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fxus64 kmob 191141 

Area forecast discussion
National Weather Service Mobile Alabama
641 am CDT Tue Sep 19 2017

Discussion...updated for latest aviation discussion below.


19/12z issuance...VFR conditions will generally prevail for the
next 24 hours, but do expect brief periods of MVFR conditions,
early this morning in patchy fog and then later this morning
through the afternoon hours in isolated to ocnly scattered
showers and storms. Don't believe coverage of storms near the
coastal taf sites will be enough for more than vcsh in tafs, but
inland locations will likely see scattered convection today.
Surface winds mainly out of the west today, 6 to 12 knots today
and less than 5 knots tonight. 12/ds


Previous discussion... /issued 425 am CDT Tue Sep 19 2017/

Near term /now through Tuesday night/...upper level flow remains mostly
zonal across the forecast area today and tonight, with upper ridge
axis to our southwest (over the Gulf of mexico). Models indicate
weak shortwave energy will move east across the area in the near
zonal flow today. At the surface, a high pressure center will
persist over the Gulf to the southwest of the forecast area, but
gradually weaken through tonight. The position of this surface high
will result in a general, light westerly low level flow over the
area, with some diurnal effects as the flow will be more
northwesterly late night and early morning hours, then become more
southwesterly during the afternoon and early evening hours. Pwat's
ranging from 1.75 inches northern zones increasing to around 1.90
inches southern zones today, and combined with daytime instability
and the weak shortwave dynamics aloft and sea breeze effects in the
lower levels, will result in scattered showers and a few
thunderstorms across the region today. Tonight, with the slight
northwesterly flow, pwat's decrease to around 1.50 inches over
interior. Loss of heating and instability will result in convection
ending by the mid evening hours and through the overnight hours.
Some patchy light fog noted across parts of the region early this
morning, and could again develop late tonight. Highs today ranging
from the upper 80s to near 90 over interior counties to the middle
80s near and along the coast. Lows tonight expected to range from
the lower 70s over most inland areas to the mid 70s at the coast.

Short term /Wednesday through Thursday night/...a broad mid to
upper trof over the western conus will begin to deepen on Wed and
continue through Thu night, eventually shifting eastward later in
the week. To the east an upper ridge generally over the Lower
Plains and western Gulf will become better amplified in the short
term period as the trough to the west deepens. Further east
Hurricane Jose is progged to track northward generally off the
eastern Seaboard allowing high pressure near the surface to build
southward from the eastern Great Lakes to the north central Gulf
states. With plenty of mid to upper moisture advecting west across
the se and northern Gulf states, ahead of Hurricane Maria
tracking northward off the east FL coast, combined with plenty of
low level moisture advecting northward from a persistent onshore
flow along the northern Gulf Coast, rain chances increase Wed
through Thu night though remaining mostly scattered in coverage.
With limited forcing aloft combined with marginal instability
during the daylight hours the threat for severe weather will
remain low. Gusty straight line winds well below severe limits,
frequent cloud to ground lightning and short periods of very heavy
rain will be the main threats with the stronger storms. With
pwats climbing to near 2 inches for most areas this week some
local localized nuisance flooding may be possible generally in
flood prone areas, especially in urban areas where drainage is
poor. With the warm air advection from the south both day and
nighttime temps will continue to be near or slightly above
seasonal averages through Thu night. With more clouds than sun
each day highs both Wed and Thu will be in the upper 80s to near
90. Heat indices each day will range from the mid to upper 90s.
Lows each night will range from the upper 60s to lower 70s inland
and the lower to middle 70s along the immediate coast.

Long term /Friday through Monday/...later in the week the upper
trof over the western conus will begin to shift eastward moving
east of The Rockies by early next week. To the east Hurricane
Maria is progged to shift northward passing well east of the east
Florida coast. A weak upper low is also noted generally over the
Carolinas shifting south and southwest towards the north central
Gulf region over the weekend and early next week, though showing
little impact to rain chances over the north central Gulf region
attm. Near the surface high pressure will become reinforced from
the eastern Great Lakes to the north central Gulf states late in
the period. Temperatures will be near seasonal averages, ranging
from the mid to upper 80s during the day, and the upper 60s to
lower 70s each night through early sun, then slightly cooler Sun
night into early Mon morning. 32/ee

Marine...high pressure centered over the marine area today through
early Wednesday will shift to just north of the marine area by
Thursday and continue relatively unchanged through the end of the
period. Initially light westerly winds expected over the marine area
with slight offshore component near the coast late at night and
early in the morning, then a slight onshore component in the
afternoon and early evening hours, again mainly near the coast. By
late Thursday, as the center of the high shifts to the north of the
marine area, light winds will become more easterly. Friday through
Saturday night the easterly flow continues, but slightly increased
winds, possibly reaching exercise caution levels offshore by
Saturday. Seas 1 foot or less through Thursday night, gradually
increasing to 2 to 3 feet by Saturday night. 12/ds


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