Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
707 PM EDT Friday Jul 31 2015
high pressure tonight will give way to a cold front on Saturday.
High pressure builds over the area on Sunday and then departs Sunday
night. A series of frontal boundaries will impact the area for the
start of the new week with weak high pressure prevailing in between.
Low pressure may impact the area late next week.
Near term /until 6 am Saturday morning/...
decent mixing late this afternoon and early evening with northwest flow
has allowed dew points to fall into the lower and middle 50s. At
ewr...the dew point was 49 at 22 UTC. This northwest flow has been strong
enough to hold the sea breeze from making much progress from the
South Shore of Long Island. With loss of daytime heating and
diminishing winds this evening...dew points should recover into
the lower 60s. Have updated the database to reflect this trend.
Dry forecast tonight with mainly clear skies giving way to partly
cloudy skies with the upper trough settling over the
northeast. At the surface...high pressure yields to a developing
Temperatures will remain quite mild overnight. MOS blend was followed
and a general range from the lower to middle 70s NYC metropolitan to the
lower 60s across the interior is expected.
Short term /6 am Saturday morning through Saturday night/...
models remain in reasonable agreement as they forecast upper level
shortwave pivoting across the northeast Saturday...passing to the
east/northeast Saturday night. At the surface...a cold front slowly
moves from west to east across the area during the afternoon
NAM seems to be the most aggressive with regard to convection and
coverage compared to European model (ecmwf)/GFS and CMC.
Lack of deep moisture should cap coverage. However...weak
instability is noted along with ample shear and weak lift. As
such...will maintain slight chance probability of precipitation at this time...and believe
southern CT and New England would be the focus for highest coverage
based on timing of shortwave...coinciding with maximum heating.
Any showers/thunderstorms diminish as they move east Saturday night...so a
return to dry weather expected.
Temperatures will be quite warm to hot...but humidity levels will remain
rather low. Due not expect a true sea breeze ahead of the
front...and more of a westerly flow will help boost temperatures well
into the 80s...to around 90 in spots. Then...temperatures remain rather
warm Saturday night behind the frontal boundary. Followed a MOS
There is a moderate risk of rip current development at Atlantic
Ocean beaches on Saturday.
Long term /Sunday through Friday/...
surface high pressure builds over the Tennessee Valley on Sunday and moves off the
middle-Atlantic coast Sunday night. Meanwhile...nearly zonal flow sets
up aloft. This results in a west-southwest flow over the area...and
with 850 mb temperatures around 14c...can expect maximum temperatures to top off
around 90 degrees in/around NYC...and in the middle to upper 80s
elsewhere. Humidity levels look to be fairly low away from the
coasts...as surface dew points will range from the middle to upper 50s east
of the Appalachians...in/around NYC...and across the interior...but
in the low 60s across coastal CT and eastern Long Island.
As high pressure moves offshore Sunday night...a warm front will lift
north into the northeast. Meanwhile...a deep closed 500 mb low over
central Canada will drift to the south and east. This will push a
series of 500 mb troughs/shortwaves and weak surface cold fronts across the
region Monday through Tuesday. Right now...not expecting much more
than slight chance to chance probability of precipitation for showers/thunderstorms during that
time. With mainly southerly flow prevailing...humidity levels will
increase as surface dewpoints climb through the 60s and approach 70. As
a result...locally heavy rain may be possible.
Surface high pressure builds into the area for Wednesday. However...a
stronger 500 mb trough/shortwave comb will pass north of the local area.
For now...this looks to be too far north to impact the County Warning Area...so will
carry a dry forecast...but it will have to be watched.
Next chance for widespread rain comes Thursday-Friday as low pressure
passes through the region. Both the 12z GFS and the 12z European model (ecmwf)
indicating potential for heavy rain...but heavy rain axis is across
northern zones in the GFS and south of Long Island in the European model (ecmwf).
Will carry chance probability of precipitation and will keep an eye on how this develops.
Hot and humid conds expected on Monday with highs in the upper 80s
to low 90s and surface dew points well in the 60s...then temperatures and
humidity levels back off a bit on Tuesday and Wednesday. Thursday
and Friday could be noticeably cooler...depending on the track of the
Aviation /00z Saturday through Wednesday/...
a weak surface trough remains across the region through Saturday.
VFR. There is a slight chance of isolated showers across the lower
Hudson Valley in the morning...with a slight chance of isolated
showers and thunderstorms during the afternoon...mainly across the
NYC area terminals and southern Connecticut. Wind will generally be
southwest to west overnight and more southwest Saturday. Speeds
increase to 10 to 15 knots with occasional gusts to 20 knots. There is a
low chance of a sea breeze at kjfk.
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: low chance of a sea breeze developing after
18z Saturday. Otherwise no unscheduled amendments expected.
Klga fcster comments: no unscheduled amendments expected.
Kewr fcster comments: no unscheduled amendments expected.
Kteb fcster comments: no unscheduled amendments expected.
Khpn fcster comments: no unscheduled amendments expected.
Kisp fcster comments: no unscheduled amendments expected.
Outlook for 00z sun through Wednesday...
Sat night-sun...VFR. SW/S flow.
Monday...gusty S flow. A chance of thunderstorms.
Monday night-Tue...chance thunderstorms. Cold front passage with S
wind...shifting to west.
Wednesday...VFR. West flow.
high pressure tonight gives way to a cold front on Saturday.
Across the ocean waters...winds will increase during the day
Saturday ahead of the cold front from the SW. Speeds likely fall
short of Small Craft Advisory thresholds. However...seas across the waters east of
Fire Island look to build close to 5 feet. As such...will Post a Small Craft Advisory
for Saturday and into Saturday evening as seas subside behind the
Otherwise...winds and seas remains rather tranquil across the non
A tight SW gradient may result in Small Craft Advisory conds on the ocean waters on
Sunday...then generally tranquil conds on tap for Monday. A series
of frontal boundaries will move across the waters early in the new
week...resulting in occasional Small Craft Advisory conds through the middle of next
no significant widespread rain expected.
Marine...Small Craft Advisory from 6 am Saturday to midnight EDT
Saturday night for anz350-353.