Weather with Bill Evans
Good Day On This Friday October 15, 2021
High pressure today will give way to an approaching frontal
system over the Midwest. A strong cold front will then pass
through the area Saturday late afternoon into evening. High
pressure builds in Sunday night and Monday and will remain in
control through the middle of the week. A frontal system
approaches late next week.
A high amplitude upper level ridge along the eastern seaboard
today will give way to a progressive longwave trough moving
across the mid and upper Mississippi Valley. The latter of which
well send a frontal system toward the area, but not before high
pressure moves offshore later this morning.
It will remain unseasonably warm as 85h temperatures approach
15C. The one limiting factor for record highs today will be a
subsidence inversion that will limit the depth of the mixed
layer. However, based on highs across the region on Wednesday,
went a few degrees above MOS and NBM. This will put readings
into the upper 70s and lowers 80s this afternoon, warmest
across the NYC metro. Current forecast highs fall a few degrees
below records.
Some mid and high level clouds will continue to ride over top
the upper ridge with partly to mostly sunny skies. It is also
possible for a late day shower across Orange County in the Lower
Hudson Valley due to warm advection on the backside of the
ridge and marginal instability.
The longwave upper trough continues to march east with high
pressure offshore across he Western Atlantic. A few showers
could linger overnight across the far NW interior. Southerly
winds will begin to ramp up late tonight into Saturday with
sustained winds of 15 to 20 mph with gusts up to 30 mph by
Saturday afternoon. The strongest winds will be along the coast.
A 30-40 kt LLJ will to develop across the western half of the
forecast area by daybreak, then shifts east across LI and CT on
Saturday. Temperatures will remain unseasonably warm with lows
about 15 to 20 degrees above normal and highs 10-15 degrees.
Cold front arrives late Saturday afternoon across western
portions of the Lower Hudson Valley, NYC metro by early
evening, and LI and CT mainly after 7 pm. While the vertical
wind profile strengthens with 40-50 kt of deep-layer shear (0-6
km) by afternoon, weak lapse rates only support CAPES of
500-750 J/KG from NYC and points north and west. The instability
lessens as the front moves across LI and CT. CAMs are in very
good agreement in weakening the line of convection as it
approaches the coast in the early evening. Due to the strong
vertical wind profile and marginal instability, an isolated
strong and/or severe thunderstorm can not be ruled out. The
best chance at this time would appear to be across NYC, NE NJ,
and the Lower Hudson Valley. To the east, the strong southerly
flow will result in a bit more stability. SPC has maintained a
marginal risk across all of the forecast area.
Post-frontal showers may linger for a short time behind the
line, but conditions will then quickly dry out with strong CAA
and gusty NW winds behind the cold front. The strongest winds
will be during the daytime hours on Sunday.
Highs on Sunday will return to seasonable levels in the lower
to mid 60s.
An isolated shower is possible NW of NYC Sunday afternoon due
to cyclonic flow and steep low-level lapse rates. Any convection
will be low-topped and weak.
Upper level trough slowly slides east Sunday night as a cut off low
settles over southeast Canada Monday night. Meanwhile, high pressure
builds in at the surface.
There does seem to be some vorticity maximums rounding the cut off
low that make their way into the forecast area, that may provide
some lift for the development of showers to our northwest.
Additionally, perhaps some lake enhanced rain showers develop over
eastern and central New York. The question is whether any of these
showers make it to any part of our forecast area. Current thinking
is that much of any precipitation will evaporate with the downslope
flow. However, a slight chance of showers is possible for northern
Orange County during the day Monday.
Otherwise, dry conditions are expected through the middle of next
week as high pressure continues to build in. The center of the high
will be situated over the southeast states by Tuesday, pushing off
the southeast coast Wednesday. This will allow the next frontal
system to approach late next week, with any precipitation holding
off until Thursday night.
Temperatures will be seasonable for Monday, perhaps a couple of
degrees below normal, as northwesterly flow continues across the
area. As we head into the middle and latter half of next week,
temperatures start to climb to above normal as upper level ridging,
and therefore height rises allow for the introduction of a
progressively warmer air mass.
Southerly winds quickly ramp up late tonight into Saturday ahead
of an approaching cold front. A SCA has been issued for all
waters on Saturday with southerly gusts of 25-30 kt. A few gusts
to gale force are possible, especially nearshore.
SCA conditions are likely to continue on the ocean waters
through Sunday, possibly into Monday, due to a strong NW flow.
Elsewhere, conditions will be more marginal and confidence is
not as high. Winds and waves diminish heading into Tuesday as
high pressure builds in from the west.
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