Hail The Main Risk Wednesday, Storms Possible through Friday at Least

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Impacts at a Glance

Through Thursday, May 14, 2020 2:00 am
Severe Thunderstorms Enhanced
Heavy Rainfall Enhanced
Flooding Slight
Tornadoes Slight
Damaging Hail Enhanced
Damaging Wind Slight
Low Visibility None

Detailed Analysis

It’s hard to think that we could have severe storms in Kansas tomorrow, when I’m sitting looking at a grey, cold, dreary day where some communities in the state will set record cool high temperatures. But this being Kansas and all…

This discussion covers storm risks from 1am CDT Wednesday (May 13) through early Friday morning (May 15). Unless the situation for Friday and Saturday changes significantly, this is the only discussion I plan this week.

Wednesday before sunrise

While the SPC has (as I write this) not outlined a risk area for the 24 hours ending at 7am tomorrow, there is enough potential for isolated thunderstorms that NWS Wichita has mentioned it in their morning weather package:

…and as I checked the NWS website for graphics, I saw they’d pulled the Situation Report off the site. Interesting….

I’m not concerned about these storms at all. They’ll be riding a layer of moist air feeding in between 1 mile and 3 miles above the surface. The forcing of that moist air over the edge of the cold air below could cause some development, but there are no dynamics above and a cold layer below the storms. While there may be a warning or two issued I don’t think we’ll get any reports of hail larger than a quarter.

Wednesday sunrise through early Thursday

This time yesterday, it looked like there was a possibility of some potent ingredients coming together over Kansas to bring a chance for all modes of severe weather. On the evening and early morning models, it was looking like the ECMWF was goign to be a major outlier, pushing the warm front (and therefore the moister air) much further north. In the latest model run, it has come more in line with the other models. The SPC outlook reflects the model consensus…

SPC Day2 Outlook official graphic, current 9:40am 2020-05-12

Precipitation Depictions

GFS

NAM3k (later with the precip)

ECMWF

Of course, it isn’t wise to take those simulated radar loops as gospel. I think the point at this phase of the system is that the risk areas have shifted south somewhat and the models are coming into agreement on that.

I would look for storms to form off the dry line, which still looks to be along or just west of US283 (let’s say a line from Ness City through Dodge City and the Ashland area down to Shattuck or Woodward, OK) about 4pm. They are lacking some upper level support in the daytime hours, and mid-level support is kind of iffy as well. I think closer to the south end of that line, let’s say from near Woodward to near Coldwater, would be the likely area for anything to form that would eventually effect Kansas with severe weather. As long as any storms that do form stay separated, there is a tornado risk, especially on the southernmost storms. Once they form into a line, which is expected to be pretty quickly, we go to a hail and wind risk.

NWS Discussions

Wichita

Low level moisture is expected to return northward through the late afternoon and evening hours. The best chance for storms redeveloping should arrive during the evening and overnight hours. These storms will likely be elevated with the primary hazard being large hail. Repeated rounds of heavy rain may also pose a threat for some ponding of water or low-land flooding concerns. If the warm front can mix north early in the period, then there could be a threat for sfc-based storms developing to our southwest along the dryline but confidence in this scenario remains rather low at this time.

Dodge City

Lots of uncertainty still exists for Wednesday as a weak disturbance approaches the high plains in the afternoon. At 7 am, the true warm sector, with dewpoints in the 60s, will be several hundred miles to the south in West Texas and southern Oklahoma, with a cold airmass still entrenched across western Kansas. While the true warm sector will likely not make it this far north by afternoon, there will still be a narrow ribbon of heating across western Kansas on the western edge of the cool but warming airmass that will be butting up against the warm and dry air to the west. With such warm air to the west moving over the cool air at the surface in elevated fashion, one would think that there would be a stout capping inversion that could inhibit convection. But, this is mid May and it is possible that by late afternoon, enough heating could occur near the bent back surface front over western Kansas to allow for isolated t-storm development–perhaps along a line from Meade to Scott City. Do to the relatively weak mid level flow, any storm that develops would be slow moving to the east at around 25 mph. This may allow for convection to become at least briefly severe with large hail before moving into the more stable air to the east.

Norman

Initial thunderstorms will likely be supercells given the aforementioned environment. The supercells may have a tendency to be high precipitation (HP) supercells given the weak storm-relative winds. Large, potentially significant hail will be the primary hazard with the supercells. The tornado risk is low and will be tempered by weak low-level (0-1 km) shear in vicinity of the dryline.

NWS Office Situation Reports

NWS Wichita | NWS Dodge City

Thursday

This may end up being the interesting day — though the SPC has highlighted eastern Kansas into the Midwest as the risk area. I’m looking more at the local discussion at this point, and waiting to see what happens with tomorrow’s storm evolution. There’s always the possibility of boundaries left (edges of cold pools, outflow boundaries, things like that) which can interact with incoming waves in the atmosphere in ways that still can’t be predicted with any degree of accuracy 48 hours ahead of time.

SPC Discussion

Low-level jet is expected to strengthen across the southern Plains (particularly from southwest TX into south-central KS) overnight. As it does, warm-air advection across the stalled front may result in thunderstorm development across portions of western/central OK into central/eastern KS. Steep lapse rates may allow these elevated storms to strengthen enough to produce isolated hail.

Models

ECMWF

GFS

I extended this one from Thursday noon to Saturday just after midnight. It shows an interesting evolution for Friday in eastern Kansas.

NAM

 

NWS office discussions

Wichita

A surface trough is forecast to bisect the forecast area during the afternoon hours on Thu with a moist and unstable airmass located to its south. This boundary may become a focus for deep moist convection and any storm that develops could become severe with large hail and damaging winds, especially along and east of the Kansas Turnpike.

Topeka

The front will be pushing southeast across northeast and east central KS during the afternoon hours. Both the ECMWF and GFS show a back building line of thunderstorms developing during the afternoon along the front, across east central KS. Given MLCAPES of 1500-2500 J/KG and sufficient effective shear, some of the the thunderstorms in the line may be strong to severe with the primary hazard being large hail and severe wind gusts. If the front moves a bit faster to the southeast, then the severe thunderstorms may only develop in the far southeast counties and shift southeast of the CWA by evening.

Kansas City

Thursday may bring the higher concern for widespread severe weather, especially for the higher population centers. A modified warm sector and slowly northward creeping warm front should push north of the area, putting the immediate area into a richer and more unstable airmass.

The airmass should see moderate destabilization by mid day Thursday with SB CAPE values around 2000 J/kg. Deep layershear will be on the marginal side (around 30 to 35 kts), with deep layer shear vectors not being totally parallel to the low level boundary. So there is a chance that convection will be able to move off that boundary and at least for a bit be somewhat discreet, but given the strong parallel component to the low level boundary, expect storm mode to be more linear as convection increases in coverage.

Springfield

A front will sag south into the area later Thursday into Friday. Storms will develop along the front. Instability and shear will support the potential for a few strong to severe storms with damaging straight line winds and large hail the main risks.

My take

I’ll be watching the area along the Kansas Turnpike Thursday, if things pan out as they look now. We’ll see how Wednesday’s activity affects things. Not ready to take any severe risk off the table yet for Thursday.

Oh, and one other thing:

We’ll have situations where the same area will get multiple rounds of rain in a fairly short time. This is a recipe for flash flooding. Please be cautious and if need be, find another route!