Scientific Forecaster Discussion
fxus61 kokx 140231
Area forecast discussion
National Weather Service New York New York
931 PM EST Wed Nov 13 2019
high pressure moves offshore on Thursday as a weak warm front
passes to the north. This will be followed by a cold front
Friday night, and then high pressure for much of this weekend.
Low pressure will move east of the area Sunday night into
Monday, with another weaker coastal low pressure system
potentially passing to the east Tuesday and Tuesday night.
Near term /until 6 am Thursday morning/...
dry weather overnight with a strengthening 1031 high building
over the region. A mid and high cloud shield continues to
progress east passing over the area. This could limit slightly
the radiational cooling potential overnight. The forecast was
not adjusted below guidance as a result, despite the anomalous
cold. Some record lows are expected to be broken. If the cloud
shield erodes sufficiently and is not as thick as the GFS
suggests, lows may be colder than forecast. Will have to
monitor this as this may have an impact on how low temperatures
Short term /6 am Thursday morning through Thursday night/...
return flow develops during the day Thursday as the high builds
offshore. This will bring a warmer, moist flow into the region.
Shortwave energy embedded in the next approaching upper trough
may provide just enough lift to produce some pockets of light
rain, particularly Thursday night. A blend of the models was
used as a starting point for probabilities, which are still low
with the best chances remaining offshore. However, did manually
increase them Thursday night giving the NAM a bit more weight.
No ice crystals in the cloud layer per model time heights, but
surface temperatures could be a concern, especially if any
precipitation breaks out away from the immediate coasts late
Thursday night. Some light freezing rain has been included in
the forecast, but the probability in this area remains below 30
percent at this time. The nbm was followed closely for
temperatures with some minor adjustments.
Long term /Friday through Wednesday/...
to begin the period on Friday a weakening cold front will slide
through the region. Friday should be mainly dry with near seasonable
temperatures. The more noticeable wind shift will occur behind the
front by Friday evening as this will serve to bring in another round
of unseasonably cold and dry air. This next round of below average
temperatures will not be as intense, nor last as long. This will be
primarily due to the core of the cold air passing by further north
this go around. Therefore this next cold airmass will be shallower
than the current cold air mass. Temperatures will still average
several degrees below average for Friday night into Saturday, but
record or near record cold is not expected for this next shot of
The weekend will begin cold and dry with low dewpoints due to a
strong lower level polar air mass. Dry conditions with mainly clear
skies will be the rule on Saturday. A stiff northeast wind due to a
tightening pressure gradient will lead to wind chill values likely
remaining in the 20s through the day on Saturday. With the northeast
wind continuing Saturday night wind chill readings will run mainly
in the teens Saturday night, before wind chills climb into the lower
and middle 30s during the day on Sunday with the air mass modifying.
High level moisture will try to move up from the south by late
Saturday night into Sunday. A positively tilted trough in the
southern branch will then have to be watched for late in the weekend
and into early next week. The latest global models by and large are
further south initially Saturday night as the system emerges
off the southeast coast, and therefore further east later Sunday
and Sunday night as the system tries to turn the corner up the
coast. Not writing off this system completely in terms of giving
at least eastern sections some rain for Sunday night into
Monday. As temps warm, especially aloft any precipitation if it
occurs would be in the form of rain along the coast, and any
precipitation inland could start briefly as frozen but it is
doubtful as to how far north and west any precipitation would
get with a track off the coast, and possibly well off the coast.
With the latest 12z package being further east overall, and
made some cosmetic downward adjustments with pops but did not
pull out precipitation and rain chances all together. Based on
teleconnections and the 12z naefs the slightly more eastward
track appears to be the way to go for now.
The northern branch will then attempt to become somewhat more active
as to reform the trough in the east. Initially in the wake of the
previous southern branch system there may be a lack of lower and mid
level moisture despite cyclonic curvature aloft developing upstream.
Then much of the global guidance attempts to develop an offshore low
pressure system along with hints at a norlun trough impeding
coastal sections. Thought it prudent for the time being to keep
some chance of precipitation through Tuesday night before high
pressure builds in from the west and southwest into the mid week
Due to the aforementioned pattern with the possibility of a
prolonged NE wind and an easterly swell developing for late in
the weekend and early next week minor coastal flooding for some
coastal locations cannot be ruled out. A mitigating factor
however is that tides will be running astronomically lower late
in the weekend and into early next week.
Aviation /03z Thursday through Monday/...
high pressure builds overnight and moves offshore on Thursday
as a weak warm front passes to the north.
VFR with mainly high clouds tonight. Winds will be light and
VFR on Thursday, although ceilings of 3500-5000 ft may develop along
the coast during the morning and continuing into the afternoon.
Light winds early in the morning will become S-south-southwest under 10 kt
through the remainder of the day.
Outlook for 00z Friday through Monday...
Thursday night-Friday...mainly VFR, although a few borderline
clouds 3-5 kft are possible along the coast Thursday night.
Friday night...VFR. Northwest wind gusts 20-25 kt.
Saturday-Sunday...VFR. North-NE gusts around 20-25 kt.
Monday...MVFR or lower possible in rain/wintry mix inland.
NE wind gusts 15-20 kt.
winds and seas will remain below advisory levels through
Thursday night with high pressure over the region.
Sub Small Craft Advisory conditions are expected on the coastal waters through Friday.
Seas will then begin to build late Friday night into Saturday due to
a tightening pressure gradient and a developing increasing easterly
swell. Small Craft Advisory conditions are expected out on the ocean, and eventually
all the coastal waters due to increasing winds during Friday night.
With high pressure to the north and low pressure well to the south
on Saturday Small Craft Advisory conditions will continue with building ocean seas.
Wind gusts may reach gale criteria out on the ocean waters by
Saturday night and continue through the remainder of the weekend.
By Monday the pressure gradient relaxes and sub Small Craft Advisory conditions will
return to the non-ocean waters. Out on the ocean however, seas will
remain elevated as Small Craft Advisory conditions will continue mainly due to high
no hydrologic impacts expected through the forecast period.
NYC National oceanic and atmospheric administration weather radio station kwo35 (162.55 mhz) is operating
at reduced power until further notice.