Special Marine Warning 212, NWS Mobile, AL

Area Forecast Discussion
National Weather Service Mobile AL
637 AM CDT Sat Jul 10 2021

.NEAR TERM UPDATE /Now Through Sunday/...Subtle weakness in upper
level ridging resides over the southeastern U.S. today as an upper
level trough slowly makes its way southeast into the ArkLaTex region
by Sunday, stretching northeastward towards the Great Lakes region.
Weak disturbances associated with this trough will round its base,
helping in providing a source of lift over our region during the day
today, and particularly on Sunday afternoon into evening as the
trough is closer in proximity. At the surface, we continue to have
the nose of a surface high pressure centered over the southwestern
Atlantic stretch into the southeastern U.S. keeping most of the CWA
embedded within southerly to southwesterly low to mid-level flow.
This will help to continue to advect in a moist low to mid level
airmass off the Gulf of Mexico. At the same time, modest westerly to
northwesterly flow above 500mb will help to bring in drier air aloft
and persist through Sunday.

An isolate shower or two linger across the CWA this morning, and
should remain that way through at least mid morning. As we head into
this afternoon, scattered showers and thunderstorms should begin
developing over the region, particularly across southeastern MS into
far southwestern AL. This activity should increase in coverage by
mid to late afternoon, and given overnight model guidance suggesting
better coverage I have opted to add in an area of likely PoPs across
southeastern MS, southwestern AL into the interior of the FL
panhandle this package. Despite the aforementioned drier air aloft
being advected in above 500mb, rich sfc-500mb moisture content will
help maintain high PWATs in the 1.7 to 1.9 inch range. Likewise,
steep low level lapse rates will develop along with high SBCAPE and
MLCAPE values upwards of 3,500/2,500j/kg respectively. With at least
subtle forcing in association with the aforementioned weak
disturbances rounding the base of the upper level trough, this
should be adequate for scattered to numerous showers and
thunderstorms during the afternoon into early evening hours today.
The caveat to this may be the drier air aloft, although this doesn't
appear to be robust enough to serve as a significant limiter to
convection. Showers and storms will be efficient rainfall producers
once again, with isolated areas of flash flooding possible under any
heavier slow moving thunderstorms. Additionally, with the
introduction of some dry air aloft, wet microburst potential may
become isolated with DCAPE values approaching 700j/kg.

With loss of daytime heating, storm coverage should greatly diminish
through tonight. Expect a similar evolution in convection to occur
Sunday, although coverage may be greater given closer proximity to
the parent trough. Overall thermodynamic/kinematic environment
remains relatively unchanged from the previous day, with perhaps
even a little more moisture throughout the column to work with.
Given this, have likely PoPs covering the entire CWA for Sunday
afternoon into early evening. Once again, heavy rainfall with
showers and storms is likely and a chance for isolated areas of
flash flooding remains Sunday.

Temperatures generally remain close to a persistence forecast of the
last couple days, with highs in the middle to upper 80's and perhaps
an isolated 90 degree reading here and there today and Sunday. Lows
will be in the lower to middle 70's for most locations, with perhaps
an upper 70's reading along the coast. A MODERATE risk of rip
currents remains in effect throughout the period. MM/25

&&

.AVIATION...
12Z issuance...VFR ceiling and visibility prevail for the region
this morning, and should remain that way through the rest of today
into tonight. Scattered to at times possibly numerous
thunderstorms will develop this afternoon into early evening,
posing the chance for reduction in ceilings and visibility to
MVFR category and perhaps IFR category under the heaviest
convection. Winds remain generally southwesterly to at times westerly
at 5 to 10kts.

&&

.PREV DISCUSSION... /issued 404 AM CDT Sat Jul 10 2021/

NEAR TERM UPDATE /Now Through Sunday/...Subtle weakness in upper
level ridging resides over the southeastern U.S. today as an upper
level trough slowly makes its way southeast into the ArkLaTex region
by Sunday, stretching northeastward towards the Great Lakes region.
Weak disturbances associated with this trough will round its base,
helping in providing a source of lift over our region during the day
today, and particularly on Sunday afternoon into evening as the
trough is closer in proximity. At the surface, we continue to have
the nose of a surface high pressure centered over the southwestern
Atlantic stretch into the southeastern U.S. keeping most of the CWA
embedded within southerly to southwesterly low to mid-level flow.
This will help to continue to advect in a moist low to mid level
airmass off the Gulf of Mexico. At the same time, modest westerly to
northwesterly flow above 500mb will help to bring in drier air aloft
and persist through Sunday.

