A good Wednesday morning to one and all...
I have a sneaking suspicion that we'll be waking up to more snow showers around the region this morning, and quite possibly more of us will see sticking than yesterday, even if the total amount of snowfall is less than in previous days.
It's another situation where the models may be under-doing snow coverage while the 'old-school' methods of lake-effect snow identification are still showing through. Here's what I mean:
|NAM - Precipitation / 850mb Temps - Wednesday Morning||NAM - Windfield - Wednesday Morning||NAM - Vorticity - Wednesday Morning|
Typically, a meteorologist may just be drawn to the first image, where the NAM model product spits out where it will be precipitating, and where it will not. I've probably done it a bunch too. In fact it works in most cases, and technically it will be correct here too. However, in the winter time (er, the quasi-winter we're in) there is reason to suspect additional areas of precipitation owing to a few factors that are also present in the models.
The left-hand map also indicates temperatures at the 850mb level. A "thermal minimum" is arriving along the northwest windflow stacked at all levels (that the middle map is showing). This thermal minimum does two things: (1) It lowers the capacity for the clouds to hold water in versus precipitating it out; and (2) It increases the snow-to-liquid ratio that governs how much snow can fall/accumulate per unit of liquid water available. This ratio is temperature based, with colder temperatures featuring more snow from less water. The right-hand map shows that ole "vorticity" thing again. Consider the peaks in the red colors as "agitators" in the sky that twist through the main wind flow forcing clouds and instigating precipitation.
Naturally the upslope provided by the mountains will act like a front unto itself, forcing air upward and wringing out snowfall (which is why the model itself will probably verify for the areas it puts moisture), but given the other ingredients it is reasonable to also suspect a more widespread coverage in snow flurries and snow showers.
* Now, there are two caveats to this: First, if the ground temperatures are below freezing (preferably below 30), we can have this snow stick to the ground, bridges, overpasses, and the like where it did not yesterday. The forecast calls for this condition to be met in more places than yesterday morning given the arrival of the thermal minimum. Second, as we get into March, the threshold for good 'snowable' temperatures at the 850mb level is adjusted colder. The last time we witnessed a similar scenario, the 850mb temperatures were more like -13 to -16 C. This is much more favorable for snow squalls and low visibility snow. A -9 C is less favorable, and if it's any warmer up there it will be an open question as to whether we'll stay snow or simply drift off into some drizzle instead once the Sun comes up. Nevertheless it will be an interesting thing to watch this morning.
Update - So we did indeed get a wide-ranging swath of snow showers cutting through in the overnight hours, but it was also patchier too-- creating areas of low-visibility snow with others getting a crystal clear view of the near full moon (for example, Huntington at 1am vs. snowy spots just a few miles drive to the south and west). The mountains still got their share too, with Richwood, WV picking up an additional 1.5" of snow to go on top of the 7" already there. This "clustery" nature of the precipitation is in response to the difference in temperature at the surface and aloft at 850mb. The wider the gap between the two, the less stable the air. When precipitation organizes into patchy bursts, it makes sense that the skies be drier/clearer in between. Do not be surprised to wake up to sunshine or a snow squall this morning, and expect either to be temporary ;-) -- The main concern will be the actual surface temperature. If you can stay above freezing there will not be too many hassles this morning, but just below throws up the threat for any flakes to stick and already existing moisture to freeze into black ice. Be sure to check the thermometer before heading out.
If it verifies that Wednesday does indeed feature more widespread snow flurries and snow showers, we may even need to keep an eye on Thursday as well, for another shot of cold air filters in.
But, by Thursday itself we'll finally turn the corner and get more sunshine to break in between flurries, especially in the west. This improving trend will peak on Saturday, with our best day of the week (right where you want it).
|GFS - Saturday Morning||GFS - Sunday Afternoon|
It's still looking rainy on Sunday, and the models are still trying to push the showers in during the second-half of the day on Easter. But, so far, there's still some wiggle room in there to get a sunrise service in (with somewhat milder temperatures) and even an outdoor egg-hunt afterward :-)
|Regional Radar/Satellite with Warnings Tracking||
From the Storm Prediction Center (below): Click For a Larger Image
|Activity Overview||Storm Outlook||Watches||Potential Watches||Storm Reports|
|Temperatures||HD Doppler Radar||Estimated Rainfall||Active Warnings|
|Click For Larger||Click For Interactive Radar||Click For Larger||Click For Larger|
Have a great day everyone!
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