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fxus64 khun 201006 aaa 
afdhun

Area forecast discussion...updated
National Weather Service Huntsville Alabama
506 am CDT sun Aug 20 2017

Update...
for 12z tafs and near term update.

&&

Near term...(today and tonight)
issued at 506 am CDT sun Aug 20 2017

Have updated to included isolated ts this morning. Rogue elevated
thunderstorm has popped up over Lincoln/Moore counties from an
otherwise innocuous mid level cloud deck. Unsure that it will last
very much longer, so have gone with the pop just this morning.

Otherwise, expecting a near repeat of saturday's weather today.
Other than some scattered cumulus and possibly some thinning high
clouds, another very warm day is ahead. Highs should reach the upper
80s to lower 90s once again. A rather deep capping inversion is still
indicated above 800 mb which should suppress deep convection today.
Patchy River Valley fog should redevelop again tonight into early
Monday morning.

Short term...(monday through Tuesday night)
issued at 224 am CDT sun Aug 20 2017

A rather strong 850 mb and 500mb ridge will still be in place across
much of the southeast U.S. On Monday into Tuesday. This should
continue to suppress deep convection over the Tennessee Valley on Monday.
Will still forecast highs in the upper 80s-lower 90s, but will adjust
hourly temps during the solar eclipse. The short range models
indicate that the cap will weaken slightly on Tuesday, enabling a low
probability of afternoon and early evening thunderstorm development.
Near persistence temperatures are expected Tuesday, depending on
areal coverage of afternoon thunderstorms. Will continue to introduce
chance pops in advance of the cold front late Tuesday night, mainly
for southern Tennessee and the far northern tier of Alabama counties.

Long term...(tuesday night through saturday)
issued at 224 am CDT sun Aug 20 2017

The upper flow pattern change that has been advertised to occur by
the middle of the week continues to be depicted in the latest model
runs. Slight changes are noted in the latest model runs with the
speed of a surface front ahead of a longwave trough moving south over
the Great Lakes/southeast Canada region. A couple of shortwave
troughs rotating around the primary upper low will push the surface
front south on Wednesday during peak heating. The saturated profile
and warm sfc temperatures may result in moderate surface based
instability (1000-2000 j/kg--depending on the model) on Wednesday
afternoon. Windex values are around 60 kts but dcape values are
highly stratified and below 1000 j/kg for much of the area. In
addition, bulk shear values are only around 35 kts. So, strong
thunderstorms with wind gusts up to 40 miles per hour are possible along with
frequent lightning.

The front should then move south of the Tennessee River on Wednesday
evening with storms diminishing as the front passes. Did keep chance
to slight chance of thunderstorms in the forecast on Wednesday
evening/overnight to account for this slow movement. Then, behind the
front on Thursday and Friday, a noticeably cooler airmass is
expected to advect over the region as a surface high pressure system
centered over the Great Lakes advects south over the region. The
ridge begins to shift east from the western half of the conus, but it
will likely be dampened by a trough moving across
Alberta/Saskatchewan.

Dewpoints should drop back into the 60s and upper 50s by Thursday
night while daytime high temperatures are in the low to mid 80s.
Overnight lows will be in the low 60s (possibly upper 50s over tn).

The pattern begins to change again as a dampened ridge leads to a
trough deepening across the Central Plains to MS River Valley by next
weekend. This could bring the potential for thunderstorms as the
maritime tropical airmass begins to move north as southerly flow
develops in the low levels and have left chance pops in for
saturday's forecast.

&&

Aviation...(for the 12z tafs through 12z Monday morning)
issued at 506 am CDT sun Aug 20 2017

VFR conditions are forecast during the next 24 hours. Isolated
thunderstorm is possible this morning, but probability is too low to
include at the tafs at this time. Otherwise, scattered cumulus will
develop today, then dissipate this evening with light and variable
flow through the period.

&&

Hun watches/warnings/advisories...
Alabama...none.
Tennessee...none.
&&

$$

Near term...17
short term...17
long term...sl.77
aviation...17

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