Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 261138

Area Forecast Discussion
National Weather Service Birmingham AL
638 PM CDT Fri May 26 2017

Aviation Discussion.


Today and Tonight.

Good radiational cooling conditions with calm winds and just a few
passing cirrus have allowed temperatures to fall into the 50s at
this hour, with some low 50s at the typically cooler locations. This
is due to the surface ridge axis extending northward from a surface
high over the northern Gulf, as the low pressure system over New
England continues to lift northeastward. The Gulf surface high will
continue moving eastward today and merge with the Bermuda high.
Meanwhile, a lee surface low over western Oklahoma will lift quickly
northeastward into Illinois while weakening. Strengthening low-level
southwesterly flow between these two features will put an end to our
late May cool-down with temperatures expected to warm into the mid
to upper 80s, except for some low 80s in far East Alabama. At upper-
levels, low-amplitude westerly to northwesterly flow will be in
place between flat ridging over the Gulf and a trough over the
Canadian Prairies. A stout elevated mixed layer will advect over the
area, and capping associated with this and continued dry air through
the column will keep the forecast area rain-free, with just a a few
passing cirrus clouds.

Tonight, low temperatures will be milder than this morning due to
light southerly winds, with low to mid 60s expected. Couldn`t rule
out a few upper 50s east of I-65 given low-level dry air advecting
in. Meanwhile low-level moist isentropic lift will result in some
low stratus developing in West Alabama. Any MCS activity is expected
to remain well north of the forecast area.


Saturday through Friday.

Low level ridging under zonal flow aloft on Saturday will lead to
continued warm weather across Central AL. A surface low moving
through the Midwest will drape a cold front down through the Ohio
and Tennessee River Valleys. However, the front begins to stall just
north of the area thanks to the ridging in the Gulf. Models have
been trending drier for much of Central AL, so have lowered PoPs a
little and kept chance PoPs mainly north of I-20 corridor for
Saturday and into Sunday.

On Sunday, a trough moves across the great plains as a cold front
pushes southward from a low pressure system in southwestern Ontario.
Rain and thunderstorms chances increase along the cold front Sunday
night into Monday. At this time, models hold off on timing of
rain/storms until closer to midnight Sunday night and into the early
morning hours on Monday. There is still some disagreement between
the models, along with some run to run inconsistency on just how
widespread the rain/storm coverage will be along the front as it
moves southeastward through the area. For the severe potential, the
best dynamics remain well to the north of the area, although the
recent warmth will aid in setting up an unstable environment across
much of Central AL. Shear is on the weaker end due to the lack of
any significant low-level jet , with only the far northern
counties forecast to surpass 40 kts 0-6km Bulk Shear. Expect some
of the storms along the front to be on the stronger side, but
without much upper level support or shear, the storms should
remain below severe limits. Therefore, I will leave out mention of
any severe weather in the HWO at this time.

By Tuesday morning, the front is stalled just to our south and will
provide enough lift for showers and thunderstorms, especially during
peak heating in our southernmost counties on Tuesday and Wednesday.
Towards the end of next week, guidance hints that a trough moving
into the Pacific NW will become somewhat cutoff over the Great
Basin. Ridging builds back in across the Southeast and models show
the previous cold front being lifted back northward as a warm front,
generating some more shower/storm activity. Have put in chance PoPs
in for Thursday and Friday, but confidence is low at this time on
exact rain/storm chances.



12Z TAF Discussion.

VFR conds thru the period. Southwesterly winds will increase this
morning, with occasional gusts of 16-18kts possible at northern
terminals through the day. Winds diminish this evening, and will
begin to see an increase in mid level clouds from the west.




Rain free conditions and lower humidity values will prevail
today and for most of Saturday. Significant rain chances hold off
until late Sunday night when the next upper level system and
surface front approach. Critical fire weather conditions are not


Gadsden     84  63  85  68  86 /   0   0  10  20  30
Anniston    85  63  87  70  86 /   0   0  10  10  30
Birmingham  86  66  88  73  87 /   0   0  10  20  30
Tuscaloosa  87  65  87  73  87 /   0   0  10  10  20
Calera      86  65  87  71  87 /   0   0  10  10  20
Auburn      83  63  87  70  86 /   0   0   0  10  20
Montgomery  88  63  90  73  91 /   0   0   0  10  10
Troy        86  61  88  70  89 /   0   0   0  10  10




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