Alert archive / Tennessee / Severe Thunderstorm Warnings in 2020

Severe Thunderstorm Warning 129, NWS Morristown, TN

July 24, 2020Polk County, Tennessee; Cherokee County, North Carolina

NWS Morristown, TN issued this severe thunderstorm warning at Jul 24, 2020, 4:40 PM EDT for Polk County, Tennessee; Cherokee County, North Carolina. It was in force for 50 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Jul 24, 2020, 4:40 PM EDT (20:40 UTC)
Expired
Jul 24, 2020, 5:30 PM EDT
In force
50 min
Issued by
NWS Morristown, TN
Area
Storm-based polygon
Hail
0.75 in
Wind
60.0 mph

Counties Cherokee County, NC, Polk County, TN

The radar

The Knoxville radar (KMRX), 141 km from the middle of the area, began a volume at 20:44 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Peachtre/Fal Fld, GA (KFFC), launched 12:00Z, 8.7 hours before the alert went out and 196 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Peachtre/Fal Fld, GA at 12:00Z on 2020-07-24Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 557 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Peachtre/Fal Fld, GA at 12:00Z on 2020-07-24The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -36 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
557 J/kg
Mixed-layer CIN
-42 J/kg
Mixed-layer LCL
665 m above ground
0-6 km bulk shear
2 kt
0-1 km storm-relative helicity
-36 m²/s²
0-3 km storm-relative helicity
-36 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Morristown, TN wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 24, 3:17 PM EDT, 1 hour 23 minutes earlier.

Area forecast discussion, Jul 24, 3:17 PM EDT, 1 hour 23 minutes before
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
317 PM EDT Fri Jul 24 2020

.SHORT TERM (Tonight and Saturday)...
Convection will decrease in coverage after loss of daytime heating
and the associated stabilizing of the atmosphere. Expect clearing
conditions overnight with fog near areas that received rainfall.

Upper ridging remains anchored across the middle of the nation
with a 594-595dam upper 500mb ridge centered across Kansas and
Missouri producing weak northerly flow across the region. Low
level SE flow between a ridge across the Mid- Atlantic and
Tropical Storm Hanna near south Texas. This will continue to
produce an area of weak 850mb-700mb convergence across southern
and central portions of the forecast area. Synoptic forcing is
very weak on Saturday allowing mesoscale factors to be the primary
contributors to convective development and organization. With
daytime heating, instability will be on the increase with NAM
soundings showing MLCAPE between 1500 to 2500 J/Kg by early
afternoon. With differential heating along the higher terrain,
thunderstorm initiation is expected by midday. Pulse convection
will be the primary mode with deep layer shear less than 10 kt. In
addition, DCAPE values will be higher on Saturday which may
enhance the risk of isolated microbursts with descending
thunderstorm cores. HREF guidance shows low-level moisture will
remain high with PW values across the southern half of the
forecast area between 1.8 to 2.0 inches contributing to locally
heavy rainfall and isolated flooding. Convective coverage will
follow a diurnal curve with a decrease in activity during the late
evening and early overnight hours.

JB

.LONG TERM (Saturday night through Friday night)...
Through the weekend, an elongated ridge of high pressure aloft
will stretch from the southern plains east through the mid
Atlantic. A northern stream shortwave will move through southern
Canada and the northern plains. Typical summertime weather will
result with afternoon scattered showers and thunderstorms
expected. Temperatures near to slightly above normal can be
expected Saturday night and Sunday. On Monday, the northern stream
shortwave drops out of southern Canada and into the Great Lakes
with an attendant cold front moving through the Ohio valley. Lower
heights and southerly low level flow will enhance precipitation
chances Monday and Monday night before the cold front approaches
on Tuesday. Increased cloud cover and precipitation should keep
temperatures slightly cooler on Monday.

