Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 190547
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
1147 PM CST Thu Jan 18 2018

.UPDATE...
For 06Z Aviation.

&&

.SHORT TERM...

Lowered overnight lows slightly with all else looking good.

Surface high pressure remains parked just west of Central
Alabama. Temperatures and dew points running some 5 degrees higher
than last night at this time. The air mass is moderating but still
remains very dry. There will be some variability due to
elevation, rural/urban, snow, and temperatures dropped slightly
colder last night. Therefore, dropped lows a few degrees but a
large majority will still be above 15 degrees, criteria for a
Hard Freeze Warning.

75

Previous short-term discussion:Tonight.

High pressure will begin to slide to the east and elongate
tonight. This will allow for a more westerly flow over the area
and a touch warmer. On a whole most of the area will be above 15
degrees so will not issue a hard freeze for tonight. A few colder
spots in the northeast may reach the lower teens but will be more
isolated than widespread.

16

.LONG TERM...
Friday through Wednesday.

A shortwave trough in the southern stream with an embedded closed
low will be located over East Texas at the start of the period.
The GFS is quicker than the model consensus with this feature.
Using the consensus of the other models, this will drift eastward
across the area Friday and Saturday. It will have little effect on
the sensible weather other than some mid and high level clouds,
however, as it will be moisture starved due to low-level ridging
over the northern Gulf and the very dry air mass currently in
place. Low-level moisture does begin to increase from the west on
Saturday as the low-level ridge moves eastward, but behind the
upper-level system, so just an increase in lower-level clouds is
expected in the west on Saturday. At the surface, high pressure
will be centered over the area on Friday, and push east of the
area by Saturday allowing light south-southeasterly winds to
develop and some warm air advection. The warming trend will
continue with low 50s for highs on Friday, and upper 50s to around
60 on Saturday.

A potent longwave trough with embedded closed low will eject into
the Plains on Sunday and move through the Midwest on Monday. At
the surface, low pressure will develop in the lee of the Colorado
Rockies, move southeastward to the Panhandles region, and then
deepen as it moves into the Great Lakes. A line of showers and
embedded isolated thunderstorms will develop along the trailing
cold front and move eastward. The slowing trend in the guidance
has continued, and will trend towards the more consistent ECMWF
timing, indicating the frontal passage during the day on Monday.
Increased PoPs on Monday to categorical for much of the area based
on good agreement among European ensemble members. Added in some
PoPs in the eastern counties Monday evening given the slowing
trend. Ahead of this activity, a dry air mass and warm air
advection will allow for a very pleasant day on Sunday with highs
in the low to mid 60s. Despite strong wind fields, severe storms
continue to look very unlikely Monday given an expected lack of
surface-based instability. This is due to dew points struggling
to reach 60 degrees and temperatures only in the lower 60s within
the narrow warm sector. Will have to monitor if any gusty gradient
winds can mix down from the strong LLJ.

Cooler air moves in behind the front, but the Arctic air mass will
remain well to our north as it wraps into the occluding cyclone,
and the flow aloft will be zonal, resulting in just seasonable
temperatures. An active pattern off of the Pacific looks to
continue, with another shortwave moving towards the area
Wednesday. The ECMWF indicates a weaker less phased shortwave
without any moisture return ahead of it. Meanwhile the GFS shows a
stronger phased shortwave with low pressure developing in the
Gulf and the bulk of the precipitation south of the area. European
ensembles favor a drier solution for Wednesday with some support
for precipitation by Thursday. Unlike previous systems this does
not have an Arctic air mass to work with.

32/Davis


&&

.AVIATION...
06Z TAF Discussion.

High pressure and a very dry atmosphere will produce VFR
conditions the next 24 hours. High pressure slowly moves over the
state and winds will be light and generally westerly.

75

&&

.FIRE WEATHER...

RH values will fall to around 25 percent for a couple hours on
Friday afternoon. However, winds will be light, thus critical fire
weather conditions are not expected. Moisture begins to gradually
increase on Saturday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     16  50  27  57  35 /   0   0   0   0   0
Anniston    18  50  27  57  34 /   0   0   0   0   0
Birmingham  19  51  31  57  38 /   0   0   0   0   0
Tuscaloosa  18  52  31  59  39 /   0   0   0   0   0
Calera      20  51  30  58  37 /   0   0   0   0   0
Auburn      19  52  29  56  36 /   0   0   0   0   0
Montgomery  19  52  29  59  36 /   0   0   0   0   0
Troy        20  52  30  57  36 /   0   0   0   0   0

&&

.BMX WATCHES/WARNINGS/ADVISORIES/...
None.

&&

$$


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