March 13-14 Iowa/Dakotas "Bomb Cyclone"

[stockwiz]

With a large snowpack in some areas including where I live combined with rainfall estimates in the 2-3 inch range in parts of South Dakota along with snowfall estimates in the 18-24 inch range in the Black Hills and Badlands, this is certainly a powerful storm. They are saying it has the pressure of a catagory 2 hurricane on land.

 

https://www.washingtonpost.com/weather/2019/03/13/historic-bomb-cyclone-sets-off-severe-storms-flooding-dangerous-blizzard-plains-midwest/?noredirect=on&utm_term=.bd80ce322c2e

 

So far I've lucked out and remained in a relative dry area... the heavier rain is still to the west of me. With 25 inches of snowpack and no storm sewer in my small town, I really don't want to see 3 inches or rain. :p The entire eastern half of Nebraska is currently under flood warnings and that's likely to spread.

[batteen]

I'm up by Faulkton (Cresbard area if you know where that is) and I'm watching it creep closer on radar.  I'm right in the uncertainty zone.  Will I get more ice or snow??  Very interested to see how this all shakes out.

[raindancewx]

I expect pictures from this event from this system. For this area of the country it's comparable in severity to the blizzard of 1993. NM alone had tornadoes, hail, heavy snow, heavy rain, record moisture and low pressure, plus winds gusting to 70-100 mph.

[batteen]

A friend tells me they had close to 2" of rain down by Huron and it's flooding bad in places.  Very little if any freezing rain so far at my location.  Mostly snow with a bit of sleet.  3" already.  So that will tip us toward the higher end of snow predictions.  We already have had a lot of snow and wind this year, so the drifting situation is already extreme.  My backyard is blown in 4 to 6 feet deep with one spot up to 8 feet maybe higher.  All of the tree belts are blown in 6-8 ft deep or better.  The ditches are completely full, if you didn't know they were there before you'd never be able to tell.  This is just from the snow up to this point, before this storm.

[jojo762]

NWS Topeka typed up one of the longer and more detailed mesoscale discussions I can recall ever seeing earlier this afternoon regarding the conditional severe risk across NC KS/SC NE... Interesting that they went into such detail considering the marginal and conditional nature of the threat. 

 

FWIW... This was written by former SPC forecaster Ariel Cohen who now works at the National Weather Service in Topeka. Hope to see more discussions like this from him later in the severe season.

Quote

.MESOSCALE DISCUSSION...
Issued at 129 PM CDT Wed Mar 13 2019

Conditional potential for severe convection:

A conditional risk for isolated severe thunderstorms will exist
across across north-central Kansas from 2:30 PM CDT until 6:00 PM
CDT for locations along and north of a line from Concordia to
Manhattan. This includes the conditional potential for low-topped
mini-supercell storms to produce hail to quarter size, damaging wind
gusts, and perhaps a tornado. Late-morning subjective surface
analysis indicates particularly deep / 971-mb surface low pressure
centered near Lamar, Colorado. The expansive cyclonic-flow
envelope surrounding this low extends throughout the entire NWS
Topeka CWA and much of the Great Plains. A shield of precipitation
associated with a preceding surge of warm-conveyor moisture
transport and warm advection -- antecedently convectively
enhanced -- coils around the eastern semicircle of the deeper
extratropical cyclone centered over the central High Plains. This
shield of precipitation is quickly departing the area to the
northeast and east. Rapid erosion of precipitation on the back
edge of the shield has been the result of an impinging dry slot
phasing with the subsident branch of the precipitation system`s
vertical circulation.

Boundary-layer theta-e deficits accompanying the precipitation
shield are reinforcing a differential-heating zone arching from
the Concordia-Belleville area toward Emporia. This shallow
baroclinic zone, reinforced by clouds and precipitation to its
north, will continue advancing northeastward/northward in tandem
with the motion of the precipitation shield and overtaking
midlevel dry slot. On the warm side of the differential heating
zone, temperatures have risen into the upper 50s -- breaching 60F
in some areas -- across central Kansas. Baroclinic circulations
along the differential-heating zone have supported the development
of small, low-topped convective elements from the Belleville area
toward Washington. Northward to north-northeastward storm motions
are resulting in this activity becoming displaced to the cool side
of the differential heating zone, limiting its residence time amid
surface-based effective inflow layers on the warm side of the
differential-heating zone. Moreover, more expansive boundary-layer
static stability accompanying the remnant precipitation shield
across northeast-central Kansas is prohibiting this initial activity
from strongly backbuilding across a larger part of the outlook area.
These factors will largely marginalize any convective hazards across
the forecast area through early afternoon.