Frontal passage occurs on Tuesday and Tuesday night. Upper
disturbance ejects northeast allowing the cold front to weaken as it
moves through the region. Coverage of showers and thunderstorms
should pick up on Tuesday with this period likely having the highest
PoPs. Start to see model diverge regarding the strength of the ridge
across the southeast. The ECMWF seems to break the ridge down more
with a more amplified pattern while the GFS keeps the ridge,
although still weak. However, guidance does agree that northwest
flow will setup across the Tennessee valley toward the end of the
period with continued chances of showers and thunderstorms and near
normal temperatures.

Diegan

&&

.AVIATION...
18Z TAF DISCUSSION.

Scattered showers and thunderstorms are expected this afternoon
with the highest coverage forecast to be near TYS and CHA. This
will result in tempo MVFR, and potential brief IFR, conditions.
Convection will decrease after sunset with drier conditions
overnight. With some clearing, expect patchy fog to develop.
Highest confidence in MVFR or lower vis is at TRI where guidance
is in good agreement with MVFR or IFR fog development late
tonight and early Saturday morning.

JB

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             73  92  72  91  73 /  30  40  20  50  20
Knoxville McGhee Tyson Airport, TN  71  90  71  91  72 /  20  30  20  50  20
Oak Ridge, TN                       71  90  70  91  71 /  20  40  20  50  20
Tri Cities Airport, TN              67  89  67  89  68 /  30  30  20  50  20

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
Hazardous weather outlook, Jul 24, 3:19 PM EDT, 1 hour 21 minutes before
Hazardous Weather Outlook
National Weather Service Morristown TN
319 PM EDT Fri Jul 24 2020

NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002-
005-006-008-251930-
Cherokee-Clay-Scott-Campbell-Claiborne-Hancock-Hawkins-Sullivan-
Johnson-Morgan-Anderson-Union-Grainger-Hamblen-Northwest Cocke-
Cocke Smoky Mountains-Northwest Greene-Southeast Greene-
Washington-Unicoi-Northwest Carter-Southeast Carter-Roane-Loudon-
Knox-Jefferson-Northwest 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-Russell-
319 PM EDT Fri Jul 24 2020 /219 PM CDT Fri Jul 24 2020/

This Hazardous Weather Outlook is for portions of southwest North
Carolina...east Tennessee and southwest Virginia.

.DAY ONE...This Afternoon and Tonight

Scattered showers and thunderstorms are expected this afternoon
and early evening with a few strong to marginally severe storms
possible. Isolated damaging wind gusts and brief heavy rainfall
are the main concerns.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter reports of severe weather or flooding are encouraged.
Please relay any information about severe weather to the NWS while
following local, state, and CDC guidelines.

In the hours before

Special weather statement, Jul 24, 3:44 PM EDT, 56 minutes before
Special Weather Statement
National Weather Service Morristown TN
344 PM EDT Fri Jul 24 2020

TNZ013-036-242030-
Anderson TN-Campbell TN-
344 PM EDT Fri Jul 24 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN ANDERSON AND
SOUTHERN CAMPBELL COUNTIES UNTIL 430 PM EDT...

At 344 PM EDT, Doppler radar was tracking a strong thunderstorm 8
miles west of Jacksboro, or 12 miles west of La Follette, moving
southeast at 15 mph.

Winds in excess of 40 mph will be possible with this storm.

Locations impacted include...
Clinton, Jacksboro, Caryville, Rocky Top, Norris, Norris Dam State
Park, Disney, Cove Lake State Park and Andersonville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3628 8400 3627 8401 3621 8397 3608 8408
      3608 8409 3606 8409 3604 8411 3624 8437
      3625 8437 3628 8436 3628 8433 3631 8433
      3636 8430
TIME...MOT...LOC 1944Z 302DEG 14KT 3630 8434

Diegan
Special weather statement, Jul 24, 3:58 PM EDT, 42 minutes before
Special Weather Statement
National Weather Service Morristown TN
358 PM EDT Fri Jul 24 2020

TNZ036-069-242045-
Anderson TN-Knox TN-
358 PM EDT Fri Jul 24 2020

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL KNOX AND SOUTHEASTERN
ANDERSON COUNTIES UNTIL 445 PM EDT...

