Sun. Eve: Big Changes Coming

Synopsis:

High pressure centered east of Boston and a warm front that has become stationary over western NY and NE PA have set-up a southwesterly flow, which will lead to one more day of above average highs before a powerful arctic front heads through overnight, the precipitation beginning around 00z. Temperatures will crash soon after the rain starts and the winds will also kick up. The precipitation will taper as a mix of rain and wet snow about 4-8 hours after arriving. Back-end snow showers will occur on Wednesday. Thursday will be quiet. And Friday could see a chance of a few snow showers from a passing upper-level disturbance.

Models Used: 00z & 18z NAM, 00z Hi-Res NAM, 15z & 21z SREF, 18z GFS, 12z ECMWF

Model Guidance:

The models were trustworthy. However, the 0.01-0.10 precipitation contour on the GFS was well ahead of the cold front – not the case on the NAM due to its finer grid scales. Therefore, the NAM & SREF were used in timing the onset and end to the cold front's precipitation. The NAM, unlike the GFS, showed holes in the back-end snows, again due to its finer grid spacing, making the GFS easier to interpret. The GFS & Euro both showed the end-of-week system, with the precipitation contours different due to the different resolutions of the models.

Short-Range:

The Hi-Res NAM reflectivity showed a chance of thundershowers in western PA, enhanced by orographic lift and weakened by the mountains. The potency (temperature gradient) of the cold front and the timing of the precipitation of 00z support thundershowers; the time of year, to a certain extent, does not. The rain will last for about six hours and the winds will be a factor over the course of the week.

Long-Range:

There's really nothing to add about the end-of-week disturbance except to watch the trends closely. The Euro was hinting at another pretty big batch of snow for early next week, also something to watch over the course of the week.

-Jaron Breen