Severe Thunderstorm Warning 46, NWS Huntsville, AL

Area Forecast Discussion
National Weather Service Huntsville AL
240 PM CDT Wed May 16 2018

.NEAR TERM...(Tonight)
Issued at 240 PM CDT Wed May 16 2018

Convection this afternoon has been focused along the terrain in NE
AL and S Mid TN. This is mainly due to mostly clear skies out east,
but the debris clouds from morning convection has kept storms at bay
west of I-65. Not expecting that to last long as last few scans of
visible imagery show CU bubbling up near the AL/MS border and we'll
probably see storms start to fire out there soon. Updated PoPs for
this afternoon to indicate numerous thunderstorms across the area.
CAPE values are a bit lower than yesterday with value upwards of
1,500 J/kg. A weak shortwave over the area and winds aloft around
15kts may allow for more movement in storms. PWATs of 1.5 to 1.6
inches should translate into very heavy downpours. Other threats with
storms will be gusty winds up to 40 mph and small hail.

Further to the west over OK/AR a stronger shortwave is evident in
satellite and radar imagery and is taking on characteristics of an
MCV. This is forecast to continue to shift E/SE towards west-central
MS overnight. Convection that develops ahead of this feature may be
able to move into the area tonight but with the loss of daytime
heating, instability drops off and should limit the convective
potential tonight.

Any areas that get rain today could see patchy fog develop overnight.
Lows will be close to what they were yesterday with values in the
60s.

.SHORT TERM...(Thursday through Friday night)
Issued at 240 PM CDT Wed May 16 2018

The stronger shortwave to our west will begin to impact the area on
Thursday but there is still some differences in latest model
guidance. Models are struggling in the interactions between this
shortwave and the remnant subtropical system that is forecast to lift
north through central GA tonight through Thursday. The ECMWF/GEM
keeps the two separate, while the GFS/NAM try to combine/pull the
system over GA back to the west a bit. Believe the differences are
really tied to how the models want to handle the MCV/shortwave to our
west. GFS/NAM maintain it as it drops S/SE into central MS/AL on
Thursday and the result is the more widespread convection may stay
to our south focused around the MCV. The ECMWF/GEM weaken the MCV and
end up moving it across our area on Thursday into Friday. So,
needless to say uncertain/unsettled the next few days as systems move
over/near the area.

Storms that form either day should occur mainly during the afternoon
hours. And with increased cloud cover and cooler temps, instability
values should be around 1,500 J/kg both days. So, primary storms
impacts will be very heavy downpours, small hail, and gusty winds.
Steering flow increases slightly both days and storms should move
enough to keep any flash flooding concerns low at this time. Both
features begin to push east of the area on Friday and some drier air
begins to work into the area.

Highs both days will be in the low to mid 80s with lows in the 60s.
Patchy fog is possible each night, especially in any areas that
receive heavy rain.

.LONG TERM...(Saturday through Tuesday)
Issued at 240 PM CDT Wed May 16 2018

Unsettled conditions will persist through the extended forecast. The
trough that phased with the tropical disturbance will have moved off
into the OH Valley/Great Lakes region by Saturday. The combo of a
weak ridge building in from the Midwest and another located off the
mid Atlantic coast will weaken the trough and continue to lift it
northeastward on Saturday. In turn, temps will warm into the mid to
upper 80s and precip chances will be lower. Drier air will filter in
allowing Saturday night to be precip free.

The dry trend doesn't last long as light southeasterly flow returns
moisture to the region starting on Sunday. Weak ridging will persist
across the southeast into next week keeping temps above normal and
allowing scattered diurnally driven convection each day. Temps will
be around 90 on Sunday and in the mid/upper 80s for Monday and
Tuesday. Overnight lows through the extended will be mild, staying in
the 60s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1220 PM CDT Wed May 16 2018

The TN Valley is stuck between two systems and will see scattered to
numerous showers/storms develop this afternoon and continue into the
evening hours. Have kept VCTS in the TAFs as the timing of any storm
remains uncertain. Will make amendments once storms develop. Expect
very heavy rain, small hail, possibly IFR vsbys, and gusty winds
with any storms. Activity dwindles after midnight with VFR conditions
expected. Winds remain variable through the period.

&&

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

NEAR TERM...Stumpf
SHORT TERM...Stumpf
LONG TERM...JMS
AVIATION...Stumpf

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

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Special Weather Statement
National Weather Service Huntsville AL
346 PM CDT WED MAY 16 2018

ALZ004-005-162115-
Lawrence AL-Limestone AL-
346 PM CDT WED MAY 16 2018

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL LIMESTONE AND
NORTHEASTERN LAWRENCE COUNTIES UNTIL 415 PM CDT...

At 346 PM CDT, Doppler radar was tracking a strong thunderstorm near
Athens. This storm was nearly stationary.

Pea size hail and winds in excess of 30 mph will be possible with
this storm.

Locations impacted include...
Athens, Tanner, Hillsboro and Ripley.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Strong gusty winds will be capable of knocking down small tree limbs
along with other small unsecured items. Seek safe shelter until this
storm has passed.

Very heavy rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 3468 8686 3466 8706 3468 8710 3465 8711
      3464 8724 3484 8716 3487 8695
TIME...MOT...LOC 2046Z 352DEG 2KT 3479 8705

12

Special Weather Statement
National Weather Service Huntsville AL
424 PM CDT WED MAY 16 2018

ALZ004-007-162215-
Lawrence AL-Morgan AL-
424 PM CDT WED MAY 16 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN MORGAN AND NORTHERN
LAWRENCE COUNTIES UNTIL 515 PM CDT...

At 424 PM CDT, Doppler radar was tracking a couple of strong
thunderstorms in the advisory area. One storm was near Courtland,
and the other was near Trinity. These storms were nearly stationary.

Pea size hail and wind gusts of 40 to 50 mph will be possible with
both storms.

Locations impacted include...
Decatur, Trinity, Courtland, North Courtland, Hillsboro, Chalybeate
Springs, Neel, Caddo and Wheeler.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Strong gusty winds will be capable of knocking down small tree limbs
along with other small unsecured items. Seek safe shelter until
these storms have passed.

Very heavy rainfall is also occurring with these storms, and may
lead to localized flooding. Do not drive your vehicle through
flooded roadways.

&&

LAT...LON 3473 8721 3461 8697 3440 8710 3462 8745
TIME...MOT...LOC 2122Z 059DEG 0KT 3463 8725

70/DD