Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
137 am EDT Friday Oct 9 2015
high pressure builds east of New England this evening...while a
frontal system approaches from the Great Lakes. Low pressure
passes to the north Friday...sending a cold front across the
region during the afternoon and evening hours. High pressure
builds in from the west on Saturday and then shifts south on
Sunday. A cold front approaches from the west on Monday and then
moves across on Tuesday. High pressure returns for the middle of
Near term /until 6 am this morning/...
forecast mostly on track with just minor changes to hourly
sky/temp/dewpoint grids to account for latest observation and trends.
A fast...nearly zonal flow from the upper Midwest east into New
England will send an amplifying short wave trough and its associated
surface low toward the forecast area. High pressure this evening will
pass off the New England coast...while low pressure approaches
from the Great Lakes. The associated warm front moves through
prior to daybreak with increasing clouds and possibly a sprinkle
Overnight lows will range from the low to middle 50s in the
suburbs...to the upper 50s NYC metropolitan. This is several degrees
Short term /6 am this morning through 6 PM Saturday/...
a gusty SW flow preceding a cold front on Friday will allow for highs
to get well into the 70s...especially across the interior where
some spots may reach 80. Cold front approaches late after/evening with
showers and possibly a thunderstorm. Rainfall amounts will average
a quarter inch or less. The jet dynamics pass well to the north
with the primary focus being along the cold front. Showers will
linger across Li/CT into the first half of the evening.
High pressure and a gusty northwest flow follow for late Friday night with
lows a few degrees cooler...but still above normal.
Long term /Saturday night through Thursday/...
upper level ridging builds over the tri-state area. At the
surface...high pressure builds in from the west. High temperatures
on Saturday will average a few degrees below normal in the lower to
middle 60s. Temperatures Saturday night will likely be the coolest
of the fall season with readings falling into the middle and upper
30s inland and the 40s elsewhere. This forecast is based on having
excellent radiational cooling conditions. However...some high clouds
could move overhead which could prevent temperatures from fully
bottoming out. Will need to monitor for potential frost across the
interior with temperatures falling into the middle 30s...near the
dew point temperatures.
The surface high moves offshore on Sunday with a weak return flow
warming temperatures closer to normal levels in the middle and upper
60s. Upper level ridging holds on Monday...with an approaching
northern stream trough from the west. Models continue to depict a
southern stream wave lifting to the northeast along the coast Monday
night. The GFS has come into better agreement with the European model (ecmwf) with
this scenario...which has shown potential for a weak wave of low
pressure to move near or just offshore. Moisture return is
limited...but with some weak positive vorticity advection across eastern sections a shower
cannot be ruled out late Monday night. Probability of precipitation increase to chance on
Tuesday as a fairly amplified shortwave approaches from the west.
Lift increases from positive vorticity advection ahead of the trough. However...the best
dynamics and moisture appear to lie to the north of the area. A cold
front associated with this trough rapidly moves across on
Tuesday...bringing a return to dry conditions behind its passage.
Temperatures will average a few degrees above normal on Monday and
Upper level troughing will linger across the northeastern states
Wednesday into Thursday. Surface high pressure will ridge into the
area from the southwest. This will keep dry and near seasonal
temperatures for the middle of the week.
Aviation /06z Friday through Tuesday/...
hi pressure will drift eastward over the Atlantic today. A cold front will pass
Areas of MVFR/IFR stratus through about 12z...otherwise mainly VFR
through the taf period. Some -ra could produce pockets of MVFR this
afternoon and evening near the front.
South-southwest flow increases through the day. Winds veer to the west then northwest
behind the front.
Outlook for 06z Saturday through Tuesday...
Friday night...VFR with northwest winds 10-20kt.
Tuesday...mainly VFR...slight chance of MVFR especially in the morning.
a gradually strengthening southerly flow tonight into Friday will reach
Small Craft Advisory criteria by late morning with gusts up to 30 knots and seas on
the ocean building to 4 to 7 feet. All but western Li sound and New York
Harbor will be under a Small Craft Advisory. There could be occasional near shore
gusts approaching 25 knots at these locations. A cold front passes
through the waters in the evening with northwest gusts on the ocean
waters approaching 25 knots by daybreak Sat. There is likely to be a
lull in the winds as the front crosses the waters Friday evening...but
due to high seas will keep the Small Craft Advisory on the waters through Friday
Winds and seas fall below Small Craft Advisory levels on the ocean Saturday morning
as high pressure builds over the waters. Sub Small Craft Advisory conditions will
then continue on all waters through Tuesday. A cold front approaches
on Monday and then crosses the waters on Tuesday. This likely
increases the pressure gradient...with winds potentially gusting to
20 knots on the ocean Tuesday.
rainfall amounts associated with a cold frontal passage Friday
after/evening will average a quarter inch or less.
Mainly dry conditions are forecast from Saturday through the middle
of next week.
Marine...Small Craft Advisory from 11 am this morning to 6 PM EDT this
evening for anz330-340-345.
Small Craft Advisory from 11 am this morning to 11 am EDT
Saturday for anz350-353-355.