The aforementioned subjective surface analysis also places a
differential-mixing boundary arching southeastward from the deep
surface low toward Ellsworth and Wellington, Kansas and farther
south toward the Oklahoma City Metropolitan area. A deeper and drier
boundary layer resides to the west/southwest of this differential-
mixing boundary in association with strong downslope flow within the
southern semicircle of the deeper cyclone. Between the differential-
mixing boundary and the aforementioned cloud- and precipitation-
reinforced differential-heating boundary, partially modified Gulf
moisture characterized by lower 50s dewpoints continues to be
transported northward/north-northwestward -- in association with the
strong isallobaric response to 3-5 mb per 2 hours pressure falls
within an area east of the surface low to southern Nebraska.
While some of the trajectories within this intervening sector
emanate from prior convection across the southern Plains locally
tempering diurnal static stability reductions, a modestly wide
corridor -- around 50-100 miles wide -- of boundary-layer
destabilization continues in this area. Continued surface heating
amid this corridor should foster around 250-500 J/kg of MLCAPE in
the 2-5 PM time frame -- strongest where the overlap of coldest
midlevel temperatures juxtaposes the returning moisture across
north-central Kansas.

Visible satellite loops indicate cumulus development throughout
the modestly-wide buoyant sector -- with the greatest cumulus
agitation in proximity to the differential heating zone (with
evolving towers becoming undercut by cooler air to the north) and
in proximity to the differential-mixing boundary. In fact, an arc
of swelling cumulus is becoming evident from Osborne to Bunker
Hill to Ellsworth, Kansas along the differential-mixing boundary.
The differential-mixing boundary should be a key focus for
potentially developing convection in the 2-4 PM time frame as it
advances northeastward -- as this convection would have the
potential to favorably optimize residence time amid surface-based
effective inflow later in the afternoon. Moreover, with surface
observations indicating an appreciable boundary-parallel component
to low-level winds, the overall forward motion of the
differential-mixing zone will be limited -- and this is related to
the only-gradual ejection of the deep-layer and surface cyclone
favoring more-gradual mixing of this boundary versus advection.
These factors should permit the overall modest width of the
marginal-buoyancy corridor to hold, as opposed to its width
quickly pinching off in response to a surging differential-mixing
boundary.

Given the marginality of boundary-layer based buoyancy,
convection-allowing model guidance has showed little in the way of
robust convective development. However, with 12-hour 500-mb
height falls over 200 geopotential meters overspreading the
buoyant sector, highlighting strong differential cyclonic
vorticity advection approaching the area, there will be the
potential for low-topped convection to form in proximity to the
differential-mixing boundary between 2 and 4 PM -- from the
Concordia area toward Manhattan. The very strong deep shear and
overall paucity of buoyancy, and some potential for parcel
detrainment owing to sufficient cross-boundary low-level flow
(despite appreciable along-boundary low-level flow), cast doubt on
sustained convection materializing. However, an adequate width of
the buoyancy sector, and oblique angle between the low-level flow
and differential-mixing boundary orientation, provide at least
some concern for self-sustaining updraft structures to
materialize -- especially in response to their induced
hydrodynamic perturbation pressure gradient forces resulting from
the interaction of incipient updrafts with strong low-level shear.
Sufficient off-boundary, boundary-relative cloud- layer mean
winds and deep shear will restrict the duration of convective
residence time in proximity to the initiating boundary, and
propensity for a trailing stratiform region to materialize,
respectively, resulting in a probable discrete convective mode.
However, multiple inflections in forecast hodographs above 3 km
AGL will support cross-shear flanking upward-motion perturbations
in alternating layers of the convective layer, perhaps fostering
cell clusters.

Given the anticipated convective mode, along with effective SRH
around 150-250 m2/s2, and the superposition of ample vertical
vorticity with low-level-lapse-rate-boosted boundary-layer CAPE in
the buoyant sector, a tornado threat would exist with any
sustained low-topped mini-supercells. Otherwise, marginally severe
hail and damaging wind gusts would be possible into late
afternoon, as cells quickly track northeastward around 50-55 mph.
Once again, this is a highly conditional severe threat.
Ultimately, sustained storms may not materialize at all, in which
case the severe risk will become negligible. As a result, the
severe risk is highly conditional, though non-zero. Any
thunderstorms should weaken while also moving northeast of the
Kansas-Nebraska border through early evening, while becoming
increasingly elevated atop nocturnally-enhanced boundary-layer
static stability.

 

[Jonbo]

https://www.nonpareilonline.com/news/weather/weather-updates-river-flood-warning-issued-water-and-mud-cause/article_e48531ac-45c3-11e9-b3bd-0fdc8938d0ef.html

Flooding in Nebraska and Iowa, especially Eastern Nebraska and Western Iowa, is devastating and it's only going to get worse with gavins point dam going up at least 20,000 cfs by tomorrow for the Missouri River. Interstate 680 shutdown. Friends just outside Logan, IA are basically landlocked. Missouri Valley (town) evacuated and more. 

[Jonbo]

Flash flood emergency for Platte River due to a major ice jam breaking up, Fremont, Ashland and other cities along it being told to evacuate ASAP. 4-5 foot wall of water. Missouri River going to be near record crest by tomorrow near Omaha. I-29 and 680 closed in/north of Council Bluffs. Bridge likely gone near the Spencer dam and some reports the dam is gone too. Feel so bad for friends and family over there. 

