Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 260457

Area Forecast Discussion
National Weather Service Birmingham AL
1057 PM CST Sat Jan 25 2020

For 06Z Aviation.


/Updated at 0239 PM CST Sat Jan 25 2020/
Through Sunday.

Surface high pressure will edge eastward across the area tonight,
slowly eroding low level moisture and the persistent low clouds
across the north. Calm winds at most locations will allow
temperatures to fall into the low to mid 30s by sunrise. High
clouds will fill in from the west late tonight and Sunday
morning, as a low pressure system organizes along the northwest
Gulf coast and a more northern stream system moves into the Lower
Mississippi River Valley. Rain chances increase tomorrow
afternoon from southwest to northeast, as the two systems merge
and push eastward. Rainfall remains light through the day. Highs
tomorrow will be in the 50s.


/Updated at 0300 AM CST Sat Jan 25 2020/

Sunday evening through Monday night.

A northern stream shortwave trough will continue an east-
southeastward trajectory toward the Lower Mississippi River Valley
on Sunday, generally becoming more phased with and complimentary to
a southern stream perturbation. This will continue an already
ongoing trend of increasing rain chances as the mid and lower
troposphere become more saturated. Areas of light rain, possibly
some light shower activity, will continue from west to east into
Monday morning. Forecast soundings suggest a surface-based moist
layer up to ~1 km into early Monday afternoon, so carried patchy
drizzle through Noon despite the decreasing PoP trend. Have no
mentionable PoPs for Monday afternoon, though low overcast and
drizzle may continue until drier air can advect back into the area.

Tuesday through Friday.

A broad, complex upper-level pattern appears likely to continue into
the long-term forecast period. Rain chances will come and go during
this time, owing to the timing of any shortwave trough that enters
our region. There are consistent signs another shortwave ejects from
the Four Corners region into the Southern Plains By Tuesday morning.
This disturbance will likely bring another chance of light rain to
Central Alabama late Tuesday and into Wednesday. Have truncated PoPs
to 30-40% until better timing and other details can be resolved
until then.

Thereafter, little forecast confidence exists on any one particular
solution toward mid/late next week. An active pattern will likely
yield yet another system by late-week and into the weekend, however.
Global models depicts this next trough/disturbance with more
amplification & resultant poleward extent of quality moisture.
Increased PoPs have been placed in the forecast later Thursday
through early Saturday as a result of latest trends suggestive of a
more moderate rainfall event. Again, PoPs are truncated to ~40% as
this remains a low confidence forecast until we get closer to this
time. Temperature trends for the entire forecast period remain quite
seasonable with highs in the 50s, and lows in the 30s & 40s.



06Z TAF Discussion.

VFR conditions expected for the next 12 hours or so. Then some
rain showers enter the picture along with lowering ceilings.
Winds will be variable to westerly overnight becoming southerly to
variable on Sunday.

Cirrus has invaded the skies ahead of the next system approaching
from the west. Mid level clouds are in central Mississippi. This
moisture advection aloft will slowly work its way downward with a
ceiling becoming restricted mainly after 00z. This terminal
forecast brings the ceilings and vis into the MVFR range with
light showers in the last 6 hours. There is a chance of even lower
ceilings just beyond the period. This will be a fast moving
system as the rain clears quickly west to east late Sunday night
and Monday morning, but some clouds and ceilings will linger.




Dry weather conditions continue tonight and Sunday morning, before
light rain moves in from the west by Sunday afternoon. Light and
variable winds tonight will become southerly through the day
tomorrow, remaining below 10kts. Recent rainfall and seasonable
temperatures will help maintain relative humidity values >40% into
next week where another chance of rain possibly affecting Central
Alabama by Wednesday.


Gadsden     30  52  42  54  35 /  10  20  70  20   0
Anniston    33  54  43  55  36 /  10  20  70  20   0
Birmingham  36  54  45  56  38 /  10  20  70  10   0
Tuscaloosa  36  55  46  58  38 /  10  20  70  10   0
Calera      36  54  44  56  38 /  10  20  70  10   0
Auburn      36  55  44  55  38 /  10  20  70  20   0
Montgomery  37  57  45  60  39 /  10  20  70  20   0
Troy        36  57  45  60  40 /  10  20  70  20   0




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