At 358 PM EDT, Doppler radar was tracking a strong thunderstorm over
Clinton, moving southeast at 15 mph.

Winds in excess of 45 mph will be possible with this storm.

Locations impacted include...
Knoxville, Oak Ridge, Clinton, Halls, Norris, Lake Forest,
Maloneyville, Mascot, Bearden and Powell.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3604 8421 3621 8411 3608 8372 3585 8388
TIME...MOT...LOC 1958Z 299DEG 13KT 3610 8408

DH
Special weather statement, Jul 24, 4:00 PM EDT, 40 minutes before
Special Weather Statement
National Weather Service Morristown TN
400 PM EDT Fri Jul 24 2020

NCZ060-TNZ101-102-242045-
Cherokee NC-West Polk TN-East Polk TN-
400 PM EDT Fri Jul 24 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN CHEROKEE AND
SOUTHEASTERN POLK COUNTIES UNTIL 445 PM EDT...

At 400 PM EDT, Doppler radar was tracking a strong thunderstorm over
Ducktown, moving east at 20 mph.

Winds in excess of 45 mph will be possible with this storm.

Locations impacted include...
Ducktown, William L. Davenport Refuge, Violet, Big Frog Mountain,
Turtletown, Hot House and Copperhill.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3507 8459 3522 8435 3521 8435 3521 8434
      3522 8432 3521 8429 3522 8429 3525 8425
      3504 8410 3499 8424 3499 8453
TIME...MOT...LOC 2000Z 248DEG 15KT 3502 8443

DH
Special weather statement, Jul 24, 4:07 PM EDT, 33 minutes before
Special Weather Statement
National Weather Service Morristown TN
407 PM EDT Fri Jul 24 2020

TNZ014-015-VAZ001-242100-
Claiborne TN-Hancock TN-Lee VA-
407 PM EDT Fri Jul 24 2020

...SIGNIFICANT WEATHER ADVISORY FOR EASTERN CLAIBORNE...WESTERN
HANCOCK AND SOUTHWESTERN LEE COUNTIES UNTIL 500 PM EDT...

At 407 PM EDT, Doppler radar was tracking a strong thunderstorm near
Harrogate, or 10 miles southeast of Middlesboro, moving southeast at
10 mph.

Wind gusts up to 50 mph will be possible with this storm.

Locations impacted include...
New Tazewell, Tazewell, Harrogate, Lone Mountain, Howard Quarter,
Cumberland Gap, Arthur, Powell River Preserve and Ewing.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3666 8346 3645 8330 3641 8339 3642 8343
      3639 8345 3638 8350 3637 8350 3637 8351
      3636 8352 3636 8353 3635 8354 3637 8356
      3636 8361 3658 8377 3658 8369 3662 8365
      3664 8361 3667 8350
TIME...MOT...LOC 2007Z 329DEG 10KT 3655 8354

DH
Local storm report, Jul 24, 4:19 PM EDT, 21 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MORRISTOWN TN
419 PM EDT FRI JUL 24 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0419 PM     TSTM WND DMG     2 E DUFF                36.45N 84.03W
07/24/2020                   CAMPBELL           TN   PUBLIC

            SEVERAL TREES DOWN.

