Areal Flood Advisory 85, NWS Mobile, AL

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
643 AM CDT Sun Jul 4 2021

.AVIATION...
12Z issuance...Scattered showers and storms develop mainly this
afternoon over the coastal counties and extreme southeast
Mississippi, with progressively less coverage further inland.
Light and variable winds transition to a south to southwest flow
at 5 to 10 knots over the coastal counties while further inland an
easterly to southeasterly flow around 5 knots is expected. After
patchy morning fog and low ceilings along the coast lift through
mid morning, VFR conditions are expected prevail through the
period except for MVFR conditions accompanying the heavier showers
and storms along the coast this afternoon and again late tonight.
/22

&&

.PREV DISCUSSION... /issued 500 AM CDT Sun Jul 4 2021/

NEAR TERM UPDATE /Now Through Monday/...An upper  trof over the
easternmost states, the axis of which extends back across the
north central Gulf coast states, lifts off to the northeast
throughout the day, and in the process leaves an upper level
weakness oriented over the northern Gulf. The upper level weakness
later dissipates as a broad upper ridge develops over the north
central Gulf coast area, and back westward into the southern
Plains. At the surface, a weak stalled frontal boundary near the
coast drifts into the interior portion of the forecast area
through Monday afternoon leaving a south to southwest flow over
the forecast area. Relatively dry deep layer air is currently in
place over the northernmost portion of the forecast area
(precipitable water values near 1.25 inch) which tapers to
abundant deep layer moisture over the northern Gulf, where
precipitable water values range around 2.0 inches. Abundant deep
layer moisture over the northern Gulf will gradually spread
northward into much of the forecast area over the remainder of the
period. Given the slow northward movement of the frontal boundary
and the moisture distribution, have opted for 50% pops along the
coastal sections today tapering to dry conditions over the
northernmost portion of the area. Will see a decrease in pops this
evening which bodes well for any Independence Day celebrations,
followed by 60-80% pops reforming along the coast after midnight.
For Monday, with the frontal boundary continuing to move
northward, and with the improved deep layer moisture over the
area along with daytime heating, have gone with likely pops for
much of the area. Will need to monitor for the potential of
flooding concerns where slow moving storms result in locally heavy
rainfall accumulations from midnight tonight through Monday.
Highs today will be in the upper 80s to lower 90s, then highs on
Monday will be moderated somewhat by convection and be mostly in
the mid to upper 80s. Lows tonight range from the upper 60s to low
70s inland to the mid 70s at the coast. A High Rip Current Risk
is expected this afternoon through Monday evening. /29 /22

SHORT TERM /Monday night Through Tuesday night/...Generally west-
southwest flow aloft persists through the period as weak upper
troughing remains over the area. At the surface, the weak frontal
boundary mentioned in the near term continues moving slowly north
out of the region while dissipating through Monday night as a weak
high over the eastern Gulf creeps north. On Tuesday, Elsa begins
to creep into the far southeastern Gulf and then continues its
progression northward just off the coast of the western Florida
peninsula. With this, our region gets continued low-level onshore
flow persisting through the period, promoting a surge of deep
layer moisture through Tuesday night causing PWAT's to increase
to 2-2.2 inches across the entire forecast region during this time.
Showers and thunderstorms can therefore be expected throughout
the short term with convection typically following a diurnal
pattern (convection over the Gulf overnight and during the
morning, and inland during the late morning and afternoon).
Temperatures during the period will generally be in the upper 80s
to low 90s. Overnight lows will be in the upper 60s to low 70s
inland and mid to upper 70s along the coast. /88 /14

EXTENDED TERM /Wednesday Through Saturday/...Benign upper level
persists during the early portions of the extended period with an
upper level ridge over the southwestern Atlantic and another to our
west over the southwestern U.S. Wednesday into Thursday. An upper
level trough during the short term period lifts out of the
northeastern U.S., leaving behind a weakness in the mid to upper
level ridging over the southeastern U.S. that will allow for Elsa to
track northward across Cuba and into the far eastern Gulf of Mexico.
A surface high pressure will reside to the east of Elsa, also aiding
in the steering of the tropical cyclone and promoting general
southerlies to southeasterlies over the region through Saturday.

Confidence continues to increase in the fact that Elsa's track
will stay well east of our local area over the far eastern Gulf of
Mexico likely hugging the Florida peninsula. More clarity has
been made thanks to NOAA Hurricane Hunters upper-air
reconnaissance missions and low-level reconnaissance missions in
and around the tropical storm. With conformation on the fact that
Elsa is undergoing a relocation of its low and mid level center
to the south and east, this could have some downstream impacts on
track and intensity, although these will be unknown for the time
being. Regardless of Elsa's track/intensity, this serves as a good
reminder to review your tropical preparedness plans and ensure
you are ready for if/when a tropical storm/hurricane comes your
way.

Outside of Elsa, a plume of higher PWATs will likely advect into the
region during the latter portion of the short term into the early
extended Wednesday, helping to increase rain and thunderstorm
chances across the region. Have opted to keep chance to likely PoPs
in the grids to account for this, with categorical PoPs Wednesday
afternoon. Elsa will have moved inland by Wednesday, and a fetch of
deep, tropical moisture will likely linger across the region into
Thursday. Given this, have continued likely PoPs for Thursday.
After this, we return to a more normal Summer-like pattern by
Friday into Saturday with chance for showers and thunderstorms in
the afternoon. Temperatures will be dependent on cloud cover,
however anticipating Elsa to remain far enough east to allow for
sufficient heating over the region. Generally anticipate highs in
the upper 80's to perhaps lower 90's each day. Lows will be in the
lower 70's. /88 /25

MARINE...Small craft operating on the Gulf waters should exercise
caution today due to westerly winds of 13 to 20 knots. We will
continue to monitor the progression of Tropical Storm Elsa as it is
forecast to enter into the southwest Gulf of Mexico Monday
afternoon. Any impacts at this time would be Tuesday night and
Wednesday with increasing long period swells resulting in 3 to 5
foot seas. Otherwise, light to moderate westerly winds become
southwesterly today and Monday. A southeasterly flow develops on
Tuesday, then switches back to a southwesterly flow on Wednesday.
Seas will gradually build through midweek. /22

&&

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

FL...High Rip Current Risk from noon CDT today through Monday evening
     for FLZ202-204-206.

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

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