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Area forecast discussion 
National Weather Service Birmingham Alabama
1227 PM CDT Friday Jul 29 2016

Update...
for 18z aviation.

&&

Discussion...

A small mesoscale convective vortex is apparent on visible satellite imagery this morning,
producing a couple showers in Cherokee County. This feature is
moving quickly off to the northeast and will not be much of a
factor in today's forecast. A weak 700 mb trough is currently
located from far northwest Alabama extending back into central
Mississippi. This feature is currently producing a few showers
across central Mississippi. The 700 mb trough looks to be the
primary driver of convection this afternoon as it moves eastward
in tandem with a southwest to northeast oriented axis of deeper
moisture and pwats near 2 inches. The WRF-arw, WRF-nmm, and NAM
generally agree on activity developing near the MS/Alabama state line
and moving east-northeastward in the west-southwest flow aloft.
Will cap rain chances at 40-50% for now with some questions over
coverage, and the hrrr is not quite yet on board. Sea breeze
activity may also approach the far southern counties later this
afternoon.

The microburst/strong storm potential remains low today due to
warm mid-levels resulting in poor mid- level lapse rates and only
modest cape values, as well as saturated profiles limiting dcape
values. High precipitable water values will result in heavy downpours, but
storms should be progressive which will limit the heavy rainfall
potential. Cloudcover will keep high temperatures in the upper 80s
to around 90 north, while more sunshine will result in highs in
the low to mid 90s southeast with heat index values in the 100-103
range south of I-85.

32/Davis



&&

Aviation...
18z taf discussion.

VFR conditions should be prevailing outside of rain through the
period. Scattered showers and thunderstorms will develop this
afternoon and will be handled with thunderstorms in the vicinity at all sites. Model
guidance indicates the best low-level moisture and low cloud
potential will stay just north of bhm/anb/asn overnight, but this
will continue to be monitored. Patchy br will be possible around
sunrise tomorrow, mainly in areas that receive rainfall.

32/Davis

&&

Fire weather...

Generally scattered showers and thunderstorms are expected over
the next several days with highs in the upper 80s and low/mid 90s.
Surface winds will be less than 10 mph and generally from the
southwest/west through the weekend. Since surface dew points are
so high, critical fire weather thresholds are not expected to be
met, with no watches or warnings anticipated.

&&

Previous discussion...
/issued 424 am CDT Friday Jul 29 2016/

A weak upper trough remains in place across the region with most of
its influence across the northern half of Alabama. This feature
along with deep moisture and daytime heating should lead to a
continuation of above normal rain chances across the north and
central part of the forecast area. Westerlies aloft will result in
faster than typical storm motions for July, leading to relatively
higher coverage of measurable rainfall for today.

87/Grantham

Saturday through Friday, precipitable water values remain around 2
inches the entire period with mean relative humidity values
generally 65 percent or higher. The model suite has been pretty
consistent and agreeable with the synoptic setup. The broad upper
ridge dominating the southern tier of the conus will oscillate west
and east as a few disturbances in the westerlies move by well
north of the region. A few subtle, rather weak features move
overhead down south, but not any significant upper support. The
general weakness in the ridge will remain near central Alabama
much of the period providing conditions favorable for daily
thunderstorms.

Most convection will be diurnally driven or have some elements of
mesoscale or lower scales for development. Due to these factors,
will keep pops higher during the daytime hours but not completely
gone at night. Additionally, these pops will be at or above
climatology the entire period, especially in the daytime. Saturday
through Monday appear to have the best coverage due to the upper
weakness nearby. 500mb heights generally range from 588-593mb the
next week with low level thicknesses and temperatures slightly
high the next several days. But due to the cloud cover and rain
chances, expect highs in the low to mid 90s with surface dew
points hanging in the 70s. Heat indices will be in the 100 to 105
range.

&&

Preliminary point temps/pops...
Gadsden 71 91 71 92 71 / 30 50 40 50 30
Anniston 71 91 73 93 72 / 30 50 30 50 30
Birmingham 74 92 75 93 74 / 30 50 40 50 30
Tuscaloosa 73 93 74 94 73 / 20 50 40 50 30
Calera 73 92 74 93 73 / 20 50 40 50 40
Auburn 73 92 74 94 74 / 30 50 30 40 40
Montgomery 74 95 75 95 74 / 20 50 20 50 30
Troy 73 92 73 91 72 / 20 50 20 40 40

&&

Bmx watches/warnings/advisories...
none.

&&

$$

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