Area Forecast Discussion
Issued by NWS Birmingham, AL
FXUS64 KBMX 200957
Area Forecast Discussion
National Weather Service Birmingham AL
457 AM CDT FRI MAY 20 2016
Today and Tonight.
MCV moving ENE along the central Gulf Coast this morning will
rotate into southeast Central Alabama. The northern extent of the
line has weakened, however, wind gusts of 50mph and frequent
lightning could be possible. Current radar trends have the
strongest part of the convective line tracking near and south of a
Montgomery to Alex City line. On the north side of the storm
complex, light to moderate rain and lightning will be possible as
far north as Calera to Ranburne. It will be a couple hours before
the line of rain and storms nears the Georgia state line. In
association with a weaker shortwave crossing north Mississippi,
scattered convection has developed north of the MCV from near
Starkville to Memphis. This activity is moving to the NNE at this
Hi-res model guidance suggests this scattered activity across
north MS will continue to develop and spread eastward through the
early morning hours into north Central Alabama, in response to a
strengthening LLJ and approach of a surface trough axis. Upper
level winds weaken slightly as the shortwave rotates toward the
Ohio River Valley, so bulk shear parameters remain conservative.
Although the low levels remain capped, CAPE values aloft have
increased over the last couple hours as mid level temps cooled
very slightly. Although not widespread, a strong wind gust could
also be possible with this activity - as well as the MCV in the
south. Coupled with heavy rainfall, small or weakened trees could
What happens behind this activity is the million dollar question
today. The MCV is certainly going to disrupt the wind field
across the area and to our south, and likely prevent the warm
front from lifting northward as quickly as earlier anticipated.
The cap will erode with daytime heating and still expect surface
CAPE values around 1000J/Kg by mid day. However, do not think we
advect the 70F dewpoint airmass as far north as previously
expected, as low level winds maintain an easterly component
before quickly becoming southwesterly due to the influence of the
MCV and the surface low this afternoon. With a weakly
strengthening surface low tracking across north Alabama and some
increase in shear parameters during the afternoon, thunderstorms
will be possible. Strong subsidence and dry air can be seen on
water vapor rotating around the base of the longwave trough and
into western Mississippi this morning. Layer RH values across the
area decrease quickly behind this initial wave of storms, and this
should keep thunderstorm activity scattered this afternoon and
early evening. Expect the better shear and synoptic forcing to be
across the north and better instability in the south, but cannot
rule out an isolated severe storm, and will keep limited wording
for threats today. Expect threats to quickly diminish with sunset
as instability decreases.
Saturday through Thursday.
Weather conditions will be quieter for the weekend and early next
week, as the weather system responsible for rain and storms today
pulls east of the area. Drier and cooler air will filter
southward as high pressure builds toward the southeast and mid
level winds remain our of the northwest to north for the weekend.
The upper level trough pulls east, and mid and upper level
ridging moves across the area early next week. Low level winds
become southerly as surface high pressure shifts eastward. Ridging
aloft should keep the main storm track to the north as impulses
rotate around the ridge. Cannot rule out a couple of these
impulses skirting the area by mid week, and will need to include
low pops for portions of the area.
Ridging weakens and southwesterly mid level flow develops across
the area late next week, and expect a return to higher POPs as
better moisture returns to the area.
06Z TAF Discussion.
A large area of low cigs over GA was advecting westward and hes
reached the far eastern counties of central AL. The leading edge
of the clouds should reach KANB shortly and then spread as far
west as I-65 by 09z. The leading edge of the clouds were arnd 1200
feet agl...but expect cigs o lower to ifr for most areas by 12z.
the exception may be KTCL where cigs may stay closer to 1500 feet
agl. The low clouds should remain thru 15z and then gradually
rise to vfr after 20z. a large MCS near New Orleans will track
eastward overnight and bring heavy rain to the immediate coast.
Showers and a few storms to the north of the MCS will impact a
majority of central Alabama between 12z and 15z. Activity should
become more sct during the afternoon and stronger.
Widespread rain and storms are possible today ahead of a frontal
system. Drier and cooler air arrives behind a cold front tomorrow
with dry conditions continuing through mid week. No fire weather
concerns at this time.
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 76 61 79 55 80 / 90 50 10 0 0
Anniston 76 62 79 57 79 / 90 50 10 0 0
Birmingham 78 63 80 59 81 / 90 40 10 0 0
Tuscaloosa 80 62 83 60 83 / 90 30 10 0 0
Calera 78 63 81 60 81 / 90 40 10 0 0
Auburn 77 64 81 61 80 / 90 60 10 0 0
Montgomery 81 67 84 61 84 / 90 40 10 0 0
Troy 81 66 84 61 82 / 90 50 10 0 0