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Area forecast discussion...updated
National Weather Service Mobile Alabama
701 am CDT Wed Jun 28 2017

Discussion...updated for latest aviation discussion below.

&&

Aviation...
12z issuance...VFR to MVFR cigs through about 28.15z followed by
MVFR to IFR cigs and visibilities mainly in scattered to numerous
showers and thunderstorms through mid to late afternoon followed
by MVFR cigs due to less coverage late this afternoon and this
evening, then IFR to MVFR cigs and visibilities due to better
coverage overnight and early Thu morning. Periods of very heavy
rain, frequent cloud to ground lightning and gusty winds mostly
from 20 to 30 knots will be the main threats with the most of the
stronger storms. A few isolated storms could produce winds
generally around 40 knots mainly during the late afternoon and
early evening hours. Easterly winds at 5 to 10 knots early today
will shift southeast at 8 to 12 knots late this morning through
this afternoon diminishing to 5 to 8 knots later this evening and
overnight. 32/ee

&&

Previous discussion... /issued 443 am CDT Wed Jun 28 2017/

Near term /now through Thursday night/...expect deeper moisture
and better rain chances through Thu afternoon as persistent mid to
upper trough over the western Gulf and East Texas begins to eject
off to the east and northeast through the remainder of the week.
Most of the model guidance shows this feature dampening by late
Thu in Fri eventually leading to a drier solution late in the
week. Near the surface a weak trof was also noted stretching from
the NE Gulf to the NW and western Gulf progged to shift northward
through the the next 48 hours. With this pattern expect scattered
to numerous showers and thunderstorms to develop to the west and
southwest early today shifting east and northeast and becoming
more numerous across most areas of the forecast area through Thu
afternoon. In the mid levels a series of mid level disturbances
track eastward near the base of the trough tracking along the
coast and just inland thus providing better lift and forcing
leading to the better coverage of showers and thunderstorms for
the next 48 hours, especially over the lower half of the forecast
area. For now the main concern with the stronger convection will
be periods of very heavy rain, especially on Thu, possibly leading
to more nuisance flooding especially in low lying areas and areas
with poor drainage. With antecedent conditions still very moist
across the region rainfall rates and amounts will have to be
closely monitored for the next 48 hours. Rainfall totals ranging
from 1 to 3 inches with locally higher amounts can be expected
through Thu night. Due to the deep moisture column setting up in
the boundary layer in the near term frequent cloud to ground
lightning will also be possible with the stronger thunderstorms
especially during the late morning, afternoon and early evening
hours. Gusty winds mostly from 20 to 30 knots will also likely
with the most of the stronger thunderstorms with maybe a few
higher gusts during the late afternoon or early evening hours.

As for temps highs will range from the middle to upper 80s inland
and the middle 80s near the coast today and the lower 80s for most
areas on Thu. Lows both tonight and Thu night will range from the
lower 70s for most inland areas and the middle 70s along the
immediate coast. 32/ee

Short term /Friday /...while Friday trends a bit drier, there
will still be active midday through evening thunderstorms.
Absolute low level moisture values remain high, deep layer winds
remain S to southwesterly and sufficient instability exists. It does appear
to be one of those patterns where the thunderstorms begin near
the coast early and development inland throughout the day with
lingering evening storms (particularly inland). Very late Friday
night, yet another approaching shortwave from the plains brings
additional deep-layer forcing into southeast MS by sunrise, but it
appears to be on the wane. The most likely scenario is that it
will leave a boundary for storms to be initiated on early
saturday). /23 jmm

Long term /Saturday through Tuesday/...Saturday appears to be
the most active day thunderstorm-wise, but just how active remains
in question. At the same time the aforementioned shortwave
approaches, it is shunted more to the north as an elongated deeply
reflected ridge begins building across the northern Gulf of Mexico.
If this were to build as currently forecast, this would allow a
transition to more of a typical summertime diurnal regime for our
area Sunday through early Tuesday. We do expect above average
coverage on Saturday, especially along and north of Highway 84
corridor, with convection again, lingering through mid-evening and
perhaps a bit later in south central Alabama. After that, lower rain
chances are forecast as the deep-layer ridge further builds. Max
afternoon temperatures will respond by warming solidly into the
lower 90s both Sunday and Monday (could be warmer, and will watch
newer guidance closely to see if heat indices reach into the 100-105
deg(f) range both days). On Tuesday, yet another mid- and upper
level weakness develops over our area and will once again increase
rain chances and slightly lower Max afternoon temperatures. /23 jmm

Marine...a broad surface ridge of high pressure over the upper
Mississippi River valley and Appalachians this morning will continue
to shift east, reaching the eastern Seaboard and western Atlantic
late tonight through early Friday. To the west an upper trough of low
pressure over the western Gulf and East Texas will shift east across
the north central Gulf through early Friday, leading to a better
onshore flow later today continuing through the remainder of the
week. Rain chances increase with this pattern today and continue
through Thursday night followed by a drier pattern over the weekend.
The best coverage of showers and thunderstorms over the marine area
will occur during the overnight and morning hours through early Friday.
32/ee

A relative light S to SW wind flow persists late Saturday. As surface
high pressure tries to close off over the northern Gulf of Mexico
for the period Sunday through Tuesday, winds may actually become
more westerly during the afternoons with light and variable flow
at other times. It also looks like a typical summertime waterspout
pattern is setting up for Sunday and Monday as each night should
have a light land breeze. /23 jmm

&&

Mob watches/warnings/advisories...
Alabama...none.
Florida...none.
MS...none.
GM...none.
&&

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