Scientific Forecaster Discussion
fxus64 kbmx 231125
Area forecast discussion
National Weather Service Birmingham Alabama
625 am CDT Fri Aug 23 2019
for 12z aviation.
/updated at 0324 am CDT Fri Aug 23 2019/
Today and tonight.
Warm southerly flow continues today and tonight across central al,
keeping moisture on the higher side. An elongated trough is sliding
through the northeast, but this doesn't make much of a southward
push due to the Bermuda high, so the main frontal boundary remains
well to our north. The upper level flow remains generally weak over
our area, so we won't have the lifting mechanisms necessary for
widespread thunderstorm activity. However, pwats are expected to be
in the 90th percentile, which means we'll have more than enough
moisture to support the development of thunderstorms today. High
resolution guidance suggests scattered to numerous pop-up showers
and thunderstorms during in the late morning and afternoon hours.
Exact coverage will likely depend on mesoscale boundary
interactions. High temperatures today will be similar as yesterday,
reaching to low 90s for most locations with heat indices nearing
100. Rain and thunderstorms diminish this evening and become more
isolated after midnight.
/updated at 0324 am CDT Fri Aug 23 2019/
Saturday through Thursday.
A wet and rainy weekend looks to be in order across the forecast
area as the trough continues moving across the far eastern Continental U.S.
With a ridge and drier airmass building in upstream over the Great
Lakes region. The east to west oriented surface front will meander
across the Tennessee Valley and inch its way into northern Alabama
on Saturday. This will support numerous to likely showers and
thunderstorms among a moist airmass with highs in the upper 80s to
near 90f across the forecast area both days. Best rain coverage will
be during the afternoon but with some rain lingering after dark as
well. Two separate developments, combined with southerly flow
around the Bermuda high, will help usher this boundary back to
the northeast before it has a chance to make it south of the
forecast area. The first being a low off the eastern coast of
Florida, which bears watching over the next few days for tropical
development, although this feature will stay well east of the
forecast area thanks to southwesterly steering winds aloft
associated with the second and more influential feature. A
shortwave trough embedded within a larger trough will deepen over
the central and Midwest Continental U.S. Extending south into the Gulf of
Mexico Sunday into Monday as southwesterly winds become more
prevalent over the forecast area. As the shortwave moves across
the southeast, rain chances are progged to remain elevated heading
into early next week with highs lowering into the upper 80s for
most of central Alabama on Monday and potentially Tuesday as well.
We could see a touch of dry mid-level air move in behind the trough
in our western counties on Tuesday which may limit overall rain
chances west of I-65, but would expect high moisture content to
remain below 500mb for continued support of 50 to 60 percent pops. A
cold front is expected to pass on Wednesday and Thursday as the
large-scale trough and low height center continues to rotate slowly
eastward over Ontario and Hudson Bay. Should see a north to south
surge of drier air behind the front towards the end of this extended
forecast with rain chances finally trending downwards due to the
drier low and mid-level airmass. Increased sunshine and lower rain
chances will allow highs to rise back into the low 90s, although
humidity values will be much lower.
12z taf discussion.
Looks like the low clouds remained to north and across the far
south. Really only toi is being impacted with LIFR cigs. We will
see scattered showers and storms across the area late this
afternoon into tonight. Low clouds and fog may develop overnight
but will add these in with the next set.
Scattered thunderstorms expected again today with min rhs in the
50s. Kbdi values remain high given the ongoing drought, and heat
indices will be near 100 degrees by the afternoon. Rain chances
increase as we go into the weekend, and rhs remain elevated through
early next week.
Preliminary point temps/pops...
Gadsden 91 70 89 69 86 / 60 50 70 50 70
Anniston 90 71 89 70 86 / 60 50 70 50 80
Birmingham 92 72 90 72 88 / 60 50 70 50 80
Tuscaloosa 92 72 90 72 89 / 60 50 70 40 80
Calera 91 70 90 70 88 / 60 40 70 50 80
Auburn 90 72 90 71 86 / 40 40 70 50 80
Montgomery 93 73 91 73 91 / 40 40 70 50 70
Troy 91 72 91 71 89 / 30 20 60 50 70