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Area forecast discussion 
National Weather Service New York New York
351 am EDT Tuesday Sep 2 2014

Synopsis...
a cold front approaches from the west today...then crosses the
tri-state tonight. Weak high pressure builds in on
Wednesday...then remains over the region into Friday. A cold
front will approach Friday night and move across the region
Saturday and Saturday night. High pressure returns for the start
of next week.

&&

Near term /until 6 PM this evening/...
convective forecast for today is a challenging one. While a pre-
frontal trough will develop and remain over mainly
western/northern zones...appears should have a weak cap develop
around 650 hpa. So even with 1500-2500 j/kg of cape forecast...the
weak cap coupled with best dynamic forcing prognosticated to our north...and
relatively weak shear 20 knots or less until maybe very late in the
day over far west zones as low-middle level jet approaches there. Appears
best chance for any convection is over areas north/west of NYC late this
afternoon with arrival of low-middle level jet.

Given above...feel that most likely cap holds on over the southeast 2/3
of the County Warning Area...so have gone with a dry forecast there. Have chance
probability of precipitation by late afternoon over mainly Orange and Putnam counties and
slight chance probability of precipitation in between. Any convection that does form will
be mainly of the pulse variety...with some multi-cellular
structures possible by late afternoon over mainly Orange County
with arrival of low-middle level jets. Based on this feel severe
threat is minimal this afternoon...but cannot be completely ruled
out.

For highs today...used a blend of mav/met guidance...NAM 2-meter
temperatures and mixing down from 875-850 hpa per BUFKIT
soundings. Should see values around 10-15 degrees above normal -
from around 90 to the middle 90s inland/NYC heat island...and middle to
upper 80s near the coast. Heat indices should reach the middle-upper
90s across urban NE New Jersey and NYC this afternoon. However...fall
short of heat advisory criteria.

There is a moderate risk of the meteorological enhancement of rip
current formation at Atlantic beaches today.

&&

Short term /6 PM this evening through 6 PM Wednesday/...
region will be in the right rear quadrant of 80-90 knots 300 hpa
jet...passing of strengthening low-middle level jets in the
evening...and the area under diffluent flow in the middle
levels...coupled with precipitable waters forecast to increase to
around 2 inches...then have the potential for locally heavy
rainfall in any storms that do form this evening. Refer to hydrology
section of the afd for further details.

However...will be working against diminish cape with the loss of
solar heating...with best dynamics passing to the north...believe that
any severe potential rapidly diminishes during the early evening
hours...and it was not all that high to begin with.

700-500 hpa shortwaves lifts to the North/East of the area tonight...with
zonal flow developing Wednesday...allowing for things to dry out
late tonight behind the shortwaves.

For lows tonight...used a blend of mav/met guidance with NAM
2-meter temperatures...with values forecast to be around 5 degrees
above normal. For highs Wednesday used a blend of mixing down from
850-825 hpa per BUFKIT soundings...with NAM 2-meter temperatures
and a blend of mav/met guidance. This yields highs around 5-10
degrees above normal.

&&

Long term /Wednesday night through Monday/...
high pressure over the region Wednesday night through Friday will
keep conditions sunny and dry. As the high moves offshore on
Thursday...expect humidity levels to increase Thursday night and
Friday.

A cold front will approach the area Friday night into
Saturday...pushing offshore sometime Saturday night. Expect showers
and thunderstorms to accompany the front. Most of the models are in
good agreement on the timing of the front. However...a few of the
models want to linger some precipitation into Sunday behind the
front. For now...do not want to rule this out...so will keep some
chance/slight chance probability of precipitation in for now.

High pressure over Canada will build south behind the cold
front...bringing cooler and less humid conditions to the region for
the start of next week.

Temperatures Thursday through Saturday will remain above normal with
highs in the middle to upper 80s. Slightly cooler conditions can be
expected right along the coastal sections. Temperatures then fall
below normal Sunday through Tuesday with highs only in the 70s.

&&

Aviation /07z Tuesday through Saturday/...
MVFR/IFR stratus/fog likely along eastern terminals...possible
across interior terminals.

Any stratus/fog should Burns off in the morning...with VFR conds
in afternoon.

Light and vrb winds the remainder of the night through the coming
morning...giving way to afternoon seabreeze development along the
coast.

Increasing chance for scattered rain showers/thunderstorms and rain the coming evening across NYC
terminals and to the west & northwest with approaching cold front. Will
maintain prob30 now...generally thinking between 02-08z.

Outlook for 06z Wednesday through Friday...
Tuesday night...mainly VFR. Winds shifting SW to northwest behind front
between 06-12z.
Wednesday-Friday night...VFR conditions are expected.
Sat...sub VFR possible in scattered shra/tsra.

&&

Marine...
winds will be 15 knots or less on the waters through Wednesday. There
is some potential that seas could build to 5 feet on anz-350
tonight...with tightening of pressure gradient ahead of the
front...and residual 1-2 feet swells. However confidence in this is
not all that high...so do not reflect in forecast at this time.
Seas should come down on Wednesday with a weakening pressure
gradient over the area.

Generally looking at sub-Small Craft Advisory conditions on the area waters Wednesday
night through the weekend. A cold front will push across the waters
Saturday night into Sunday...which will result in higher winds and
seas.



&&

Hydrology...
spotty rain showers/thunderstorms mainly over areas north/west of NYC...could produce
isolated locally heavy rainfall. Areas experiencing locally heavy
rainfall could experience minor urban/poor drainage flooding.
Outside of areas experiencing locally heavy rainfall...less than
0.2 inches of basin average precipitation is expected from any
precipitation that does fall this afternoon and tonight.

It should then be dry from Wednesday through at least Friday.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...none.

&&

$$

Synopsis...BC/maloit
near term...maloit
short term...maloit
long term...British Columbia
aviation...Sears
marine...BC/maloit
hydrology...BC/maloit

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