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TN valley heavy rain/flooding week of whenever


janetjanet998
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22 hours ago, dwagner88 said:

Western parts of middle TN have been hit with catastrophic flash flooding this morning. Dual pol estimates max out at over 17” of rain near McEwen TN. 

There is a tragedy unfolding in Humphreys county as we speak. 15 now confirmed dead, and dozens still missing. Many of the dead and missing are children.  Not a lot of media coverage on this, unfortunately. Some of the photos coming out of Waverly are just breathtaking. NWS Nashville recorded a record shattering 17.02 inches of rain in a 24 hour period. Some of the worst Flash Flooding I have ever seen.

 

https://www.radionwtn.com/2021/08/22/death-toll-climbs-many-missing-in-flood-emergency-area-first-responders-on-scene/

https://www.newschannel5.com/news/photos-heavy-rainfall-causes-severe-flooding-in-middle-tennessee#id33

 

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Take a look at the topography on Google Maps.  It's a small drainage area, a narrow valley about 1.5-2 miles wide that only extends 11 miles up creek from Waverly.  If I read correctly, 20 of the 21 deaths were in town.  Red roofs were public housing:

Unfortunately much of the town, including public housing, is in the floodplain right up against the creek.  This is the 4th major flood starting with 1984, but this was the worst.  Apparently few with flood insurance.  If the gov't is going to bail them out, then buy out property and force all rebuilding to be out of the 500-year floodplain.

A big part of the small town also got destroyed in the infamous explosion during clean up from a train derailment in 1978.

https://en.wikipedia.org/wiki/Waverly,_Tennessee,_tank_car_explosion

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Pretty much a worst case scenario for that area. I live about 50 miles west and have been down that way a few times, it is indeed a flood plain.  No way would I rebuild there. This area has a past history of flooding, but what made this exceptional was the massive amount of rain upstream. Residents keep referring to it as a tidal wave. 

 

 

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Some speculation that a massive debris buildup at the railroad and highway bridge 3 miles upstream of Waverly may have created that 'tidal wave' when it gave way.  The long RR fill parallel to the creek acted like a dam, given the relatively narrow opening of the concrete RR bridge.  This vid shows where it was overtopped and partially breached:

 

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  • 4 weeks later...

Areas around Tullahoma and Manchester has gotten around 10",about 6 " here so far,that is per RS estimation

 

Mesoscale Precipitation Discussion 0995
NWS Weather Prediction Center College Park MD
1146 AM EDT Mon Sep 20 2021

Areas affected...western/Middle Tennessee, northern Alabama,
northern Mississippi

Concerning...Heavy rainfall...Flash flooding likely

Valid 201545Z - 202200Z

Summary...Flash flooding is likely today as slow-moving convection
develops and moves over moist soils from prior rainfall.

Discussion...A cluster of slow-moving showers and thunderstorms
was observed over Middle Tennessee this morning.  Meanwhile,
additional showers and isolated thunderstorms were deepening to
the south/southwest acrosss portions of Alabama, Mississippi, and
western Tennessee.  The environment supporting the ongoing
convection was characterized by weak low-level confluence
(southerly 850mb flow across Middle Tennessee and
south-southwesterly 850mb flow across Mississippi), abundant
moisture (near 2 inch PW values), and increasing surface-based
instability (500-2000 J/kg MUCAPE - highest in Mississippi).  Weak
flow aloft was contributing to slow movement of ongoing
convection, which was already resulting in a few areas of 1"/hr
rainfall rates near the Nashville area.  Three-hour rainfall
totals around 2-3 inches have also been observed southwest of
Nashville Metro.

Although the ongoing convective cluster near Nashville may pose a
few localized flash flood issues this morning, a higher
flash-flood risk is possible later this afternoon as convective
coverage increases in tandem with the peak diurnal cycle.  Models
and high-resolution guidance suggest that the greatest coverage of
storms this afternoon will exist from northern Alabama into Middle
Tennessee.  These areas also have very low FFG values (generally
less than 1.5"/hr thresholds, with spots as low as 0.5"/hr). 
These thresholds should easily be exceeded with convection this
evening, especially given the slow storm motions and efficient
rainfall production expected.  Within the discussion area, the
greatest likelihood of flash flooding will exist where FFGs are
lowest (Middle Tennessee, Alabama, and far northwest Georgia). 
Farther west, flash flooding is still possible (Mississippi,
western Tennessee) given the favorable atmospheric conditions,
although FFGs are higher as this region hasn't experienced the
heavier antecedent rainfall as areas farther east.

