Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 220028
AFDMOB

Area Forecast Discussion
National Weather Service Mobile AL
628 PM CST Thu Feb 21 2019

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

&&

.AVIATION...
00Z issuance...Fog will persist overnight and through mid-morning
along the coast. Visibilities and ceilings are already LIFR to
VLIFR at many coastal locations like PNS and BFM as of 00Z. A bit
inland from the coast at sites like MOB, visibilities and ceilings
are MVFR to IFR as of 00Z, but will drop to LIFR or VLIFR before
midnight. Visibilities should begin to improve by mid-morning
with ceilings improving to MVFR by early afternoon. Southerly
winds increase to 8-12 knots by early afternoon. 07/MB

&&

.PREV DISCUSSION... /issued 405 PM CST Thu Feb 21 2019/

NEAR TERM /Now Through Friday/...For tonight, main forecast issue
will be the continuation of widespread fog, which will be dense at
many locations. Periods of dense fog persisted for most of the day
near coastal sections of Alabama and the western Florida panhandle.
With little change in overall pattern (onshore warm and moist flow
across cool near shore waters), and with short range hi-res models
all indicating continued dense fog along the coast slowly spreading
inland once again tonight, we went ahead and issued another Dense
Fog Advisory for all of our coastal counties as well as Stone and
George counties of Mississippi for tonight through Friday morning.
Visibilities across much of the that area will drop down below one
quarter of a mile tonight through Friday morning.

Other than the fog, expect some isolated to widely scattered showers
across the forecast area tonight and Friday, especially up over our
northwestern counties. Rainfall will generally be light, and no
severe weather is anticipated in the near term.

Temperatures remain well above normal for this time of the year
through the near term period. Lows tonight only a couple degrees shy
of record high min temps for the date, mainly in the mid 60s across
the area. Max temps on Friday will be approaching record highs in
some areas, ranging from the upper 70s to lower 80s over inland
areas and mid 70s at the coast. 12/DS

SHORT TERM /Friday night Through Sunday night/...Friday night
through Saturday night, a strong upper shortwave trough moves from
over the Desert Southwest to the Southern Plains before taking an
northeast path on the west side of an upper ridge that has built
north over the Eastern Seaboard. The upper system strengthens and
becomes negative tilted Saturday into Saturday night as it heads
towards the Great Lakes. A surface low associated with this system
develops over the western Central Plains and heads northeast with
the upper dynamics, with a trailing cold front moving southeast
across the surrounding region late Saturday afternoon through
Saturday night, and across the forecast area Saturday night into
early Sunday. Southerly low level flow ahead of the frontal passage
will continue to increase moisture levels over the area, with
guidance advertising precip H20 values rising to around 1.8" ahead
of the approaching front Saturday afternoon. Sunday into Sunday
night, a cooler, drier airmass moves over the area for the rest of
the weekend.

For the Short Term, the biggest item to deal with is the chance of
severe weather Saturday into Saturday night. Guidance is advertising
MLCapes rising to 500-700 J/kg. Bulk shears values rise to 50-60
knots Saturday afternoon, enough for a few strong to marginally
severe storms as a line of thunderstorms move across the area late
Saturday afternoon/Saturday night. Helping to limit the chance of
severe weather in our piece of the Conus, the bulk of the mid/upper
level support passes just northwest of the forecast area, with the
tail of a 45knot low level jet passing over northwestern portions of
the forecast area the only upper support indicated at this time. At
this point, there is a Marginal Risk of mainly damaging winds over
areas northwest of I65, with a Slight Risk to the northwest of the
forecast area.

The next important item to deal with is fog development, especially
near the coast and coastal bays. Guidance continues to advertise
coastal fog forming Friday night, with stronger winds limiting
development Saturday night as the front approaches. Have put in
areas of fog developing near the coast Friday night into the
forecast.

Not to forget, temperatures well above seasonal norms are expected
through most of the Short Term, until cooler air moves over the
forecast area behind the front`s passage. With record highs for the
area in the 80F +/- range, a few records may be tied or broken
Friday and Saturday. Lows Friday night are expected to be well above
seasonal norms, with the front bringing lows closer to, but still
above seasonal for Saturday night. A cooler, but still above
seasonal day is expected Sunday, due to the slowing of the cold
advection due to the upper dynamics moving off quickly. It`s not
until Sunday night that near seasonal temperatures return to the
area as winds settle with the dry airmass over the area.
/16

LONG TERM /Monday Through Thursday/...The front which passed over
the area during the weekend stalls over the central Gulf, with the
upper ridge over the Eastern Seaboard moving off over the open
Atlantic. An approaching shortwave moving east through the now zonal
flow brings increasing coverage of isentropic upglide rainshowers
early Tuesday with elevated thunderstorms mixing in Tuesday night
through Wednesday before the rain moves off Wednesday night.
Temperatures rebound to above seasonal seasonal, but with the
influence of the upper ridge present in the Short Term gone, am not
expected the near record temperatures we saw early in the forecast.
/16

MARINE...A light onshore flow will continue through Friday night.
Expect increasing onshore flow late Saturday and Saturday evening as
a cold front approaches from the west. This next cold front is
expected to push east across the marine area by early Sunday with a
moderate to strong offshore flow expected in its wake. Areas of fog,
dense at times, will likely continue over the near shore coastal
waters and areas bays through the remainder of the week. 12/DS

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Dense Fog Advisory until noon CST Friday for ALZ261>266.

     High Rip Current Risk through late tonight for ALZ265-266.

FL...Dense Fog Advisory until noon CST Friday for FLZ201>206.

     High Rip Current Risk through late tonight for FLZ202-204-206.

MS...Dense Fog Advisory until noon CST Friday for MSZ078-079.

GM...Dense Fog Advisory until noon CST Friday for GMZ630>636-650-655.

&&

$$

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