Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 202005

Area Forecast Discussion
National Weather Service Huntsville AL
305 PM CDT Thu Jul 20 2017

.NEAR TERM...(Tonight)
Issued at 305 PM CDT Thu Jul 20 2017

Unseasonably hot and humid wx conditions prevail across the cntrl TN
Valley this Thu afternoon, with the heat index at KHSV reaching 109F.
This looks to be the hottest location by far, with heat indices more
in the 100-103F range elsewhere. In any case, a Heat Advisory remains
in effect thru 7 PM for NW AL leading into portions of N cntrl AL.
There has been a little bit of convection across NE AL earlier this
afternoon, courtesy of a weak upper disturbance moving swd along the
ern fringe of the upper ridge axis. Conditions should begin to
gradually improve with the onset of the evening hrs, as temps quickly
fall into the 80s this evening and eventually into the lower/mid 70s
after midnight, under predom mostly clr skies.

.SHORT TERM...(Friday through Saturday)
Issued at 305 PM CDT Thu Jul 20 2017

Another very hot/humid day is xpcted on Fri, with very similar wx
conditions xpcted as today. High pressure is xpcted to be layered
across the mid/srn Atlantic states while the upper ridge axis
gradually translates ewd across the SE region. This should again
allow for afternoon temps to climb well into the mid/upper 90s for
most locations, with associated heat indices around 105F or higher. A
Heat Advisory has been issued on Fri from noon thru 7 PM which covers
just about all of the local area except for NE AL. Small chances for
rain also remain in place as weak upper disturbances continue to move
swd across parts of the region. Slightly cooler conditions/higher
rain chances are then xpcted going into the weekend period, as Gulf
moisture begins to increase into the area and a weak cold front
approaches from the NW.

.LONG TERM...(Saturday night through Wednesday)
Issued at 305 PM CDT Thu Jul 20 2017

Sunday looks to be rather warm and humid again. However, expect an
uptick in thunderstorm activity as a H7-H5 disturbance helps to
trigger afternoon/evening convection. CAPE values will likely exceed
2 kj/kg by Saturday afternoon and with very steep low level lapse
rates would not be surprised to see a few strong storms.

The beginning of the upcoming work week will continue the active
pattern across the Tennessee Valley. A strong northern stream
shortwave will deepen an existing longwave trough across northern
New England/southeast Canada. This will help push a front southward
across the region. Although lacking baroclinicity as it makes its
way into the Tennessee Valley, this front will have enough
convergence to interact with a moist and unstable airmass to product
scattered/numerous storms again on Monday.

Depending on the eventual progression/longevity of the frontal
boundary we may see precip potential linger into Tuesday as well
before northerly flow and ridging takes hold by mid week. This
warm/dry period may be short lived however as another trough again
becomes established across the Great Lakes in the Day 6-8 time
period. For the time being, will maintain warm/mainly dry weather
for next Wed/Thu and wait for consensus in later model guidance.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1234 PM CDT Thu Jul 20 2017

A few shra/tsra associated with a weak upper disturbance moving swd
across the ern half of the area may approach the KHSV terminal before
the end of the afternoon period. Otherwise, with high pressure in
place across the mid/srn Atlantic states, VFR conds are xpcted well
into the evening hrs. Some -br/tempo MVFR vis may develop overnight
for a couple of hrs, but should quickly diminish shortly after 12Z.


AL...Heat Advisory from noon to 7 PM CDT Friday for ALZ001>008-016.

     Heat Advisory until 7 PM CDT this evening for ALZ001>006.

TN...Heat Advisory from noon to 7 PM CDT Friday for TNZ076-096.




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