The Bad, The Good, and The Bad - and Maybe Ugly (12/29/20)

If you didn't get a chance to read the previous post I did on the 24th, click here.  

The advertised precipitation event I discussed back on the 17th, was just a tad slower in evolving.  Some of the precipitation began the night of the 27th with a band of snow that moved across west central Kansas into northeast Colorado, northern Kansas and into Nebraska.  The second wave of precipitation began last night and into this morning (29th).  Here is a precipitation map from late on the 27th until 7 AM this morning....

The rain, freezing rain and sleet that started overnight and continued through much of the day as it shifted east was not necessarily a single storm.  Rather it was a maxima in the upper level wind field that promoted what is called a "warm conveyer belt" and produced lift across the relatively shallow cold airmass aided by a surface warm front that was moving up into southern Oklahoma.   Here is the 24 hour precipitation map for Kansas, ending at 4 PM and provided by the Kansas State Mesonet...

So, the bad.  Well, this "significant" precipitation event was farther east than what would have been preferred for the drought area of the high plains.  That has been a common theme for much of the fall and now early winter.  Comparing the map above to what occurred around in early November...this pattern of precipitation was farther east by about 50 miles (in regards to the heavier precipitation).  These sharp gradients of very little to a whole lot have repeatedly occurred this past 70-80 days.

The Good?  It was another significant precipitation generating weather system for the central U.S. that was "right on track" as far as long range predictability.  This boosts confidence going forward for other potential impacting events.

The bad or maybe ugly?  The same area that has missed the big events may miss many of storms going into spring.  The caveat is that some of the forcing areas around the northern hemisphere generating these storms have changed slightly.  My hope would be the pattern could shift west a little, with time.  

Looking at this mornings upper level chart....

                                                          500 MB - 12/29/20 at 12 Z

The main upper level storm was located across western Arizona.  Typically this would be a nearly perfect location to impact the high plains.  However, because of upper level ridging across the north Pacific and something referred to as Rosby Wave Propagation across the entire Pacific basin, this upper level low is predicted to take a track closely resembling the red arrow.  That is, the upper level low will intensify/amplify as it dives across northern Mexico before lifting rapidly northeast and then north across the mid-Mississippi Valley.  That will result in a tremendous amount (remarkably high) of precipitation (mainly rain)!  However, that track also keeps the precipitation out of the high plains.  IF, the storm were to take a track annotated by the green arrow, then we'd be in good gravy.  That won't happen (99% chance it won't).  Here is the outlook from the Weather Prediction Center (and keep in mind this in addition to what fell today)...

The western edge may be a bit too far west. 

You may also notice lots of precipitation across the west coast.  Great for them!  It also is an indication of an active upper level pattern across the Pacific.   I'm seeing indications of a developing extended east Asian jet stream (very energetic winds coming off the mainland due to very high pressures across Siberia).  That could very well impact the central U.S. once again around January 9, give or take a day.  That should be the next significant chance of precipitation after this Thursday/Friday (again east of the high plains).