Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 242012

Area Forecast Discussion
National Weather Service Huntsville AL
312 PM CDT Sun Jun 24 2018

.NEAR TERM...(Tonight)
Issued at 236 PM CDT Sun Jun 24 2018

A complicated forecast this evening, as we have a weakening, but
still present convergence boundary extending from Chattanooga
west through Moore county Tennessee and into Hardin and Henderson
counties in Tennessee. Stronger thunderstorms have developed along
this boundary in earnest over the last hour or so. With SBCAPE values
between 3000 and 4000 J/KG and DCAPE values between 1000 and 1200
J/KG, microburst producing damaging winds up to 60 mph are possible.

A big question is what will happen late this evening into Monday
around daybreak as stronger upper level energy pushing east into the
area. Will likely still be pretty unstable and models keep shear
around 30/35 knots on the southeastern edge of this feature (better
shear/forcing remains between Memphis and southwestern Kentucky
overnight). We could have another wave of shower and thunderstorm
activity clip locations north of the Tennessee River and southern
middle Tennessee after 3 am into the daybreak hours. With better
shear cannot rule out some stronger thunderstorms (maybe even a
severe one or two). Again same threats look possible, mainly damaging
winds, small hail, and heavy rainfall.

.SHORT TERM...(Monday through Tuesday)
Issued at 236 PM CDT Sun Jun 24 2018

At this point, kept pop at 40 to 50 pop in southern middle Tennessee
into the early morning hours on Monday, before they begin becoming
more widely scattered. Storms should be less intense Monday
afternoon, as the atmosphere becomes more saturated. It will be another
hot and humid day with highs in the lower 90s and heat index values
100 to 105 degrees. Strong storms capable of producing 50 mph gusts and
frequent lightning will remain possible in any isolated storms that
develop. By Monday evening, the upper ridge amplifies and becomes
more firmly entrenched over northern Alabama and southern middle
Tennessee. This should limit any shower and thunderstorm activity
even further.

Tuesday looks even warmer, with highs 90 to 95 degrees west of I-65.
Again with humid conditions in place, heat index values could reach
around 105 degrees in the afternoon with isolated to widely scattered
thunderstorm activity returning. This should be mainly diurnally
driven and lessen in coverage and intensity in the evening.

.LONG TERM...(Tuesday night through Saturday)
Issued at 236 PM CDT Sun Jun 24 2018

Weak frontal boundary looks to be on the doorstep of the Mid
South/mid TN Valley regions as mid week approaches, although this
may be as far as the front travels according to the latter half of
the global model suites. The latest ECMWF/GFS models quickly shift
this boundary back to the N as a warm front in the Thu/Fri time frame,
with high pressure over the srn Atlantic states generally remaining
in control of the overall wx pattern across the SE region. In
addition to this, a strong upper ridge axis out of the mid/srn Plains
states will steadily make its way ewd into the wrn/cntrl Gulf states
Thu/Fri. This should translate into highs trending slightly above
normal after mid week, with afternoon temps climbing well into the
mid 90s Thu-Sat for many locations. The seasonably mild pattern will
certainly continue at night as well, with overnight lows only
managing to fall predom into the lower/mid 70s range for most areas.
Given an abundant supply of Gulf moisture streaming nwd into the
local area, coupled with a weakly sheared environment, iso/low sct
showers/tstms look prob each day in the long term portion of the
forecast, aided by an increase in buoyant energy/latent heating.
Given the lack of better mid/upper forcing coupled with the near lack
of any deep layer shear, most of these tstms should be pulse in
nature, with brief strong gusty winds and locally heavy rainfall the
main threats. As is typical this time of the yr, any lingering tstms
should quickly diminish going into the early evening hrs.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1110 AM CDT Sun Jun 24 2018

MVFR CIGS will remain possible at KHSV through 19Z at times, before
cloud cover become more scattered in nature. Further west, expect
predominantly VFR conditions, with cloud cover remaining more partly
cloudy. Although isolated to widely scattered -tsra cannot be ruled
out, confidence is extremely low that they will affect either
terminal directly. Therefore, leaving any precipitation (even
vicinity) out of the forecast for now. An increase in cloud cover
(possibly MVFR) will be possible later this evening and along
with -TSRA. Left out precipitation for now as models are not in
great agreement with this and may keep the activity further north in
Tennessee. Otherwise, expect a wind shift after 16Z on Monday at both
TAF sites more to the northwest.





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