Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 201214 AAA

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
614 AM CST Tue Feb 20 2018

.DISCUSSION...Updated for latest aviation discussion below.


12Z issuance...Periods of LIFR and IFR ceilings across the Mobile
metro area will slowly improve this morning into the MVFR
category before noon. Meanwhile, VFR ceilings across the Pensacola
metro area early this morning will slowly degrade into the MVFR
category by mid morning. A few showers are forecast to develop
throughout the day, so kept vicinity showers in for all TAF sites
beginning at 17z. Ceilings along the north central gulf coast will
degrade further into the LIFR and IFR categories this evening.


.PREV DISCUSSION... /issued 435 AM CST Tue Feb 20 2018/

NEAR TERM /Now Through Tuesday night/...Another very warm day in
store across the forecast area with record high temperatures
north of I-10 forecast to range from 78 to 83 degrees, with mid
70s south of I-10. The forecast high temperature for Mobile today
is 80 degrees, and the record high temperature is 79 degrees set
just last year. The forecast high temperature for Evergreen today
is 82 degrees, and the record high temperature is 82 degrees set
just last year. The forecast high temperature for Pensacola today
is 78 degrees, and the record high temperature is 80 degrees set
in 1981. All three locations could see record heat today.

A strong surface high pressure ridge and upper level ridge over
the southeast states and eastern Gulf of Mexico will persist over
the next 24 hours. A light southerly to southeasterly wind flow
will be maintained across the region along the western periphery
of the surface high pressure ridge. Low level moisture below 850
mb will also remain, with mainly mostly cloudy skies forecast
through the near term.

Isolated to scattered light rain showers are expected mainly this
afternoon and evening due to with boundary layer over-running
occurring on the backside of the surface high pressure ridge in
combination with decreasing stability from surface heating. Patchy
fog early this morning will dissipate by mid morning, and then
redevelop overnight, mainly across the southern half of the
forecast area. /22

SHORT TERM /Wednesday Through Thursday night/...The upper-level
pattern remains highly amplified to begin the short term, with
deep troughing in the western CONUS and strong ridging over the
southeastern states and western Atlantic. Between these features,
a broad region of southwest flow extends from Mexico up into
eastern Canada, beneath which a surface cold front remains
stalled. Much of the rain associated with this pattern will be
focused along that stalled front and well to our northwest.
However, warm and moist onshore flow, coupled with additional
low-level ascent via a weak pre-frontal trough, will support
scattered shower development across our region throughout the day
Wednesday. While the nose of greatest instability is expected to
remain to our west, model guidance still indicate a modest amount
of destabilization occurring across our area, with around 500
J/kg of SBCAPE (200-400 J/kg MLCAPE) developing by the afternoon
hours. Thus, have included a slight chance for some rumbles of
thunder to mix in with the showers Wednesday afternoon. Rain
chances then taper off Thursday as the front begins to lift back
to the north and subsidence beneath a mid-level ridge building
over our area helps to suppress shower development.

Expect temperatures to remain well above normal through the short
term, threatening records both Wednesday and Thursday afternoons.
Highs reach the upper 70s near the coast and low to mid 80s inland
each day. Lows only dip into the mid to upper 60s each night. /49

LONG TERM /Friday Through Monday/...Looks like the upper pattern
finally begins to shift as we head into the weekend and next week.
The blocking ridge that has remained parked over the Southeast all
week finally begins to flatten and push south as the deep
troughing over the western CONUS progresses east. The mid-level
ridge sticks around over our area long enough to keep Friday
mostly dry, except for a few isolated showers possible across our
southeast Mississippi counties. A potent shortwave digs into the
Desert Southwest Friday night, triggering rapid lee cyclogenesis
at the surface over western TX/OK and forming a surface low over
the South Plains by midday Saturday. This low quickly lifts
northeast into the Great Lakes region by Sunday, dragging another
cold front towards the southeast. With the surface ridge over the
western Atlantic weakening and a more progressive pattern
developing aloft, this front should have less difficulty making
its way into our area by late Sunday or early Monday. Ahead of
this front, sufficient moisture and instability develops for
convective showers and thunderstorms. This is followed by a brief
reprieve from the rain Sunday night in the wake of the front. As
we look further into next week, a warm and moist southwesterly
mid-level flow sets up and overruns the shallow pool of cool air
left behind by the front, leading to increasing rain chances once
again Monday into early next week.

Temperatures continue to run warm Friday and Saturday, reaching or
even surpassing record highs each afternoon. Slightly cooler temps
(mid 70s) are expected Sunday as showers and overcast skies help
to mitigate diabatic heating. Temps then finally cool back to
around seasonal (mid 60s) Monday into next week in the wake of
Sunday night`s frontal passage. /49




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