Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 231545 AAB
AFDMOB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
945 AM CST Fri Feb 23 2018

.DISCUSSION...See updated information for land areas below.

&&

.UPDATE...A few observations show lingering very patchy mid
morning fog with visibility at 5 miles or so. Expect this to
dissipate soon. Made an update to zones to remove morning fog
wording. No other changes at this time. /10

&&

.PREV DISCUSSION... /issued 533 AM CST Fri Feb 23 2018/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...
12Z issuance...With continued moist flow off the Gulf, IFR to LIFR
CIGs/VISBYs will generally rise into MVFR levels before settling
back into IFR to LIFR levels again tonight. With seemingly ever-
present subsidence inversion less of a limit this afternoon, ts
mixing in with shra this afternoon/evening.

/16

PREV DISCUSSION... /issued 451 AM CST Fri Feb 23 2018/

NEAR TERM /Now Through Friday night/...An upper ridge present
over the  Gulf and Caribbean will continue to get a squeeze as
yet more shortwave energy moves through an upper trough centered
over the western Conus. A surface ridge that has been maintained
by the upper ridge does continue to maintain its position
stretching west over the northern Gulf coast, continuing to bring
a light to moderate onshore flow over the forecast area through
the near term. Looking at model soundings for the area, light
onshore flow that has set up overnight will continue into the
morning hours, then as the land begins to warm, shra begin to
form. A weakening subsidence inversion centered around 700 mb
limits the vertical extent of the showers, though. As afternoon
approaches, guidance is advertising the subsidence inversion
becoming less of a limiter, so am expecting tsra begin to mix in
into the early evening hours. After the sun sets, precip coverage
decreases. Overnight fog development is expected to continue,
though with water temps along the coast on the increase, dense fog
will be less clear cut.

For temps, with the upper high still maintaining its presence,
albeit less strong then earlier this week, above seasonal temps
continue.

With the warm temps allowing for more persons to visit area beaches,
a moderate onshore flow continues. Adding in a wide tidal cycle,
have issued an RP.S for a high risk of dangerous rip currents over
area beaches. /16

SHORT TERM /Saturday Through Sunday night/...An elongated upper
level ridge of high pressure extending from southern Mexico
northeast across the Florida peninsula to the western Atlantic
will drift very slowly to the southeast. This southeast drift is
in response to two upper level shortwaves exiting the Rockies
through the near term. The first upper shortwave will lift
northeast over the central and northern Great Plains toward the
western Great Lakes on Saturday, followed by a second shortwave
moving eastward over the Great Plains toward the Mississippi River
on Sunday.

Meanwhile, a surface high pressure ridge across the southeast
states and northeast Gulf of Mexico will also drift southeastward
and weaken in response to a series of surface low pressure areas
passing northwest of the forecast area. A light southerly wind
flow will persist across the forecast area between these features
through Sunday evening, followed by a cold front moving into the
forecast area late Sunday night. Isolated to scattered showers and
thunderstorms will occur on Saturday, with numerous to definite
showers and thunderstorms occurring on Sunday.

A strengthening upper level jet max of 130 to 160 knots ahead of
the second upper shortwave will form over the eastern conus, while
a low level jet of 20 to 40 knots is expected to develop over
weekend. Maximum mixed layer CAPE values over the weekend are
forecast to range from 150 to 300 J/kg, with maximum SFC-1km SRH
values forecast to range from 100 to 200 M2/S2. Still expect a
few strong to marginal severe thunderstorms during the day
Saturday northwest of I-65, and across the entire forecast on
Sunday, with strong thunderstorm wind gusts the main threat.

Patchy fog will linger into Saturday morning, with near record
high temperatures on Saturday climbing into the low to mid 80s,
except for the upper 70s along the immediate coastal sections.
/22

LONG TERM /Monday Through Thursday/...The cold front will move
southeast of the forecast area on Monday, with the showers and
thunderstorms quickly decreasing from northwest to southeast
Monday morning as a much drier airmass spreads into the area in
the wake of the front. Drier weather is expected Monday night
along with noticeably cooler temperatures, before rain chances
increase Tuesday into mid week ahead of the next approaching
shortwave trough. Another shortwave trough and associated cold
front could then bring the next round of showers and possibly a
few storms Thursday. Above normal temperatures are expected
Tuesday through Thursday. /22

MARINE...A surface ridge will continue to stretch west over the
northern Gulf coast into Sunday, bringing light to moderate
onshore flow. Fog development will continue with the onshore
flow, though dense fog will have to play by ear with water temps
on the rise due to the southerly flow. A front will move south,
then stall along the northern Gulf coast late Sunday through
Sunday night, bringing unsettled weather. A passing upper system
will push the front south of the coast Monday night, bringing a
small period of offshore flow late Monday night into Tuesday
before a surface ridge becomes re- established over the Southeast
Tuesday night. /16

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...High Rip Current Risk through Saturday afternoon for ALZ265-266.

FL...High Rip Current Risk through Saturday afternoon for FLZ202-204-
     206.

MS...None.
GM...None.
&&

$$

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