Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
639 PM EDT Sat Jul 12 2014
high pressure will continue moving offshore through Sunday. A cold
front will slowly approach the region from the west on Sunday...then
stall near the region through Wednesday. High pressure returns for
the end of the week.
Near term /until 6 am Sunday morning/...
forecast on track this evening. Dew points are mixing out into the
upper 50s in some locations which is not well forecast. Expect
they will slowly rise again after sunset. A few showers and
thunderstorms are developing west of the region so will continue
the slight chance for Orange County this evening.
Otherwise...continued dry forecast tonight. Surface high pressure
will continue shifting offshore during this period.
Aloft...heights will slowly fall in response to developing upper
level trough across the Great Lakes.
Patchy fog is possible towards daybreak as low level moisture
increases. Low temperatures near normal in the 60s are forecast.
Short term /6 am Sunday morning through Sunday night/...
southerly flow increases with tightening gradient between high
pressure offshore and low pressure across southeastern Canada.
This brings a warm and humid air mass to the region. It will also
become quite breezy...especially near the coast. Low level
moisture will be on the rise as dew points reach the upper 60s and
possibly lower 70s by late afternoon.
Daytime heating along with prefrontal trough development west of the
city should trigger afternoon and evening showers and thunderstorms.
Upper level heights slowly fall...but the main closed low will still
be a significant distance away from the area. Cape values increase
to around 1000-1200 j/kg and 0-6 km bulk shear increases to 25-30 knots
on Sunday...mainly from the city north and west. Precipitable waters also surge to
around 1.9 inches by Sunday evening. With these ingredients...heavy
rainfall is possible in any storm. An isolated strong to severe
storm cannot be ruled out. Damaging wind gusts would be the main
threat if a storm does become severe.
Shower and storm activity will weaken some with loss of daytime
heating in the evening and overnight. With surface trough lingering
across the region and continued warm advection...showers and storms
with heavy rainfall remain possible.
High temperatures on Sunday will be near normal in the low to middle
80s. Locations near the coast may stay in the upper 70s due to
onshore flow. Warm and muggy Sunday night with temperatures in the
Long term /Monday through Saturday/...
the long term forecast starts off with unsettled weather for the
Monday through Wednesday time frame thanks to a strong cold front
slowly approaching from the west.
On Monday...the main cold front remains over the Midwest with the
main upper low as a weaker front develops in central PA. Rain
chances increase quickly on Monday and showers and thunderstorms are
likely by Monday afternoon. Strong thunderstorms and flooding are
possible on Monday. Precipitable water values over 2 inches and dew points in the
lower 70s will be in place along with the stalling front creating
training of cells so will continue heavy rain wording. See hydrology
section for additional details. As well...mu cape values increase
to over 2000 j/kg for areas west of NYC Monday afternoon and shear
values will be gradually increasing. Cannot rule out a few strong to
severe storms. Heavy rain and likely probability of precipitation continue through Tuesday
morning. Areas east of NYC...with the stabilizing southerly
flow...there will be less of a chance of severe storms.
Starting Tuesday morning...confidence drops in pop amounts for Tuesday.
Large discrepancy in model guidance with the one extreme...the
NAM..with no precipitation west of NYC after 12z. On the other side...the
12/12z European model (ecmwf) is the slowest with precipitation over the longest period. The
European model (ecmwf) brings the main cold front through late Wednesday while GFS/gefs/CMC
has it through by Wednesday morning. Will keep chance probability of precipitation through Wednesday
morning to account for this but trends will have to be monitored.
Cannot completely rule out this solution. If this solution is
correct...Tuesday will be another day of heavy rain and potentially
strong storms with 0-6km shear of 45-50 knots but less cape than Monday.
Behind the front...a deep upper trough will continue its way east
with high pressure building in at the surface. Zonal flow returns
for the end of the week.
Highs Monday-Tuesday will be in the lower to upper 80s with lows remaining
in the lower 70s. Temperatures Thursday-Sat will be generally near
to slightly below seasonal normals.
Aviation /00z Sunday through Thursday/...
high pressure will remain offshore through tonight...then move
farther east on Sunday as a cold front approaches.
South to southwest winds have increased. This afternoon. Speeds are
around 10-12 knots. Seabreezes will enhance the winds along the
coast...with speeds as high as 15 knots.
MVFR fog development more likely tonight with a light onshore flow.
Few to scattered 005 kft to 010 kft clouds possible. Low chance of
IFR ceilings along the coast after 09z.
All terminals should return to VFR by 14z...however clouds will
gradually increase through the day. For the 30 hour tafs west of
NYC...have included a prob30 group for thunder late in the day.
Outlook for 18z Sunday through Thursday...
Sunday afternoon-Wednesday...scattered to numerous shra/tstms.
Stronger thunderstorms during this time frame could produce periods of MVFR
or lower conditions...locally heavy rainfall...and gusty winds.
Conditions improve late Wednesday.
tranquil conditions on the waters through early Sunday morning.
Southerly flow increases on Sunday and winds increase to Small Craft Advisory
levels with winds in the afternoon and evening on the ocean
waters. Have issued a Small Craft Advisory for The Harbor and ocean waters
starting at 16z. Seas will also be rising to around 5 feet Sunday
night over the ocean with the increased southerly flow. The Small Craft Advisory
currently GOES to 04z Monday on The Harbor and 10z Monday on the
Southerly flow remains elevated on Monday with ocean seas rising to
5-7 feet by Monday evening and wind gusts of 20-25kt. This will
continue on Tuesday with winds slowly diminishing Tuesday evening.
Seas will be slow to diminish with 5 feet seas possible through
Wednesday evening. Sub Small Craft Advisory criteria expected on Thursday. .
no significant precipitation is forecast through Sunday morning.
There is the potential for significant rainfall from late Sunday
into early Wednesday. At this time there is too much uncertainty
to specify exact amounts or specific threats...other than to note
flooding is possible in areas that experience rounds of locally
Marine...Small Craft Advisory from noon Sunday to 6 am EDT Monday for
Small Craft Advisory from noon Sunday to midnight EDT Sunday
night for anz338.