Severe Thunderstorm Warning 181, NWS Morristown, TN

Area Forecast Discussion
National Weather Service Morristown TN
327 PM EDT Thu Aug 16 2018

.SHORT TERM...(Tonight and Friday)...
Showers and thunderstorms that have been developing across the
Cumberland Plateau and Middle TN will move toward the NE in a
prevailing low to midlevel flow from the SW. This convection will
be encountering drier midlevel air as it moves into the TN Valley,
so a diminishing trend is expected through the evening, which is
supported by the short term convective models. Any threat of
strong to isolated severe storms appears low and isolated to the
northern Plateau counties over the next few hours.

A closed low over the northern Plains today will transition to an
open trough as it moves into the Great Lakes and OH Valley region
tonight and tomorrow. A low level convergence zone and a 40 kt LLJ
set up ahead of this system across central KY tonight, with the NAM
showing blossoming convection in that area between midnight and 08Z,
tracking into our northern Plateau counties around 11Z. The HRRR and
RAP have slightly faster timing, but are in the ballpark with the
NAM, so will have likely PoPs entering from the NW early Friday
morning, speading into the Valley through the mid/late morning
hours. Instability during the morning hours appears too weak to
support any more than a very marginal severe threat. Behind the
morning activity along the convergence zone, dynamic forcing and
instability are weak so we may have a lull of little precip in the
afternoon, but will keep chance PoPs going across the area as deep
saturation will remain in place.

.LONG TERM...(Friday night through Wednesday)...
A fairly active weather pattern through the extended with some
timing differences between GFS and ECMWF.

For Friday night and Saturday, an upper level trough moves into the
southern Appalachians with a frontal boundary remaining north of the
area. Plenty of instabiity and moisture with MLCAPES near 1500 J/Kg
and PWs of 1.7-2.0 inches. Scattered to numerous convection is
expected with the main concern being strong/gusty winds, frequent
lightning, and torrential rains which could lead to localized runoff
issues.

For Sunday, the GFS keeps the frontal boundary north of the area
with continued scattered coverage of storms while the ECMWF pulls
front farther south. Will keep chances of storms going, especially
south and east.

For Monday and Tuesday, another unseasonably strong upper trough
moves out of the Plains toward the Ohio/Tennessee Valleys with
increasing coverage of storms. Again, MLCAPES of 1500-2000 J/Kg and
PWs approaching 2 inches will produce another round of strong/gusty
winds, frequent lighting and heavy rains/localized flooding issues.

For Wednesday and Thursday, drier air and more pleasant airmass for
August are expected as the upper trough swings east of the southern
Appalachians.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             73  85  72  84 /  30  60  60  70
Knoxville McGhee Tyson Airport, TN  72  84  71  83 /  30  60  60  70
Oak Ridge, TN                       72  83  71  82 /  40  70  70  70
Tri Cities Airport, TN              68  83  68  80 /  20  60  60  70

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...None.
TN...None.
VA...None.
&&

DGS/DH

Hazardous Weather Outlook
National Weather Service Morristown TN
402 AM EDT Thu Aug 16 2018

NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002-
005-006-008-170815-
Cherokee-Clay-Scott TN-Campbell-Claiborne-Hancock-Hawkins-
Sullivan-Johnson-Morgan-Anderson-Union-Grainger-Hamblen-
Northwest Cocke-Cocke Smoky Mountains-Northwest Greene-
Southeast Greene-Washington TN-Unicoi-Northwest Carter-
Southeast Carter-Roane-Loudon-Knox-Jefferson-NW Blount-
Blount Smoky Mountains-North Sevier-Sevier Smoky Mountains-
Sequatchie-Bledsoe-Rhea-Meigs-McMinn-Northwest Monroe-
Southeast Monroe-Marion-Hamilton-Bradley-West Polk-East Polk-Lee-
Wise-Scott-Russell-Washington-
402 AM EDT Thu Aug 16 2018 /302 AM CDT Thu Aug 16 2018/

This Hazardous Weather Outlook is for portions of Southwest North
Carolina...East Tennessee and Southwest Virginia.

.DAY ONE...Today and Tonight

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

There will be numerous showers and thunderstorms around Friday and
Saturday. A few of these storms may become strong to marginally
severe Friday, with damaging winds and large hail the primary
threats. In addition, very heavy rainfall will be possible at
times both Friday and especially Saturday which may lead to
localized flooding.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed Friday and for flooding reports
Saturday.

Special Weather Statement
National Weather Service Morristown TN
422 PM EDT THU AUG 16 2018

TNZ012-013-162100-
Scott TN-Campbell TN-
422 PM EDT THU AUG 16 2018

...SIGNIFICANT WEATHER ADVISORY FOR CAMPBELL AND SCOTT COUNTIES UNTIL
500 PM EDT...

At 421 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Zion Hill to 9 miles south of Helenwood.
Movement was east at 10 mph.

Half inch hail and winds in excess of 40 mph will be possible with
these storms.

Locations impacted include...
La Follette, Oneida, Jacksboro, Huntsville, Helenwood, Jellico,
Caryville, Winfield, Elk Valley, Smokey Junction, Honey Creek State
Park, Robbins, Ketchen, Indian Mountain State Park, White Oak, Royal
Blue, Norma, Elgin, Slick Rock and Cove Lake State Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3659 8398 3650 8396 3621 8435 3621 8439
      3617 8441 3616 8444 3621 8448 3623 8456
      3626 8457 3627 8460 3637 8470 3640 8466
      3642 8467 3660 8436
TIME...MOT...LOC 2021Z 275DEG 9KT 3657 8418 3628 8455

mjb

Special Weather Statement
National Weather Service Morristown TN
505 PM EDT THU AUG 16 2018

TNZ082>084-162145-
Rhea TN-Bledsoe TN-Meigs TN-
505 PM EDT THU AUG 16 2018

...SIGNIFICANT WEATHER ADVISORY FOR RHEA...NORTHEASTERN BLEDSOE AND
MEIGS COUNTIES UNTIL 545 PM EDT/445 PM CDT/...

At 505 PM EDT/405 PM CDT/, Doppler radar was tracking strong
thunderstorms along a line extending from near Spring City to near
Dayton. Movement was east at 20 mph.

Half inch hail and winds in excess of 40 mph will be possible with
these storms.

Locations impacted include...
Dayton, Decatur, Spring City, Graysville, Evensville, Peakland,
Stinging Fork Falls State Park, Old Washington, Grandview, Piney
Falls State Park, Ten Mile and Big Spring.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3544 8506 3543 8507 3549 8519 3575 8502
      3577 8494 3576 8492 3583 8480 3578 8474
      3576 8476 3575 8475 3574 8470 3572 8470
      3572 8468 3570 8467 3572 8465 3569 8462
      3566 8462 3534 8489
TIME...MOT...LOC 2105Z 279DEG 15KT 3576 8488 3547 8506

mjb