Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
146 PM EDT Wednesday Oct 7 2015
Canadian high pressure builds over the region through Thursday.
A warm front lifts to the north Thursday night...followed by a cold
front crossing the tri-state Friday afternoon and evening. High
pressure then builds in through Saturday...then slides offshore
Sunday and Sunday night. An area of low pressure tracks up the middle
Atlantic and northeastern coasts Monday and Monday night...followed
by a cold front crossing the tri-state on Tuesday.
Near term /until 6 PM this evening/...
subtle changes made to afternoon highs based on initial
conditions with most locations topping out around 70 under sunny
Overall...a weak pressure gradient at the surface with a broad
middle to upper level northwest to west flow. Northwest sfcwinds will back
to the west ahead of an approaching cold front.
Short term /6 PM this evening through 6 PM Thursday/...
aloft there will continue to be a quasi-zonal flow. High pressure
will continue to build in at the surface. The center of the high
is forecast to move east of the Great Lakes and into the
northeast tonight. The radiational cooling will be more optimal
tonight with light winds and mostly clear sky conditions. The
lower met MOS guidance was used for lows.
For Thursday...the zonal flow remains aloft. Meanwhile...at the
surface...the center of the high pressure area moves across. The
weak pressure gradient will allow for light winds through the day.
Models agree that southeast flow develops in the afternoon. This and the
lack of winds within the boundary layer will make for a slightly
cooler day compared to the previous day despite mostly sunny sky
conditions. A mav/met blend was used for highs.
Long term /Thursday night through Wednesday/...
850 hpa warm front pushes into the area Thursday night...with
associated warm advection increasing cloud cover. Low levels are
rather dry...so kept the forecast for Thursday night dry based on
this. For lows Thursday night...a blend of mav/met/ecs guidance and
the previous forecast was used...with values expected to be around 5
degrees above normal.
A northern stream trough approaches on Friday...with its axis
crossing the area Friday evening. Ahead of the trough...and its
associated surface reflection/cold front...there should be some
showers across the tri-state mainly Friday afternoon and evening.
Based on a blend of European model (ecmwf)/GFS/NAM showalter indices being between 0
and 2 Friday afternoon/early Friday evening...a GFS/NAM blend
yielding forecast surface based convective available potential energy of 500-1000 j/kg Manly across
the interior...and the region being in the right front quadrant of a
100+ knots 300 hpa jet...have a slight chance of thunder in the
forecast as well from Friday afternoon into Friday evening. The
NAM/GFS/ECMWF/CMC all dry things out fairly rapidly from northwest to southeast
Friday night...so have lowered probability of precipitation much more rapidly after 00z
Saturday than previously forecast.
For highs Friday...a blend of mav/ecs/met guidance...NAM 2-meter
temperatures and a mix down from 975-925 hpa per BUFKIT soundings
was used...with values forecast to be around 5 degrees above normal.
A blend of mex/men/ekd/ece/ecm/wpc guidance and NAM 2-meter
temperatures was used for lows Friday night...with readings expected
to be around 5 degrees above normal.
The European model (ecmwf) has stayed away from its previous idea of a wave
developing along the front over the weekend...and the 00z CMC has
speed up its timing of the front similar to the ECMWF/GFS/NAM...so
have gone with a dry forecast through the weekend as weak northern
stream ridging gradually builds in by Sunday/Sunday night.
The CMC/ECMWF/GFS all have a southern stream cutoff low emerge off
the southeastern coast Monday morning. They differ in how it tracks
as it opens and lifts to the northeast...with the CMC much more out
to sea than the European model (ecmwf) and GFS. The GFS/European model (ecmwf) bring the cutoff...with
its associated surface low towards the region into Monday
night...before merging the low with an approaching frontal system by
Tuesday morning. Given that this is a relatively new wrinkle to the
forecast...though the 00z GFS was hinting at something like this
last night...have only brought slight chance probability of precipitation into mainly the
eastern 1/2 of the area Monday afternoon/night...and increased cloud
cover. If trends in the GFS and European model (ecmwf) hold...more extensive
adjustments towards a cloudier/wetter forecast would be needed in
the Monday/Monday night time frame.
The GFS and European model (ecmwf) have also trended wetter with a cold frontal
passage on Tuesday...so have upped probability of precipitation to slight chance County Warning Area
wide...once again further refinement will be needed if the latest
For temperatures Saturday-Tuesday a blend of mex/men/ekd/ece/ecm/wpc
guidance was used...with temperatures tweaked downward Saturday
night across normally colder areas. Temperatures Saturday and
Saturday night are forecast to be below normal...then near normal
temperatures are forecast Sunday-Sunday night. For now forecasting
temperatures to be above normal Monday-Tuesday...but could end up
seeing mondays temperatures ending up below normal...if the latest
trends in the European model (ecmwf) and GFS hold.
Aviation /18z Wednesday through Monday/...
hi pressure builds over the area tonight and offshore late Thursday.
VFR through the taf period...although ceilings may drop to just above
3000ft at times.
A high amount of variability in winds due to the light flow. Flow this
afternoon and evening mainly expected to be west to northwest.
... 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: low chance of a sea breeze. High amount of
variability in wind direction possible through 00z.
Klga fcster comments: variability in wind direction possible through
Kewr fcster comments: variability in wind direction likely through
Kteb fcster comments: variability in wind direction likely through
Khpn fcster comments: no unscheduled amendments expected.
Kisp fcster comments: no unscheduled amendments expected.
Outlook for 18z Thursday through Monday...
rest of Thursday...VFR. East-southeast flow veering to the S.
Friday...cold front passes in the evening. Chance of MVFR with -ra. SW winds
shifting to the northwest.
Small Craft Advisory have been dropped on the ocean waters with long period swells
pf 4-5 feet. This should have little impact on smaller vessels...except
near shoaling areas and inlets. Seas will continue to subside
In terms of winds...they will be below Small Craft Advisory thresholds through
Thursday with high pressure being dominant through that time
For tonight...the ocean seas will lower to 2 to 4 feet...below Small Craft Advisory
thresholds. The seas remain below Small Craft Advisory then through Thursday.
A relaxed pressure gradient should yield winds 10 knots or less on all
waters Thursday night.
Small craft conditions are probable on the coastal ocean waters from
mainly Friday afternoon into Saturday due to a passing cold front.
The pressure gradient then relaxes later Saturday and Sunday...with
winds diminishing to 10 knots or less.
On the non-ocean waters...sub-sca conditions are forecast Friday-
Sunday. However...gusts to around 20 knots are probable on these waters
from Friday afternoon into Saturday.
dry weather is forecast through Thursday. It should be dry
Thursday night. Rain is likely Friday and Friday night...with a
1/3-1/2 inch of rainfall on average...with locally higher amounts
possible in areas experiencing strong convection. Areas that do
have locally heavy rainfall have the possibility of ponding of
water on roadways and a very low chance of minor urban/poor
drainage flooding. It should then be dry for the upcoming weekend.