Scientific Forecaster Discussion
fxus64 kmob 230257 aab
Area forecast discussion...updated
National Weather Service Mobile Alabama
957 PM CDT sun Oct 22 2017
Discussion...see updated information for land areas below.
Update...the rain has come to an end over the western half of the
area while moderate to occasionally heavy rain persists over the
far eastern zones late this evening. The back edge of the rain
will gradually advance east overnight and mostly dry conditions
are expected for all areas by just after daybreak, with just
small chances lingering in the far east zones for Monday
morning. Updated forecast to reflect this slightly quicker timing.
The cold front is currently moving across central MS and
southeast Louisiana. It will move through the region overnight and
will clear the far eastern zones by mid Monday morning. Cooler
drier air will filter into the area behind the front with lows in
the western half of the area dropping into the mid to upper 50s by
Also increased winds over the most of the marine area to exercise
caution levels (15-20kt) in the wake of the front, which is in
better agreement with the high res guidance and makes sense given
what we typically see in the wake of this strength of frontal
Previous discussion... /issued 659 PM CDT sun Oct 22 2017/
Discussion...updated for latest aviation discussion below.
LIFR ceilings and IFR visibilities associated with the ongoing
convection will continue into the late evening. The line of
thunderstorms is expected to move eastward through the evening.
MVFR conditions after midnight though low ceilings remain over
the area until morning. After which winds will shift out of the
northwest with VFR conditions through the rest of the period.
Previous discussion... /issued 351 PM CDT sun Oct 22 2017/
Near term /now through Monday/...sharp long-wave upper level
trough axis exiting the plains this evening is progged to make
steady eastward progress to the lower MS river Delta late tonight
then pivots over The Heart of the forecast area by daybreak
Monday. Ahead of the eastward moving trough axis this evening,
the local area remains on the favored side for enhanced deep
layer ascent within an anomalously high moist environment
(pwat's) ~ 2.00 inches. Radar is quite active with widespread
showers/storms streaming northward off the Gulf. Efficient warm
rain processes today have resulted in heavy rainfall rates and
excessive storm totals mainly over the coastal zones where area
mesonet sites and National Weather Service surface observing equipment have reported
upwards of 2 to 4 inches with a few sites reporting 5+ inches.
Thus, with the front still to the west and additional rains
developing upstream to expand into the area tonight, could have
some isolated flash flooding problems and will increase the local
flood threat level to elevated over the coastal zones this
evening. There remains some potential for a few tornadoes this
evening generally east of the convective band as well. Stay
weather aware tonight.
As best dynamics shift east, categorical chances (80 to 100%) of
showers and storms this evening over much of the area shifts east
to the eastern half of the area by midnight and into the pre-dawn
hours Monday. Rain chances progged to slowly taper off over the
western zones through the course of the night. Attendant frontal
passage occurs Monday morning, bringing an end to the rain.
Overnight lows dropping off into the mid to upper 50s over the
northwest zones by daybreak while mid to upper 60s elsewhere.
Daytime highs Monday in lower to mid 70s interior to mid to upper
70s coast. /10
Short term /Monday night through Wednesday night/...a reinforcing
frontal boundary sweeps southward over the deep south Monday
night, bringing lowering deep layer thickness values, deep layer
dry air and lowering temperatures which last into the middle of
the week. To begin the short term, much cooler conditions to start
the morning commute to work or school Tuesday morning with
temperatures in the lower to mid 50s interior, 56 to 62 coast.
Daytime highs on Tuesday in the lower to mid 70s which is a few
degrees below climatic normals. The coolest period is Tuesday
night and Wednesday where lows will likely dip down into the 40s
for much of the area. The exception being right along the beaches
where numbers in the lower to mid 50s forecast. Wednesday's highs
in the mid to upper 60s for most locations. /10
Long term /Thursday through Sunday/...a moderation in highs and
lows anticipated to close out the week as surface high pressure
lifts up across the southeast. Highs Thursday and Friday trend
back into the 70s. Lows Friday and Saturday mornings in the lower
to mid 50s interior to lower to mid 60s coast.
Next cold front appears to dive into the deep south by Friday and
pushes thru Saturday, bringing a return to a small chance of
showers and storms through Saturday night. Of note: there is a
high degree of disagreement in the weather models with the timing
of next weekend's frontal passage which will dictate temperature
forecasts going into Saturday or Sunday. For now, the blended
guidance suggests highs will lower back into the lower to mid 60s
by Sunday with morning lows lowering into the mid to upper 40s
Marine...an unsettled pattern continues tonight ahead of a cold
front approaching from the west. Winds, waves and seas will be
locally higher in and near showers and storms tonight. Visibility
likely to be reduced to less than a mile as well, with the passage
of heavy rain. Frontal passage is forecast Monday morning, bringing
a wind shift and an end to showers and storms in its wake. A light,
to at times moderate northwest flow continues into the middle of
the week before turning more onshore by late week with high pressure
lifting up into the southeast. /10
Alabama...high rip current risk until 1 am CDT Monday for alz265-266.
Florida...high rip current risk until 1 am CDT Monday for flz202-204-206.