Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 212359 AAA
AFDMOB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
559 PM CST Mon Jan 21 2019

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

&&

.AVIATION...
00Z issuance...Visbys/cigs will continue at VFR conditions
tonight with a few high clouds drifting over the area. Light
northeast winds at 5 knots will slowly turn east-southeast later
tonight. By early tomorrow morning, cigs will begin to lower to at
or near MVFR levels and southeasterly winds will increase to 10
to 15 knots. BB/03

&&

.PREV DISCUSSION... /issued 349 PM CST Mon Jan 21 2019/

NEAR TERM /Now Through Tuesday/...Short-wave upper ridge was
moving eastward over the MS River Valley. At the surface, analysis
shows a large surface high from the Great Lakes, southward to the
northern Gulf. Central pressures within the axis of the high are
measured near 1036 MB over the Ohio River Valley. The high
migrates east over the Appalachians tonight with light low
level/surface flow becoming more southeast. There are indications
that an increase in low level moisture in the 1000 to 925 MB layer
favors the development of and increased coverage of stratus
spreading from west to east late in the night and into the day
Tuesday. Although deep environmental moisture remains low (PWAT`s
mostly .75" to 1.00") by the close of the day, the presence of
weak low level isentropic lift may be enough to generate a small
chance of light rain showers mostly over the southwest half of the
local area. Precipitation amounts expected to be less than a tenth
of an inch Tuesday.

Overnight lows not as cold. Daytime highs Tuesday moderate.

Along area beaches, a high risk of dangerous to potentially deadly
rip currents exists and begins late tonight continuing into Tuesday
due to increase in onshore winds, surf and spring tidal cycles.
/10

SHORT TERM /Tuesday night Through Thursday night/...The upper
level trough extending from south central Canada to northwest
Mexico Tuesday evening will continue to dig east- southeast
through midweek. Additional shortwave energy will exit the Pacific
Northwest and move southeast over the Rockies and Great Plains
Wednesday and Wednesday night. These features will carve out a
large trough over the entire conus by late Wednesday night. Large,
strong surface high pressure across the eastern conus, with a
central pressure of 1037mb across the eastern portions of Virginia
and North Carolina will shift east over the western Atlantic
Tuesday night, while a strong cold front approaches the region
from the northwest Wednesday morning. This will allow a light
southeasterly wind flow Tuesday evening to shift to the south by
late Tuesday night and Wednesday morning, bringing and increase in
moisture across the forecast area.

Rain chances will increase Tuesday night through Wednesday afternoon
ahead of the trough and cold front, with numerous to definite rain
showers expected west of the line from Camden Alabama to Orange
Beach Alabama by late Tuesday night, with isolated to scattered
coverage to the east. There is a 100 percent chance of rain showers,
along with a slight chance of thunderstorms, throughout the day
Wednesday across the entire forecast area as the strong cold front
approaches I-65. The precipitation will taper off from west to east
Wednesday night as the cold front moves southeast of I-65 and off
the coast.

A cold, dry period will follow Thursday and Thursday as the upper
trough moves east of the region, followed by the reinforcing upper
trough late Thursday night. Surface high pressure will also build in
from the west throughout the day Thursday, followed by a reinforcing
shot of cold air moving through the forecast area late Thursday
night. /22

LONG TERM /Friday Through Monday/...The dry period will persist
Friday through Saturday afternoon as a strong surface high pressure
area settles across the southeast states. The GFS and ECMWF models
are in better agreement in the upper levels bringing another upper
trough that exits the southern plains and moves over the western
Gulf of Mexico Saturday night. However, in the low levels, the
ECMWF continues to develop an associated surface low pressure
area over the northwest Gulf of Mexico Saturday afternoon and
evening, but now tracks it further south across the central gulf
Saturday night through noon Sunday, while the 12z GFS does not
generate a surface low at all. Due to the potential surface low
tracking further south, precipitation chances from the ECMWF have
lowered significantly and GFS continues to be dry. Due to the low
forecast confidence at this time, will keep a slight chance of
rain showers in the forecast for Saturday night and Sunday, and
keep the precipitation in the form of rain across the region. A
dry period will then follow Sunday night through Monday. /22

MARINE...Difference in pressure between high over the Mid-
Atlantic and next cold front exiting the Plains Tuesday causes
onshore flow to increase and seas to trend higher. Frontal passage
is forecast late in the day Wednesday, bringing wind shift and a
moderate to strong northwest flow in its wake Wednesday night into
Thursday AM. Coverage of showers increase into the middle of the
week. A slight chance of storms mixed in as well Wednesday. No
changes made to small craft advisories which will remain in place
for southern Mobile Bay, adjacent MS Sound to out over the open
Gulf waters from late this evening, continuing into Thursday AM.
/10

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...High Rip Current Risk from midnight CST tonight through Thursday
     morning for ALZ265-266.

FL...High Rip Current Risk from midnight CST tonight through Thursday
     morning for FLZ202-204-206.

MS...None.
GM...Small Craft Advisory from 9 PM this evening to 9 AM CST Thursday
     for GMZ631-632-650-655-670-675.

&&

$$

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