Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Birmingham Alabama
702 PM CDT sun may 24 2015
for 00z aviation.
Humid conditions have returned to central Alabama with dewpoints in
the 60s and 70s across the state. Current water vapor imagery and
rap upper air analysis indicates a longwave ridge to the east
centered across the Florida Peninsula with a closed low to the west
across the Rocky Mountain region. A shortwave trough can be noted
moving across the lower Mississippi River valley and this has set
off a few showers and storms across southwestern portions of central
Alabama early this afternoon. Looking at satellite estimated precipitable water
values have already increased to over 1.5 inches in this area and
expect convection will continue to progress to the north over the
next few hours. Looking at the mesoanalysis...SBCAPE values are over
2000 j/kg across southwestern portions of central Alabama but deep
layer shear values are only around 15-20 kts. Therefore...there
could be a few storms pulse up to produce wind gusts around 40 miles per hour
but storms will remain below severe limits. Convection is mostly
diurnally driven and expect activity will decrease in coverage and
intensity after sunset. There is still some question as to how much
activity will continue into the overnight period with the shortwave
trough approaching...there will be some synoptic lift that could
keep coverage going a bit more than a typical summertime setup
with best chances across western portions of central Alabama.
Another upper level trough will move out of the Southern Plains
on Labor Day into the middle-Mississippi and Tennessee River valleys.
Precipitable water values will increase to 1.7-1.9 inches which is well over the 90th
percentile for this time of year. Expect widespread showers and
storms mainly during the afternoon hours and have increased probability of precipitation
into the 60-70% range for all of central Alabama. Models indicate
that SBCAPE values will range from 1000-2000 j/kg Memorial Day
afternoon with 0-6km shear values around 30 kts. Therefore...expect
a few strong storms will be possible again with wind gusts of 40
miles per hour. In addition...expect heavy downpours will be possible with
storms that form and there could be a few isolated areas of minor
flooding in areas of poor drainage. However...do not expect any
widespread flooding issues with the dry start to the month of may.
Expect similar conditions on Tuesday as another shortwave trough
moves through the Southern Plains into the middle-Mississippi and
Tennessee River valleys. Moisture values will continue to be
elevated with models indicating precipitable water values approaching 2 inches.
Severe weather parameters are about the same and expect a few
strong storms will be possible but expect activity will remain
below severe limits. On Wednesday...the pattern should begin to
shift as the last of a series of shortwave troughs moves through
the area as the ridge to the east breaks down. Precipitable water values will
begin to drop slightly but remain elevated for this time of year.
Therefore...probability of precipitation in the 50- 70% range continue Wednesday
Late in the week an upper level ridge tries to develop along the
Gulf Coast with weak flow aloft. Expect more of a typical early
Summer time pattern during this period with a chance for scattered
afternoon showers and storms with temperatures warming into the middle
and upper 80s.
00z taf discussion.
Storms that rolled through bhm/eet a bit earlier have weakened and
begun to diminish. Have only carried thunderstorms in the vicinity at anb/asn for a couple
hours as confidence in any ts impacts are low at this time. It's
uncertain as to how much convective activity we'll have overnight.
Have not included anything at this time but will watch trends closely.
Ceilings are expected to drop to at least MVFR...with some IFR
possible...by 09z or so as isentropic lift increases. Conditions
may be slow to improve on Monday. Another round of showers/storms
will move in from the west by Monday afternoon. Winds will
generally be out of the southeast at 5-10 kts.
Preliminary point temps/pops...
Gadsden 69 81 69 81 69 / 20 70 50 80 60
Anniston 70 82 70 82 69 / 20 60 50 80 60
Birmingham 70 81 70 81 69 / 40 70 50 80 60
Tuscaloosa 71 80 70 81 69 / 40 70 50 80 60
Calera 70 82 69 82 68 / 30 60 50 80 60
Auburn 68 83 68 82 68 / 20 60 40 70 60
Montgomery 71 84 71 83 70 / 20 60 40 80 60
Troy 69 84 69 82 68 / 20 60 40 70 50