10:00am Monday, October 20:
Despite the season's first widespread frost this morning, we continue
in a relatively mild pattern; and it looks likely that October will
conclude as the warmest month of 2014 relative to average. Through
October 19th, the month-to-date
departure from normal is about +1.5 degrees. The month's final 12
days look to continue this trend, so that October should conclude 1.5
to 2.0 degrees above normal.
Short-term, we have a clipper system digging in tonight and Tuesday
with scattered showers developing. If this was an ordinary clipper it
would exit quickly and dry conditions would arrive for Wednesday.
Unfortunately, this is a rare clipper that will sharpen up and "close
off" as it reaches the East coast--the result will be a large,
slow-moving upper-level low that will take two or three days to clear
the coast. Right now, an extended period of steady rain looks most
likely from NJ and the Poconos up through eastern New England, while
persistent clouds and scattered showers dominate the eastern half of
PA. So while I don't expect a washout here, a shift in the location of
this upper-level low will affect the midweek forecast. My current
position is that a few showers are possible Tuesday and the best
chance for scattered showers or a few hours of steadier rain is
Tuesday evening through Wednesday night. Conditions should gradually
improve Thursday, though a lingering shower is certainly still possible.
Assuming this upper-level system exits on schedule, the period
Friday through Sunday looks pretty good with a seasonable high
pressure taking control. A backdoor cold front may attempt to drop in
early next week with a shallow push of Canadian air. Otherwise, I
expect a warming trend next week--highs possibly returning to near 70
degrees--as westerly flow prevails across much of the country.
11:00am Thursday, October 16:
Wednesday's showery rains outperformed expectations thanks to a
moisture-rich plume of subtropical moisture drawn north into the
Commonwealth from the Bahamas. So in single day our somewhat dry Fall
has turned "wet" with our year-to-date
rainfall total back above the long-term average. Officially,
Millersville received just over 3 inches, while up to 5 inches fell in
a narrow swath roughly aligned along Route 222. Extreme eastern and
western parts of the county received the least rainfall with a between
1.25" and 2.5" reported in these border areas.
Looking ahead, the storyline described below (Monday's discussion)
is holding true with two more seasonably mild days preceding a shot of
chilly Canadian air. Lots of clouds and a hit-or-miss shower or two
are possible today (Thursday) as a large upper-level system moves
overhead. Southwest surface winds will transport mild air from the
Midwest across the Commonwealth today into Friday, so peeks of
sunshine will be able to lift high temps into the upper 60s to near 70.
A cold front will then cross the Commonwealth early Saturday, so
you'll notice a cooler northwest wind developing during the midday and
afternoon. A brief isolated shower is possible Saturday and Sunday,
however most of the weekend will be rainfree. Sunday and Monday will
be the coolest days with highs only in the mid to upper 50s. Monday
morning will be the coldest of all with lows dropping to around 32
north and mid 30s south--therefore, some frost is likely across the
A passing upper-level system may then trigger a shower or a period
of cool, light rain on Tuesday. Clouds and coolness will likely linger
into Wednesday, before another warming trend develops late next week
and into the following weekend.