Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1056 am EDT Sat Aug 1 2015
a weak cold front will approach from the west today...and move
across tonight. Weak high pressure will then provide dry and fair
weather on Sunday. A series of frontal boundaries will impact the
area during the first half of next week...followed by the
potential for a few areas of low pressure to impact the area
during the latter portion of the week.
Near term /until 6 PM this evening/...
latest hi-res guidance including the hrrr/rap and ncar WRF
ensemble is emphasizing potential for afternoon convection more
across the interior...with at least isolated coverage...and in
particular across southern CT with scattered coverage. Pop has been
adjusted accordingly. Instability is marginal so have worded forecast
to mention shower or thunderstorm. Given dry middle levels and sub-cloud
layer and middle level flow up to 40 knots...showers/storms are capable
of producing gusty winds.
A broad upper trough will remain across the northeast for the
next several days and will be reinforced from time to time as
shortwaves move around a vortex over Ontario and Quebec.
The first of these impulses will move through the northeast this
afternoon and evening...although the best upper support will be in
northern New England. Model consensus remains consistent in indicating
isolated to widely scattered rain showers/thunderstorm development along a thermal/pre-frontal
trough during the afternoon and along the cold front this evening.
Another hot day is anticipated with 850 mb temperatures ranging between
14-16c. This should yield highs in the middle to upper 80s at most
locations...lower 90s in the New York/New Jersey metropolitan area. Heat indices will
be at or slightly lower than these values due to dewpoints in the
upper 50s to lower 60s this afternoon.
There is a moderate risk for the development of rip currents at
the ocean beaches today.
Short term /6 PM this evening through Monday night/...
cold front moves across the area this evening...with any rain showers/thunderstorm
activity weakening and pushing east.
Weak high pressure will then prevail over the forecast area providing
a fair and slightly cooler Sunday.
Another cold front will approach on Monday as the second middle-level
shortwave moves towards the area. SW flow and Theta-E advection
ahead of this will bring the humidity back briefly. Chance probability of precipitation
maintained across the interior Monday aftn/night. With the potential
for moderate instability and similar bulk shear to today and better
upper support there could be a some strong to severe storms
around mainly north and west of NYC.
Some timing difference exist with the passage of the front...but
it should clear the area sometime Monday night.
Long term /Tuesday through Friday/...
another cold front is expected to move across the area Tuesday night
with a low chance of probability of precipitation preceding it on Tuesday.
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 /15z Saturday through Wednesday/...
a weak surface trough slowly moves across the area this afternoon
VFR through the period. Isolated gusty showers or thunderstorms are
possible through 22z or so from west to east.
West to southwest winds around 10 to 15 knots can be expected this
afternoon. Gusts to 20 knots are also anticipated for a few hours
this afternoon. Then gusts become less frequent by 21-22z.
Due to gusty west/SW flow...sea breezes should have a hard time making
progress inland...but will monitor.
Winds lighten behind the front this evening as they turn to the northwest
before becoming variable overnight.
Outlook for 12z sun through Wednesday...
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.
a cold front moves across the region today.
On the ocean waters...southwest winds will increase during the day
today ahead of a cold front. Speeds will likely fall short of 25 knots.
Seas east of Fire Island look to build to 5 or 6 feet. Will not make
any changes to the Small Craft Advisory in effect for today and tonight until 4z.
There is a chance the far eastern ocean waters may need a few extra
hours added to the end time...however will let the day shift re-
evaluate the new 12z data.
Across the remainder of the waters...winds and seas will remain
below Small Craft Advisory levels.
A tight SW gradient may result in 4 feet seas on the ocean waters on
Sunday...then generally tranquil conditions are on tap for Monday. A
series of frontal boundaries will move across the waters early in
the new week...resulting in occasional small craft conditions
through the middle of next week.
no significant widespread rain expected into early next week.
Locally heavy rainfall is possible in thunderstorms on Monday...which
could lead to minor poor drainage flooding.
Marine...Small Craft Advisory until midnight EDT tonight for anz350-353.