Hopefully by now you have heard from somewhere that a snowstorm is looming for the Wednesday before Thanksgiving….
The computer guidance models have been in fairly good agreement over the last couple of days in bringing a high impact storm system north along the East Coast of the United States during the day on Wednesday. It appears that travel will be impacted from the Carolinas through New England or as is known; the Interstate 95 corridor.
So for anyone looking to travel to Grandma’s or wherever it is that you share your Holiday feast be sure to make the necessary travel arrangements to get there safely.
And to make sure that you know when to travel let’s take a look at the timeline for this system: All images show the same thing, just different pictures in time. The lines are isobars (lines of constant pressure) and the colors of green and blue represent the precipitation that fell in the previous 3 hours.
7 am Wednesday Morning (all images courtesy of WxBell):
7 am Wednesday Morning
1 pm Wednesday Afternoon:
1 pm Wednesday Afternoon
7 pm Wednesday Night:
7 pm Wednesday Night
1 am Thursday Morning:
1 AM Thursday Morning
From the images above one can understand that preciptation moves in from south to north between 10 am and noon. Initially precipitation will likely fall in the form of rain but this will be short lived in locations north and west of Rte. 495 where temperature will quickly fall below freezing and rain will change to snow. Inside of 495 this changeover will take a while longer and will occur sometime during the afternoon and evening hours; reducing potential accumulations. Down on the Cape & Islands and along the coast the changeover never comes and this will be a wind swept rain event.
Now for accumulations. First let me show you in a probabilistic terms using these images from the Weather Prediction Center:
Chance for 4″ of snow by 1 am Thursday:
Probability of 4″of Snow
Chance of 8″ of snow by 1 am Thursday:
Probability of 8″ of Snow
Chance of 12″ of snow by 1 am Thursday:
Probability of 12″ of Snow
From the top image showing the probability of 4″ of snow it highlights a greater than 50% chance of greater than 4″ of snow north and west of the Boston to Providence corridor with probabilities increasing north and west from that line. The same orientation of the higher probabilities is also seen in the 8″ and 12″ probabilities with the region from northwest Connecticut through central Massachusetts northeast into southern Vermont & New Hampshire having the highest probability of seeing 8-12″+ of snow.
So how about my forecast and thoughts. I’m inclined to agree with the Weather Prediction Center’s images above and feel that they have a good handle on the orientation of the both the rain/snow line and the axis of heaviest snow.
Pre-Thanksgiving Snowstorm Amounts
At the moment this is my thinking for this system. The ranges are a little bigger than I typically like but there is still a bit of uncertainty with this one. Mainly revolving around the push of warm air as the storm passes just to the southeast of the Cape. Hopefully by tomorrow afternoon I’ll have a better handle on the storm and will be able to give a more specific range of possible accumulations.
-Chris
Chris Hampton Weather 