Special Weather Statement, NWS Nashville, TN

Area Forecast Discussion
National Weather Service Nashville TN
229 PM CDT Sun May 20 2018

.DISCUSSION...

Active weather pattern remains for the forecast period over the
mid state, with some breaks during the overnight hours and
towards the end of the work week. Chances for showers and
thunderstorms plague most of the forecast, and even look to
continue next weekend and the beginning of next week.

Today is looking similar to yesterday, with daytime heating
breaking out cu over the area. MUCAPE values are on the rise, with
most of the area looking to see between 1000-2500 J/kg. However,
like most days so far in May, deep layer shear is very weak and
similar to a summer pattern. This weak shear is also evident with
weak storm motion, which isn't doing much to help out developing
cu and showers early this afternoon. As daytime heating continues,
additional showers and thunderstorms look to develop, and possibly
carry over from western TN similar to last night. A few CAM's like
the HRRR and WRF-ARW suggest scattered thunderstorms will develop
near the TN River late this afternoon and progress slowly towards
I-65, before dissipating rapidly around 9 PM likely due to the
loss of diurnal support. CAM's also suggested the developing
showers and storms in the southeast part of the area, and are
currently popping up early this afternoon. Kept chance pops across
the area for the afternoon, and carrying over into the evening
around and east of I-65. A few showers and possibly a thunderstorm
may continue into the early morning hours as well. Any stronger
cells that develop may drop some hail and produce some gusty
winds as well.

For Monday, upper ridging slowly begins to slide eastward, and the
Plains trough moves towards the Great Lakes region as an upper
closed low weakens over the Gulf Coast states. This should keep
southerly flow present in the low levels, and bring more moisture
into the area. PWAT values climb above 1.5 inches for most of the
mid state and even get close to 2 inches for parts of the
northwest. MUCAPE values climb again in the afternoon, with the
higher values >2000 J/kg holding strong in the northwest part of
the CWA. With storm motions even slower than today with the
absence of any strong upper wave, and weak shear as well, showers
and thunderstorms that develop in the afternoon will be able to
produce heavy rainfall in a short timeframe. Any localized areas
that receive training of storms or any stagnant heavy rain from
slow storm progression may receive flooding, in addition to any
gusty winds and small hail with the stronger cores.

Tuesday and Wednesday look similar, with the upper flow pattern
becoming more zonal ahead of the next ridge. Kept schc/chc pops in
for now as abundant moisture and diurnal showers and storms will
be possible. Wednesday night through Friday morning looks to be
the driest period in the forecast as the upper ridge moves
overhead. Similar to the previous few days went ahead and kept in
mention of schc pops for the isolated shower/storm that could pop
up in the afternoon, mainly south of I-40.

A tropical low tries to develop over the Gulf Coast, and the
GFS/ECMWF begin to show different solutions at this point. Both
models agree on keeping the mid state wet through the weekend, and
have a strong trough dig southward from the Plains/Midwest
Saturday through early Tuesday. This will keep south/southwesterly
flow in the low levels, which will keep moisture advection over
the region and thus chances for showers and storms in the
forecast. Greatest chances will remain during the afternoon hours,
again largely due to diurnal support. Looking further past the end
of the forecast Monday shows the upper trough closing off over the
Gulf Coast states, which unfortunately looks to continue rain
chances through at least Wednesday next week.

&&

.AVIATION...
18Z TAF DISCUSSION.

CKV/BNA/MQY/CSV...Overall VFR conditions expected thru 21/18Z.
With convection developing S of terminals presently, will only
mention VCTS potential thru 21/01Z. This activity could develop
further north across the mid state too thru 21/01z although
air mass north of present convection area more worked over.
Current activity most likely based on initiation from an outflow
boundary for yesterday late afternoon/evenings convection. Per
this reasoning, will only mention VCTS at terminals thru afternoon
hrs with best chance per orographic lifting influences CSV. Per
the diurnal driven nature of this convection, most convection
should dissipate by 21/01Z. Maybe some MVFR fog 21/08Z-21/16Z CSV
per clearing skies, light to calm winds, and best overall potential
for low level moisture condensation with rainfall currently
in this area. Models not depicting as well weak shortwave passage
approaching NW portions of mid state around 21/12Z as previously,
but can not totally rule out, and thus will shift time scale
impacts for terminals by a couple of hrs or two forward. Per
diurnal impacts kicking in also, along with weakness in overall
upper ridging dynamics expected, expect at least VCTS potential
at all terminals by 21/16Z.

&&

.PRELIMINARY POINT TEMPS/POPS...
Nashville      69  86  67  86  68 /  20  50  20  40  20
Clarksville    67  83  66  84  65 /  40  50  40  40  10
Crossville     63  79  62  78  62 /  20  60  30  50  20
Columbia       66  84  65  84  65 /  30  50  20  40  20
Lawrenceburg   65  83  63  84  64 /  40  50  20  40  20
Waverly        67  83  65  84  66 /  50  50  20  40  20

&&

.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

DISCUSSION......Barnwell
AVIATION........31

Hazardous Weather Outlook...UPDATED
National Weather Service Nashville TN
912 AM CDT Sun May 20 2018

TNZ005>011-023>034-056>066-075-077>080-093>095-211000-
Stewart-Montgomery-Robertson-Sumner-Macon-Clay-Pickett-Houston-
Humphreys-Dickson-Cheatham-Davidson-Wilson-Trousdale-Smith-
Jackson-Putnam-Overton-Fentress-Perry-Hickman-Lewis-Williamson-
Maury-Marshall-Rutherford-Cannon-De Kalb-White-Cumberland-Bedford-
Coffee-Warren-Grundy-Van Buren-Wayne-Lawrence-Giles-
912 AM CDT Sun May 20 2018

This Hazardous Weather Outlook is for portions of Middle
Tennessee.

