Tuesday Night Technical Discussion

Synopsis:

High pressure will continue to make its way east and sit over New England until Thursday night. A cold front will traverse the state Friday and produce scattered rain showers across the region. Artic air will move into the region behind this system, along with scattered lake effect snow showers, especially for northwestern portions of the state, during the weekend.

Short Term: (Tuesday night through Thursday night)

High pressure will dominate the weather pattern for the northeastern states Tuesday night through Thursday night. Low temperatures for Tuesday night will be in the low to mid 20's statewide, indicated by the 18Z 12km NAM. As the flow become more southerly and skies remain mostly clear, high temperatures will moderate, with the entire state at least reaching the low 40's and southwestern PA reaching low 50's by Thursday. Clouds will begin to move in Thursday afternoon and, along with a southerly flow, will keep low temperatures for Thursday from dropping.

Long Term: (Friday into the weekend)

A mean southerly flow will allow temperatures to rise Friday just ahead of the cold front. The 12z GFS has the pre frontal precipitation reaching northwestern PA by 18Z Friday, but the 12Z NAM is a bit quicker and has the precipitation reaching the state by 12Z on Friday. GFS is currently slow and the NAM is doing much better with the timing. Expect some precipitation in the northwestern counties on Friday between 10Z and 12Z. The low pressure associated with the frontal passage will move north over Canada and sit for the weekend. A northerly flow behind the front will allow for cold air advection, which will usher in a cold air mass for the weekend. The flow will shift northwesterly and lake effect snow showers are possible for the northern and western portions of PA for Saturday night through Monday. High pressure will begin to make its way towards the state for the beginning of the workweek and the northwesterly flow will subside, cutting off the lake effect activity.

~ A.J. Herbert