Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
359 am EDT Wednesday may 6 2015
a slow moving cold front south of Long Island will continue to sag
south of the region today...allowing high pressure to build in for
Thursday. A frontal boundary will back into the region from the
northeast on Friday...then lift out on Saturday. High pressure
over the Atlantic then remains in control through the rest of the
weekend. Low pressure off the southeast coast will track slowly
along the middle Atlantic coast into early next week...then track out
to sea as a cold front approaches from the west.
Near term /until 6 PM this evening/...
the 00z models are basically dry for today. However...satellite and
radar indicate bands of showers rotating into the region from the
west...the remnants of Midwest convection. The 00z okx sounding had a
precipitable water of 1... the additional moisture advection should allow for
at least some pockets of measurable precipitation across the southwestern 2/3 of
the County Warning Area. The limiting factor will be the developing NE flow behind
the cold front just S of Li...where the 00z chh sounding just upstream
had a precipitable water of 0.83. Gyx was even lower at 0.23. As a result...probability of precipitation
were capped at scattered coverage for today...with decreasing chances from
NE to SW in the afternoon...ending by this evening. The cloud shield will
likewise erode...but with infrared showing the middle cloud belt still
stretching from Lake Ontario westward to Lake Michigan...have forecast
a mainly overcast day. Temperatures a blend of the guidance...with the warmest
readings across the interior valleys.
Short term /6 PM this evening through 6 PM Thursday/...
upper ridge builds in with decreasing moisture and increasing
subsidence. There is a hint of convective initiation in all the
00z models Thursday afternoon...but it appears to be terrain induced...and
with the weak steering flow do not expect any of the precipitation to reach
the County Warning Area at this time. The end result is a dry forecast. Temperatures a blend of
guidance tonight...and a blend of the mosg25 and namdng5 for
Thursday...where the weak gradient flow should allow for extensive and
early sea breeze development yielding much cooler temperatures along the
Long term /Thursday night through Tuesday/...
model guidance looks to start off in good agreement with an
amplified ridge over the northestern Continental U.S. And eastern Canada. They start to
diverge fairly quickly as the GFS moves the ridge offshore and
breaks it down quicker than the ec. Since this is a known bias of
the GFS...have sided with the ec solution which has support from the
CMC. As a result...have kept the weekend dry...which may also
continue into Monday...although there is uncertainty with a low
pressure system tracking along the eastern Seaboard early next week
as well as how far S a frontal boundary drops down from the north. Have
decided not to make huge changes Monday through Wednesday...but we may not
see a widespread rainfall until an upper trough and surface cold frontal
passage Tuesday/Tuesday night.
There is also the signal for several days of fog and stratus at
night and into the morning beginning Friday night (could have patchy
fog in some isolated spots Thursday night) with several days of southerly flow in
place. Have added this to the forecast Sat and sun for now.
Temperatures are expected to be above normal levels through the period.
Aviation /08z Wednesday through Sunday/...
high pressure builds over the terminals through tonight.
VFR through the taf period.
Shower activity along the western New York state and Pennsylvania
border continues to drift east. The best chance for some of these
showers is at kswf early this morning. There is a low chance that
a few of these showers will affect city terminals around day
Light north-northeast winds veer to the NE this morning with speeds around 10
knots. Winds veer to the east and then southeast this afternoon into the early
evening hours. Winds diminish tonight and become light and
Outlook for 00z Thursday through Sunday...
Saturday-Sunday...stratus/fog possible during the morning.
winds and seas will remain blw Small Craft Advisory levels through Thursday as hi pressure builds
in from the northwest.
For Thursday night through Monday...winds are expected to remain below advsy
criteria through the period...although could gust around 20 knots Sun
afternoon/evening with a tightening pressure gradient. Seas could reach
marginal Small Craft Advisory levels on the ocean waters Sun night into Monday as
swells from low pressure off the middle Atlantic coast develop. Otherwise
..sub-advsy conds are expected.
a few hundredths of an inch of precipitation are possible today.
Thereafter...no precipitation is expected through the weekend.