Fast zonal jet stream flow means our weather will evolve quickly
from mild to cold and then back to mild over the next 5 days. High
temps early this week reached 60 degrees--not bad for early November.
A strong clipper system is now crossing the region and a 36-hour shot
of Canadian chill will follow this system. A passing shower and
increasing winds will signal the passage of the cold front later
today, and temperatures will plummet from a midday high near 50 down
to near freezing by midnight; the mountains of northwestern PA may
even pick up a coating of snow from lake effect snow showers tonight.
Friday and Friday night will feature December-like chill with highs in
the 40s and lows in the 20s.
High pressure will then take control, so a completely dry weekend
is on tap for the first time in weeks (or months?). Afternoon highs
will warm into the 50s on Saturday and low to mid 60s on Sunday. By
early next week, deep southwest flow may lift temperatures into to
near 70 degrees, although I have some concern of clouds forming as
warm are noses back into the region late in the weekend and early next
week. Mild conditions will likely last into the second half of next
week (with highs at or above the normal of 55 degrees), although there
are two systems to keep an eye on. The first is a weak cold front that
may slip through late Tuesday or Wednesday; the second system is a
possible tropical disturbance that might send moisture northward from
the Gulf of Mexico. Either one of these systems--or perhaps both
combined--could threaten with clouds and showers sometime during the
midweek.
Monday's discussion:
It's the time of year when an increasingly fast and disturbed jet
stream brings a rapidly changing weather pattern with occasional
pre-winter storms. A little over two weeks ago parts of central and
northern PA experienced a noteworthy snowstorm (up to 10 inches
fell!). This past week it was the central Rockies turn as up to 48
inches of snow fell in the mountains and near-blizzard conditions hit
parts of the western Plains. The pattern the next week looks less
dramatic by comparison as the jet stream deamplifies for the time
being. The result will be a parade of weaker disturbances and no big
storms.
Short-term, high pressure is taking control (briefly) ahead of a
cold front that will cross the Commonwealth on Tuesday. Windy
conditions will be the greatest impact from the front, along a frosty
night with lows in the upper 20s to low 30s. A second front, supported
by a strong disturbance aloft, will then dig in Wednesday night into
Thursday. This system will bring a 50 percent chance of showers
Wednesday night into Thursday, and with temperatures in the 30s to low
40s I can't rule out some wet snow mixing in across parts of central
and northern PA. Some lake effect snow showers might even accumulate
in the mountains of western PA early Thursday. Thursday night into
Friday will then bring clearing skies and unseasonably cool conditions
before a warm-up develops for the weekend (and perhaps beyond).
The first weekend of November may shape up into a classic Fall
weekend across the Commonwealth. A jet stream ridge will crank up in
the East while a trough deepens in the West. After a chilly start
Saturday morning, temperatures will climb into the 60s both Saturday
and Sunday afternoons, thanks to abundant sunshine and a breeze from
the southwest. While it's uncertain how long this warm-up will last,
there's a chance it might extend into the middle of the following week
with high temps that might even exceed the 70-degree mark!
