Area Forecast Discussion
Issued by NWS Birmingham, AL
FXUS64 KBMX 251602
Area Forecast Discussion
National Weather Service Birmingham AL
1102 AM CDT THU AUG 25 2016
Deep layer easterly flow will be in place today south of an mid-
level anticyclone that will be drifting northward into Tennessee.
A weak wave moving through produced some high clouds and a couple
showers this morning but these have largely dissipated. The
easterly flow will bring in some dry air aloft that will help to
suppress convective chances across the area, but there will still
be enough moisture in the north and west to produce isolated
afternoon showers and storms. The PWAT on the BMX sounding was
still 1.79 inches, but the FFC sounding only had a PWAT of 1.53
inches and the TAE sounding had a PWAT as low as 1.24 inches. The
dry air aloft could enhance downdrafts and gusty wind potential
with any stronger storms that do form, but the limited
instability will make it difficult for strong updrafts to form.
Mid to upper 70s dewpoints continue to be pooled across West
Alabama. Lower dewpoints will be trying to work in from the east
as drier air aloft mixes down, but may not arrive soon enough to
prevent heat indices from briefly reaching 105 degrees.
Confidence/coverage/duration remains too low for a heat advisory
but a low confidence mention of heat was once again added to the
12Z TAF Discussion.
VFR forecast the next 24 hours. An axis of low to mid level
convergence was just enough to allow clouds to develop over
central Alabama. These clouds were 4-7k ft. In addition, a few
showers have developed in this area, but overall chances of
anything affecting a terminal is too low at the present time.
Easterly flow kicks in this afternoon and overall drier air
filters in from the east. Limited the rain chances to north and
west, and isolated at best. Once again, it appears any convection
will be too limited to mention in the terminals. Continued light
easterly flow overnight with only scattered cirrus.
A prolonged period of generally dry conditions will continue thru the
weekend, with only low rain chances at times. Temps will remain
slightly above normal thru Sunday. Critical fire weather
conditions are not expected.
/Issued 405 AM CDT THU AUG 25 2016/
Today and Tonight.
The models suite is in good agreement that the 597dam upper ridge
moves northeastward today and tonight and decreases slightly.
Therefore, the mid and upper flow will be east to northeast on the
southern periphery of this ridge. Feel that the NAM/WRF and Hi-Res
models best depict the subtle upward motion near a vorticity axis
west and north of the I-59 corridor. This is also where the best
precipitable water and mean moisture are co-located. Farther south,
the surface ridge located along the spine of the Appalachians will
bring a dry easterly near surface flow. Dew points will drop into
the 60s today and spread from east to west. This in itself will be a
boundary of sorts, but the overall column moisture drops low enough
that not much is anticipated south. Since the lift, upward motion,
proximity to ridge, poor mid level lapse rates, SBCape, and moisture
convergence are all rather limited, dropped pops to isolated north
and west with nothing mentioned elsewhere. There appears to be some
convergence or leftover boundary from near Birmingham to Montgomery,
so its no completely out of the question we may need to add a 10 pop
farther east, but coverage will be very low. Did not mention
anything into the evening hours. Easterly flow brings lower 850
temps and thicknesses, but highs should still manage the low to mid
90s with the warmest west and south. Heat indices will range from
near 100 along the I-65 corridor to and 100 to 105 near the
Mississippi state line. Due to coverage and duration of near 105
Heat Indices, will not issue an advisory at this time. Partly cloudy
to mostly clear overnight with lows near 70 east and 70 to 75
Friday through Wednesday.
The upper ridge will gradually migrate northeastward into the
Appalachians by Friday with weak sfc ridging still in place
across the forecast area. Weak shortwave energy combined with
higher moisture content across the northern counties will lead to
low rain chances Friday and Saturday in the north, with dry
conditions expected across at least the southern half of Central
Alabama. Models indicate a weak easterly wave moving into the
state on Sunday, therefore a few showers/storms will be possible,
mainly in the east. Temperatures will be a couple degrees above
normal with highs generally in the low/mid 90s. With the easterly
flow and slightly lower dew points across the southern portions of
the area, heat indices should remain below heat advisory criteria.
Not much change in the extended forecast for early next week as
there is still a lot of uncertainty with the potential tropical
system development and track. Since the system hasn`t actually
developed yet, models are still having a difficult time with the
potential intensity/landfall. The strength and placement of the
upper ridge will be a major determining factor in the track of the
system, but at this time, there is a decent possibility that the
system could enter the eastern Gulf of Mexico. Needless to say,
all eyes will be on the tropics over the next few days. As always,
for the latest tropical information, please visit the National
Hurricane Center website at www.nhc.noaa.gov.
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 92 72 93 72 92 / 20 10 30 10 10
Anniston 92 72 92 72 92 / 10 10 20 10 10
Birmingham 94 75 93 74 94 / 20 10 20 10 10
Tuscaloosa 95 74 95 73 96 / 20 10 20 10 10
Calera 93 73 93 73 94 / 10 10 20 10 10
Auburn 90 72 93 72 93 / 10 10 10 10 10
Montgomery 94 74 96 72 96 / 10 10 10 10 10
Troy 92 71 93 71 94 / 10 10 10 10 10