FXUS64 KHUN 210529

Area Forecast Discussion
National Weather Service Huntsville AL
1229 AM CDT Fri Jul 21 2017

For 06Z TAFS.


.NEAR TERM...(Rest of tonight)
Issued at 928 PM CDT Thu Jul 20 2017

While low and mid-level clouds have cleared out across the Tennessee
Valley, a veil of translucent cirrus has pushed into the region and
seems likely to stay in place. Temperatures across the area are
cooling off reasonably well despite this impediment, with most spots
now within a few degrees of the lower 80s.

Tonight should stay fairly quiet as a weak upper low centered off the
southeast Atlantic coast begins retrograding south of the upper
high, placing the high right over the Tennessee Valley. Sky cover
will be tweaked slightly in anticipation of greater cirrus cloud
cover. GFS LAMP guidance has hinted at some fog formation late, but
other models/ensembles are less impressed, and the cirrus would seem
to hurt fog formation despite rapidly falling dewpoint depressions.
So it will be left out of the public forecast for the time being, and
revisited for aviation purposes later this evening.

.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 06Z TAFS through 06Z Friday night)
Issued at 1229 AM CDT Thu Jul 20 2017

VFR conditions are generally expected through 06Z/22. There is a low
chance of MVFR fog around sunrise at both KMSL and KHSV; however,
persistent cirrus moving over the region suggests keeping it out of
the TAFs at this time.


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

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




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