26
Oct
11

First (and second) chance for snow, on the way!

So, for you weather enthusiasts out there, I’ve decided to “ramp up” the technical aspects of this blog, with regards to meteorological analysis. So, some of you may get it, some may not. Read at your interest, and you’re welcome to post questions or comments as you see fit. After the analysis paragraphs, will follow my forecast, as usual. And I will include links to the charts/analysis, so bookmark them. Here we go.

http://mag.ncep.noaa.gov/NCOMAGWEB/appcontroller?prevpage=index&MainPage=index&cat=MODEL+GUIDANCE&page=MODEL+GUIDANCE

(click on the model you want to see, NAM, GFS. Then, click on the “4 panel charts” for the 500mb etc chart. Then, click on the hour(s) going ahead in time that you wish to see, ie, 12 hrs, 15 hrs, 18 hrs, etc)

So, a low pressure system (storm, cyclone) is moving away tonight, leaving us with mist, drizzle, and fog. However, another is headed out of eastern Colorado and across the NYS/PA border tomorrow afternoon and evening. This track is very favorable for frozen (versus liquid) precip, by the way, because it keeps us on the northern/western side of the storm, which is almost always the “cold” side a storm. Now, if the storm tracked TOO far south, we’d miss it entirely, and “precip-type” would be a moot point. But that’s for another day, and another storm. In this storm’s case, I am watching both the 500-1000mb (mb=millibar) thickness, and the 850mb 32F isotherm. What does any of that mean? Well, for simplicity sake, the closer the “thickness” is to 540 mb (or below), the closer that that layer is to being at or below freezing, throughout the layer. As for the 850mb temperature, when the 32F isotherm (in purple) is near or south of us, it indicates that falling moisture will either stay frozen, or freeze up before hitting the ground. Well, tomorrow afternoon, the line where the 540mb “thickness” is located will be racing southward from the Adirondacks towards Poughkeepsie, and the 850mb 32F line will likewise be progressing southward across the area. Both of these indicate a clear changeover from rain to snow, provided that something (rain or snow) is actually falling at that time.

We will be on the tail end of the storm by that time, but I feel strongly that several hours of wet snow will therefore fall, and with the onset of sunset, and temps falling towards 32F where you and I live (the last 6 feet of the atmosphere!), an inch or two of slushy snow will fall, and maybe accumulate on car tops, grass, etc. And, since temps will go sub-freezing at night, any remaining moisture left on the ground may freeze, ergo the risk for black ice.

So, having said all of that, here’s the forecast…

Little has changed in tomorrow’s (Thursday) storm, for me. Cloudy with
mist, drizzle, fog and an occasional shower tonight, lows near 38-40F. Light
rain tomorrow morning will gradually change over to snow, from north to south,
in the afternoon. Highs will occur in the morning, in the low-mid 40sF. So
again, it will change from rain to snow SOONER in say Rome, Remsen and Poland
(Noon to 4pm) than it will in Cooperstown, Oneonta, and Hamilton (4-7PM). A
slushy inch may accumulate Thursday evening (rooftops, trees, and grassy
surfaces…not roadways). Snow will end early evening, and Friday will be fair.
Saturday a coastal storm will bring more clouds, and Sunday still looks nice.
Monday, a weak system will bring what looks like all snow…but just
flurries…to the area, much of the day, maybe a dusting.

Important footnote: regarding tomorrow evening. Regardless of whether any snow falls or
not, regardless of how much, the temperatures will quickly fall below freezing  tomorrow evening. This means WHATEVER moisture will be on the ground, has a chance of freezing, ergo…black ice. So be aware of this, so you are not the one caught in a fender bender because of potentially slippery conditions overnight.

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