* Mild Start to October - Cooler Mid-month *
* Cold, Windy Weekend...but Mild Air Returns Next Week *

1:00pm Friday, October 31:
Just a brief update today, since the storyline detailed Wednesday remains on track. The big east coast storm this weekend will be largely a miss for our area with just a modest amount of chilly rain here, while the heaviest rain falls along the coast and offshore. A few snow flakes may fly in the PA mountains, but it's the ridges in NH, WV, VA, and especially NC that are most likely to see some accumulation (perhaps up to a foot of snow on high NC peaks). Wind and unseasonable cold will be the main impacts here in Lancaster. Winds Saturday will be 10 - 20mph; and a bit stronger Sunday with gusts to 35mph quite possible.

The large scale pattern will then flatten out next week, and so milder temperatures will return with highs back in the 60s. The bottom line: November will get off to a cold, blustery start, but the pattern going forward--perhaps into mid-November--does not look especially wintry.


1:30pm Wednesday, October 29:
Tuesday brought delightful Indian Summer conditions with high temps reaching 77 at Millersville and 83 in York! Today, however, a cold front is crossing the region with a few showers and increasing winds out of the Northwest. A weak area of high pressure will take control with near-seasonable temps Thursday into Friday, although afternoon clouds are likely both days.

The weekend remains a difficult forecast to pin point...but here's what I'm confident in right now. A sharp jet stream amplification will lead to a closed upper-level low forming somewhere over the Carolinas or along the Mid-Atlantic coast. This will trigger a rapidly developing coastal storm--the final storm track is somewhat uncertain, although I suspect a relatively offshore (east) track. Regardless of the exact track, it will be a very windy weekend with gusts possibly exceeding 30mph...and given this strong North-Northeast wind flow there will be a sharp (but brief) discharge of Canadian air into the region. The result will be the coldest air mass of the season with high temps of just 45 - 50 degrees (both Saturday and Sunday) and wind chills in the 30s. Precipitation outcome remains uncertain...but I expect LanCo will see some showers or a period of rain Friday night into midday Saturday. While a shower may linger into Saturday night, the second half of the weekend should be mainly dry (assuming I'm right about the storm tracking relatively far offshore). Any snow will be confined to the higher terrain of NC/WV/PA and the mountains of New England.

After a frosty Monday morning, next week will bring jet stream de-amplification and a moderating trend with highs temps likely returning to the 60s.


1:00pm Monday, October 27:
This week begins with a beautiful two-day spell of Indian Summer....but it may end with the Commonwealth's first measurable snowfall of the season. Such contrast is the stuff of late October and early November, and so we are pretty much on track and midway through our seasonal transition period.

Short-term, retreating high pressure and increasing southwesterly flow will lift temps into the mid 60s today and mid 70s Tuesday. A modest cold front will then traverse the Commonwealth with a few showers early Wednesday, before a seasonably cool high pressure system takes control Thursday into early Friday (highs 55 - 60). Then things get interesting....

A potent upper-level system will dig from the Great Lakes to the Mid-Atlantic coast Friday afternoon into Saturday, ushering in the coldest air of the season. Lake effect snow showers will fall in parts of MI, IN, OH, PA, and NY as sub-freezing air crosses the Great Lakes Friday into Saturday. Here in Lancaster, clouds will increase Friday with a period of chilly rain likely Friday night into early Saturday. The tricky part of the forecast relates to possible coastal development of a low pressure system late Friday night into Saturday. The location and timing of this system is very uncertain as of midday Monday--it's a complex situation that our weather models struggle with and often "fail" on. Anyway, at this point I'd say there's a 60% chance of a few inches of wet snow in the mountains of NY and New England by midday Saturday...but a lesser 30% chance of a couple inches in some mountain locations within PA. In Lancaster, I can't rule out a few wet snow flakes mixing in with the rain around daybreak Saturday, but only the higher spots (Furnace Hills, Welsh Mtn., SoLanco hills, etc.) might be just cold enough to see a little snow briefly stick (20% chance). Check back here in a couple days for a more definitive forecast, one way or the other.

After a windy, cold weekend (highs in the mid 40s to low 50s), I do see another warming trend next week with highs returning to the 60s. So this weekend's possible taste of Winter is not an early turn to a wintry pattern, but rather just another bump on the road towards winter.