Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1046 PM EDT Sat Aug 30 2014
high pressure moves well to the east through Sunday. Low pressure
tracks across the Great Lakes and into eastern Canada...sending a
low pressure trough across the area late Sunday. This trough weakens
and eventually dissipates within the region on Monday. This will
leave behind a weak pressure gradient. A cold front moves through
Tuesday night with high pressure then building in from the south
and west through Thursday. The high moves offshore Friday with
another cold front approaching into the beginning of next weekend.
Near term /until 6 am Sunday morning/...
aloft...large ridge remains anchored southeast of the region as a
trough moves across the Great Lakes region tonight.
Surface high pressure sits southeast of the region tonight.
Plenty of clouds...warm and increasingly muggy conditions are
forecast overnight. Dew point increase per MOS as south flow
persists. Low temperatures in the 60s per MOS blend followed.
High res models signalling potential late tonight into early
Sunday morning for an isolated shower with Theta-E advection and a
weak vorticity moving through.
Short term /6 am Sunday morning through Sunday night/...
deep southwest flow through this time frame as shortwave moves well
to the north...with ridge anchored over the western Atlantic.
Warm and muggy conditions will prevail. Plenty of clouds
expected...along with an increasing chance for showers/tstms.
Moderate instability is expected by afternoon Sunday...and
precipitable waters increase to 2 inches...or close to 200
percent above normal late in the day and into the evening.
Marginal to moderate shear is present...with ki right around 35c.
Expect scattered to numerous...although will keep probability
wording...showers and thunderstorms. Some of which will produce heavy
downpours. Best timing is late afternoon western zones...and through
the evening/overnight coastal and eastern zones.
Models continue to vary with regard to heavier shower/thunderstorm
location...due to the scattered nature of the activity and varying
placements of embedded middle level shortwaves. Surface trough approaching
to the west should trigger activity.
After collab with surrounding offices...will not issue a Flash Flood
Watch at this time. The threat will be urban...with perhaps flashier
streams susceptible to flash flooding. Otherwise...County guidance
likely too high outside of metropolitan.
Warm temperatures in the 80s Sunday...with warm upper 60s to 70s Sunday
night lows. Followed a MOS blend...which included ecs numbers.
A moderate risk of rip currents is expected for the first half of
the day Sunday...but this may increase to high by late in the day
with increasing southerly winds and resultant winds
waves...interacting with a background long period southeast swell.
Long term /Monday through Saturday/...
the dominant pattern in the long term is that of ridging on average.
On a large scale...an upper level ridge is apparent on the model
height fields aloft from Quebec to the mid-Atlantic. A relatively
stronger upper level trough passes north of the region late
Tuesday into early Wednesday with some more height falls and a
transition to zonal flow. Ridging resumes thereafter with the
large ridge across the southern U.S. Pushing north from Wednesday
At the surface...a surface trough moving in from the west
dissipates within the region without much upper level support on
Monday. A weak pressure gradient is left in its place without a
strong presence of high pressure. The jet stream will be lifting
north away from the region helping explain the lack of support
aloft. The jet pushes back south Tuesday night into early
Wednesday...so this will help push a cold front through the
region. This will transition winds to more of a northerly flow for
Wednesday. The flow weakens Thursday...allowing for sea breezes
to develop as high pressure builds in from the south and west. The
high moves offshore Friday into the next weekend. Another cold front
approaches into the beginning of next weekend.
Outside of Wednesday...a general south to southwest flow dominates
next week. This will result in temperatures well above seasonal
averages for this time of year. The jet stream overall keeps to the
north of the region. Temperatures will be generally 5-10 degrees
above normal Monday through Wednesday and a few degrees above
normal Wednesday night through Saturday.
In terms of weather...highest chances for showers and
thunderstorms will be on Monday with the instability and remnant
frontal boundary across the region. Chances decreasing by late in
the day and into Monday night. Estimating these to be more of the
pulse variety with the lack of upper level support. Bulk shear
0-6km mostly 20-25 knots with cape being the greater driver for
convection. Another chance of showers and thunderstorms from
northwest to southeast Tuesday into Tuesday night with a little
more shear to work with. Mainly dry thereafter with a slight
chance of showers and thunderstorms towards end of the work week
into the next weekend with next front approaching.
Aviation /02z Sunday through Thursday/...
high pressure off the New England coast will move out to sea
overnight as a trough of low pressure approaches from the west late
VFR ceilings this evening likely to gradually lower through the
overnight...with low MVFR/locally IFR ceilings likely late
tonight/sun am. Heating should raise ceilings to VFR in the late
Isolated rain showers/thunderstorms and rain possible along seabreeze boundaries Sun
afternoon. Otherwise...increasing chance for rain showers/thunderstorms late
afternoon/evening mainly from city terminals and points north/west as trough
Outlook for 00z Monday through Thursday...
Sun night-Mon...numerous rain showers/embedded thunderstorms and occasional MVFR
translating eastward across terminals Sun night through Monday
morning. Additional scattered rain showers/thunderstorms and rain possible Monday aft/eve. MVFR
status/fog possible late Monday night.
Tuesday...scattered after/evening rain showers/thunderstorms and rain possible.
southerly winds persists tonight as high pressure drifts further to
The southerly winds increase ahead of a surface trough later Sunday
into Sunday evening. Expect winds to remain just below 25 kts on
the waters...so will not issue a Small Craft Advisory at this time per surrounding
office collab. Seas build in response to these increasing
winds...and may come close to 5 feet over the ocean waters late
Sunday and into Sunday night.
Overall...the pressure gradient remains weak in the long term period
of Monday through Thursday. Seas will be on a downward trend early
Monday with a cold front dissipating within the region. Conditions
are expected to remain below Small Craft Advisory on the waters through the long term
deep moisture in place with trough approaching Sunday and into the
region Sunday night...so any showers and thunderstorms will be
capable of producing locally heavy downpours. Localized flooding
threat will remain which would vary from minor and poor drainage
to possibly flash flooding.
Heavy rain potential with any showers or thunderstorms will remain
as precipitable waters remain around 2 inches Monday. This will pose
a flooding threat varying from possible minor and poor drainage
flooding to some possible flash flooding.
short term...precipitable water