[beavis1729]

1 hour ago, Jonbo said:

Flash flood emergency for Platte River due to a major ice jam breaking up, Fremont, Ashland and other cities along it being told to evacuate ASAP. 4-5 foot wall of water. Missouri River going to be near record crest by tomorrow near Omaha. I-29 and 680 closed in/north of Council Bluffs. Bridge likely gone near the Spencer dam and some reports the dam is gone too. Feel so bad for friends and family over there. 

Sorry to hear about this.

[Jonbo]

Thanks man. I hope the levees hold up in Council Bluffs, that's my biggest worry right now (hometown and half my family and most friends live there) since it could put most of the town underwater if one or more burst. I'm not confident they've strengthened them properly after the 2011 floods. 

 

Insane video of boulders of ice all over the road. Unsure exactly where in Nebraska 

https://www.facebook.com/osborneearthmoving/videos/2267573233292880/

[batteen]

Hard to really tell how much is here without knowing where the ground was, but a lot of this is blown in 6-8 feet deep and there are some crests higher than that.  If it was bare ground before the blizzard, for the most part it was bare ground after the blizzard.  But if it was drifted in before, oh boy, the drifts doubled in size or better.  At the very end of the blizzard, after it stopped snowing but the wind was still blowing, the sun came out and it got up to 34.  This resulted in a bit of slush and eventually crusted over the snowpack pretty good so that there wasn't much blowing snow despite high winds.  I took these pictures this evening.

http://imgur.com/gallery/zChc4R7

[raindancewx]

Those are pretty interesting pictures. Really incredible storm in the grand scheme of things -

Flooding, a derecho, heavy snow, blizzard conditions, fierce winds, heavy rain, tornadoes, hail, and over a huge area - basically the entire eastern two thirds of the US. Saw areas by the Lakes got to 75F today, so the temperature contrast and air-mass contrast is nothing to sneeze at either. 

[Jonbo]

****. Just south of Omaha and Council Bluffs. Missouri River breaking records 

Edit: NWS confirms levees on both sides of the Missouri River by Plattsmouth are being overtopped. Gavins point dam increase still on the way as far as I know.... 

[Jonbo]

Valley, NE being evacuated. Basically anyone living near I-29 and Missouri River south of Omaha being told to evacuate, levees topping. Dam that failed running unchecked into Missouri River north of Omaha along with the gavins point dam increases coming. 

[beavis1729]

17 hours ago, batteen said:

Hard to really tell how much is here without knowing where the ground was, but a lot of this is blown in 6-8 feet deep and there are some crests higher than that.  If it was bare ground before the blizzard, for the most part it was bare ground after the blizzard.  But if it was drifted in before, oh boy, the drifts doubled in size or better.  At the very end of the blizzard, after it stopped snowing but the wind was still blowing, the sun came out and it got up to 34.  This resulted in a bit of slush and eventually crusted over the snowpack pretty good so that there wasn't much blowing snow despite high winds.  I took these pictures this evening.

http://imgur.com/gallery/zChc4R7

Congratulations, and great pictures! Glad you are having a good old-fashioned winter. 

[Jonbo]

Levee failures south of Omaha ongoing, mandatory evacs by 5pm today. Still rising around Omaha...I'm extremely concerned about the levees around Omaha/Council Bluffs with police patrolling to keep people off them now. New picture of formerly Spencer Dam...
 

 

[jcwxguy]

I work full-time in Fremont, ne and am only provider for my family (I live in Gretna, ne).  Needless to say this flood is an absolute disaster for everyone affected.  Where I work is flooded and no end in sight when I'll be able to work again. I have some reserve money but not enough for food and supplies and bills plus rent.  Just asking for your prayers 

[mayjawintastawm]

Yikes, you got 'em. So sorry.

[METALSTORM]

I truly hope your luck changes soon. Terrible situation you folks have going on. Best wishes and prayers to all affected by the flooding and other severe weather this month.

[raindancewx]

https://www.omaha.com/news/plus/an-utter-disaster-ag-losses-from-nebraska-flooding-could-top/article_0e11ad70-41e4-568c-8ef9-190400af4080.html

Nebraska has been hit really hard.

[donsutherland1]

On ‎3‎/‎17‎/‎2019 at 1:38 AM, jcwxguy said:

I work full-time in Fremont, ne and am only provider for my family (I live in Gretna, ne).  Needless to say this flood is an absolute disaster for everyone affected.  Where I work is flooded and no end in sight when I'll be able to work again. I have some reserve money but not enough for food and supplies and bills plus rent.  Just asking for your prayers 

I'm really sorry to hear this. Your family and you are in my prayers. I hope there will be emergency assistance available for what is a real and still growing catastrophe.

[batteen]

Best wishes.  It's warming up in the north now so hopefully we don't contribute too much to the flow.  It's going to be a rough few weeks ahead.

[raindancewx]

Good overview of the 3/12 storm in NM here -

https://noaa.maps.arcgis.com/apps/Cascade/index.html?appid=373f768d438046dba729395b27643fcd