Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 222239
AFDMOB

Area Forecast Discussion
National Weather Service Mobile AL
539 PM CDT Sun Apr 22 2018

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

&&

.UPDATE...Very quick update. Despite some recent veering of the sfc
winds, which has acted to decrease vertical wind shear values SW
of the warm front, the vertical wind shear and thermodynamic
instability values on the latest mesoanalyses are still
sufficiently elevated enough to warrant the formation of long-
lived mesoscyclones (some of which may produce isolated
tornadoes). Therefore, am in no hurry to clear any portion of
Tornado Watch 56 which is currently in effect over eastern portion
of our areas. /23 JMM

&&

.PREV DISCUSSION... /issued 358 PM CDT Sun Apr 22 2018/

..This will be an abbreviated AFD due to ongoing active
weather...

NEAR TERM /Now Through Monday/...In the very near term, forecast
area is bisected by surface warm front that lies in a NW-SE
fashion across our area. The feature is lifting to the NE with
time. A few hours ago mesocyclones, some of which may likely produced
tornadoes, exploded over the NE Sector of our area (and over the
interior NW FL Panhandle). Currently the ambient environment
remains favorable for more mesocyclone and isolated tornado
formation the next several hours along and just SE of the sfc
warm front. EffSrHel is maxed out in the 300-500 m^2 s-^2 and
there are some 1000-1500 J/kg SBCAPES south of the warm front
(MLCAPES generally range under 1000 J/kg). This will continue
through around 9 PM CDT and a Tornado Watch is in effect. By
midnight, an upstream cold front will have moved through the
western portion of our area. By 3 AM, sfc winds will have shifted
to a W-NW direction behind the cold front. There will be periods
of patchy drizzle and fog in the sfc low wrap-around moisture
after the more significant and deeper precipitation departs the NE
zones during the mid evening. Give the orientation of the upper
system as it lifts to the NE on Monday, it will likley be mostly
cloudy on Monday north of Highway 84 with possible drizzle
lingering into the late morning. Temperatures will range below
normal.

Look for us to start trimming back the western edge of Tornado
Watch 56 over the next few hours. /23 JMM

SHORT TERM /Monday night Through Wednesday night/...A N-S cloud
gradient remains Monday night through Tuesday as another upper
level vorticity maximum passes to the N. Yet another system
approaches Wed night, and clouds and rain chances will be on the
increase from the NW. /23 JMM

LONG TERM /Thursday Through Sunday/...No changes to previous
package. Afternoon high and morning low temperatures remain below
seasonal values through the period. /23 JMM and /10 GJM

MARINE...A cold front moves through the coastal waters this
evening and very early Monday morning. Showers and thunderstorms end
from the west. Winds shift to the west and then northwest around
daybreak. West to northwest flow is then expected to gradually weaken
in the wake of the front through midweek.

A Tornado Watch remains in effect out to 60 nm east of Pensacola
through 9 PM CDT. Also a Small Craft Exercise Caution remains in
effect through most of the evening and may cancelled with the
1030 PM CDT update. /23 JMM

&&

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

FL...High Rip Current Risk through Monday evening for FLZ202-204-206.

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

$$

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