Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 232330 AAA

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
630 PM CDT Thu Mar 23 2017

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


00Z issuance...Will begin with prevailing VFR conditions except
for a few spots near the coast where MVFR ceilings will be
present. MVFR ceilings are expected to develop across the western
half of the area overnight, with primarily VFR conditions
expected over the eastern portion. MVFR ceilings may improve to
near VFR by midday over the western portion of the area as breezy
and gusty southeast winds develop. /29


.PREV DISCUSSION... /issued 254 PM CDT Thu Mar 23 2017/

NEAR TERM /Now Through Friday/...Another 24 hours or so before we
get a weather pattern change. Tonight through Friday the surface
ridge will continue to ridge in across our area from the northeast,
providing a continued mainly southeast low level windflow across the
region. This moist onshore flow will result in a gradual increase
in low/mid cloud cover as the Gulf marine layer works its way
further inland in conjunction with increased 850-700mb flow out of
the south provides increasing isentropic lifting over the area.
Although we will be seeing an increase in clouds, overall not a
noticeable increase in rain chances across most of the area
through Friday, although we do indicate a slight chance for
showers over our westernmost counties where deeper moisture and
slightly better forcing is expected. Nighttime temperatures are
still expected to run about 10-12 degrees above normal for this
time of the year tonight, ranging from the mid/upper 50s over
interior northeast zones to lower 60s coastal and southwest zones.
Friday`s daytime temperatures are expected to be above, but
closer to normal, with highs in the mid to upper 70s over inland
areas and in the lower 70s at the coast. 12/DS

SHORT TERM /Friday night Through Sunday night/...Forecast
geo-potential height fields start off with an amplifying upper
level trof moving over the plains with a downstream, short-wave
mid level ridge over the southeast Friday night. The upper trof
makes a steady eastward progression out of the Plains on
Saturday. East of the upper trof, high level flow becomes
increasingly diffluent favoring an increase in large scale deep
layer ascent which spreads east over the forecast area ahead of a
cold front moving into the Lower River Mississippi River Valley
Saturday. Co-located with the larger scale ascent will be an
improvement in deep Gulf moisture, where pwat values lift to
around 1.35" along the Central Gulf coast. Organized storms are
forecast to move eastward over the ARK-LA-TEX Friday night and
looks to spread east across the local area on Saturday. The latest
forecast remains mostly unchanged maintaining highest chances of
showers/storms occurring on Saturday. Given assessment of
atmospheric instability, moisture, and lift, it appears we will be
dealing with the potential for some strong to a few severe storms
Saturday with the better potential for this looking to occur over
the northwest half of zones as these areas may be more influenced
by the tail end of a departing, stronger low level jet streak.
Dynamics lift northeast and threat diminishes by Saturday evening.
There are uncertainties in amount of instability between the
latest weather models, but think there will be enough to maintain
a slight risk of severe storms Saturday for much of the area. The
main threat looks to come from localized damaging winds along
with marginal severe hail potential. Locally heavy rains will be
possible with the passage of the stronger storms, but the expected
steady eastward progression would mitigate widespread flooding
concerns. Will maintain a chance of showers and few storms
Saturday night as axis of upper trof passes across. Despite lead
feature lifting well away, moving northeast over the Appalachians
and Ohio River on Sunday, a high level southwest flow is
maintained. Out of respect for subtle impulses embedded in these
type flows aloft, will carry a slight chance of showers/storms for
Sunday. Next upper level storm system moves eastward out of the
Plains Sunday night.

Unseasonably warm days and nights continue in the short term. /10

LONG TERM /Monday Through Thursday/...The passage of next upper
level storm system brings return chance of showers and storms
Monday and Monday night. Eastward building mid-level ridge over
the southern US by Tuesday night supports rain-free conditions
into Wednesday. The latest 23.12Z run of the ECMWF is quicker at
bringing yet another storm system east and thus next potential
round of showers/storms into the Lower Mississippi River Valley
during the day Thursday, with the GFS slower. Will lean to the
ECMWF solution which is also consistent with the latest National
Blend of Models (NBM). Unseasonably warm days and nights look to
continue thru the medium range. /10

MARINE...An area of high pressure will build over the Mid-Atlantic
and western Atlantic through late week, ridging back to the southwest
over the eastern Gulf of Mexico. An area of low pressure developing
over the Plains through the end of the week will lift to the
Great Lakes area over the weekend, with an associated trof moving
east across the marine area on Saturday. As a result, a moderate
to strong onshore flow and resultant building seas will develop
through late week, along with increasing chances of showers and
thunderstorms by Saturday. A Small Craft Advisory is now in effect
for portions of the Marine Area from this afternoon through late
Friday night. Through most of next week, the predominately
moderate (occasionally strong) onshore flow will continue as
several more weather systems pass just to the north of the marine
area. 12/DS


GM...Small Craft Advisory until 1 AM CDT Saturday for GMZ631-632-650-



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