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Area forecast discussion 
National Weather Service Mobile Alabama
614 PM CST sun Nov 29 2015

Discussion...updated for latest aviation discussion below.


00z issuance...VFR conditions are expected through most of the
evening...though broken decks between 3-5 kft above ground level will impact
interior portions of southeast MS and southwest Alabama...along with
broken middle/upper cloud decks passing overhead across the entire
region. Middle and high clouds should decrease late tonight and
conditions will again become favorable for development of IFR to
LIFR category fog across southern portions of the area...including
our coastal taf sites primarily after 30.06z. VFR should return by
middle to late Monday morning. /21


Previous discussion... /issued 347 PM CST sun Nov 29 2015/

Near term /now through Monday/...a frontal boundary draped across
central Mississippi remains stationary. This pattern has provided for
another unseasonably warm day as the low level southerly fetch
continues to advect warm air over the region. This trend will
continue through tomorrow as the frontal boundary remains stalled
upstream. Surface heating combined with middle level subsidence has
created a ragged stratocumulus deck across the area and a weakening
upper level shortwave trough has spread some upper level cloud cover
across the region. Sky cover will gradually thin from the west. Fog
is expected to develop again overnight with dense fog (reducing
visibility to 1/4 mile or less) very possible over southeast MS, SW Alabama and
Escambia and Santa Rosa counties in the Florida Panhandle...elsewhere
fog is also likely but expected to be more patchy with only very
localized dense fog expected at this time. Fog should dissipate
shortly after sunrise tomorrow morning and temperatures will again
climb to near record highs...generally reaching the middle to upper 70s
with a site or two reaching 80. Kept the forecast dry through the
period except for keeping a slight chance over Wayne and Choctaw
counties where model runs have indicated the outside potential of a
light shower or two being triggered on the southeastern periphery of
some minor upper level shortwaves rippling along the west to
southwesterly flow aloft. /08

Short term /Monday night through Wednesday night/...high level trough
from the central and northern High Plains to the southwestern US
Monday night undergoes amplification Tuesday through Wednesday. East
of the trough axis...high level southwest flow remains positioned from
the western Gulf...into the southeast. Within the mean high level
flow aloft...a quasi-stationary surface frontal zone will be aligned
from the Tennessee/Ohio River valley to across central Louisiana
Monday night. As energy aloft pivots across the middle Mississippi River
valley and upper Midwest...the front begins a slow eastward move. The
front is prognosticated to enter (albeit slowly) the interior southeast
Mississippi and interior southwest Alabama zones by Tuesday
afternoon...then offshore by after daybreak Wednesday morning. A
narrow band of modest frontal lift...operating on deep moisture
(pwats ~ 1.5 inches) initially brings a small chance of showers by
Monday night along and west of a line from Thomasville Alabama in
Clarke County to Janice Mississippi in Perry County. East of where
the showers develop on Monday night...there are signals in the high
resolution arw...the nam12 and sref guidance of late night fog
formation. Considering this...will add this to the forecast. Small
chances of showers ease eastward with the front during the day
Tuesday mainly along and west of I-65...then areawide Tuesday night.
Rainfall amounts are forecast to range from a quarter to a half inch
over the northwest zones with lighter amounts east. Monday night
lows remain mild with highs on Tuesday being well above seasonal.

Wednesday and Wednesday night...although the front is south of the
area by Wednesday...Post frontal moisture continues to stream across
the central Gulf Coast with the axis of the high level trough remaining
well west of the area. Embedded in the flow aloft...the passage of a
series of middle level impulses favors keeping clouds in place with a
chance of stratiform rain. Cooler conditions moving in. Surface high
pressure building in from the west brings northerly flow to the local
area with the cooler daytime high temperatures in the upper 50s/lower
60s being confined to along and northwest of I-65. Upper half of the
60s east of the Interstate.

Rain chances continue into Wednesday night for most of the area as
the high level trough axis to the west will be slow to move trough.
With cool advection processes to be underway...overnight lows dip
into the 40s north of the coast. /10

Long term /Thursday through Sunday/...the upper level trough axis
pivots across the central Gulf Coast on Thursday causing moisture to
gradually move out of the area by Thursday night. The 29.12z operational
GFS wants to close off an upper low over Alabama and wrapping
moisture back in from the east on Friday and Saturday...while the
European model (ecmwf) shows a drier west northwest flow aloft moving in for early
part of the weekend. The latest official forecast leans to the drier
European model (ecmwf) solution. As far as temperatures...large surface high pressure
axis to our north keeps daytime highs cool. Middle/upper 50s most areas
Thursday...lift to near seasonable levels Friday through Sunday.
Nighttime lows mostly in the 40s. /10

Marine...a light onshore flow will continue through Tuesday night in
advance of an approaching cold front. A moderate offshore flow will
follow in the wake of the cold front moving across the marine area
Wednesday morning. A moderate to strong offshore flow will then
persist through the weekend...likely reaching small craft cautionary
levels. /08


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