Ramblings of a Graduate Student

There are many disappointed snow lovers in Norman, OK tonight after the big snow storm has (so far) been a bust.  There is a chance that snow developing in far southeast Oklahoma could work its way back into the Norman vicinity, but it most likely will be light and is far from certain.

I’ve been asked a lot tonight, “What went wrong?” and, in my opinion, the lack of rich, deep moisture for this storm to work was ultimately it’s undoing (here in central Oklahoma).  This was not a complete surprise; I even mentioned it here in the blog (check out the last paragraph of Day 76 and the last paragraph of Day 77) as well as in the Hazardous Weather Testbed Map Discussion on Friday.  With this said, it doesn’t mean I’m not disappointed.  I really wanted a big snowfall.

So how did all this play out?  Well, during the morning to early afternoon hours (in the wake of the 850-700mb front), a mid-t0-upper level dry slot overspread much of south-central Oklahoma.  This act to shut off the precipitation throughout this region.  (The dry slow is the portion of the storm where dry air wraps into the storm.  It is responsible for causing the storm to take a comma shape [ , ] instead of a backslash [ \ ]).  In fact, you can see evidence of this drying aloft in tonight’s 00 UTC (7 PM CDT) sounding from Norman, OK (shown above, annotated below).

This drying aloft occurred very close to what is known as the “Dendritic Growth Zone” (DGZ), which is the layer of the atmosphere that promotes large ice crystal development.  These large ice crystals ultimately turn into large snowflakes should they make it all the way to the ground.  Unfortunately, when drying aloft occurs very near the DGZ, and strong lift is present, the large ice crystals struggle to develop.  As such, the snow that fell in Norman was being generated lower in the atmosphere where smaller ice crystals develop.  This manifested itself in the form of  ”snow grains” that seemed to fall all day at my house, not the large snowflakes needed for rapid snow accumulation.

If more robust moisture had been available to this storm, the dry slot might not have pushed as far north and east as it did, resulting in large snowflakes falling instead of the snow grains.

This isn’t to say that large snowflakes weren’t present anywhere today.  In fact, just north of the strong mid-level jet streak (and associated “new” dry slot), a new area of precipitation is curently developing.  Reports from underneath this developing area of precipitation indicate that “half dollar” sized flakes are falling and accumulating quite quickly.

This new area of precipitation is developing in a region of strong lift on the nose of the jet streak, and is quite robust as a result of deeper moisture beginning to work its way into the storm (green arrow below).  Once again, had the deeper moisture worked its way into the storm earlier, the heavier precipitation would have developed a bit further earlier in the day, closer to central Oklahoma.

As the precipitation in eastern Oklahoma continues to develop, expand, and intensify it will begin to “use up” most of the moisture that has been feeding into central Oklahoma, which has been necessary for snow production there.  As such, one would expect the snow to decrease in central Oklahoma, and current radars indicate this to be the case.  This trend should continue for the next several hours until all that is left is flurries.

With this said, the storm is just now beginning to intensify (meteorology students should think latent heat release) and as it does so, the precipitation in eastern Oklahoma should begin to wrap around the mid-level low located along the Red River.  If the mid-level low moves slowly eastward, there is a chance that the “wrap around precipitation” would make it all the way into central Oklahoma.  This is a long shot, but essentially the only shot left at seeing measurable snow in this part of the state.

And for good measure, I thought I’d show the same kind of plot used on Day  77 (linked above).  Notice how the deeper moisture is now working its way into the storm via the Gulf of Mexico.  I guess I’m left asking myself, “What could have been?”