Weather with Bill Evans
Good Day On This Monday May 16, 2022
A strong cold front moves through the area this evening, followed by
a secondary cold frontal passage on Tuesday. High pressure will
briefly return on Wednesday, then a series of weak disturbances may
skirt the area Thursday and Friday as a warm front slowly approaches
from the southwest. The front should lift through Saturday
morning.
Dense fog has not been a problem over land overnight like it has
been the past several nights. On night fog satellite imagery it
can actually be seen eroding away from the eastern half of the
area. However, with some clearing over the western half of the
area, patchy radiation fog has been able to develop.
The main story today is the round of severe thunderstorms expected
later this afternoon and through the evening. SPC`s 06z update has
nudged the "enhanced" risk east just slightly and then extended the
"slight" risk eastward to the edge of the cwa. The "enhanced" risk
includes the Western half of the Lower Hudson Valley and
northeast NJ.
In the mid-upper levels a negatively tilted trough approaches from
the west, as associated surface low pressure forms and deepens
as it passes to our north and west. A strong cold front
extending down from the surface low will pass through the area
tonight, with severe thunderstorms possible ahead of and along
the front.
There will be two chances at seeing severe thunderstorms today. The
first will be out ahead of the cold front and will be more in
the form of discrete cells. With an environment mainly north and
west of NYC characterized by MLCAPE ~1500 J/kg, effective deep-
layer shear ~45 kts and effective SRH 100-150 m2/s2, any
discrete cells that get going could produce large hail or even
an isolated tornado. With the passing of the cold front storm
mode will be QLCS and damaging wind gusts will be the main
threat at that time. As for timing, any discrete cells would
likely develop around 1pm - 3pm. The more organized line of
storms will follow, likely reaching far western portions of the
cwa ~5pm, nyc by ~6pm. As the line of storms continues east it
will run into a more stable airmass and likely weaken quickly,
common for this time of year.
Any thunderstorms will be able to produce heavy downpours as
well. See hydrology section below.
Highs reach the upper 70s across northeast NJ, Lower Hudson
Valley and interior CT. Across NYC, coastal CT and Long Island
highs will tap out in the mid 60s to low 70s. Behind the cold
front, skies will clear and dewpoints drop from the low 60s to
the upper 40s. Lows will be in the lower to upper 50s.
On Tuesday a secondary cold front will move through at the
surface while shortwave energy rotates around an upper level low
in eastern Canada. A dry day is expected, with some gusty
conditions in the afternoon with northwest wind gusts 20 - 25
kt.
Brief high pressure builds in on Wednesday and another dry day
is forecast. Skies remain clear in the morning hours, but cloud
cover increases in the afternoon ahead of the next system.
Highs both days will be similar. Lower 70s on Tuesday and a few
degrees lower on Wednesday. Dewpoints in the low 40s Tuesday
afternoon lower to the mid 30s by Wednesday afternoon.
To start the long term period, models suggest multiple
disturbances riding along a warm front but differ on exact
impact to the CWA. Will have some slight chance PoPs on
Thursday. Will keep POPs out of the forecast for Friday, however
will need to keep an eye on the timing of one of the weak
waves.
Models then in good agreement with a warm frontal passage Saturday
morning and then a very warm day, with highs close to 90 in NE NJ
per NBM. A blend of the NBM 50th/75th percentile suggests potential
for temps a few deg warmer than that, with lower 90s most areas NW
of NYC, 80s most elsewhere, and 70s for the south facing coastlines
out east.
.MARINE...
A Dense Fog Advisory remains in effect over the eastern two ocean
zones and South Shore Bays of Long Island through 14z this
morning. Visibilities will be as low as less than a mile. Fog
can be seen eroding from west to east on satellite imagery, so
it is possible the Advisory could end earlier than 14z.
Winds and waves remain below SCA criteria through the day. Gusts up
to 25 kts are likely just ahead of and behind a cold frontal passage
tonight on the eastern two ocean zones. A SCA is in effect for these
two zones from 00z tonight until 10z Tuesday morning. Waves will
also build to 5 ft during this time period.
Pwats are progged to be 1.5 inches or slightly higher. According to
SPC`s Sounding Climatology Page, this is between the 90% moving
average and the max moving average for OKX. Given these high
pwat values any showers or thunderstorms that move through the
area today could produce heavy downpours. This could lead to
minor flooding in urban and poor drainage areas. Generally, 0.50
- 0.75 inches of rainfall is expected for NYC and points north
and west, with locally higher amounts possible. WPC has placed
the western half of the area in a marginal risk for excessive
rainfall. Rainfall rates will generally between 0.25 - 0.50
inches per hour. The CAMs are showing a few bulls-eyes of 1 inch
per hour rainfall rates, so this cannot be ruled out
completely, but will likely be very localized if at all. HREF
and NBM probabilities of >1 inch per hour rainfall rates suggest
it is unlikely.
Astronomical tides are running higher than usual. Departures of only
about 1/2 ft are needed to cause minor coastal flooding along the
western Sound, Nassau back bays, and possibly also lower NY Harbor
with the high tide cycles tonight.
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