Hello gang, lots to discuss...
First off this weekend's system. Two H5 shortwaves, One in the deep south and the other digging southeast through the Plains towards the Ohio and Tennessee Valleys.
The southern short has most of the moisture with it. The baroclinic zone seems to be setting up way to our south and east. This is where the H85 low will track and as a result, the heaviest precip will stay to our east and south. As a matter of fact, it's distinctly possible we won't get any precip from this southern shortwave.
The second wave continue to dig towards our region Friday night into Saturday. As the speed max / vort work southeast and then gradually make the easterly turn across TN, this will place our region in the favored left front quad of the upper jet.
Widespread lift will continue to work to saturate the column with light precip developing later Friday night into Saturday. Looking at the thermal profiles from both the NAM and the GFS, it looks like the precip will start off as some light rain then change over to snow later Friday night or early Saturday morning. The best moisture will have already been "eatin' up" by the lead, southern shortwave but there will still be enough in the column to squeeze out .1 to .2" liquid equiv. At this time we think there will be some light accumulations - mainly on grassy areas. Surface temperatures will be at or above freezing so accumulations should not be much of a problem on the roads - although bridges and overpasses may have a slick spot or two especially early on Saturday. How much snow ?? Really hard to say as it depends on when the exact changeover occurs and sfc temps. As I mentiuoned previously, sfc temps are progged to be at or above freezing for much of this event so there will likely be some melting going on even as the snow is falling especially as we move into the daylight hours of Saturday. Actual snowfall could be upwards of 2 inches but what really accumulates will likely be less than this to the tune of an inch or less. Plenty of time to watch it so wee'll keep you updated.... I will say this, this weekend's system does NOT look like a major system for us.
Next week.... that could be a different story ! Chances for a significant winter event may be increasing across our area. The main reason why is the huge block across Greenland and the resultant -NAO pattern. This will likely force systems coming in from the west to take the southerly route. The confluent northwestly flow across portions of the Great Lakes and northeast U.S. will keep the cold high pressure at the sfc in place (i.e. the cold air source). As the western system moves our way, the increasing moisture will encounter the cold air in place and ...bingo !!!
Okay, gotta get to work... I'll keep you updated. C'mon Snow !!!!!!
Jay
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