.DAY ONE...Today and Tonight

Isolated to scattered thunderstorms are forecast for today. A few
of these thunderstorms, especially for locations north of I-40 and
along and west of I-65, by the afternoon through early evening
hours, may become strong, producing brief heavy rainfall, gusty
winds, and possibly localized flooding.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

Scattered to numerous thunderstorms are forecast for Monday. A few
of these thunderstorms may become strong, producing brief heavy
rainfall, gusty winds, and possibly localized flooding.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and again on
Monday.

Spotter Thunderstorm Reporting Criteria...
Tornado
Funnel Cloud
Hail >= 1/2 inch
Winds > 50 MPH (Measured)
Structural Damage
Trees or Power Lines Down

31

Special Weather Statement
National Weather Service Nashville TN
129 PM CDT SUN MAY 20 2018

TNZ061-201900-
Marshall TN-
129 PM CDT SUN MAY 20 2018

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL MARSHALL COUNTY UNTIL 200
PM CDT...

At 129 PM CDT, Doppler radar was tracking a strong thunderstorm near
Lewisburg, moving north at 25 mph.

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

Locations impacted include...
Lewisburg, Farmington and Belfast.

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.

&&

LAT...LON 3536 8682 3556 8683 3559 8675 3559 8666
      3546 8667 3537 8665
TIME...MOT...LOC 1829Z 175DEG 22KT 3544 8673

31

Special Weather Statement
National Weather Service Nashville TN
206 PM CDT SUN MAY 20 2018

TNZ058-093-201930-
Wayne TN-Lewis TN-
206 PM CDT SUN MAY 20 2018

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN LEWIS AND
NORTHEASTERN WAYNE COUNTIES UNTIL 230 PM CDT...

At 205 PM CDT, Doppler radar was tracking a strong thunderstorm 9
miles northeast of Waynesboro, moving west at 10 mph.

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

Locations impacted include...
Waynesboro.

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.

&&

LAT...LON 3543 8782 3546 8756 3540 8753 3540 8757
      3534 8758 3528 8778
TIME...MOT...LOC 1905Z 081DEG 8KT 3540 8761

31

Special Weather Statement
National Weather Service Nashville TN
210 PM CDT SUN MAY 20 2018

TNZ077-079-202000-
Coffee TN-Grundy TN-
210 PM CDT SUN MAY 20 2018

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN COFFEE AND WESTERN
GRUNDY COUNTIES UNTIL 300 PM CDT...

At 210 PM CDT, Doppler radar was tracking a strong thunderstorm 8
miles northwest of Tracy City, or 15 miles southeast of Manchester,
moving northwest at 5 mph.

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

Locations impacted include...
Monteagle, Altamont, Coalmont, Pelham and Hillsboro.

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.

&&

LAT...LON 3526 8590 3529 8592 3529 8593 3530 8594
      3531 8594 3531 8595 3530 8596 3531 8596
      3532 8599 3537 8608 3553 8587 3552 8584
      3551 8582 3551 8581 3536 8570 3524 8586
TIME...MOT...LOC 1910Z 135DEG 5KT 3536 8584

31

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NASHVILLE TN
247 PM CDT SUN MAY 20 2018

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

0218 PM     TSTM WND DMG     10 SW ALTAMONT          35.33N  85.85W
05/20/2018                   GRUNDY             TN   911 CALL CENTER

            CALLED GRUNDY COUNTY DISPATCH. SEVERAL TREES REPORTED
            DOWNED ACROSS WESTERN PORTIONS OF THE COUNTY WEST OF
            COALMONT NEAR THE GRUNDY/COFFEE COUNTY LINE.

&&

EVENT NUMBER OHX1800041

31

Special Weather Statement
National Weather Service Nashville TN
259 PM CDT SUN MAY 20 2018

TNZ060-061-095-202030-
Maury TN-Giles TN-Marshall TN-
259 PM CDT SUN MAY 20 2018

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL MARSHALL...SOUTHEASTERN
MAURY AND NORTH CENTRAL GILES COUNTIES UNTIL 330 PM CDT...

At 259 PM CDT, Doppler radar was tracking a strong thunderstorm 12
miles southeast of Mount Pleasant, or 13 miles west of Lewisburg,
moving northeast at 40 mph.

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

Locations impacted include...
Columbia, Lewisburg, Lynnville, I-65 East Of Columbia and Culleoka.

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.

&&

LAT...LON 3531 8699 3542 8716 3571 8694 3557 8666
TIME...MOT...LOC 1959Z 217DEG 36KT 3543 8702

31

Special Weather Statement
National Weather Service Nashville TN
303 PM CDT SUN MAY 20 2018

TNZ095-202015-
Giles TN-
303 PM CDT SUN MAY 20 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN GILES COUNTY UNTIL
315 PM CDT...

At 303 PM CDT, Doppler radar was tracking a strong thunderstorm 12
miles north of Pulaski, moving northeast at 10 mph.

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

Locations impacted include...
Lynnville.

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.

&&

LAT...LON 3535 8722 3537 8722 3543 8714 3542 8705
      3537 8696 3525 8705
TIME...MOT...LOC 2003Z 206DEG 7KT 3537 8710

31