I have decided to begin blogging on the upcoming winter storm to affect the central plains since significant impacts look to include at least a portion of western Kansas. Western Kansas has had a dearth of precipitation this cold season, and this upcoming storm looks to be the best shot at widespread significant snow for at least some locations of the western plains that have not seen much at all this winter. To give you an idea how bad it’s been for western Kansas, the total snowfall for Dodge City through December 28th has been a whopping 0.2“! At Goodland, Kansas, 0.4” of snowfall has been recorded so far this winter. Now granted, The first half of the cold season is typically fairly scant with snowfall in western Kansas as compared to January-March, when most of the cold season average occurs, but still, this is certainly below average.
Now that we are within 72 hours of the event, the focus is becoming a bit more clear on potential impact. Snow and wind. Just exactly where these impacts will be depends on the track of the mid level cyclone. This appears to be a classic case of Rossby Wave downstream development as a Pacific trough centered just west of the dateline pumps a ridge around 145W longitude…and then subsequent trough development further downstream along the west coast of the U.S. All along the models have shown the ridging to be fairly broad over the Gulf of Alaska, which in turn would suggest a downstream mid-latitude cyclone development over the Rockies with the cyclone undergoing its most significant deepening as it exits the Rockies and enters western Kansas/Nebraska. Typically, this kind of track would not favor heavy snow for Southwest Kansas. If the ridge amplifies more than the GFS and ECMWF suggest, then the downstream equatorward transport of high-Potential Vorticity (PV) air would likely be driven farther south…and mid-level cyclogenesis occurring over New Mexico. Interestingly enough, the last couple runs of the GFS model have suggested a slightly deeper, southern solution. This would put more of western Kansas in play for potential heavy snow and wind.
I’ve attached two figures to this first post. Figure 1 shows water vapor loop from the evening of 28 December showing the source of the PV air that is the seed of the upcoming central Plains storm. Figure 2 is model output from the 18z run of the GFS model earlier today. I’ve annotated on both Figures some important features such as the jet core in white in Figure 1 and the PV air stream is also noted in both figures (along with what the ideal PV anomaly track is for heavy snow in Southwest Kansas). It should be noted that a shift in the PV anomaly of 70-120 miles farther south would put Dodge City on the southern edge of a nice snow and wind event. It’s obviously what I’m hoping for as a snow nut, but I’m not exactly anticipating it at this point. It will (hopefully) become much more clear tomorrow whether this will be yet another classic miss for Dodge City or if, in fact, we actually do see some nice accumulating snow for a change!