Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 281155 AAA

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
555 AM CST Tue Feb 28 2017

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


12Z issuance...MVFR to IFR cigs and visibilties through 28.15z
followed by MVFR cigs and visibilties through about 01.01z
followed by MVFR to IFR cigs and visibilties through 01.12z.
Winds will be southeast to south at 8 to 13 knots with gusts to
20 knots later this morning continuing through tonight. 32/ee


.PREV DISCUSSION... /issued 429 AM CST Tue Feb 28 2017/

NEAR TERM /Now Through Tuesday night/...Deepening mid to upper
trof over much of the western conus this morning will shift east
to the central plains states through 12z Wed. Ahead of the this
system weak mid to upper forcing continues to shift east across
the central plains and lower MS river valley allowing for mostly
cloudy skies along with a few isolated rainshowers to occur over
northern sections of the forecast area this morning exiting to the
north and east by afternoon. Little to no accumulation is
expected through this morning. Model soundings continue to depict
pwats lowering to around 1 inch for most areas by afternoon along
with a better warm nose developing between 5 and 8kft this
afternoon and tonight. Most of the hi res guidance also depict fog
development before sunrise this morning continuing through mid
morning. With this will continue to monitor for dense fog this
morning and issue any advisories if needed. For tonight skies
remain mostly cloudy with patchy fog possible after midnight
continuing through sunrise wed. As for temps highs today will
climb to near record levels reaching the lower 80s for most inland
areas and the mid 70s along the immediate coast. The record high
for Mobile is 81 set in 1976...and 78 for Pensacola 78 last set in
2011. Low temps tonight will range from the upper 50s to lower
60s for inland areas generally along and east of the I-65 corridor
and the mid 60s for all other locations to the west and along the
coast. 32/ee

SHORT TERM /Wednesday Through Thursday night/...A well defined
upper trof over the central states broadens while advancing into
the eastern states through Wednesday night, with an associated
surface low near the Great Lakes region moving off well to the
northeast, meanwhile bringing a cold front through the forecast
area late Wednesday afternoon into Wednesday evening. MLCAPE
values increase to about 500-750 J/kg ahead of the approaching
front while precipitable water values increase from near 1.1
inches to near 1.5 along the immediate front. While the 850 mb
flow will initially be 30-40 knots (higher over the northern
portion of the area) Wednesday morning, the flow decreases to
25-30 knots during Wednesday afternoon, then further still
Wednesday evening as the front moves through. So, while 0-1 km
helicity values will be 100-200 m2/s2 Wednesday morning, shear
values drop off to near 100 m2/s2 by late Wednesday afternoon and
decrease further Wednesday evening.

Taking into considering that forcing will be generally modest
Wednesday morning, the period from near noon through mid Wednesday
afternoon looks to have the highest potential for possible severe
storms which diminishes late Wednesday afternoon into early
evening as shear and instability values drop off. As the shear
values will be the highest over the northern portion of the area,
this would be the areal portion most at risk for some possible
severe storms. SPC has a slight risk for severe storms over the
northern fringe of the area based on these conditions, with a
marginal risk for the remainder of the area where less favorable
conditions will be present. As the flow from the surface to 3 km
will be essentially southwesterly, expect severe storms to be
mainly capable of damaging wind gusts although there could be some
instances of large hail given low wet bulb zero values early on.

Will have pops increasing to likely for Wednesday afternoon over
a portion of southeast Mississippi and interior southwest Alabama,
tapering to slight chance mainly near the coast. Likely pops
follow for Wednesday evening mainly over south central Alabama
with chance to good chance pops over the remainder of the area as
the front moves through, then pops taper to dry conditions by
early Thursday morning. Dry conditions follow for the remainder of
the period as the eastern states upper trof maintains a deep
layer northwesterly flow over the forecast area in the wake of the
front with very dry deep layer air flowing into the region. Highs
on Wednesday will be near 80, just shy of record high values of
82 at both Mobile and Pensacola. Highs on Thursday will be
seasonable and in the mid 60s. Lows Wednesday night range from the
mid/upper 40s well inland to the mid 50s at the coast, then lows
Thursday night range from around 40 inland to the mid 40s at the
coast. /29

LONG TERM /Friday Through Monday/...Dry conditions continue
through Saturday night as a surface highs shifts eastward across
the region. A slight chance for rain due to daytime heating returns
to the western portion of the area on Sunday then for the entire
area on Monday as a southerly flow returns deep layer moisture to
the region. Seasonable daytime highs on Friday in the mid 60s
trend to the mid 70s by Monday. Lows Friday night range from the
upper 30s inland to mid 40s at the coast, then trend warmer to the
mid 50s to near 60 by Sunday night. /29

MARINE...Weak high pressure will continue over the eastern and north
central gulf through midday Wed then become reinforced Wed night
through early Sat in the wake of a strong cold front that moves
across much of the northern gulf and marine area late Wed evening
through early Thu morning. With this pattern a moderate easterly
wind flow early this morning will shift mostly southeast then south
late this morning through Wed afternoon ahead of the front. Isolated
to scattered showers and thunderstorms are expected ahead and along
the front Wed afternoon through Wed night clearing to the south and
east by early Thu morning. The best coverage of precip will be Wed
evening along the front. In the wake of the front a strong offshore
flow at 20 to 25 knots with higher gusts will develop early Thu
morning diminishing to 15 to 20 knots by Thu afternoon then rebuilds
to around 20 knots mostly well offshore late Thu evening through
late Fri morning. A moderate to strong easterly wind flow will
develop late Fri into Sat as strong high pressure to the north
shifts east to the eastern seaboard and western Atlantic. 32/ee




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