Areal Flood Advisory 151, NWS Mobile, AL

Area Forecast Discussion
National Weather Service Mobile AL
658 PM CDT Tue Jul 27 2021

.NEAR TERM UPDATE...Forecast remains on track with no significant
adjustments necessary at this point. A cluster of storms over the
Florida panhandle is currently kicking out an outflow boundary
that is propagating to the west at the same time that the sea
breeze is moving to the north into parts of southeast Mississippi
and southwest Alabama. We continue to monitor for the development
of strong storms where this outflow boundary intersects the sea
breeze (and other outflow boundaries). Minor flooding remains a
concern as this evening's storms are efficient rain producers and
are moving very slowly. 07/mb

&&

.AVIATION...
00Z issuance...Outside of thunderstorms, VFR conditions generally
prevail through the period. Scattered showers and storms
continue to develop across the area this evening and this trend
will continue throughout the early evening hours. MVFR to IFR
restrictions remain possible near any thunderstorms. Winds remain
generally light and southerly overnight. Expect winds to gradually
turn westerly to northwesterly in the morning and southerly again
by Wednesday afternoon due to the sea breeze. Scattered to
numerous showers and storms expected to develop by Wednesday
afternoon. 07/mb

&&

.PREV DISCUSSION... /issued 335 PM CDT Tue Jul 27 2021/

NEAR TERM UPDATE /Now Through Wednesday/...Let's start with the
current water vapor imagery. A very well-defined upper cyclonic
gyre is observed over the western Gulf of Mexico and is moving
westward. Deep convection is being forced within its diffluent NE
quadrant over the Central Gulf of Mexico waters and this can be
seen advecting to the northwest on the outer reaches of the KMOB
WSR-88D. This feature could potentially keep a bit more coverage
over our southwestern coastal waters overnight, but will mostly
remain beyond 60 nm. Synoptically, our region lies in the break
between two mid- and upper ridges, one over the Central US and
another over the Southwestern Atlantic. The deep- layer steering
flow is weak within this break, so any thunderstorms will be slow
movers and they can quickly dump two inches of rain (or more
depending on the exact nature of boundary-interactions). There is
also deep convection being initiated on the western periphery of
the SW Atlantic ridge across eastern AL and Georgia currently.
This will likely move into our area from the east later this
afternoon and/or early evening. Its westernmost progress/extent
will be highly dependent upon second and third generation
thunderstorm outflows to initiate additional updrafts, especially
once peak solar insolation wanes during the early evening.
Currently areas east of I-65 and all the way to the Destin area
stand the greatest chance of showers and thunderstorms through 9
PM this evening.

Meanwhile a progressive mid- and upper trough is currently over
Great Lakes and will be digging into the Mid-Atlantic Region
overnight. This will force a large scale deep-layer moisture band,
currently this afternoon extending from eastern NC westward to near
AR, into the Deep South overnight and that feature will become the
impetus to increase shower and thunderstorm coverage beginning later
tonight generally north of the Highway 84 Corridor and then moving
into the heart of our county warning area by mid-afternoon tomorrow.
This scenario is depicted by both global spectral models and feel
the higher rain chances is more than warranted. So, expect a better
coverage of showers and thunderstorms tomorrow afternoon and this
will take the edge off of the afternoon maximum temperatures (mostly
lower 90s). Overnight lows tomorrow morning in the low to mid 70s
inland ranging to near 80 along the beaches. Rip current risk
remains low through the period. /23 JMM

SHORT TERM /Wednesday night Through Friday night/...Upper level
ridging that has dominated the western and central CONUS builds
into our CWA Thursday into Friday. Meanwhile long-wave upper level
troughing remains rooted across the northeastern U.S. through the
period. As our upper level ridge builds in, weak large scale
subsidence in the upper levels will act to start suppressing
convective coverage Thursday into Friday, helping to allow
temperatures to increase across the region.

