Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 292057

Area Forecast Discussion
National Weather Service Mobile AL
357 PM CDT THU SEP 29 2016

.NEAR TERM /Now Through Friday/...Initial front moved across
the region last night shifting winds to northwest and west and
allowing slightly drier air to begin filtering into the area.
Secondary boundary and surge of even drier and cooler air moving
through fcst area at this time should be off the coast by sunset
this evening. Deep layer dry north to northwest flow will then
continue over the region through the day on Friday as a large upper
level low pressure area continues over the Ohio Valley region and
sfc high pressure ridges into our area from the northwest. Clear pcpn and cooler temperatures with lower humidity expected
tonight and Friday. Low temps tonight will be a good 10 to 15
degrees lower than last night for most of the area (especially for
inland locations). Min temps tonight ranging from the low 50s well
inland to the low 60s at the coast. On Friday...around 5 to 10
degrees cooler on max temps with highs generally in the lower 80s...
with a few mid 80s for some interior locations. 12/DS

.SHORT TERM /Friday night Through Sunday night/...A closed upper low
over the Tennessee River Valley meanders north to the eastern Great
Lakes through the weekend, but still leaves an upper trough
stretching south along the Lower Mississippi River Valley. The
exiting upper system allows a weak surface ridge to organized over
the Mississippi River River as an upper ridge over the Plains edges
east. The upper trough keeps the surface ridge from becoming to
organized, and for the fa, this creates a light northerly low level flow
over the area through the weekend. The weakness of the low level flow
will allow for the increased likelihood of a Gulf breeze forming
during the afternoon and evening, helping to bring some Gulf moisture
inland, but at this point, not enough to warrant a chance of rain
over the fa.

As the upper ridge over the Plains edges east, bringing increased
subsidence, an upward moderation temps through the weekend occurs
with the weak upper trough east of the Mississippi River tempering
the rise. Overnight lows Friday night in the low to mid 50s rise to
mid 50s to around 60 for Sunday night. Highs generally in the mid


.LONG TERM /Monday Through Thursday/...Monday through mid week, a
strong upper low digs south over the northern US Rockies, pushing the
PLains ridge east of the Mississippi River. The medium range guidance
differs in the handling of the southern end of the upper trough. The
GFS breaks the southern end off, creating a closed low that meanders
to over the Fl peninsula. As Matthew rounds the west side of an upper
ridge over the western Atlantic, the GFS is advertising a quicker
movement along the eastern seaboard to near the DelMarVa peninsula by
Thursday. This enhances northerly flow from a surface ridge formed by
the upper ridge as it crosses the Mississippi River. The result is a
generally dry extended forecast, with a wide diurnal temp range than
the ECMWF.

The ECMWF weakens the trough,and the upper flow over the Caribbean,
allowing Matthew to meander around over the Caribbean through mid
week. The surface ridge over the eastern Conus builds more and
quickly re-establishes a more organized onshore flow off the Gulf.
Result, a warmer, more wet forecast.

For the forecast, have went with a blended forecast, more inline
with the NHC forecast for Matthew. Temps in the mid to upper 80s,
with overnight lows moderating upward from the mid 50s to around to
mid to upper 60s by Wednesday night. Will also see an increase in
the chance of rain, though have kept best chance closer to the coast
and open waters with the onshore flow being less organized than the
ECMWF is advertising, but more than the GFS.



.MARINE...With the secondary surge of cooler air moving offshore
early this evening...expect a stronger offshore flow to develop over
the marine area...especially over the Gulf zones...tonight.
Northerly winds will increase this evening into early Friday morning
to around 15 to 20 knots. May see a brief period just slightly
higher than 20 knots...but prevailing conditions should be more in
line with Small Craft Exercise Caution conditions. As mentioned in
the previous forecast package...given the expected brevity of such
conditions...will not issue a Small Craft Advisory. Overnight shifts
will monitor in case need arises for a potential short fuse advisory
tonight. Otherwise...a generally light diurnal flow (onshore during
the afternoons and early evenings and offshore overnights and early
mornings) and small sea states expected through the fcst
period. 12/DS


Mobile      57  81  56  84 /   0   0   0   0
Pensacola   60  81  58  83 /   0   0   0   0
Destin      65  81  62  84 /   0   0   0   0
Evergreen   53  82  51  85 /   0   0   0   0
Waynesboro  53  81  51  83 /   0   0   0   0
Camden      52  84  51  84 /   0   0   0   0
Crestview   54  82  54  86 /   0   0   0   0


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