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
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
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.