January 2017 Observations & Discussions

Here's my forecast for the clipper, for those interested:

Admittedly, the 3-5" zone may be better served as a 2-4", but I have some reasoning behind it. Although this is a clipper, which usually means the system won't be good for much more than an inch or two, it is moving into a more favorable spot. As it approaches our region, it does phase in some additional mid-level energy which is clearly shown to amplify the mid-level energy and differential potential vorticity advection (forcing for ascent). While there is no jet help to really fuel this system, the lower levels do provide some additional simultaneous support. Based on the season's tendency to develop systems shortly prior to reaching the coastline, likely due to the warmer than normal coastal waters, I am sticking with that trend here. Therefore, not only will there be a closed surface low pressure that develops prior to reaching the coast, but because there is a phase at H5, this should also allow the lower levels to close off in rather quick succession (H925 and then H850). As a direct result, this should work to quickly, although relatively briefly, enhance the low-level frontogenetical forcing for ascent. Third, there also appears to be a mild signature of H700 frontogenesis developing as a result of the lower levels closing off, thus changing the thermal gradient orientation to a more warm air advective profile and providing further forcing for ascent through this layer. With H5 energy and differential positive vorticity advection quickly increasing thanks to the phase, a band of moderate precipitation should develop just on the northwestern side of the lower level lows as the system swings through. One last thing to consider, is once the lower levels close off, this should also aid in increasing moisture fluxes off the Atlantic some, and wiith thermal profiles and saturation vapor pressures appearing to be conducive for plate snow crystal habits, accumulations should occur fairly efficiently through most of the window of moderate precipitation. Assuming ratios of 15:1 at minimum, with more likely 18:1, I do feel 3" should be achievable, with a few spots eclipsing 4". We'll see!!

Frank_Wx wrote:Started a thread for Tuesdays clipper. Tomorrow's event we can keep observations in this thread. Ray, nice writeup.

Thank you, sir! Now hopefully it verifies