Well it is inevitable.  The dry intrusion is approaching.  It is through Liberal.  Just ahead of it, though, snow is moderate.  Another burst of snow may occur around midday as the main vorticity max (red “X” in the image below) passes just to the south of Dodge City, however I’m not holding much hope out of that.  It looks like another quarter inch of accumulation has occurred since I went out and measured at 4:30.  I’ll take my official CoCoRaHS measurement at 7:00am.  I think 2-3″ is all we will get for a storm total here in Dodge.  There is no escaping the dry intrusion.

I woke up at about 4:20am to find 1.2″ of new snowfall since midnight at my house which is 5 N downtown Dodge City.  Looking at radar, it appears most of this fell in the 2-3am hour as a healthy east-west band of 24-28dbz echoes moved northeast through Ford County.  The 3-5″ forecast still looks to be on track as some good looking radar echoes are still coming up from the southwest all the way back to Guymon, OK.  Dry intrusion appears to be showing up, though, southwest of Guymon into most of the Texas Panhandle, which is a bit worrisome for later in the morning.  Hopefully that will not shift north very much… and there is hope that it will not based on the track of the mid-level vorticity max as mentioned in the previous post.  Will take a look at the latest RUC progs here in a bit.

This is another interesting mid latitude cyclone case involving a compact, potent mid level jet streak.  Since the jet streak and mid level PV anomaly is so compact, the greatest lift and heaviest snow may lie a little bit closer to the actual mid level vorticity track than is usual.  The chart below depicts the latest NAM model 15-hr forecast of 500mb height/wind and I noted the vorticity max in a red “X”.  The arrow then depics the primary 500mb vorticity max…expected to track due east (instead of lifting northeast) as it crosses the plains.  This is important in the sense that the heavy snow track could very well be tucked a bit closer to the vort… including Dodge City.  Of greatest interest for heavy snow will be the 6-8 hour period from roughly 12z to 20z (6am to 2pm).  This is when the mid level vorticity max will be tracking from roughly Gallup, NM to Gage, OK.  3-5″ of snow is a solid bet for Dodge City, and if the vorticity max tracks ever so slightly farther south… like even 40-50 miles… then there could be even heavier snow for Dodge City.  It will be interesting seeing the latest RUC model trends overnight!  I won’t sleep much, I love the anticipation of heavy snow and the compact mid latitude cyclones that cause them.  Call me a meteorology freak I guess.  Or weather weenie.

The latest RUC model solutions seem to suggest that persistent 2 and 3-star snows should begin around or shortly after midnight here in Dodge City.  Both the Amarillo and Dodge City doppler radars are showing widespread precipitation in the 7,000 to 21,000 foot layer in the troposphere…  There are only a few periods so far when some of this heavier snow aloft briefly reaches the surface.  Below is an excellent example of the radar revealing snow in this layer (a characteristic donut-hole appearance around the radar site) as the radar beam shoots through these altitudes as the radar beam travels away from Dodge City.  I annotated approximate range rings at the point where the radar beam enters the precipitation at about 7,000 foot elevation (roughly 25 miles downrange) and exits the precipitation-bearing cloud at approximately 21,000 foot elevation (roughly 70 miles downrange).  My updated thinking for total snowfall here in Dodge City is 3-5″ with the heaviest occurring between 6am and 3pm Tuesday.

Interesting storm shaping up for the Great Plains…impacting much of Kansas, particularly along and north of I-70 late tonight and Tuesday (December 8th).  I wasn’t going to blog about this storm because it didn’t appear as if it would impact southwest Kansas much… including here in Dodge City… but trends are just a bit farther south with the lower tropospheric response and precipitation.  The arctic air protruded farther south down the western Plains than any of the models suggested.  See the map below, which is a surface chart valid this afternoon at 2:00pm:

The surface winds in the arctic air will try to veer around in response to cyclogenesis in the Rockies, but it is difficult.  Each model run has trended just a bit farther south with the track of the surface low in time…taking it now into the TX Panhandle then into north-central Oklahoma…which would place heavy snow track from roughly Ness City to Hays to Salina and points northeast from there.  Any farther south and it would put Dodge City in the heavy snow track…but as it stands now, Dodge City will be on the southern periphery of this storm.  Below is the Snowfall run-total accumulations from the 12z model runs of the GFS and the NAM (from Earl Barker’s site):

Below is the Canadian GEM model valid 6pm CST Tuesday 12/8/09:

I am expecting 2-4″ here in Dodge City, mainly falling between midnight tonight and noon Tuesday 12/8.  That said, we will be near or within the gradient in snowfall… so we may get a lot more than that… or not much at all — the higher confidence in heavy snow is going to be up along I-70… as it has been looking pretty much all along.  We shall see!  With the colder airmass than anticipated, things may wind up being farther south!  I’ll be at the house watching it unfold tonight and tomorrow before going into work at 4pm Tuesday.

Mike U