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Area forecast discussion 
National Weather Service Mobile Alabama
423 am CDT sun Jul 13 2014

Short term (today and tonight)...surface high pressure ridge over the
interior southeastern states today will shift slightly south toward
the coast and over the northeastern Gulf of Mexico tonight. At the
same time...a middle upper level ridge also generally continues to poke
into the region from the west...but a weakness noted on water vapor
imagery over coastal Louisiana this morning will remain and drift
west only very slowly. This pattern will result in a low/middle level
southeast to south flow today...becoming more southwesterly tonight.
Water vapor imagery also depicts some slightly drier air over
interior sections of Alabama and Mississippi...however this appears
to be moistening as the middle/upper weakness drifts west of the
region. Radar is indicating some isolated showers and storms over
the coastal waters this morning...these will likely stay offshore as
they move west across the marine area. Only real forcing today for
showers and storms over inland areas will be diurnal heating and sea
breeze boundary interactions near the coast. Once isolated storms
develop by late morning today or midday...outflow boundaries will
also become an additional forcing mechanism...allowing for scattered
convection this afternoon (especially over southern half of forecast
area...with more isolated showers and storms farther inland). Highs
today in the upper 80s and lower 90s coastal...and low to middle 90s
interior (although slightly cooler rain modified areas will be very
possible across portions of the forecast area). Lows tonight lower 70s
inland (maybe even a few upper 60s over interior) and low to middle 70s
coastal. 12/ds

(monday through tuesday)...we expect monday's convection to be
driven by a combination of outflow boundaries and seabreeze
dynamics. Scattered showers and thunderstorms will increase through
the afternoon and decrease after sunset and rain-cooled boundary
layer causes the atmosphere to stabilize. Convective available potential energy 1500 to 2000 j/kg
Monday and often over 2500 j/kg Tuesday. The lifted index will be
generally around -4. Precipitable water above 1.6 to 1.80 inches
Monday but closer to 2 inches and above Tuesday. At that time
convection should be a bit more organized. 77/blowing dust

Long term [tuesday night through saturday]...GFS prognoses show a
trough at 500 mb having a slight positive tilt located over the
Tennessee and Ohio valleys. It becomes slightly more positively
tilted as it stalls while its parent low moves from southern Quebec
moving into central Labrador. At the same time at 500 mb...a ridge
with a closed geopotential height of 5940 will collapse and remain
over the southwest states by Tuesday. The outputs now agree on a
cold front reaching much further south over our area but the GFS
does not push it as strongly as the Euro which picked that up with
the Euro MOS showing colder temperatures Thursday morning along with
our neighbors. This is due to the alignment of the feature with the
deep wavenumber 5 trough to our north which will bring a northwest
flow aloft over our region around midweek. We expect middle level
perturbations in the 500 mb flow along the front...and with convective available potential energy
2500 to 3500 j/kg both days...lifted index generally around -4
during that period...and precipitable water around 2 inches both
days. We therefore expect numerous showers and thunderstorms
Tuesday through possibly Wednesday. In that 48 hour period basin
average rainfall of an inch to an inch and a quarter is possible
with higher totals possible where shower/thunderstorm trains set up.
Thursday should be cloud and rain free following passage of a robust
front but when it gets to the beach Thursday evening we expect it
will start backing up and dissipating.

We continue to see model outputs plunging Post-frontal temperature
into the low 60s Thursday morning. Close coordination and discussion
with our colleagues at bmx and Jan has resulted in concurrence that
adding 3 to 4 fahrenheit degrees to the Euro guidance is a prudent way
to go at least at this point...while watching the outputs. The GFS
MOS is starting to come around but we still believe it is behind.
As mentioned yesterday...we had a big ridge aloft that shielded US
from cooling trends in the northern plains but that ridge has eroded
even further as indicated by physical model output. Will keep
watching these model calculations in future runs. Thanks to our
colleagues at Jan and bmx. 77/blowing dust

&&

Marine...high pressure ridge remains over the northeastern Gulf
through Tuesday but breaks down somewhat by Wednesday as a cold
front moves south to the Gulf Coast (or just a little offshore into
the northern gulf). This front will then become nearly stationary
while gradually becoming more diffuse along the coast late week and
into the early part of the weekend. South winds today becoming a
general light to moderate southwest to west wind through the remainder
of the forecast period. Seas up to around 2 feet through most of forecast
period as well. Isolated convection...especially overnight through
early Tuesday...then increased chances for showers and storms
Tuesday through Thursday as the aforementioned front sags south to
near (or over) the marine area. 12/ds

&&

Aviation (13/12z issuance)...VFR conditions will prevail through
much of the period. Scattered showers and thunderstorms will
redevelop this afternoon and have included thunderstorms in the vicinity at all terminals
after about 18z today. Any convection is expected to diminish during
the evening hours tonight. 12/ds

&&

Preliminary point temps/pops...
Mobile 91 73 92 74 89 / 30 20 40 30 50
Pensacola 90 75 91 77 89 / 30 20 30 20 50
Destin 87 79 90 77 86 / 20 20 30 20 50
Evergreen 93 70 93 72 90 / 20 20 40 30 60
Waynesboro 93 70 93 71 90 / 20 10 40 40 60
Camden 94 71 94 72 89 / 20 20 40 40 70
Crestview 93 69 93 72 90 / 30 20 40 20 50

&&

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

$$

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