Area Forecast Discussion
Issued by NWS Huntsville, AL
FXUS64 KHUN 252022
Area Forecast Discussion
National Weather Service Huntsville AL
322 PM CDT THU AUG 25 2016
A fairly typical summertime expansive, stacked anticyclone pattern
remains across the Southeast for the next couple of days before
successive upstream mid-level shortwave troughs move across Plains
states dampen the anticyclone. The ridge is centered over the
Southeast and stretches to the OH river valley states as mean
troughing remains over the western half of the country. Daily
chances for thunderstorms will likely continue into the weekend as
the ridge shifts to the northeast.
Meanwhile, the tropical wave over the Hispaniola region is expected
to move northeast towards the Bahamas over the coming days. Any
possible impacts from this tropical wave are still unknown given the
high uncertainty with its track, its structure, and intensity.
Hot and humid conditions are anticipated this evening with isolated
storms possible mainly from diurnally driven convective cells and
various outflow boundaries moving across the area. Due to the very
hot conditions today, overnight temperatures should be slow to cool
to the low to mid 70s. Then, within the prevailing ridge rotating
almost atop the region, a weak sfc to 850mb convergence
zone/boundary develops across or just to the south of the TN valley.
This convergence zone may provide the focus for more isolated to
scattered activity especially over the higher elevations of the
cumberland plateau. Due to this possibility and the high amounts of
instability tomorrow afternoon, have raised POPs to around 40-50%.
The low wind shear profile aloft and inverted V signatures will
result in the potential for microbursts with gusty winds up to 50
MPH possible. Another impact for tomorrow will be heat indices with
values approaching 105F as temperatures rise into the low 90s and
dewpoints rise/remain in the mid 70s. Am not inclined to issue a
heat advisory at this point due to the storm and cloud potential
that could act to mitigate daytime heating.
The ridge axis (anticyclone) gradually shifts to the northeast by
Saturday due to a series of upstream mid-upper level shortwave
troughs moving within the polar jet over the Intermountain
West/Canada. As it does so, an inverted trough may impact the region
on Saturday afternoon resulting in isolated to scattered
thunderstorms as well.
Storm chances continue on Sunday as the ridge begins to dampen as
those aforementioned shortwave troughs continue to move across the
polar jet. Still could see some isolated to scattered storm
activity, especially over northeast AL/southern Middle TN. The early
part of next week may actually be drier with a stacked ridge
returning and almost stacked on top of the TN valley. Kept POPs near
10% for Monday and Tuesday (SuperBlend) but expect this to change
over the coming days as the forecast for the current tropical wave
over Hispanola become more apparent. Otherwise, hot and humid
conditions will continue with daytime highs in the 90s and lows in
the 70s through the middle part of next week.
(Issued 1241 PM CDT THU AUG 25 2016)
For 18Z TAFs: Strong heating beneath mid/upper-lvl ridge will
continue to force the development of isolated-widely sct shra and
perhaps a few tsra this aftn. However, given uncertainties on direct
impacts at a terminal, only VCSH will be included in the forecast
attm. Otherwise, we expect VFR conds to prevail with sct-bkn high-
based cu and an increasing coverage of higher altitude clouds
overnight. Patchy fog may once again develop near the MSL terminal --
and a tempo for 5 SM/BR has been included at this airport. A slightly
greater coverage of storms is anticipated tomorrow, courtesy of a
southward drifting cold front -- and VCTS was introduced at MSL
beginning at 26/15Z.
.PRELIMINARY POINT TEMPS/POPS...
Huntsville 74 92 73 94 / 10 40 20 20
Shoals 74 92 73 93 / 10 40 20 20
Vinemont 72 91 71 91 / 10 40 20 20
Fayetteville 72 92 71 92 / 10 50 20 30
Albertville 73 92 72 91 / 10 40 20 20
Fort Payne 71 91 71 91 / 10 50 20 30
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