Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service New York New York
950 PM EST Mon Feb 27 2017
a warm front approaches tonight and lifts through the area on
Tuesday. Another warm front will then move through Tuesday
night. The warm front will lift well to the northeast on
Wednesday, followed by a strong trailing cold front late
Wednesday into Wednesday night as intensifying low pressure
moves northeast up the Saint Lawrence River valley. The low will
move across the Canadian Maritimes on Thursday, followed by
weak high pressure Thursday night. A weak Alberta clipper low
may move across or pass just south on Friday, followed by high
pressure passing to the south for the weekend. Another low
pressure system will begin to approach on Monday.
Near term /until 6 am Tuesday morning/...
biggest challenge tonight will be with the amount of cloud
cover, at least through the first half of the night. Satellite
trends over the last few hours have shown some dissipation of
clouds over eastern PA with mostly clear skies across New
England. This has allowed for temperatures drop more then
forecast due to better radiational cooling conditions. However,
warm advection increases overnight and there will be an
approaching 700-500 hpa shortwave. These factors should lead to
clouds overspreading the region after midnight.
A warm front is also progged to approach the tri-state area
tonight as well, just reaching the southern portion of the County Warning Area
towards daybreak. Associated isentropic lift ahead of this front
looks too weak with the given moisture depth, especially below
850mb, to produce any rainfall. Have continued with a dry
Overall, low temperatures will end up above normal. A few
outlying locations could fall into the lower 30s before
remaining steady or slowly rising due to weak warm advection
and increasing clouds.
Short term /6 am Tuesday morning through Tuesday night/...
the warm front pushes through Tuesday morning. So after a cloudy
start, it appears we get into at least partial sunshine. Higher-
level clouds probably filter the sunshine until lower clouds shift
in from the west and possibly from off the ocean as well late in the
day. Isentropic lift is a little stronger this time around, but
moisture still isn't very deep. Will at least go with a slight
chance of light rain for southern and western sections.
An onshore flow will limit mixing particularly for coastal sections,
but it will still end up well above normal for high temperatures.
Most of the area ends up in the 50s, and expecting parts of the city
and NE New Jersey to top the 60 degree mark.
For Tuesday night, isentropic lift becomes stronger as another warm
front moves through, plus there will be additional lift from a mid
level shortwave passing through. Models vary with the depth and
placement of moisture, but feel confident enough to go with the
likelihood of rainfall for at least a short period during the night.
The amount and density of fog that occurs during the night becomes a
tricky forecast. On one hand, low level wind profiles look too
strong for widespread or dense fog, but surface dewpoints around 50
advecting over sea surface temperatures in the low to mid 40s could
result in advection fog in spite of this. Will go with areas of fog
in the forecast and keep vsbys above dense.
Will go with a non-diurnal temperature trend during the night with
the warm front moving through. Low temperatures will be warmer than
Long term /Wednesday through Monday/...
as a warm front lifts to the north Wed morning, light rain and
areas of fog will slowly diminish. With the area in the warm
sector and partial sunshine for late morning and early
afternoon, expect an unseasonably mild day with high temps on
the high side of MOS guidance, with lower 70s from NYC west and
into the 60s elsewhere. There could be enough instability for
some isold-sct convection from NYC Metro west by midday, but the
main push for strong to possibly severe tstms expected late day
into early evening well in advance of the approaching front.
Faster GFS timing was preferred here over the 00z ECMWF, though
it appears the 12z European model (ecmwf) is trending toward the GFS. Damaging
winds the main threat here, though with model fcst strong of 0-1
km shear and strong SW winds aloft, could not rule out other
modes especially inland northwest of NYC as was the case this past
Saturday. The threat area will also extend a little farther east
than it did on Sat as low level flow will be SW rather than se,
extending to at least Nassau/Fairfield and possibly into
northern New Haven and westernmost Suffolk, which is in
agreement with the latest Storm Prediction Center day 3 outlook.
Cold fropa will take place later Wed night, with strong cold air
advection and temps cooling through the night and perhaps not
rising much if at all daytime Thu, with highs in the 40s to near
50. Expect a cold night Thu night with diminishing winds and
lows in the 20s to lower 30s.
Models differ somewhat on track of a weak Alberta clipper low
dropping into the base of the longwave trough that becomes
established over the east for Fri, with the GFS bringing it
right through with a potential light snowfall, and the European model (ecmwf)/CMC
taking a more southerly track. Will continue to carry chances
for a light snowfall.
Fair and cold wx expected to last for one more day into Sat,
then Sunday/Monday are shaping up to be on the mild side as high
pressure passes offshore and SW return flow becomes established.
Aviation /03z Tuesday through Saturday/...
VFR as high pressure builds farther offshore and a warm front
approaches from the SW on Tuesday. SW winds diminish this
evening and back around to the east-southeast by daybreak. Winds may be
light and variable at times overnight.
MVFR conditions with light rain is possible by late Tuesday
afternoon. The greatest uncertainty is with how quickly cigs
lower, eventually to IFR Tuesday evening.
Outlook for 00z Wednesday through Saturday...
Tuesday night-Wednesday morning...areas of fog with rain.
MVFR/IFR and possibly lower. Low level wind shear possible with SW winds 45-55
kt at 2kft. SW winds g15-20kt possible Wednesday morning.
Wednesday afternoon-Wednesday night...showers and a chance of
thunderstorms. MVFR or lower possible. SW winds g20-30kt. Winds
become westerly late Wednesday night.
Thursday...VFR. West-northwest winds g25-35kt.
Friday...MVFR/IFR possible with a chance of light snow. Northwest
Saturday...VFR. Northwest g20-25kt.
winds on the ocean have diminished with speeds around 10 kt.
Ocean seas are generally 3 to 4 ft, although 44017 has seas
just under 5 ft. Do not think this will continue and seas should
subside to around 4 ft overnight.
Otherwise, winds and seas will continue below advisory criteria
until late Tuesday night. Will hold off on headlines for this
event with it starting late in the 3rd period and allow the
midnight shift to issue any headlines as appropriate.
For the longer term, increasing SW flow on Wed will likely
result in Small Craft Advisory conds for all waters, and perhaps minimal gales on
the outer ocean waters. The better chance for gales on the
ocean will come after a strong cold frontal passage late Wed
night into Thu, then again late day Fri into Fri night with the
passage of a weak Alberta clipper low, with Small Craft Advisory conds on the
remaining waters. Small Craft Advisory conds should last on all waters into Sat,
then remain confined to the ocean Sat night.
rainfall from late Tuesday through Wednesday night should run
from 1/2 to 1 inch, with locally higher amounts double that
possible that could cause localized minor flooding.
Release from Spring snow melt is occurring down the Connecticut
and Housatonic rivers.
record highs for Wednesday March 1
Location.......record high/year set.....Forecast high
j f Kennedy.............58/2004*..............67
* = and in previous years
Record high minimum temperatures for Wednesday March 1
Location....record high min/year set.....Forecast low
j f Kennedy.............42/1974*..............50
* = and in previous years