Scientific Forecaster Discussion
fxus64 kbmx 182033
Area forecast discussion
National Weather Service Birmingham Alabama
233 PM CST Thu Jan 18 2018
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.
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 European model (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 low level jet.
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 European model (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.
18z taf discussion.
VFR for the next 24 hours and beyond as high pressure remains
remain. Winds will be generally less than 10kts from the northwest.
Relative humidity 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 20 50 27 57 34 / 0 0 0 0 0
Birmingham 20 51 31 57 38 / 0 0 0 0 0
Tuscaloosa 20 52 31 59 39 / 0 0 0 0 0
Calera 21 51 30 58 37 / 0 0 0 0 0
Auburn 22 52 29 56 36 / 0 0 0 0 0
Montgomery 21 52 29 59 36 / 0 0 0 0 0
Troy 21 52 30 57 36 / 0 0 0 0 0