Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
749 am EDT sun Apr 26 2015
an upper level system will produce a few showers today and Monday.
High pressure builds in for the middle of the week. Low pressure
develops south of the area over the Atlantic during the end of the
Near term /through tonight/...
water vapor indicates a large cyclonic circulation over eastern
Canada drifting westward. The models indicate this trend will continue
today. Shortwave energy associated with the system has weakened
significantly in the models. As a result...quantitative precipitation forecast is minimal in the
forecasts. Have kept probability of precipitation around 20 percent as a result...going with
isolated coverage. The NAM indicates maybe a few sprinkles spreading
southward down the Hudson Valley into the evening before fizzling over the
County Warning Area. Otherwise the data suggests dry. Went with a dry forecast after 1z
with loss of surface based instability. Guidance was in good agreement
with respect to temperatures...so went with a blend. Mixing above 850 mb per model
soundings...and the temperature cap looks to be in vicinity of the developing
Short term /Monday through Wednesday night/...
scattered showers appear on track for Monday as the upper low center makes its
closest approach and slides down the eastern New England coastline. The
most robust activity eastern zones closer to the upper support. The NAM
only indicates 50-150 j/kg SBCAPE...with the highest values in vicinity of
the Rhode Island border. Rhode Island into eastern Massachusetts gets above 200 j/kg...if this entire system
shifts slightly westward...the isolated thunderstorm threat could extend into the
County Warning Area. For now...thunderstorms not included in the forecast. Temperatures around 0c at
850 mb...but deep mixing to around 800 mb will keep highs only a few
degrees blw climatology. The ribbon of shortwave energy then slides eastward Monday
night and Tuesday. As a result...gradually end precipitation chances Monday night and
kept Tuesday dry. Temperatures approach climatology with heights increasing and
deep mixing continues on northwest flow. Upper ridging then builds in on
Wednesday. A dry forecast Wednesday and Wednesday night. The warming trend continues as
the upper ridge axis builds in. Temperatures should reach into at least the
upper 60s along and west of the Hudson...but the weak pressure field should
result in fairly deep penetration of sea breeze flow.
Long term /Thursday through Saturday/...
the GFS has trended towards the European model (ecmwf) notion of deepening low pressure
somewhere near Hatteras Thursday...then tracking northeastward over the Atlantic Friday
and into the North Atlantic Sat. The model consensus in still that the system
misses US...with perhaps some showers in the warm air advection pattern on Thursday.
Maintained the low probability of precipitation in the forecast through the period...but changes weather
type to rain Friday-Sat as it appears the focus will be on the northern
extent of the precipitation shield as opposed to the development of showery
precipitation at this time. Temperatures a blend of previous and the gmos25.
Aviation /12z Sunday through Thursday/...
a thermal trough sets up across the area this afternoon. High
pressure then reestablishes itself tonight.
This will result in a north/NE flow at less than 10 knots this morning...
which then backs around the the west/SW by afternoon. Seabreezes are
likely at the coastal terminals...developing as early as 15z along
the CT coast. Kewr and klga may seabreeze late. Winds are likely
to vary as the trough sets up in the afternoon. Winds then become
northwest this evening as high pressure strengthens.
Outlook for 12z Monday through Thursday...
Monday-Monday night...possible MVFR with showers.
Thursday...possible MVFR with showers.
sub-Small Craft Advisory conditions are forecast through the middle of next week as a
large area of high pressure over the middle section of the country
works slowly east. Marginal gusts are possible Monday night into Tuesday on
the ocean waters as a northerly flow strengthens between a broad area of
low pressure over the western Atlantic and high pressure building in
from the west. Low pressure moving off the southeast coast Thursday may impact
the waters with a strengthening easterly flow and building seas.
significant precipitation is not expected through next week.