10:00am Thursday, September 18:
A weak area of Canadian high pressure building across the Northeastern
US will sustain the pleasant Fall-like weather a couple more days
before a brief return of warmer conditions this weekend. As this high
pressure exits the coast Friday afternoon, a period of easterly flow
will affect the region Friday night into early Saturday. The result
will be some low clouds late Friday into Saturday, however, developing
south and southwesterly flow Saturday will ultimate lead to warmer and
a bit more muggy conditions Saturday afternoon into Sunday. While high
temps will hold in the low 70s today and Friday, the weekend will warm
a few degrees above normal with highs in the upper 70s to low 80s.
The next front will move through Sunday evening with a just a
couple of showers possible late Sunday afternoon into the overnight.
There's a chance that Sunday night's front may entrain some of the
remnant moisture from ODILE (the tropical cyclone that moved in over
Baja and into the southwestern US early this week); if so, the showers
could produce a little more in the way of some needed rain Sunday
night....but don't bet on it.
The first half of next week will be dominated by deepening
northwest flow as a trough pivots over the Great Lakes and Northeast.
A large area of high pressure will then usher in another cool,
comfortable air mass Monday night through Wednesday. Daytime highs
will hold in the upper 60s to low 70s Monday and Tuesday, and
overnight lows will drop into the low 40s...and perhaps even the upper
30s. Patchy frost is likely in parts of central and northern PA, but
the first widespread frost in our area is unlikely for at least a few
Beyond that, I see another moderating trend late next week into the
final weekend of September as high temps return to around 80 degrees.
And looking ahead to October, I see more of the same...as a mild
pattern may take hold in the East for part of the month.
11:30am Monday, September 15:
Persistent west and northwesterly flow will bring us a comfortable
week with temps running a few degrees below normal. Highs will be
mainly in the low to mid 70s and overnight lows in the mid 40s to low
50s. Only a passing front late tonight looks to bring a brief round of
showers (between midnight and daybreak Tuesday); otherwise we have a
mainly dry week ahead.
While relatively benign, nearly zonal flow prevails over the lower
48 to start the week, there are a couple of things of interest to
track over the next week or so. First is Hurricane ODILE now moving in
off the Pacific into southern Baja. This system will weaken while
tracking slowly northward towards Arizona--remnant moisture from this
storm unfortunately may bring another round of heavy rain to parts of
Arizona on/around Thursday. Beyond that, the moisture will be
entrained by a mid-latitude trough crossing the Rockies on
Friday...and this moisture may help fuel showers farther east, perhaps
in the Midwest on Saturday and Ohio Valley or Great Lakes Sunday (and
possibly here in PA next Monday?). Ahead of this trough, southwesterly
flow will result in a warming trend across the Commonwealth with highs
reaching the upper 70s to near 80 on Sunday.
Next week may begin with a few showers on Sunday night or Monday,
before another large Canadian high pressure system settles in with
cool, dry conditions into the midweek. Some long-range guidance points
to a large jet stream ridge developing in western North America next
week--if so, a deep trough may develop over the Eastern states late
next week bringing much below normal conditions and possibly the first
snow flakes of the season at the highest terrain of the region (places
above 4,000 feet such as Blue Knob, PA and Snowshoe, WV).
P.S. Here's a link to the latest episode of MU's
Weather Watch, a fully student-produced bi-weekly show.