&&

DH
Local storm report, Jul 24, 4:37 PM EDT, 3 minutes before
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The office that day

Everything else NWS Morristown, TN issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 24, 12:11 PM EDTAreal Flood AdvisoryMRXSevier2 hr
Jul 24, 1:34 PM EDTSpecial Weather StatementMRXBlount41 min
Jul 24, 2:05 PM EDTSpecial Weather StatementMRXMorgan40 min
Jul 24, 2:10 PM EDTSpecial Weather StatementMRXScott50 min
Jul 24, 2:45 PM EDTSpecial Weather StatementMRXMorgan45 min
Jul 24, 2:53 PM EDTSpecial Weather StatementMRXMorgan52 min
Jul 24, 3:05 PM EDTAreal Flood AdvisoryMRXMorgan, Scott115 min
Jul 24, 3:11 PM EDTSpecial Weather StatementMRXBlount49 min
Jul 24, 3:18 PM EDTSpecial Weather StatementMRXAnderson42 min
Jul 24, 3:25 PM EDTSevere Thunderstorm WarningMRXScott20 min
Jul 24, 3:27 PM EDTSpecial Weather StatementMRXCampbell48 min
Jul 24, 3:31 PM EDTSpecial Weather StatementMRXHancock44 min
Jul 24, 3:44 PM EDTSpecial Weather StatementMRXAnderson46 min
Jul 24, 3:49 PM EDTAreal Flood AdvisoryMRXAnderson, Campbell, Scott116 min
Jul 24, 3:49 PM EDTSevere Thunderstorm WarningMRXCampbell, Claiborne, Union56 min
Jul 24, 3:58 PM EDTSpecial Weather StatementMRXKnox47 min
Jul 24, 4:00 PM EDTSpecial Weather StatementMRXPolk45 min
Jul 24, 4:07 PM EDTSpecial Weather StatementMRXClaiborne53 min
Jul 24, 4:12 PM EDTSevere Thunderstorm WarningMRXClaiborne, Hancock48 min
Jul 24, 4:15 PM EDTSevere Thunderstorm WarningMRXAnderson, Knox, Union45 min
Jul 24, 4:32 PM EDTSevere Thunderstorm WarningMRXHancock, Hawkins43 min
Jul 24, 4:34 PM EDTSevere Thunderstorm WarningMRXClaiborne, Grainger, Jefferson, Union56 min
Jul 24, 4:56 PM EDTSevere Thunderstorm WarningMRXBlount, Jefferson, Knox, Sevier52 min
Jul 24, 4:59 PM EDTSevere Thunderstorm WarningMRXClaiborne, Grainger, Hamblen, Hancock, Hawkins61 min
Jul 24, 5:09 PM EDTSevere Thunderstorm WarningMRXHancock, Hawkins41 min
Jul 24, 5:26 PM EDTSevere Thunderstorm WarningMRXMonroe, Polk25 min
Jul 24, 5:35 PM EDTSevere Thunderstorm WarningMRXCocke, Greene, Hamblen, Hawkins, Jefferson30 min
Jul 24, 5:59 PM EDTSpecial Weather StatementMRXMonroe46 min
Jul 24, 6:06 PM EDTSpecial Weather StatementMRXPolk24 min
Jul 24, 6:08 PM EDTSevere Thunderstorm WarningMRXMonroe37 min
Jul 24, 6:12 PM EDTSevere Thunderstorm WarningMRXHawkins, Sullivan63 min
Jul 24, 6:44 PM EDTSevere Thunderstorm WarningMRXCarter, Johnson, Sullivan, Washington61 min
Jul 24, 7:45 PM EDTSpecial Weather StatementMRXRhea45 min
Jul 24, 4:48 PM EDTSpecial Weather StatementMRXRussell57 min
Jul 24, 5:16 PM EDTSevere Thunderstorm WarningMRXRussell, Scott, Washington, Wise59 min
Jul 24, 6:21 PM EDTAreal Flood AdvisoryMRXRussell, Scott, Wise3 hr
Jul 24, 1:09 PM EDTSpecial Weather StatementMRXClay51 min
Jul 24, 2:06 PM EDTAreal Flood AdvisoryMRXCherokee, Clay3 hr

Nearby

Severe Thunderstorm Warnings in Tennessee, 2020Severe Thunderstorm Warnings in North Carolina, 2020Every severe thunderstorm warning in 2020

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.