Areal Flood Advisory 166, NWS Mobile, AL

Area Forecast Discussion
National Weather Service Mobile AL
246 PM CDT Wed Aug 4 2021

.NEAR TERM UPDATE /Now Through Thursday/...An anomalous deep trough aloft is
currently over the eastern CONUS with our region in its base. This
trough progresses east through tonight before lifting out to the northeast
on Thursday, with another trough beginning to dig into the Central
Plains while progressing east. With this pattern, our region remains
in generally zonal flow aloft through a majority of the period before
a transition to more southwesterly begins taking place late Thursday
afternoon and going into the short term. At the surface, a frontal
boundary is currently stalled off the coast with a broad surface
low over the north Central Gulf, embedded in an inverted surface
trough also near the coast. Going into tonight and Thursday, the
surface boundary remains stalled just off the coast; however, there
are guidance differences in whether the low is maintained over
the north- Central Gulf, or organizes into a more pronounced low
that heads towards the western Florida panhandle. Regardless of
model solutions, south to southeasterly flow returns to the
northeastern Gulf coast, with some moisture pushing back into the
southeast portion of the forecast area, mainly southeast of I-65,
and drier air still pushing into the region from the northwest. All
this said, the best PoPs through the period remain along and southeast
of I-65 during the afternoon today and Thursday, with coverage
pushing offshore overnight.

For temps, highs through the period remain generally in the upper
80s to low 90s across the region, with the cooler temps closer to
the coast. Lows for tonight will ranges from the mid/upper 60s to
low 70s northwest of I-65, with low to mid 70s southeast. JEH/88

&&

.SHORT TERM /Thursday night Through Saturday night/...This period
is all about a rather potent shortwave that currently can be seen
digging across the northern Rockies and into the Plains. This
feature amplifies and deepens as it moves from the Central Plains
tomorrow evening to the Lower MS Valley by Friday morning. Although
nowhere near as impressive as the current anomalous longwave
trough currently over the TN/OH Valleys, it essentially drops into
the mean longwave trough position late in the period before dampening
occurs. In all, the approaching wave begins to interact with our
current weak baroclinic zone so that a weak surface low forms in
response by midday Friday across our area and it quickly zips NE
through the flow during Friday night. The boundary layer on Friday
will be relatively dry, still feeling the effects of the current
air mass we are under the influence of, but rain chances will
gradually increase further west as the aforementioned trough
approaches and lower tropospheric winds will be southerly by that
time. Am not too bullish on Friday afternoon rain chances, but
the subsequent quick airmass recovery in the low level moisture
department should support a solid re-introduction of rain chances
by mid Friday evening through early Saturday. rain chances become
more unclear for Saturday afternoon. There are major differences
in the deep layer moisture fields for the EC vs. GFS on Saturday
afternoon with the former being much drier because it has a faster
phase speed in its solution for the incoming wave and thus blows
it through our area much quicker with subsidence and drying on
Saturday. I say, "Not so fast!" and prefer at least a blend of the
two since their synoptic patterns are not 'too' dissimilar. So
will forecast Saturday afternoon to have solid chance PoPS in the
30-40% range - similar to Friday - and that goes against the EC.
There is more consensus from Saturday evening on as we should
experience drying from the west. The best rain chances Saturday
evening and overnight will be along the coast and further
offshore. Lows each morning ranging from the lower 70s inland to
the mid 70s along the coast with afternoon maximum temperatures
both Friday and Saturday in the 90-95 F range across the interior
to around 90 along the beaches. /23 JMM

&&

.EXTENDED TERM /Sunday Through Wednesday/...Actually this period
becomes one of persistence after the departure of Saturday's
wave. It is about subtleties as to where deeply reflected high
pressure cells set up and have enough influence to change our day
to day weather. Will we be in a break between two cells or one's
western periphery? Both models seem to favor the latter as Sunday
beings on the western periphery of a far SW Atlc ridge. There
then appears to be westward retrogression by late Monday and upper
heights rise to near 594 dm (and it will once again feel hot).
Tuesday is similar and then a return to the ridge center being
over the far SW Atlc again by Wednesday. With all that said, there
is 'very little' change in the low level wind flow pattern as it
persists south to southeast most of the period. This adds up to a
typical summertime pattern for our region with a good chance of
shower and thunderstorm activity each afternoon ahead of an inland
propagating sea-breeze front, shifting to a greater coverage of
showers and thunderstorms offshore at night as nightly land-
breezes try to form and move offshore. As for temperatures, we
will have a very diurnal pattern with highs in the lower to mid
90s across the interior to around 90 along the beaches. Heat
indices will creep back into the 103-107 degree range each day of
the extended after Sunday. /23 JMM

&&

.MARINE...The only concerns throughout the period is the potential
for higher winds and waves near scattered to occasionally numerous
showers and thunderstorms. Otherwise, a mainly light to occasionally
moderate northeasterly to easterly flow continues through Thursday,
with a mainly light southerly to southwesterly flow developing by
Friday and lasting into the weekend. Little change in seas expected
through the period. JEH/88

&&

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

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