Scientific Forecaster Discussion
fxus64 kbmx 221138
Area forecast discussion
National Weather Service Birmingham Alabama
638 am CDT Fri Jun 22 2018
for 12z aviation.
today and tonight.
Outflow from overnight convective complex has picked up speed as
it pushed southward towards the I-85 corridor. The outflow has
outrun the instability and all the lightning was located well
north of the surface boundary. Expect the remaining showers and
isolated storms to continue weakening through the remainder of the
pre-dawn hours. The outflow boundary has ushered in some slightly
cooler air along with with lower dewpoints. Increasing southwest
winds later this morning should advect higher dewpoints back into
the area this afternoon, and forecast surface based cape will
climb to between 3000 and 3500 j/kg. There will be a lull in the
shower activity after sunrise, before the next mesoscale convective system begins to take
takes shape over Mississippi. This complex will bring a threat of
severe weather to central Alabama this afternoon and early
evening. The main threat will be damaging straight-line winds.
Confidence in forecast for tonight is not very high due to model
uncertainties beyond the activity this afternoon. The trend should
be for the activity to shift more into east Alabama this evening,
so carried likely pops for areas along and east of I-65. It looks
steering level winds will be from the west at 30-35 knots, so any
threat of flooding will come from training of cells.
Saturday through Thursday.
The southern extent of moderate westerly flow at 500mb will reside
over north Alabama on Saturday along with a thermal gradient
associated with prior convection. Warm advection and lift near
this feature should continue to serve as a focus for showers and
storms with the highest chances across the north.
After Saturday, the 500mb pattern will become more typical of
Summer, and the aforementioned thermal gradient should retreat
northward on Sunday as higher heights develop across the deep
south. Convection should be isolated and limited to north of
Interstate 20. Rain chances may slowly increase for Monday through
Thursday as the ridge weakens.
12z taf discussion.
An outflow boundary from overnight convection has pushed southward
to near the I-85 corridor. The boundary mixed out the low cigs
over north central Alabama with the IFR cigs confined to areas
along and south of the boundary. A few showers will continue
across the area through the morning hours, but not enough to
warrant including at any taf site. Thunderstorms will develop
over Mississippi later this morning and spread eastward into
central Alabama by early afternoon. Sct to nmrs showers and
thunderstorms will impact the northern taf sites during the
afternoon hours, shifting southward to kmgm by 23z. Southwest
winds will increase after 15z with sustained winds of 10 to 15 kts
with gusts above 20 kts at times. The winds will diminish by 23z.
Convection will settle down by 06z with low clouds likely to form
Relatively high rain chances will continue through Saturday
especially across the northern half of the area. Patchy fog may
develop in the overnight and early morning hours where rainfall
occurs. There are no fire weather concerns at this time.
Preliminary point temps/pops...
Gadsden 84 70 88 71 92 / 70 60 60 20 20
Anniston 87 71 89 71 92 / 70 60 60 10 10
Birmingham 88 73 90 73 93 / 70 60 50 10 10
Tuscaloosa 89 73 93 74 94 / 70 50 40 10 10
Calera 88 73 90 73 92 / 70 60 40 10 10
Auburn 88 72 89 73 91 / 60 50 40 10 10
Montgomery 89 75 93 74 94 / 60 40 30 10 10
Troy 89 75 92 73 92 / 50 20 20 10 10