Cook

ATTN...WFO...BMX...FFC...HUN...JAN...LMK...MEG...MRX...OHX...
PAH...

ATTN...RFC...LMRFC...OHRFC...SERFC...NWC...

 

 

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  • 2 weeks later...
  • 2 months later...

US National Weather Service Nashville Tennessee 

53m  · 

For Official Release:

New 24-hour Record Rainfall for the State of Tennessee

The State Climate Extremes Committee (SCEC) in coordination with the National Weather Service in Nashville, Tennessee and the Tennessee State Climate Office at Eastern Tennessee State University has confirmed that 20.73" of rain in 24 hours is a new State Record. This new 24-hour Precipitation Record occurred on August 21, 2021 at the McEwen, TN Wastewater Treatment Plant. It breaks a previous record of 13.60" in Milan, TN on September 13, 1982.

The SCEC carefully reviewed the meteorology and equipment conditions for this event. A unanimous vote of 5-0 determined that the 20.73" observed in McEwen, TN on August 21, 2021 was valid and constituted a State Record for 24-hour total precipitation. Catastrophic flooding occurred in Waverly, TN and surrounding areas as a result of this record rainfall.

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  • 1 month later...

I'm going to resurrect this thread for heavy rain expected next week. Saves the winter thread for any threats of winter precip.

Somewhat stationary front will set up over our Region. Several impulses will come out early to midweek. Mostly above freezing, we can focus on flooding threats. Then the main energy brings what could be more severe weather late week. 

QPF moves with the tracks of the waves. Totals should be robust. Pattern makes it hard to dodge the heavy rain, unless the frontal position shifts markedly.

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5 minutes ago, Holston_River_Rambler said:

GFS seems to be trending a bit north with the worst rainfall this week. 

WPC seems to like that solution:

c9vHMEd.png

 

Looks pretty much like the NBM, but hedging on the higher side. Seems reasonable to me. Will be interesting to see exactly where the firehose sets up. 

Does not look good any way you slice it honestly; essentially all of the rain we got last week ran off; any amount of rain will not be  good for my area, north of Nashville

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1 minute ago, Weathertree2 said:

Does not look good any way you slice it honestly; essentially all of the rain we got last week ran off; any amount of rain will not be  good for my area, north of Nashville

Euro was still a little bit south with the firehouse, so yeah somebody in the TN Valley watershed is going to get it. Hopefully nothing like the 14" amounts come to fruition anywhere. 

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Hydrologic Outlook
National Weather Service Nashville TN
516 AM CST Sun Feb 20 2022

...Flooding Possible Washingtons Birthday through Friday...

Moderate to heavy rainfall will impact Middle Tennessee Washingtons
Birthday through Friday afternoon as two distinct weather systems
move across mid state region. As of this time, total rainfall
amounts will range from around 3 inches southwest to approaching
6 inches northwest through Friday afternoon. Currently corridor
of heaviest rainfall amounts look to be across northern portions
of mid state region as Tuesday progresses. There may be a brief lull
in rainfall on Wednesday. However, another round of heavy rainfall
is expected to arrive Wednesday Night and last through at least
Thursday night, with heaviest rainfall amounts expected Thursday
night.

Soil moisture continues to remain relative high especially across
northern portions of mid state region. Due to this rainfall
potentially causing additional rises on rivers, several rivers
across area could reach action if not flood stage as week
progresses. Flash flooding could also be possible across mid state
region.

While the exact location of higher rainfall amounts not yet totally
certain, it is imperative that if you have interest near areas that
are known to flood, that you pay close attention to rainfall
forecasts over the upcoming week. Updated information concerning
this rainfall event will be provided during morning hours on
Washingtons Birthday.
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53 minutes ago, jaxjagman said:
Hydrologic Outlook
National Weather Service Nashville TN
516 AM CST Sun Feb 20 2022

...Flooding Possible Washingtons Birthday through Friday...

