453
FXUS64 KMOB 170721
AFDMOB

Area Forecast Discussion
National Weather Service Mobile AL
221 AM CDT Thu Jul 17 2025

...New Aviation, Discussion, Marine...

.DISCUSSION...
Issued at 218 AM CDT Thu Jul 17 2025

A weak low level circulation now just south of Mobile Bay over our
nearshore open waters continues to move westward this evening. This
low has been devoid of deep convection much of the evening,
potentially a result of a cluster of deep convection that developed
along a low level convergence zone over southeast Louisiana earlier
this evening. This cluster of storms continues to race off to the
southwest as a well organized MCS as of midnight. This has likely
resulted in less subsidence over the low level circulation to the
east and now (just after midnight) deep convection has developed
along the western edge of the circulation. It is likely taking
advantage of the typical diurnal convective maximum often observed
with tropical systems over marine areas. To this point, overall
surface pressures have remained the same and it will be interesting
to see if convection can persist near the center and allow surface
pressures to lower prior to reaching southeast Louisiana by sometime
Thursday afternoon.

Latest CAMs and CAMs ensemble guidance and even to some extent the
latest global model runs hint at better organization of the low
level circulation through Thursday evening. As the low moves west
and potentially organizes and slowly deepens, increasing
southeasterly to southerly flow will continue to advect abundant
deep layer moisture. In fact, latest model guidance suggests that
PWATs over the area will likely range between 2.25 to 2.5 inches.
These are near the maximum PWAT values for this time of year which
is greater than 3 standard deviations above the mean. There will be
an area of better low level convergence along the coastal counties
of Mississippi, Alabama, and far western portions of the Florida
Panhandle which combined with the extreme moisture content and
destabilization from daytime heating could lead to some bands of
very heavy rainfall in localized areas. Latest probabilistic HREF
ensemble guidance suggests that a general 1 to 3 inches of rain
could occur across the coastal zones with localized areas upwards of
4 to 6 inches. This could lead to localized flash flood potential
later this afternoon. This will be focused diurnally with the
greatest potential during the afternoon peak heating time period.

The steering flow around a high pressure ridge to our east will
result in the surface low slowing and lifting gradually northward
across the Lower Mississippi River Valley through Friday. There is
an increased signal for the enhancement of a low level jet on the
eastern side of the surface low over western Mississippi by Friday
morning in response to improved organization and some predicted
strengthening through today and into tonight. The 850mb flow on a
few individual CAM guidance outputs are on the order of 30-40 kts
and the latest HREF ensemble mean showing a large swatch of 25-30
kts southwesterly 850mb flow over the area. To a lesser extent this
is hinted at by the global model guidance as well, albeit of weaker
intensity. If this low level jet enhancement occurs and orients
itself from southwest to northeast across our area on Friday there
would be an increasing threat for more significant flash flooding
and potentially low topped supercells.

On Friday, the signal from the latest probabilistic HREF guidance
suggests the potential for an additional more widespread potential
for between 2 and 4 inches of rain along the coastal counties with a
greater potential for more significant amounts as high as 8 to 10
inches in localized bands where slow moving storms will be capable
of training and backbuilding. In addition, the continuation of
highly anomalously high PWATs and additional signals from the CAM
ensemble guidance for high rainfall rates, potentially greater than
2 inches per hour, all falling on grounds potentially saturated from
rainfall on Wednesday and Thursday, could lead to a more enhanced
flash flooding threat. We will continue to monitor this situation
very closely and a Flood Watch may become necessary for coastal
areas on Friday.

In addition to the heavy rain and flooding threat, a few low topped
supercells could develop as well on Friday if the low level jet
enhancement is realized in the presence of potentially moderate
instability supported by very high theta-e air and some daytime
heating. This combination of increased shear and instability could
support a low end severe threat. Some forecast hodographs from the
models supporting the stronger low level flow indicate longer
counter-clockwise curved hodographs. If this materializes, it would
support dominant left moving mini supercells or storm splits with
dominant left movers. There could be a low end threat for tornadoes
in this type of environment along with intense rainfall rates.
Although this is an unusual setup, we will closely monitor this
potential to see if it can materialize.

By the weekend, the surface low will lift out to the northeast and
the upper ridging to the east will retrograde westward over the
northern Gulf Coast as surface high pressure remains positioned
across much of the Gulf in the wake of the subtropical surface low.
Although the airmass will remain seasonably moist, increased
subsidence will allow for a return of more typical Gulf Coast summer
weather dominated by diurnally driven sea breeze convection on land
during the day and land breeze convection at night over the Gulf
waters. In addition, precipitation chances will lower back to
scattered outside of the favored sea breeze/land breeze locations.
Temperatures will also increase again with high temperatures well
into the middle and upper 90s and lows in the middle 70s to near 80
along the coast late this weekend into early next week. These hot
temperatures combined with continued high humidity may result in a
return to dangerously high heat indices and heat advisories my
become necessary during this time period. /JLH

&&

.AVIATION...
(12Z TAFS)
Issued at 218 AM CDT Thu Jul 17 2025

06Z issuance... VFR conditions are in place at issuance
time and should generally prevail through the period. Bands of
showers and thunderstorms will develop throughout the period, with
the highest coverage expected from late morning through the
afternoon hours. Expect reductions in visibilities and ceilings in
some of the heavier activity, and some storms could produce gusty,
erratic winds. Winds throughout the morning will turn southeasterly
as low pressure over the northern Gulf pushes towards Louisiana.
Winds today could gust as high as 20 knots especially over coastal
counties. /96

&&

.MARINE...
Issued at 218 AM CDT Thu Jul 17 2025

Moderate southeasterly flow will develop Thursday morning and may
become strong Thursday night. Winds will become southerly Friday
and then southwesterly over the weekend as overall intensity
diminishes as high pressure builds over the region. /JLH

&&

.PRELIMINARY POINT TEMPS/POPS...
Mobile      88  76  89  75  90  75  93  75 /  80  50  90  30  80  10  60  20
Pensacola   88  79  89  79  91  79  93  79 /  80  50  80  20  60  10  50  20
Destin      90  81  91  81  92  81  93  81 /  80  40  70  10  50  10  40  20
Evergreen   90  74  91  73  93  74  95  73 /  80  20  70  10  60  10  40  20
Waynesboro  91  74  89  73  93  73  94  73 /  80  30  80  10  70  10  40  10
Camden      90  74  91  73  92  74  93  73 /  70  20  70  10  50  10  40  20
Crestview   89  74  91  74  93  74  95  74 /  90  30  80  10  70   0  50  10

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...High Rip Current Risk from 7 AM CDT this morning through
     Saturday morning for ALZ265-266.

FL...High Rip Current Risk from 7 AM CDT this morning through
     Saturday morning for FLZ202-204-206.

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

$$

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