toward the west
as the line of showers nears the TAF sites. Winds will then shift
to the north-northwest on the backside of the showers, with
sustained winds between 15 to 20 knots, gusting to near 30 knots.
Skies will clear early Sunday morning. /22

&&

.PREV DISCUSSION... /issued 355 PM CST Sat Nov 18 2017/

NEAR TERM /Now Through Sunday/...Gusty southwest winds at 18 to 28
mph will continue across many locations of the forecast area through
this evening ahead of a strong cold front approaching from the west.
Latest hi res data also shows some instability or cape combined with
moderate vertical shear ahead of the front through this evening.
With this have mentioned a slight chance for an isolated
thunderstorm tonight, occurring mainly just ahead and along the cold
front as it pushes east across the forecast area later this evening.
Gusty straight line winds, possibly from 30 to 40 mph with
occasionally lightning, will be the main concerns with some of the
stronger convection just ahead and along the front. In the wake of
the front expect wind gusts ranging from 18 to 28 mph for most
inland areas and from 28 to 38 mph further south along the immediate
coast. As result a wind advisory is now in effect for the immediate
coastal areas of Alabama and Northwest Florida from midnight tonight
through 9 am Sun morning. Northerly winds will slowly diminish
through late Sun afternoon. Expect mostly cloudy skies with mild
temps this evening followed by good clearing from west to east and
much colder temps in the wake of the front early Sun morning through
Sun afternoon.

Lows tonight will fall to the low to mid 40s for most inland areas
generally north of a line from Andalusia to Mobile in Alabama and
the upper 40s to lower 50s further south to the immediate coast.
Highs Sun will range from the upper 50s to lower 60s generally along
and north of the I-10 corridor and the lower to middle 60s further
south to the immediate coast. 32/ee

SHORT TERM /Sunday night Through Tuesday night/...A longwave trof
over the easternmost states moves off into the western Atlantic
Sunday night into Monday while another amplifying upper trof
advances across the Plains. This next upper trof continues to
amplify while moving into the eastern states through Tuesday
night. A dome of cold surface high pressure builds into the region
Sunday night (in the wake of a cold frontal passage in the NEAR
TERM period), and with winds becoming calm or light along with an
open radiative window (precipitable water near 0.1 inch - very
low), the potential for a light freeze exists for interior areas.
Have issued a Freeze Watch for late Sunday night into early
Monday morning from approximately New Augusta, MS to Luverne, AL
where temperatures drop to freezing or slightly below. May see a
few patches of freezing temperatures in normally colder spots further
south and the Freeze Watch may need to be expanded further
southward on later shifts, but for now expect lows in the mid 30s
for the remainder of the area except for upper 30s at the coast.

The surface high shifts eastward and well off into the western
Atlantic through Tuesday while a surface low well to the north
brings a cold front across the Plains to near the lower
Mississippi river valley. A light southeasterly flow develops on
Monday and promotes a modest increase in deep layer moisture ahead
of the front, with precipitable water values increasing to
0.5-0.75 inches or about to 60 to 90% of normal. May see some
isolated patches of rain generally over the coastal counties
Tuesday into Tuesday night due to modest isentropic lift followed
by the weak front moving through, but otherwise dry conditions
are expected. Highs on Monday will be in the lower 60s with highs
on Tuesday ranging from the mid 60s inland to upper 60s closer to
the coast. Lows Monday night range from near 40 inland to the
mid to upper 40s at the coast, then lows Tuesday night will be in
the mid 40s inland with upper 40s at the coast. /29

LONG TERM /Wednesday Through Saturday/...A longwave upper trof
over the eastern states weakens significantly on Friday as a
powerful embedded shortwave ejects off into the Atlantic, but then
another strong shortwave advances across the Plains on Saturday
and reforms the longwave trof pattern, albeit a bit further to the
west. A surface high builds into the region through Thursday in
the wake of a frontal passage which occurred Tuesday night then
shifts gradually eastward through Saturday with a light
northwesterly flow prevailing over the forecast area through
Friday then switching to a light southerly flow on Saturday. With
the absence of any forcing mechanisms and deep layer moisture
also remaining too limited to support much in the way of
precipitation anyway, will continue with a dry forecast through
the period. Highs on Wednesday range from the lower 60s well
inland to the mid 60s for much of the remaining portion then trend
cooler for Thursday with highs ranging from the mid 50s well
inland to near 60 close to the coast. A warming trend then ensues
Friday into Saturday with highs for Saturday in the upper 60s to
near 70. Lows Wednesday night and Thursday night range from the
mid 30s well inland to the lower 40s at the coast then trend
warmer for Friday night with lows around 40 inland and in the mid
40s closer to the coast. /29

MARINE...A moderate to strong southwest to west wind with continue
over the marine area through this evening ahead of a strong cold
front approaching from the west. The front will move across the
marine area from midnight tonight through about sunrise Sun morning
with possible frequent gusts to Gale force occurring mostly over the
open gulf waters of Alabama from 0 to 60 nm out and the open gulf
waters of NWFL from 20 to 60 nm out from midnight tonight through
about 9 AM cst Sun morning. As a result a Small Craft Advisory is in
effect for the entire marine area this evening, upgrading to a Gale
warning in the areas mentioned above Sun morning, followed by a
Small Craft Advisory for the entire Marine area through late Sun
afternoon. Seas will build to 5 to 7 feet out to 20 nm and 6 to 9
feet from 20 to 60 nm out through Sun afternoon.

Northerly winds and seas will gradually subside Sun night through
early Mon as a broad surface ridge of high pressure builds from the
lower Mississippi River valley to the Southeast states through Mon
afternoon. A light east to southeast wind is expected by Mon
afternoon continuing through Mon evening then shifting mostly north
to northeast and building Tue through Thu in response to another
surge of colder air moving south over the northern and central gulf
late Tue through the remainder of the week. As result a Small Craft
Advisory may be needed for some areas later in the week. 32/ee

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Freeze Watch from late Sunday night through Monday morning for
     ALZ051>058.

     Wind Advisory from midnight tonight to 9 AM CST Sunday for
     ALZ263>266.

FL...Wind Advisory from midnight tonight to 9 AM CST Sunday for
     FLZ202-204-206.

MS...Freeze Watch from late Sunday night through Monday morning for
     MSZ067-075-076.

GM...Small Craft Advisory until midnight CST tonight for GMZ650-670-
     675.

     Small Craft Advisory from 9 AM to 6 PM CST Sunday for GMZ650-670-
     675.

     Gale Warning from midnight tonight to 9 AM CST Sunday for GMZ650-
     670-675.

     Small Craft Advisory until 6 PM CST Sunday for GMZ630>635-655.

&&

$$

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