Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 252059

Area Forecast Discussion
National Weather Service Birmingham AL
259 PM CST Sun Feb 25 2018

Through Tonight.

Areas of light rain continue to stream northeastward across
Central Alabama this afternoon. The cold front is finally
entering extreme northwest Marion County, behind which dewpoints
have fallen into the 40s. As expected, another upper level wave
has developed and is moving northeastward along the front. A
surface low will strengthen this evening, cross the area, and
finally pull the front slowly southward through the area tonight
and tomorrow morning. In advance of these features, widespread
light to moderate rainfall is moving across Mississippi and will
spread into Central Alabama over the next several hours.

For tonight, expect widespread light to moderate rainfall for most
of the area. Cannot rule out a thunderstorm across the south later
tonight where the airmass will be slightly warmer. Severe storms
are not expected.


Monday through Saturday.

Rain chances along and east of I-59 will end through the late
morning and early afternoon hours on Monday as the cold front gets
booted eastward by an upper-level shortwave. Drier air will move
into the region Monday night, and temperatures should drop to near
40F in the North to the lower 50s in the Southeast on Tuesday

Rain-free conditions should continue into Tuesday afternoon, but
the progressive weather pattern will make for a busy period
Tuesday night through Thursday. A shortwave in the Southwest U.S.
is expected to eject eastward, and a surging warm front should
cause increasing rain chances Tuesday night into Wednesday. At
some point between early Thursday morning and late Thursday night,
a frontal passage is expected along with the potential for
showers and storms, some of which could be severe.

Models are currently not showing much instability, but this should
not be taken at face value. Surface temperatures and dewpoints in
the warm sector of the ongoing system have been underestimated,
and trends over the Gulf of Mexico and inland areas showed an
increase of 2-5F in the lead up to the current system. Even with
these trends, model temperatures and dewpoints are still too low
when compared to current observations. This will be critically
important for our next system arriving Wednesday night into
Thursday, and CAPE values appear to be underestimated by all model
guidance. With the potential for very strong wind shear over the
region, it will not take much of a change in the quality of the
low-level airmass for this system to become an "overachiever"
compared to expectations. Since models are having serious problems
with run-to-run consistency regarding the evolution of the upper
air pattern, a severe risk will not be mentioned in the HWO for
this forecast package. Once better agreement is reached, a threat
is likely to be introduced for late Wednesday night into Thursday.



18Z TAF Discussion.

SHRA will continue to move northeast across the area as a cold
pool outflow boundary has nearly cleared our far southeast
counties, resulting in a general northwest low level flow with
cooler temperatures late this morning. The surface cold front is
decelerating and extends from central Mississippi through
northwest Alabama and into central Tennessee at this time. Expect
the front to drift into the heart of our forecast area late this
afternoon and evening.

Lighter precipitation with generally higher cloud bases will be
common despite isolated SHRA through this afternoon and into the
early evening. A shortwave impulse will move over the forecast
area tonight and will induce a surface low that is expected to
track northeast close to the central Gulf Coast. This will result
in lowered CIG`s along with increased coverage of RA at all
terminals generally from 21Z to 03Z from west to east. Potential
for TSRA will exist this evening and overnight south near MGM/TOI
but probabilities are too low to mention at this time.

The surface front will clear our forecast area from northwest to
southeast during the day on Monday, resulting in a generally
northerly low level flow and decreasing clouds with higher bases.




High RH values and rain chances will continue through Monday
morning. No widespread fog development is expected for tonight
through Monday morning. Dry weather is expected for Monday night
and Tuesday, but high rain chances will return Tuesday night
through Thursday. There are no fire weather concerns.


Gadsden     52  64  41  69  54 / 100  50   0  10  80
Anniston    53  65  44  71  53 / 100  60   0  10  80
Birmingham  54  66  45  72  56 / 100  40   0  10  80
Tuscaloosa  54  67  45  73  58 / 100  30   0  10  80
Calera      54  66  46  72  57 / 100  40   0  10  80
Auburn      57  68  51  69  56 /  90  80   0  10  50
Montgomery  58  71  50  74  58 /  90  80   0  10  40
Troy        61  70  52  73  58 /  80  90   0  10  30




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