Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
352 PM EDT Wednesday Sep 17 2014
high pressure remains over the region most of the time through
Sunday. A weak cold front moves through Thursday. Another cold
front moves through the region to start the new week. High
pressure builds back in the wake of the front.
Near term /until 6 am Thursday morning/...
cyclonic northwest flow remains across the northeast through tonight
as a weak upper and middle level short wave moves through the southern
tier of Canada from the Great Lakes into Quebec and northern New
England. While at the surface high pressure slowly weakens with the
approach of a cold frontal boundary. A dry air mass remains in place
tonight with a light to calm northwest flow. With generally clear
conditions and light wind out lying areas will radiate well and
quickly. For overnight lows leaned toward the cooler GFS
There is a moderate risk of rip current development at the
Atlantic beaches into this evening.
Short term /6 am Thursday morning through Friday/...
the upper and middle level short wave continues to track east through
southern Canada Thursday while a weak cold front moves through the
area during the day. Upper level height begin to rise Thursday
afternoon as another Canadian air mass build toward the region.
Little moisture and lift will be associated with the front and only
an increase in clouds will accompany the passage. Kept probability of precipitation near
zero with the front. Again will be a cool day with northerly flow
and used GFS guidance for highs.
There is a moderate risk of rip current development at the
Atlantic beaches on Thursday.
Thursday night and Friday will remain tranquil as an upper ridge
remains across the eastern third of the United States. And at the
surface high pressure moves out of south central Canada and off the
New England coast. With a much cooler air mass moving in the NAM and
GFS temperature guidance seems a little too high so used the cooler
ecs for temperatures Thursday night and Friday.
Long term /Friday night through Wednesday/...
weekend starts off with high pressure pushing offshore under a near
zonal flow. Generally expecting the dry conditions to continue
Friday night into Saturday with this set up. Partly cloudy skies
over eastern areas with subsidence aloft...increasing cloud cover to
the south and west with weak embedded vorticity maximum riding the flow. 12z
runs of NAM/GFS suggestive of light precipitation formation Sat afternoon though
failing to really see any trigger at the surface or aloft
combining with a still moistening atmo. So will maintain dry probability of precipitation
heading into Sat night.
Changing conditions by Sunday as the next amplifying middle/upper level
trough swings south across the Great Lakes region with surface low
pressure trekking through southern Canada. First thing of note for
Sunday to be addressed is the formation of low pressure forming off
the southeast US with associated middle level energy swings north ahead
of the trough. 12z CMC bit quicker with the progression...allowing
for the phasing of the detached energy with the main trough
developing in a much deeper/stronger system moving through the northeast.
For now...sided with a solution leaning more to the European model (ecmwf) and
GFS...which has the low riding the cold front as it moves through on
sometime Sunday night into Monday...then lingering just offshore
into Monday night and finally exiting the region by Tuesday morning.
Concerning probability of precipitation...introduced slight chance by Sun afternoon for extreme
northwest areas right ahead of the front...then spreading to the
east Sun night and Monday...then tapering off from west to east by
06z Tuesday. Enough moisture should be ushered in with the southerly
flow ahead of the front to result in at least light showers for some
time Sun night-Mon. However...uncertainty on the timing so will
maintain lower end chance probability of precipitation.
Model solutions then come back into decent agreement by 12z
Tuesday...with high pressure building in behind the front...resulting
in dry conditions for middle week.
Period of below normal temperatures will be short lived with warm air advection along the
southerly flow pushing temperatures back to near normal levels by Sat. Cold air advection
with the cold front Monday through middle week will see temperatures dropping
a few degrees below normal once again.
Aviation /20z Wednesday through Monday/...
high pressure/VFR through taf period.
Sea breeze across coastal terminals on Southern Shores. Have doubts
about the boundary reaching far enough north/west to reach
klga/kewr/kteb but see comments below regarding uncertainty. Flow
more 240-280 true at terminals that do not see the see breeze
influence. Speed around 5-10 knots everywhere.
Winds turn light and more westerly everywhere overnight.
New York metropolitan enhanced aviation weather support...
Detailed information...including hourly taf wind component forecasts can
be found at: http:/www.Erh.NOAA.Gov/zny/n90 (lower case)
Kjfk fcster comments: medium-high confidence in wind staying left of
230 mag through 00z.
Klga fcster comments: low potential for sea breeze to reach terminal
around 22-23z. Winds may stay 20-30 degree right of taf this
Kewr fcster comments: low potential for sea breeze to reach terminal
around 22-23z. If it does occur...wind direction may be closer to
Kteb fcster comments: low potential for sea breeze to reach terminal
around 23z. If it does occur...wind direction may be closer to 170-180
Khpn fcster comments: wind direction may stay 20-30 degree right of taf
this evening if sea breeze does not reach terminal.
Kisp fcster comments: wind direction may be +/- 20 degree of forecast.
Outlook for 21z Thursday through Monday...
Sunday night-Monday...chance of MVFR or below with possible showers.
with high pressure over the waters tonight into Thursday the flow
will be rather light. A weak cold front does move through Thursday
afternoon into Thursday evening. Another high builds in from Canada
Thursday night into Friday. A northeast flow around the high
increases late Thursday night into Friday. Some gusts may approach
small craft levels on the eastern ocean waters during Friday. In
addition to the flow a southeast swell may allow for seas on the
ocean to build to around 5 feet during Friday.
Generally expecting sub-Small Craft Advisory conditions through the coming week. Seas
will attempt to build to 5 feet on the ocean waters sun-Monday with the
persistent southerly flow...but overall should remain at 3-4 feet.
no rainfall is expected through the first half of the weekend. No
significant precipitation resulting in hydrologic issues is
expected Sunday through next week.