I am confident that our region will see a large swath of snow. Most areas will see 1-3 inches with some regions getting 3-5 inches depending on the exact track and intensity of the storm. The model guidance for this storm has been very consistent across the board for its effects on the Mid-Atlantic giving me more certainty upon the event. The only variables up for grabs are whether or not this storm strengthens up the coast into a nor-easter for states like Pennsylvania, New York, Massachusetts, Connecticut, Rhode Island and more.
FIRST CALL FORECAST
I am confident in these numbers and there is up-side potential for some areas in the 1-3 inch zone to get more.
FOR THOSE INTERESTED IN METEOROLOGY
THE SET UP
GFS MODEL 6Z
A large area of high pressure across the middle of the country brings cold temperatures and creates areas where the divide between cold and warm is great. This is where the storm will form and travel along the brown line. A stronger more intense high pressure would make the jet stream more pronounced and curved. This would bring a more powerful storm which would ride up the coast. This scenario is outlined by the Canadien Model.
GEM 6Z
You can see that there is a stronger high pressure reaching further south. This will create a stronger, more curved jet stream for the storm to form upon. One more thing I would like to point out are the dotted blue and red lines which signify 500 mb height. The lower this height (dotted blue line) the colder the column of air is, the higher the height (dotted red line) the warmer the air is. You can see that these lines are closer together and their curvature is more pronounced in the GEM model to the right of the high pressure or the leading edge of the cold upper air. This difference in air masses so close to one another creates energy for the storm to feed and ride upon. While the GFS shows this to an extent it is not nearly as pronounced, leading to a weaker storm.
By looking at vorticity at the 500 mb height you can clearly see the differences I bring up.
GFS 6Z Vorticity
As you can see the vorticity or energy max is highlighting by the red X. Again this forms along the upper air trough, the placement and intensity of this trough determines where and how evident vorticity is.
GEM 6Z
This vorticity max is more towards the west and is stronger, there is a deeper purple. The 500 mb heights are closer together and more pointed. Again this will create a stronger and more curved storm track up the coast, while the GFS would create a significant storm that tries to ride the coast but lacks the atmospheric infrastructure, i.e. a deep upper air trough and high jet stream energy.
STORM TRACK GFS 12 Z vs GEM 12Z
Both are similar and will bring snow but the GEM is stronger and will ride up the coast more while the GFS is weaker, quicker and will head out to sea more
Later today I will check out the short range models for storm track and intensity and monitor the developing high pressure to see whether or not there will be enough energy from the jet stream to drive and strengthen our storm.
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