Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 240533

Area Forecast Discussion
National Weather Service Birmingham AL
1133 PM CST Thu Feb 23 2017

For 06Z Aviation.



Skies were mostly clear this evening with a light southeast
breeze. The latest upper air sounding shows a relatively dry air
mass, even below 850mb. Despite increasing southerly low level
flow overnight, clouds will be slow to develop and any low clouds
that form will likely be patchy. Mild temperatures overnight with
lows in the 50s. A few spots already reporting fog, but increasing
boundary layer winds overnight should hinder any widespread dense


Saturday through Wednesday.

A brief period of more seasonable temperatures and dry conditions
will occur over the weekend behind the front. Lows will be around
freezing Saturday night as a surface high moves through the area.

An unsettled pattern will take hold for the first half of next
week with moist southwest flow in place between an elongated
upper-level ridge from the southern Gulf to the Bahamas and broad
troughing over the western US. In this southwest flow some
shortwaves will move through, predominately just north of the
area, with low predictability. Meanwhile PWATs will be increasing
to near 1.5 inches, with the potential for beneficial rainfall in
some areas. An unstable, sheared air mass will develop with steep
mid-level lapse rates, so some stronger storms may be possible in
this period, but with weak upper-level forcing there is nothing
synoptically that warrants inclusion of anything severe in the HWO
at this time.

The GFS is stronger than the ECMWF with an initial shortwave and
associated surface low ejecting from the Southern Plains to the
Ohio Valley Sunday night into Monday. This solution lifts a warm
front quickly northward through the area Monday with a moist and
unstable air mass developing south of the front. The strongest
LLJ and low-level shear parameters remain north of the warm front,
however. The ECMWF is weaker with these features and slower to
move the warm front northward, but looks wet on Monday as well.
The GFS sends a trailing cold front into the area that stalls
across the area on Tuesday and serves as a focus for continued
showers and thunderstorms while the ECMWF keeps the forecast area
solidly in the warm sector. Despite these differences, models are
generally in agreement on a warm and wet period.

Models are in good agreement on a stronger shortwave moving across
the northern US on Wednesday and an associated frontal passage for
Central Alabama. Both the GFS and ECMWF indicate plenty of
instability with the frontal passage and strong deep layer shear,
but the LLJ is weak and very veered as the surface low will be
over the northern Great Lakes. This will be monitored as the time
gets closer.



06Z TAF Discussion.

Except for some low clouds that may or may not develop before
sunrise, VFR conds will prevail during the period. Satellite
imagery indicates very little cloud cover late this evening, but
conditions remain somewhat favorable for cloud formation after 09z
with bases arnd 1500-2000. Cloud cover will likely be patchy, so
went with tempo MVFR cigs between 10z and 14z, with more cloud
cover after sunrise as the air mass heats up quickly. Good low
level mixing during the day should thin out cloud cover after 18z
with scattered clouds. Fog should not be an issue due to moderate
boundary layer winds.




Dry and warm conditions are expected through Friday. The next
chance of light rain should come Friday night into early Saturday with
a front, followed by low relative humidity values over the
weekend. There are no fire weather concerns at this time.



Record high temperatures for Friday, February 24:

Birmingham:  78 (1930)
Montgomery:  80 (1890)
Tuscaloosa:  78 (2011)
Anniston:    78 (1982)


Gadsden     54  78  50  58  31 /   0  10  60   0   0
Anniston    56  79  52  59  32 /   0  10  50   0   0
Birmingham  60  79  48  58  33 /   0  10  50   0   0
Tuscaloosa  57  81  48  60  33 /   0  10  40   0   0
Calera      57  79  51  60  34 /   0  10  50   0   0
Auburn      57  78  55  63  36 /   0  10  30  10   0
Montgomery  60  82  56  65  37 /   0  10  30   0   0
Troy        56  81  56  65  37 /   0  10  30  10   0




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