Severe Thunderstorm Warning 103, NWS Huntsville, AL

Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
1158 AM CDT Thu Jun 15 2017

.UPDATE...
For 18Z TAFS.

&&

.NEAR TERM...(Rest of Today)
Issued at 813 AM CDT Thu Jun 15 2017

Patchy dense fog in the Jackson County portion of the TN valley
should dissipate within the next hour or two. Have gone with an SPS
until 1430Z for this. No other major adjustments are needed at this
time, but we will be monitoring the mesoscale trends closely today.
Confidence in any one of the mesoscale model solutions is still
uncertain. The 00Z NSSL WRF run seems to be handling the linear MCS
now tracking southeast through KY/MO/AR. Elevated convection ahead of
this line may be forming in advance of the upper shortwave noted on
water vapor imagery, which is progged to drop southeast through the
area today. This may team up with the advancing MCS cold pool to
generate strong-severe convection by midday into the afternoon. The
greatest downdraft potential noted by DCAPE was located in NW AL and
points north and west where values of 1100-1500 J/kg are noted.

.SHORT TERM...(Tonight through Saturday)
Issued at 334 AM CDT Thu Jun 15 2017

Isolated showers/storms should linger overnight unlike the past few
nights as the upper wave sits over the area through the night and
outflow boundaries linger. Model POPs are probably slightly overdone
given the reality of the last few days so will stick with a slight
chance pop overnight.

The mid and upper ridge do not start to build back in on Friday and
the day is plagued by another shortwave or two moving through aloft.
A weak westerly wind may lower dew points slightly more than
forecast but either way, plenty of moisture and instability will be
in place to once again create isolated to scattered showers/storms.
Kept the chance pops in the forecast but like was mentioned early,
guidance has been overdoing the pops so storms could be more
isolated in nature in reality. More of the same expected on Saturday
but this time we have more of a southerly return flow in moisture
and a boundary lingering in the southeast, lending to higher pops
there. Like normal in the summer, any of these storms if they can
tap into deeper moisture and lift could produce strong gusty winds
and locally heavy rainfall. A few storms may once again linger into
Saturday night.

Highs Fri/Sat will again be in the upper 80s/lower 90s with a few
spots a deg or two higher depending on cloud cover. Lows will be
warm, in the upper 60s/lower 70s.

.LONG TERM...(Saturday night through Wednesday)
Issued at 334 AM CDT Thu Jun 15 2017

A fairly stormy wx regime looks to be in place across the cntrl TN
Valley to start this part of the forecast package. Even with
seasonably warm and humid conditions persisting into the latter half
of the weekend period, with heat indices perhaps climbing into the
mid/upper 90s for the cntrl/wrn zones, latest global model suites
are still hinting at an upper trough pattern digging into much of
the ern CONUS Sun, as the moisture profile across the area thickens
once again out of the sw. This upper trough axis will also drag a
weak cold front sewd into the region late Sun into Mon. Weak
isentropic lift spreading nwd into the mid TN Valley ahead of the
oncoming front coupled with some increase in dynamical forcing
should translate into sct/num showers/tstms developing along/ahead
of the sfc boundary. Given some low level convergence/vertical shear
developing with the approaching front, coupled with ample latent
heating/instability, a few strong tstms certainly look reasonable
starting the new work week, and will be capable of gusty outflow
winds/locally heavy rainfall. Rainfall or lingering showers/tstms
will then taper off from the nw Mon night into Tue, following the
passage of the cold front coupled with the upper trough pattern
beginning to fill over the cntrl Gulf states.

A little bit of a reprieve in convective development then looks to
evolve heading into mid week, as high pressure out of the Plains
states quickly builds ewd into much of the region in the wake of the
frontal passage. Unfortunately, little relief is anticipated in
overall temps thru Wed, as afternoon highs remain predom in the
upper 80s/near 90F while overnight lows trend mainly in the upper
60s/arnd 70F. Slightly drier air though is xpcted to fill into the
local area from the n after Mon, which may help keep max afternoon
heat indices in the lower 90s into Wed. Showers/tstms may also
return to the forecast at the end of the period, as sly flow and
Gulf moisture stream back into the cntrl TN Valley.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1158 AM CDT Thu Jun 15 2017

Line of strong thunderstorms will arrive in the KHSV and KMSL areas
between 18-20Z. Visibility of ~2sm (IFR) in moderate thunderstorms is
expected, although pockets of heavy rain and gusty winds are
possible. Once these thunderstorms pass, additional thunderstorms are
possible into early this evening, so have carried VCTS until 23Z.
Then VFR conditions are expected through tonight until patchy BR/FG
develops after 09Z through 12Z when MVFR conditions are possible.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&

NEAR TERM...17
SHORT TERM...LN
LONG TERM...09
AVIATION...17

For more information please visit our website
at weather.gov/huntsville.

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