Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Birmingham Alabama
615 PM CDT Thursday Apr 17 2014
for 00z aviation.
Short term...tonight through Sunday.
Convection is blowing up across the northern Gulf of Mexico in
response to a digging short wave trough over Texas. Expect rain to
move inland over Alabama and northwest Florida this evening and reach the
southern counties of central Alabama before midnight. Rain...heavy
at times...will spread northward across the southern half of
Alabama between midnight and 6 am Friday. A surface low will move
across the eastern Florida Panhandle Friday evening...so central
Alabama will stay on the cooler and more stable side of the
system. Cross sections of Theta-E show a very tight gradient of
contours below 700mb...which indicates very limited thunderstorm
potential. There is a small layer of near adiabatic lapse
rates aloft...so an isolated elevated thunderstorm is possible across
the southeast counties. Rainfall totals for areas south of I-85
will likely be in the 1-2 inch range through Friday evening.
..with some isolated amounts near 3 inches. Flash flood guidance
is near 2.5 inches per hour across the southeast counties...so
will hold off issuing any flood or Flash Flood Watch at this time.
The rain will dissipate from west to east Friday evening as the
center of the upper low moves into Georgia. As the upper low closes
off and deepens...there is some wrap around rain that will linger
across east Alabama through Saturday morning. Temperatures during
the day on Friday will be well below average due to the rain and
easterly low level flow. Many areas across east Alabama will not
get out of the 50s on Friday. Temperatures on Saturday will be
warmer...especially across the western counties...but the eastern
counties will stay about 10 degrees cooler than the western
counties due to the presence of clouds and cooler air on the back
side of the exiting low. Expect the the rain to be out of east
Alabama Saturday evening...but the clouds may linger into Sunday
morning across the east. Sunday should be a much warmer and nicer
day as this pesky system finally moves out of the southeast
Long term...Monday through Thursday.
Another short wave trough will quickly advance into the Southern Plains
states on Monday. The air mass will not have much time to recover
from the weekend system...so this system does not not look very
organized or produce any significant rainfall amounts. The best
chance for rain will be during the day on Tuesday. There will be
enough instability for the production of thunderstorms...but
nothing severe as 0-6km bulk shear values are forecast to be less
than 30 knots. This system is fairly progressive and should be out
of the area Tuesday night.
00z taf discussion.
VFR conditions currently across the terminals. Middle to high clouds
have increased throughout the day as an upper level system moves
along the northern Gulf Coast. Moisture will continue to increase
throughout the taf cycle with the northern terminals remaining VFR
and the southern terminals going MVFR around 05-07z. IFR
conditions will be possible at ktoi after 08z. Showers will move
from southwest to northeast across the terminals. Rain could be
heavy enough at times to reduce visibilities to IFR at kmgm and
ktoi. There will be a sharp cut off in the precipitation and
expect rain will remain light at the northern terminals.
Note...the National Weather Service will be issuing seasonal
terminal forecasts for the Talladega Municipal Airport (kasn) in
Talladega...Alabama. The forecasts will be issued from April 20th
00z through at least may 8th 00z. Due to the limited availability
of observations...kasn taf will have amend not schedule appended to the
end of the forecast.