Moderate to heavy rainfall will impact Middle Tennessee Washingtons
Birthday through Friday afternoon as two distinct weather systems
move across mid state region. As of this time, total rainfall
amounts will range from around 3 inches southwest to approaching
6 inches northwest through Friday afternoon. Currently corridor
of heaviest rainfall amounts look to be across northern portions
of mid state region as Tuesday progresses. There may be a brief lull
in rainfall on Wednesday. However, another round of heavy rainfall
is expected to arrive Wednesday Night and last through at least
Thursday night, with heaviest rainfall amounts expected Thursday
night.

Soil moisture continues to remain relative high especially across
northern portions of mid state region. Due to this rainfall
potentially causing additional rises on rivers, several rivers
across area could reach action if not flood stage as week
progresses. Flash flooding could also be possible across mid state
region.

While the exact location of higher rainfall amounts not yet totally
certain, it is imperative that if you have interest near areas that
are known to flood, that you pay close attention to rainfall
forecasts over the upcoming week. Updated information concerning
this rainfall event will be provided during morning hours on
Washingtons Birthday.

Definitely will be some river flooding along with certain areas this week.  My back yard will be a small pond & swamp for sure. 

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37 minutes ago, Matthew70 said:

I saw where OHX NWS only has 3-4” now for area.  That’s not nearly as much as first thought.  Guess models have backed off a lot. 

Little more convection shown this afternoon,most of us should see a fllood watch it seems right now

 

 
< Day 2 Outlook
 
WPC Day 3 Excessive Rainfall Outlook
Risk of 1 to 6 hour rainfall exceeding flash flood guidance at a point
 
Updated: 2027 UTC Sun Feb 20, 2022
Valid: 12 UTC Feb 22, 2022 - 12 UTC Feb 23, 2022
 
Day 3 Excessive Rainfall Forecast
 
Forecast Discussion
 
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
340 PM EST Sun Feb 20 2022
 
Day 3
Valid 12Z Tue Feb 22 2022 - 12Z Wed Feb 23 2022 

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF 
THE MID-MISSISSIPPI, TENNESSEE AND OHIO VALLEYS...

...Mississippi and Ohio River Valleys...
Showers and thunderstorms should be ongoing across 
Missouri/Arkansas into the Lower Ohio Valley at the start of the 
period, ahead of a shortwave trough tracking from the Central 
Plains into the Upper Midwest. While instability is expected to be 
weak across the region Tuesday morning, standardized precipitable 
water (PW) anomalies of +3 will be present along with confluent 
850 mb flow of 40-60 kt. Areas of WSW to ENE training are likely 
early in the period with rainfall totals of 1-2 inches in an hour 
atop a region of the nation that has high soil moisture values 
(over 90th percentiles for 10-40 cm depth) and low flash flood 
guidance values. Weakening of forcing and moisture values through 
00Z Wednesday should transition the event to more of a longer 
duration and less intense rainfall for the latter half of the 
outlook period.

Model guidance was mixed with placement, but the 12Z NAM appeared 
too heavy and north with its axis of QPF. Better deterministic and 
ensemble placement for 2-4 inches of rain was located closer to 
the Ohio River, with magnitude of rainfall and probabilities 
lowering with eastward extent into Ohio, West Virginia and 
southwestern Pennsylvania. However, flash flood guidance values of 
only 1-2 inches in 3 and 6 hours was present across the central 
Appalachians, and these values might be exceeded despite the lower 
rainfall intensity later in the period.

...Lower Mississippi to Tennessee Valleys...
As a surface low tracks northeastward from the Midwest into New 
England Tuesday/Tuesday night, a southwestward trailing cold front 
will extend across the Lower Ohio Valley to Southern Plains. 
Moisture return ahead of the cold front combined with daytime 
heating should allow for increasing instability from the Lower 
Mississippi Valley into Tennessee, Mississippi and Alabama. 
Southwest to northeast oriented convergence, parallel to the 
deeper-layer mean flow, will be in place across the southern U.S. 
which should support an axis of training convection, mainly from 
21Z Tuesday through 12Z Wednesday. Rainfall rates of 1-2 inches in 
an hour are likely given the moisture and instability in place, 
and training could support 2-4 inches of rain. Model agreement on 
this axis was good on its occurrence but not as good with 
placement. Therefore, the existing Slight Risk area inherited from 
continuity was expanded a bit into southwestern Tennessee and 
northeastern Mississippi, in accord with the latest model spread. 
With the increasing signal for 3-4+ inches, there may be a need to 
upgrade to a Moderate Risk as the event gets closer, but 
confidence in its placement is too low at this time.  

Otto
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