Wednesday evening will feature gradual waning of scattered to
numerous showers and thunderstorms that had developed earlier that
afternoon as the aforementioned deep moisture band in the near
term continues its push south across the CWA. Most model guidance
suggests this will shift offshore which should allow rain chances
to diminish as the evening progresses. Expect a diurnal shift in
convection offshore overnight, perhaps lingering along the coast
through early morning Thursday as the land breeze pushes offshore.
As we push into late morning and afternoon Thursday, a scattered
coverage of showers and thunderstorms will develop inland where
convective temperatures can be reached and nearer the coast where
some lift associated with the sea breeze boundary will occur.
Very weak flow through the atmospheric column will support slow
moving to nearly stationary convection, only attaining any
meaningful forward propagation through outflow boundary
production. PWATs remain high for Thursday generally near 2 to 2.1
inches. Given this and expected slow storm motions, heavy
rainfall and localized flash flooding can not be ruled out with a
quick one or two inches of rainfall. In addition to heavy
rainfall, a storm or two may manage to produce an isolated
damaging wind gust or two via wet microbursts. As the upper level
ridge strengthens over the area mid to upper level dry air
situated above the 850mb level will become increasingly prominent,
allowing for the development of sizable DCAPE values in the 1,000
to 1,200j/kg range. This coupled with SBCAPE values of 3,000 to
4,500j/kg and MLCAPE values of 2,500 to 3,500j/kg will aid in
strong updraft and downdraft generation in any thunderstorm.
Temperatures Thursday will rise into the middle to upper 90's for
most locations, and likewise high dewpoints in the lower to middle
70's during peak heating can be expected. This is going to result
in heat indices rising into the 105 to 112 range. In future
forecast packages a heat advisory may be necessary for the day
Thursday.

Thursday night convection follows the diurnal cycle and becomes
isolated to scattered offshore to along the immediate coast as
lows drop into the middle to upper 70's. Friday will feature
lesser convective coverage than Thursday, generally remaining
isolated to at best scattered where convective temperatures are
reached. The upper level ridge will be at its peak over the
region, helping to increase subsidence in the column and likewise
suppressing convective coverage. Similar to Thursday, plenty of
DCAPE and SBCAPE/MLCAPE will be present for any storm that tries
to form, which will promote the chance for a strong to damaging
wind gust in any storm. This threat will likely remain a bit more
limited than Thursday solely due to lesser coverage and more dry
air due to subsidence above the 850mb level. Localized flash
flooding also remains possible given the slow storm motions
(virtually stationary), although PWATs will generally be less in
the 1.6 to 1.9 inch range. The bigger story will be the heat for
Friday. High temperatures will range in the middle to upper 90's
for most spots with isolated areas managing to crack 100 degrees
inland. Surface dew points are expected to at least remain in the
lower 70's inland and lower to middle 70's along the coast. This
is going to support heat indices ranging in the 106 to 113 range.
If this forecast holds it would necessitate a heat advisory for
Friday. Heading into Friday night temperatures cool into the
middle to upper 70's as any residual shower and storm coverage
becomes focused offshore. MM/25

EXTENDED TERM /Saturday Through Tuesday/...The extended period
features a shift in the upper level pattern where the upper level
ridge begins to break down over the southeastern U.S. and shift
west into the western and west-central CONUS. Meanwhile, broad
long-wave troughing becomes the dominant feature over the eastern
CONUS Sunday through Tuesday. Over time, the mid to upper levels
moisten back up and PWATs climb back into the 2 to 2.3 inch range.
Forecast models vary on extent of convective coverage but as
shortwaves track along the southern periphery of the trough base
it can be expected to have times of scattered to numerous showers
and thunderstorms. This is particularly the case early next week
Monday into Tuesday as models hint at a surface front managing to
begin working its way into the CWA. With the increased convective
coverage and breakdown of the ridge, temperatures will feature a
gradual downtrend from the middle to upper 90's Saturday to lower
to middle 90's on Sunday. Monday and Tuesday will be the coolest
days with highs in the upper 80's to lower 90's. Lows will
generally stay steady-state in the lower to middle 70's. MM/25

MARINE...Thunderstorms will be the main impact during the next
several days for mariners. With the exception of tomorrow afternoon,
when thunderstorms will move from land to water, the tendency will
be for thunderstorms coverage to increase during the very early
morning hours lessen during the afternoons. Seas will generally
range less than 1 foot, except in localized squalls, and winds will
be light onshore during the day and light offshore at night at
night. /23 JMM

&&

.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

Special Weather Statement
National Weather Service Mobile AL
452 PM CDT Tue Jul 27 2021

FLZ205-272230-
Okaloosa Inland FL-
452 PM CDT Tue Jul 27 2021

...A STRONG THUNDERSTORM WILL AFFECT THE FOLLOWING COUNTIES...CENTRAL
OKALOOSA COUNTY UNTIL 530 PM CDT...

At 451 PM CDT, the strong thunderstorm was located near Crestview,
moving southwest at 20 mph.

