Along US-283 and east of there to I-135, we expect to see a line of storms advance along a cold front/dryline that extends from an upper trough in northern Kansas well to the south. The major models, both global and convection-allowing, have converged on a fairly small area as a potential tornado target between 7 and 8 pm. But there’s one important model that disagrees, and it was closer to reality in the scenario two weeks ago than any of the others.
Enhanced Risk for Severe Storms
Here is the SPC graphic with today’s storm outlook. The enhanced area is, as I expected, marginally smaller than yesterday’s. The east edge is 10 miles or so further east. And it has taken on a slightly positive tilt (south end east of the north end).
Warm temperatures aloft will likely limit storm development throughout much of the day. Potential exists for isolated late afternoon/early evening development along the dry line from southwest KS southward along the TX Panhandle/western OK border into northwest TX. However, confidence in this early initiation is currently low, with capping expected to prevail amid the modest moisture return and anticipated mixing. All severe hazards would be possible with any storm that is able to persist.
Thunderstorms development is expected from central KS into southwest TX as the cold front approaches and then overtakes the dry line during the evening (00-04Z time frame). Given the strong meridional flow, this development should quickly grow upscale into one or more bowing line segments. Within a few hours of initiation, a more coherent, solid line of thunderstorms will likely exist along the length of the front. Strong wind gusts will be the primary threat, with some significant severe wind gusts possible. Large hail could also occur, particularly early with initial development. The strongly veered low-level flow also suggests the threat exists for embedded/QLCS tornadoes.–SPC Day 1 Outlook issued 1am 2021-10-26
SPC Individual Risk Graphics
These have changed somewhat, especially the addition of the silver area on the wind graphic, which was not in place yesterday. This is where forecasts have placed a 10% chance of significant severe weather within 25 miles of a point. The hail graphic yesterday had this area. Overll, the risks are in good alignment with the area NWS discussions and Hazardous Weather Outlooks.
Here are three models’ predictions for a specific point in Kansas, as shown on the map that starts the sequence. The models are (in order) HRRR 0z/7pm CDT last night), HRRR 08z (3am CDT today) , GFS 0z, and ECMWF 0z. The HRRR is an hourly run model that takes into account the effect of thunderstorms on the atmosphere near them. The GFS and Euro do not resolve details small enough to be effected by storm development, and are run every 6 hours. There is a good consistency among these models for the point I chose.
The graphics are what are known as Skew-T and Hodographs. The mildly-technical explanation is they show the forecast twist in the wind with height, and this particular set also gives some numerical values for many calculated parameters. While they don’t indicate a tornado will happen, they are an indication that potential for a tornado is higher in that location than others nearby.
But there is an outlier..
The 3km resolution NAM, which does not have a science package that includes feedback from thunderstorms, doesn’t develop precipitation until 8pm (the models above are for 7pm) and overall it is somewhat slower, putting the main risk area a few counties west. The top image is at 7pm, before any rainfall is depicted by the model. So the second image’s projection of a PDS tornado (very strong), is probably not right, as no storms are in the area for another hour.
What do the area NWS Offices say?
Critical fire weather conditions this afternoon for areas west of a Scott City to Liberal line as relative humidity values fall to below 15% and winds out of the southwest will pick up to 20-35 mph with higher gusts.
Severe weather is expected this evening starting around the highway 283 corridor and then moving east through midnight. Main threat will be straight line winds as the storms quickly grow into a line. Brief spin up tornadoes will also be possible in the line. If the initial storms can stay discrete it will be for a short amount of time and these storms could contain hail up to 2 inches in diameter.— Day1 Hazardous Weather Outlook issued this morning
Thunderstorms are expected to develop over western Kansas late this afternoon and early evening, developing into a line of storms as they move northeast across central and south central Kansas late this evening and overnight. Severe storms capable of damaging wind gusts to 65 mph will be possible for locations primarily along and west of a Salina to Wichita to Arkansas City line. A few strong storms with wind gusts to 50 mph will be possible later in the night across the Flint Hills and southeast Kansas.– Day1 Hazardous Weather Outlook issued this morning
My Bottom Line
First, I’m still uncertain of this enough that I haven’t decided if I’ll chase tonight. There are a few things I’ll be looking at around 1:30 this afternoon that will be my deciding factors.
- does the area between Pratt and Meade get solid sunshine by then?
- have 60+ degree dew points made it north of the state line?
- have the faster models slowed or have the slower models sped up? And does the FV3 show anything chaseable at all?
My general target area remains unchanged (if I go). I’d aim to be in Greensburg around 5pm and decide where to go from there. I’d pull it back to the east if it looks like we’re close to the faster forecasts.