An isolate shower or two linger across the CWA this morning, and
should remain that way through at least mid morning. As we head into
this afternoon, scattered showers and thunderstorms should begin
developing over the region, particularly across southeastern MS into
far southwestern AL. This activity should increase in coverage by
mid to late afternoon, and given overnight model guidance suggesting
better coverage I have opted to add in an area of likely PoPs across
southeastern MS, southwestern AL into the interior of the FL
panhandle this package. Despite the aforementioned drier air aloft
being advected in above 500mb, rich sfc-500mb moisture content will
help maintain high PWATs in the 1.7 to 1.9 inch range. Likewise,
steep low level lapse rates will develop along with high SBCAPE and
MLCAPE values upwards of 3,500/2,500j/kg respectively. With at least
subtle forcing in association with the aforementioned weak
disturbances rounding the base of the upper level trough, this
should be adequate for scattered to numerous showers and
thunderstorms during the afternoon into early evening hours today.
The caveat to this may be the drier air aloft, although this doesn't
appear to be robust enough to serve as a significant limiter to
convection. Showers and storms will be efficient rainfall producers
once again, with isolated areas of flash flooding possible under any
heavier slow moving thunderstorms. Additionally, with the
introduction of some dry air aloft, wet microburst potential may
become isolated with DCAPE values approaching 700j/kg.

With loss of daytime heating, storm coverage should greatly diminish
through tonight. Expect a similar evolution in convection to occur
Sunday, although coverage may be greater given closer proximity to
the parent trough. Overall thermodynamic/kinematic environment
remains relatively unchanged from the previous day, with perhaps
even a little more moisture throughout the column to work with.
Given this, have likely PoPs covering the entire CWA for Sunday
afternoon into early evening. Once again, heavy rainfall with
showers and storms is likely and a chance for isolated areas of
flash flooding remains Sunday.

Temperatures generally remain close to a persistence forecast of the
last couple days, with highs in the middle to upper 80's and perhaps
an isolated 90 degree reading here and there today and Sunday. Lows
will be in the lower to middle 70's for most locations, with perhaps
an upper 70's reading along the coast. A MODERATE risk of rip
currents remains in effect throughout the period. MM/25

SHORT TERM /Sunday night Through Monday night/...An upper
trough will try to dig southward, however it will be blocked by a
building ridge over the western Atlantic. At the sfc, southerly
flow will continue with precipitable water values of 1.7 to 1.9
inches. This will result in a typical summertime diurnal
convective pattern with scattered to numerous showers and
thunderstorms during the day and isolated coverage overnight.
Highs on Monday will be in the upper 80s. Lows remain very muggy,
in the low to mid 70s inland to mid and upper 70s along the
coast. /13

EXTENDED TERM /Tuesday Through Friday/...A summer time pattern can be
expected throughout the period as an upper level ridge over the
western Atlantic extends across the region. A similar situation
persists at the surface with a high pressure over the western
Atlantic extending across the southeast and northern Gulf.
Southeasterly flow will at the surface will keep sufficient moisture
in place with PWAT's ranging between 1.7 and 2.1 inches. Scattered
showers and thunderstorms can be expected each day with the
exception of Tuesday which has likely rain chances (due to a lifting
upper level trough to our west). Storms are expected to follow the
sea and land breeze cycle where convection forms offshore early in
the early morning and transitions inland during the afternoon. With
sufficient instability, a few strong storms cannot be ruled out

Temperatures start to heat up in the extended as the high pressure
builds in. Daytime highs will reach into the upper 80s to lower 90s,
with a few localized areas potentially seeing mid 90s later in the
week. Heat indices generally range from 98 to 102F. Overnight lows
dip into the lower 70s inland with mid to upper 70s along the
coast. /14

MARINE...A light to occasionally moderate onshore flow
persists through midweek. Seas remain steady around 2 feet through
Sunday, building slightly into the early part of next week.
Scattered showers and thunderstorms remain possible over the marine
area through the period. Lightning, gusty winds, and locally higher
seas will accompany any stronger storms. MM/25

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...None.
&&

This product is also available on the web at:
http://weather.gov/mob