Wind gusts around 40 mph will be possible with this storm.

Locations impacted include...
Crestview and Baker.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3055 8667 3083 8673 3092 8639 3067 8639
TIME...MOT...LOC 2151Z 062DEG 16KT 3075 8652

Special Weather Statement
National Weather Service Mobile AL
559 PM CDT Tue Jul 27 2021

FLZ203-204-272345-
Santa Rosa Coastal FL-Santa Rosa Inland FL-
559 PM CDT Tue Jul 27 2021

...A STRONG THUNDERSTORM WILL AFFECT THE FOLLOWING COUNTIES...CENTRAL
SANTA ROSA COUNTY UNTIL 645 PM CDT...

At 558 PM CDT, the strong thunderstorm was located near Milton,
moving west at 5 mph.

Wind gusts around 40 mph will be possible with this storm.

Locations impacted include...
Pace, Milton, Bagdad, Pea Ridge, Roeville, Floridatown and Point
Baker.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3077 8729 3074 8700 3059 8691 3058 8701
      3060 8702 3059 8702 3057 8715 3058 8718
      3057 8719
TIME...MOT...LOC 2258Z 073DEG 5KT 3064 8708

Special Weather Statement
National Weather Service Mobile AL
659 PM CDT Tue Jul 27 2021

ALZ054-280045-
Wilcox AL-
659 PM CDT Tue Jul 27 2021

...A STRONG THUNDERSTORM WILL AFFECT THE FOLLOWING COUNTIES...
EASTERN WILCOX COUNTY UNTIL 745 PM CDT...

At 657 PM CDT, the strong thunderstorm was located 11 miles south of
Belknap, or 17 miles east of Camden, moving south at 10 mph.

Wind gusts over 40 mph will be possible with this storm.

This storm will remain over mainly rural areas of southeastern Wilcox
County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3189 8696 3194 8715 3205 8707 3205 8694
TIME...MOT...LOC 2357Z 013DEG 7KT 3204 8701

Special Weather Statement
National Weather Service Mobile AL
806 PM CDT Tue Jul 27 2021

ALZ051-280145-
Choctaw AL-
806 PM CDT Tue Jul 27 2021

...STRONG THUNDERSTORMS WILL AFFECT THE FOLLOWING COUNTIES...
NORTHERN CHOCTAW COUNTY UNTIL 845 PM CDT...

At 804 PM CDT, strong thunderstorms were located along a line
extending from 6 miles northeast of Lisman to 3 miles north of
Pennington. These storms were moving very slowly to the southwest
at 5 mph.

Wind gusts up to around 40 mph will be possible with these storms.

Locations impacted include...
Lisman and Pennington.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3231 8795 3230 8796 3230 8800 3228 8801
      3228 8802 3227 8802 3226 8801 3218 8801
      3215 8802 3214 8804 3209 8805 3217 8841
      3231 8839
TIME...MOT...LOC 0104Z 358DEG 3KT 3225 8821 3226 8803

Special Weather Statement
National Weather Service Mobile AL
949 PM CDT Tue Jul 27 2021

ALZ052-261-262-MSZ067-076-280330-
Baldwin Inland AL-Washington AL-Mobile Inland AL-Greene MS-Wayne MS-
949 PM CDT Tue Jul 27 2021

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT THE FOLLOWING
COUNTIES...NORTHEASTERN MOBILE...NORTHWESTERN BALDWIN...SOUTHERN
WASHINGTON...SOUTHEASTERN WAYNE AND NORTHEASTERN GREENE COUNTIES
UNTIL 1030 PM CDT...

At 947 PM CDT, the strong thunderstorms were located along a line
extending from 6 miles southwest of State Line to 3 miles northeast
of Deer Park to 5 miles west of Calvert, and moving southwest at
10 mph.

Wind gusts of 30 to 40 mph will be possible with these storms.

Locations impacted include...
Citronelle, Deer Park, Tibbie, Mount Vernon, Calvert, State Line,
Fruitdale, McIntosh and Movico.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3156 8859 3137 8812 3122 8793 3121 8795
      3116 8794 3115 8795 3115 8794 3114 8794
      3116 8793 3115 8790 3117 8790 3114 8787
      3115 8787 3118 8789 3118 8788 3114 8783
      3099 8804 3116 8844 3134 8872
TIME...MOT...LOC 0247Z 069DEG 9KT 3138 8857 3126 8829 3113 8810