Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 230446 AAA
AFDMOB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
1146 PM CDT Mon May 22 2017

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

&&

.AVIATION...
06Z issuance...Mostly MVFR cigs and visibilities through 24.06z.
Lower cigs and visibilities mostly in and around heavy showers and
thunderstorms, becoming better developed late tonight continuing
through early to mid afternoon on Tue, then tapering off slowly
from west to east by mid to late afternoon. Winds will be mostly
southwest at 5 to 10 knots with occasional higher gusts to 16
knots. Higher wind speeds will be likely with the heavier showers
and thunderstorms late tonight through early Tue afternoon. 32/ee

&&

.PREV DISCUSSION... /issued 1013 PM CDT Mon May 22 2017/

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

UPDATE...No significant changes to the forecast are planned
tonight.

Mid-evening surface analysis shows a weak stationary frontal
boundary draped from southeast LA through central portions of AL
ahead of an area of low pressure centered over southern portions
of LA. Short range model guidance is in agreement that the surface
low will lift northeastward toward southeast MS and interior
portions of southwest and south central AL late tonight into
Tuesday morning. These features in combination with a series of
shortwave troughs translating across our region within a very
moist west to southwest flow aloft will result in increasing
coverage of showers and thunderstorms over the area late tonight
into Tuesday morning. Regional radar imagery already shows rain
showers increasing in coverage just to our west as of 10 PM, and
this activity should begin to impact southeast MS and adjacent
southwest AL over the next couple of hours. Precipitable water
values around 2" will support locally heavy rainfall overnight
into Tuesday morning, and a Flash Flood Watch remains in effect.
/21

PREV DISCUSSION... /issued 746 PM CDT Mon May 22 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...
00Z issuance...Mostly MVFR cigs and visibilities through 24.00z.
Lower cigs and visibilities mostly in and around heavy showers
and thunderstorms, becoming better developed late this evening
and overnight continuing through early to mid afternoon on Tue
then tapering off slowly from west to east by mid to late
afternoon. Winds will be mostly southwest at 5 to 10 knots with
occasional higher gusts to 16 knots. Higher wind speeds will be
likely with the heavier showers and thunderstorms late tonight
through early Tue afternoon. 32/ee

PREV DISCUSSION... /issued 425 PM CDT Mon May 22 2017/

NEAR TERM /Now Through Tuesday/...A stationary front will continue
across the Central Gulf Coast through the the period. This boundary
will continue to provide a focus for the development of showers and
storms as shortwaves track along the boundary. The next shortwave
will approach this evening with an area of low pressure expected to
develop along the front along southern Louisiana and track eastward
through the overnight hours. This will bring more organized showers
and thunderstorms to the area late this evening through Tuesday
morning. Heavy rainfall will be the main threat as precipitable
water values remain above 2 inches and a Flash Flood Watch remains
in effect. An additional 2 to 3 inches of rain can be expected with
isolated totals as high as 5 inches possible. While deep layer shear
will also increase, instability levels are expected to be on the low
side with only a marginal risk for severe storms. The heaviest showers
and storms are expected to move east of the area Tuesday morning,
however the boundary is not expected to move much and additional
showers and thunderstorms can be expected through the day. A very
moist airmass will remain over the area through Tuesday, so additional
heavy rains can be expected. Lows tonight will range from the low to
mid 60s inland to low 70s along the coast. Highs on Tuesday will be
in the upper 70s and low 80s. 13/JC

SHORT TERM /Tuesday night Through Thursday night/...As we go into
Tuesday night, the slow moving frontal boundary will likely be
situated over northwestern portions of our forecast area. The
primary axis of 2+ inch PWAT will have likely shifted just east of
our forecast area by the beginning of the short term period, but
PWAT still around 1.25 to 1.5 inches will still exist across the
majority of our forecast area Tuesday night into early Wednesday.
While precipitation coverages will be a little less widespread
Tuesday night than those of the Near Term forecast period, and
gradually tapering off from west to east during the day on
Wednesday, potential for at least some additional heavy rainfall
will continue through Tuesday night. As a result, the Flash Flood
Watch (FAA) that we already have out for the area will remain in
effect through late Tuesday night. On Wednesday with the frontal
passage, any lingering rains should be moving out of the area to
the east, with PWAT quickly dropping to less than an 1 inch by
late in the day as much drier and cooler air begins to move into
the area. Surface high pressure will briefly move east across the
region Wednesday night through Thursday, allowing things to dry
out and also bringing some cooler and less humid conditions. There
could be a few lingering light showers and cloudy skies Wednesday
night into Thursday as the trailing upper trof moves east across
the region, but really not expecting too much with this. Surface
high pressure moves east of the area by Thursday night with Gulf
return flow developing, while upper flow becomes nearly zonal. No
precipitation expected on Thursday. Lows Tuesday night in the 60s
over the interior and lower 70s along the coast. Highs Wednesday
in the upper 70s and lower 80s. A little cooler Wednesday night
through Thursday night, with overnight lows in the 50s over the
interior and 60s closer to the coast and daytime high on Thursday
around 80. 12/DS

LONG TERM /Friday Through Monday/...Return flow continues to moderate
atmosphere through the early part of the long term period. Stays dry
on Friday, but rain chances return over the weekend into the early
part of next week. Daytime highs in the 80s. Nighttime lows in the
mid 60s to lower 70s Friday night warming to the upper 60s to mid
70s by the early next week. 12/DS

MARINE...An area of low pressure moving along a stalled boundary
will bring an increase in showers and thunderstorms along with
increasing winds and building seas late tonight through Tuesday. A
cold front will move through the Marine area Wednesday with a
moderate to strong west to northwest flow in the wake of the front
through Wednesday night. A light southerly flow returns for the end
of the week. 13/JC

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Flash Flood Watch through late Tuesday night for ALZ051>060-
     261>266.

     High Rip Current Risk through Wednesday evening for ALZ265-266.

FL...Flash Flood Watch through late Tuesday night for FLZ201>206.

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

MS...Flash Flood Watch through late Tuesday night for MSZ067-075-076-
     078-079.

GM...Small Craft Advisory from 7 AM Tuesday to 7 PM CDT Wednesday for
     GMZ650-655-670-675.

&&

$$

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