Light snow event becoming more likely for Tuesday and Tuesday night

In a pattern with a growing PNA ridge and a polar vortex sitting in SE Canada, many shortwaves travel down the downstream side of the ridge as they get squeezed between the ridge and the vortex and forced southward into the United States. Often times, computer models are not good at picking up the strength of these disturbances until we get closer to the event. This time around, that seems to be the case, as many computer models are slowly showing a strengthening system.

Let’s take a look at the GFS model:

Today's 12z GFS model shows some favorable, and some unfavorable factors for snow along the East Coast come Tuesday. (NCEP)

Today’s 12z GFS model shows some favorable, and some unfavorable factors for snow along the East Coast come Tuesday. (NCEP)

Above is today’s 12z GFS 500mb and vorticity forecast, valid for Monday night. We see a strong PNA ridge to the west, providing some amplitude to the pattern and supporting a trough in the East. It also helps to displace a big chunk of the Polar Vortex in SE Canada, further providing cold and supplying the trough in the East. As a result, a shortwave disturbance can be seen in the Plains and Midwest, as it is getting squeezed between the ridge and vortex, and is forced to amplify somewhat. This all sounds good for a snow event so far, but there are still several caveats.

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