Area Forecast Discussion
Issued by NWS Mobile, AL

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500
FXUS64 KMOB 200933
AFDMOB

Area Forecast Discussion
National Weather Service Mobile AL
423 AM CDT Fri Apr 20 2018

.NEAR TERM /Now Through Friday night/...The reinforcing cold front that
passed through the forecast area yesterday is now well to the south
over the Gulf of Mexico, with cool and dry surface high pressure
ridging into the area from the north. The surface high pressure will
drift east through tonight, with a light to occasionally moderate
northeast to east windflow expected with only slight low level
moisture return. Ridging aloft is expected to increase from the west
through tonight, maintaining the stable conditions over the area.
Only scattered and mainly thin mid to high level clouds expected
through the period. Should have plenty of sunshine today, but high
temperatures should be slightly below normal, generally in the low
to mid 70s. Lows tonight a little below normal as well, especially
over inland areas where temps should fall into the upper 40s and
lower 50s overnight. Near normal low temps tonight closer to
the coast, where upper 50s are expected. 12/DS

.SHORT TERM /Saturday Through Sunday night/...Short wave upper
level ridge axis from the Gulf, northward across the TN Valley
Saturday morning moves to the southeast as upper level storm
system over the Plains ejects eastward. A slight moderation in
highs on Saturday. Upper level height falls associated with the
Plains storm system overspread the Lower MS River Valley Saturday
night, then across the TN River Valley southward to the Gulf coast
Sunday morning. At same time, a well established diffluent flow
aloft moves atop the area. This favors an increase in deep layer
ascent as a cold front/associated wave of frontal low pressure
approach from the west Sunday within a zone of much improved deep
layer moisture. Weather models are in fair alignment on this
morning`s runs, showing complex frontal low positioned from AR to
western MS Sunday morning, tracking only very slowly eastward
during the day. Ahead of this feature, despite strengthening low
level wind shear, there is substantial spread in the models on
amount of buoyancy/daytime instability that will be available
Sunday. The operational GFS/ECMWF shows 0-1 KM CAPE generally from
200 to 400 J/KG with the NAM output on MUCAPE building its values
from 700 to 1100 J/KG by late in the day Sunday. The short range
ensembles for CAPE greater than 500 J/KG shows a general 30 to 60%
probability of occurrence over the local area. Considering the
differences mentioned, the risk of severe weather is marginal.
Highest rain chances (Categorical PoPs) move from west to east
during the day Sunday. Best deep layer ascent begins to shift east
Sunday evening with showers likely and a few storms over the
eastern zones and a mid range chance west. Daytime highs on
Sunday trend lower given thickened cloud cover and high rain
chances. /10

.LONG TERM /Monday Through Thursday/...Frontal passage occurs
Monday morning as surface frontal low eases across southeast AL
and southern GA. A small chance of showers north of the coast
Monday morning in the wrap-around moisture on the west side of the
low. The low lifts northeast up across the Carolinas on Tuesday
and quickly up across the DELMARVA on Wednesday. A slight chance
showers remain in the forecast over the far northern zones Tuesday
as secondary short-wave energy aloft at the base of southern
states long-wave trof passes through, combined with lingering
wrap around moisture on the west side of departing low. Next front
looks to make passage late Wednesday into Thursday bringing
another small chance of showers to the local area.

Daily highs not far off seasonal normals. Overnight lows trend
close to seasonal by the middle of next week. /10

&&

.MARINE...A strong northeasterly wind flow over the marine area
early this morning will weaken slightly today. A Small Craft
Advisory is in effect until 6am this morning for the Gulf marine
zones as well as southern Mobile Bay and the Mississippi Sound, and
may have to be extended for at least a few more hours this morning.
Will monitor trends and make that change a little later in the shift
in necessary. Even after the SCA conditions subside sometime this
morning, still expect Exercise Caution conditions to prevail over
most of the marine area through most of the morning hours today
(with winds of 15 to 20 knots) before gradually decreasing late
today. A light to moderate easterly flow is anticipated for tonight,
but gradually increasing somewhat again on Saturday as another
frontal system develops to the west of the marine area. A moderate
to sometimes strong southeast to south flow is expected Saturday
night into Sunday as the front approaches. Winds become westerly in
the wake of the front by Monday, with a light to moderate west to
northwest flow then continuing into the middle part of mid next
week. Showers and thunderstorms are expected ahead and along the
front this weekend, with this best coverage occurring Sunday and
Sunday night. 12/DS

&&

.PRELIMINARY POINT TEMPS/POPS...
Mobile      72  54  75  62  74  59  74  55 /   0   0  10  40  90  30  10  10
Pensacola   72  58  74  64  75  62  75  59 /   0   0  10  40  80  50  10  10
Destin      72  59  73  65  73  65  75  62 /   0   0  10  40  80  70  10  10
Evergreen   73  50  76  60  73  60  77  56 /   0   0  10  30  90  60  30  10
Waynesboro  70  48  76  59  72  56  72  54 /   0   0  10  50  90  40  20  10
Camden      71  47  75  59  72  59  75  55 /   0   0   0  30  90  60  20  10
Crestview   74  51  76  61  75  61  78  57 /   0   0  10  40  80  70  20  10

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...Small Craft Advisory until 6 AM CDT early this morning for
     GMZ631-632-650-655-670-675.

&&

$$

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