Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1031 PM EDT Wednesday may 6 2015
high pressure builds in tonight and Thursday...then eventually
moves into the western Atlantic Ocean this weekend. Meanwhile...
low pressure will drift from the southeast coast into the middle-
Atlantic...where it will meander until a cold front moves through
the region and pushes it out to sea next week.
Near term /until 6 am Thursday morning/...
slight adjustment downward with respect to cloud
coverage...temperatures...and dewpoints. Overall...forecast
mainly on track.
Ridging at the surface and aloft tonight will dry out the
atmospheric column. Skies will continue to clear as drier air
filers in from the north. This will promote radiational cooling
overnight along with light to calm winds. Overall...min temperatures
forecast are below the relatively cooler of MOS guidance with
values ranging from the upper 30s to lower 50s for much of the
region with some middle 30s in the vicinity of Westhampton Long
Short term /6 am Thursday morning through Thursday night/...
deep layered ridging continues on Thursday. Associated subsidence
helps keep low relative humidity aloft...bringing US a sunny day...but also limits
the mixing layer somewhat. The mixing layer depth will be further
reduced by sea breezes that are likely to develop due to a light low
level synoptic flow. Based on temperatures at the top of this layer...a
mav/NAM MOS blend looked good for high temperatures...which will be above
Dry weather continues into Thursday night. Low temperatures not as cool as
Long term /Friday through Wednesday/...
surface high pressure over the northeast will move offshore on Friday and
remain offshore through the weekend. With upper level ridging along
the northeast...can expect a prolonged period of SW flow with
unseasonably warm temperatures through the weekend.
Low pressure will meander off the southeast U.S. Coast through the
weekend and then slowly drift to the north early in the new week.
There are differences between the GFS and the European model (ecmwf) in terms of
where the low will go...but the high over the western Atlantic and
the upper ridge over the northeast should keep the low too far to
the south to dramatically impact the weather in the local area.
Depending on where the low GOES...could have some light rain
spreading north and into southern zones early in the new week.
In addition...low pressure over the Great Plains states will slowly
track to the east over the weekend...making it through the Ohio
Valley and into western New York/PA by Tuesday morning. As this system
presses to the east...chances for showers/thunderstorms will increase
beginning Sunday night and Monday...and the highest probability of precipitation will occur
Tuesday-Tuesday night as the system works its way across the region.
High pressure builds into the Ohio Valley on Wednesday.
With SW flow across the region and increased low level moisture...
can expect patchy fog to develop Friday night and Saturday night...
and that fog will dissipate late in the morning.
Deep SW flow will also result in above normal temperatures through the
start of the new week with highs generally in the upper 70s to low
80s across NYC/northeast New Jersey/lower Hudson Valley/parts of interior
portions of southern CT. Highs across Long Island and coastal CT
will be in the middle to upper 70s as flow comes off the colder waters.
Highs will be in the upper 60s to around 70 along the coast.
Afternoon sea breezes are likely Friday through Sunday...resulting
in cooler temperatures each afternoon.
Temperatures will be a few degrees cooler on Tuesday with abundant cloud
cover on Tuesday as the frontal system moves through the region.
More seasonal airmass returns to the area on Wednesday with near
Aviation /03z Thursday through Monday/...
high pressure remains over the area overnight into Thursday
morning...then moves east of the area Thursday afternoon.
Unlimited ceilings and visibilities through the taf period.
Light and variable to near calm wind becomes southerly...160 to 200
true...5 knots to 10 knots Thursday morning.
Moderate to high confidence forecast.
Outlook for 00z Friday through Monday...
Saturday-Monday...potential for IFR or lower in stratus and/or
fog at night and the morning. Otherwise VFR.
seas and wind forecast on the waters remains mainly on track
With high pressure over the area waters...there will be a lack of a
tight pressure gradient. This will result in a tranquil period with
light winds and seas of 1 to 2 feet through Thursday night.
Sub-Small Craft Advisory conds will then continue through the weekend and into the
start of the new week. Some near-shore gusts to 20 knots possible
each afternoon due to local sea breezes.
Southerly gradient increases by Tuesday...resulting in at least seas
building to Small Craft Advisory levels.
no rain is expected through the weekend. The next chance for widespread
rainfall will be Monday through Tuesday as a frontal system moves
through the region.