Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 260818

Area Forecast Discussion
National Weather Service Birmingham AL
318 AM CDT MON SEP 26 2016

Today and Tonight.

At least one more day of unseasonably warm temperatures before a
cold front arrives later this afternoon. The models continue to
slow down southward progression of cold front, which is the reason
todays high temperatures have been raised several degrees from
previous forecast. High-res models show a zone of warmer air just
ahead of the approaching cold front, with mid 90s along the I-20
corridor. Slightly cooler conditions across the southeast counties
where easterly low level flow has brought in some slightly cooler
air. The High-res models are also keeping the convection today
near the cold front, with little activity elsewhere. The main
inhibitor today for thunderstorm development will likely be the
presence of low level drier air. There is no southerly inflow
component ahead of the cold front, and thus no advection of gulf
moisture. Drier air aloft will likely mix downward like previous
days, and inhibit convection from developing away from convergence
zone along front. The lower surface dewpoints will also produce
lower afternoon CAPE values, but DCAPE values near 1000 j/kg could
produce gusty winds in some of the stronger storms, but no severe

The front is forecast to stall out near the I-20 corridor this
evening as the upper trof axis flattens out. With loss of upper
level lift and daytime heating, pre-frontal convection will
quickly weaken during the evening hours.


Tuesday through Sunday.

Models have trended slower with the progression of a cold front
for Tuesday into Wednesday in response to a shortwave expected
to be near Memphis at 00Z Wednesday. This should result in little
to no northern component in surface to 700mb flow and weaker
cool/dry air advection. PWAT values of 1.5+ inches near and east
of the I-59 corridor may support scattered convection on Tuesday,
and POPs have been raised and shifted NW. This activity could
continue overnight across the southern/eastern part of the area as
the front slowly moves southward. Temperatures Tuesday night have
been raised fairly substantially especially across the southeast
counties where dewpoints are likely to remain in the mid 60s.

A large upper low should be centered over the Great Lakes and
Ohio Valley on Wednesday, suggesting cold advection will be
limited with westerly flow around the base of the trough and no
strong shortwave passage. We`ll have to wait until Wednesday night
into Thursday for the real deal cold front to move through as the
upper low rotates southward. There could even be a narrow band of
showers early Thursday morning due to strong height falls
coincident with the frontal passage. The coolest day appears to be
Thursday before the upper low moves to the northeast for Friday
and into the weekend. Rising heights will coincide with a warming
trend with widespread 80s for the weekend though residual dry air
should promote good radiational cooling and an extended period of
overnight lows in the 50s.



06Z TAF Discussion.

A couple thunderstorms have developed between MGM and TOI. They
have moved past TOI but will reach the vicinity of MGM early in
the period. A stray shower/storm is possible elsewhere but
coverage is too low to mention. Model guidance is trying to
indicate low clouds developing near TOI near sunrise with
southeasterly flow developing; however, low-level moisture is
expected to be insufficient to produce any low cigs. A cold front
will move through the northern TAF sites Monday afternoon/early
evening, resulting in a broken line of thunderstorms that was
timed out with a PROB30 at the northern sites and a shift from
southerly to northwesterly winds.




A front with relatively higher rain chances will move into the
region later today and into Tuesday. Drier weather returns for
Wednesday and beyond. No fire weather concerns are anticipated.


Gadsden     91  64  84  55  85 /  40  40  30  10   0
Anniston    94  66  85  59  86 /  40  40  40  10   0
Birmingham  94  66  85  58  86 /  40  40  20  10   0
Tuscaloosa  95  65  86  58  87 /  40  40  20  10   0
Calera      94  67  86  60  87 /  30  40  30  10   0
Auburn      93  68  88  66  87 /  20  20  40  20  10
Montgomery  95  69  91  66  89 /  20  20  40  20  10
Troy        92  68  91  68  89 /  20  20  30  30  10




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