Saturday morning forecast

Synopsis:

Westerly to northwesterly winds will continue through the weekend across much of the Commonwealth, ahead of high pressure to the west. The 540 mb. height line will stay in the southern part of the country through the weekend and into early next week, ensuring very cold temperatures across the eastern part of the United States, including here in Pennsylvania. Temperatures will stay in the teens and 20s for highs through Monday, with lows likely going below zero Sunday night into Monday for the northern and central parts of the state. A couple of low pressure systems will skirt across the Great Lakes over the next few days, giving areas around Erie and Bradford a chance of a bit of snow tonight into the first part of tomorrow. Otherwise, expect pleasant and dry conditions until Monday. At that point, a more interesting area of low pressure will swing down from the northern Great Plains, move eastward, and develop out over the Atlantic. There could be some snow for the southern and eastern areas of PA later Tuesday into Wednesday from this one, but it will probably not be a significant snow event. However, do keep your eyes out for this feature.

Short-term:

All the model runs (ETA-3z, WRF, GFS) are consistent on the westerly to northwesterly winds through this weekend - again, keeping that cold air entrenched across the state. GFS model has the low skirting to the north tonight and early tomorrow bringing in a bit of lake-effect snow up north, but even it keeps totals down (probably no more than an inch or so). Otherwise, the models are pretty consistent with keeping things dry. Some 850 mb moisture will move through the state tomorrow (as a result of that weak trough moving through up north), but at 700 mb, things are quite dry. So, for most areas Sunday, it will stay dry, albeit cloudier than today. Monday, the next low pushes a bit to the south of PA (which will strength over the Atlantic long-term), possibly giving the mountains a little snow Monday night into Tuesday. More snow will occur towards the middle of the week ...

Long-term:

The models seem to be somewhat inconsistent with the timing of the development of this area of low pressure. WRF shows the same low still just away from the Florida coast come Tuesday. However, the ETA-3z and GFS models show that same low pressure system just off the Virginia coast, which seems more favorable, considering the upper-level winds and where this low is coming from. Again, it seems like the low will be too far off the coast for this to be a big snow event, but if the pattern of the jet stream changes at all (putting the low-pressure system closer to the coast), then it could be a potentially bigger snow event. Winds from the SE (from this low-pressure system) will try to bring a little bit milder air towards PA, possibly resulting in a rain-snow mix during the day across extreme SE PA (Philadelphia area) Wednesday. However, with the general meridional pattern across the country (big ridge out in the western half of the nation, big trough here in the eastern half), it looks like we will not get much above freezing anywhere for the next week or so.