Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
415 am EDT Wednesday Apr 1 2015
high pressure builds to the west...then south of the tri-state
through tonight. A warm front passes to the north on Thursday. A
cold front will approach from the northwest Thursday
night...stall near the area on Friday...then pass through
late Friday night into Saturday morning. High pressure will build
in for the weekend. Weak low pressure will pass to the north late
Sunday night into Monday. A frontal system will slowly approach
Monday night into Tuesday.
Near term /until 6 PM this evening/...
deep layered ridge axis begins to build in from the west
today...resulting subsidence by afternoon will limit mixing to
875-825 hpa per BUFKIT soundings. It also limit low level clouds
due to low level instability to few-sct. So only real source of
clouds is middle-High Deck to the west...which should also work on
thinning under the ridge. As a result went with a sunny to mostly
sunny forecast for today.
For highs today...used a blend of mav/met/ecs guidance with NAM
2-meter temperatures and a mix down to 875-825 hpa. Highs should
be around 5 degrees below normal.
Short term /6 PM this evening through 6 PM Thursday/...
the deep layered ridge continues to build in tonight...then
its axis crosses the area Thursday. Associated subsidence more
than likely will keep things dry. However...passing surface to
850 hpa warm front Thursday morning could bring a few
-shra/sprinkles to mainly northern zones. For now...appears
subsidence under the building ridge will win out...but cannot 100
percent rule out any precipitation across northern zones Thursday
The passage of the surface and 850 warm front though will bring
some clouds in late tonight and Thursday morning...otherwise there
should be minimal cloud cover tonight and Thursday...until high
clouds build in over mainly west zones late Thursday afternoon ahead
of the next system.
For lows tonight...used a blend of mav/met/ecs guidance with the
previous forecast. The aforementioned warm front generated clouds
likely will be the limiting factor on the lows...so did not
significantly undercut guidance in normally colder locations. Lows
should be around normal in NYC to around 5-10 degrees below normal
A blend of mav/met/ecs guidance with NAM 2-meter temperatures and
a mix down from 1000-875 hpa per BUFKIT soundings was used for
highs on Thursday. SW low level flow will result in a wide range
of temperatures with only the middle-upper 40s over the Twin Forks
and far southeast CT to the lower to maybe middle 60s over NE New Jersey/western
portions of the lower Hudson Valley.
Long term /Thursday night through Tuesday/...
clouds will increase
Thursday night ahead of an approaching cold front. Chance showers
mainly after midnight and mainly northwest of the city...with still the
potential for some elevated thunder.
Showers then become likely Friday into Friday night as the front stalls
near the area...passing through late Friday night into early Sat
morning only after an amplifying upper trough and associated
surface low pressure pass through. Maintained chance thunder from
previous forecasts there should be at least some elevated
instability...possibly surface- based for a time Friday afternoon from
NYC north/west as highs there reach the lower 60s. Farther
east...with more of an onshore flow expect highs in the lower 50s
right at immediate south facing shores...and middle/upper 50s across
interior southern CT and the North Shore of Long Island. The
onshore flow should also bring increasing potential for fog as
higher dewpoint air traverses cold Atlantic waters.
Just a lingering chance of a shower Sat morning as the cold front
exits...then a gusty drying northwest flow should help clouds diminish
clouds and keep US dry during the afternoon. Highs will be in the
Lower/Middle 50s...near or just below average.
Medium range guidance still suggests a cold front dropping down
close to the area on Sunday...and thereafter have sided with 31/21z
and 00z European model (ecmwf) idea of a clipper-type low riding the front in quasi-
zonal flow aloft...with chance pop for snow/rain showers mainly for
the interior late Sunday night into Monday.
Guidance also maintains good continuity on the idea of a frontal
system approaching from the west late Monday night into Tuesday...with
prolonged chances for rain. Temperatures should continue near to slightly
Aviation /09z Wednesday through Sunday/...
high pressure builds into the region today.
VFR through the taf period.
Northwest winds this morning...backing to the west-northwest after 14z. An occasional gust
possible through 14z...with prevailing gusts thereafter. Winds
decrease late this afternoon into the early evening becoming light and
..NY metropolitan enhanced aviation weather support...
Detailed information...including hourly taf wind component forecasts can
be found at: http://www.Erh.NOAA.Gov/zny/n90 (lower case)
Kjfk fcster comments: no unscheduled amendments expected.
Klga fcster comments: no unscheduled amendments expected.
Kewr fcster comments: no unscheduled amendments expected.
The afternoon kewr haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.
Kteb fcster comments: no unscheduled amendments expected.
Khpn fcster comments: no unscheduled amendments expected.
Kisp fcster comments: no unscheduled amendments expected.
Outlook for 06z Thursday through Sunday...
Wednesday night-Thursday...VFR. Flow becoming southerly on Thursday.
Thursday night-Friday night...MVFR in rain showers.
Saturday...sub-VFR possible in showers early...then VFR late.
seas across the waters were at 2 feet as of 7z. Looking upstream 25
knots wind gusts were contained with the strongest pressure rises
over Virginia. The trajectory of these rises is not over the area
waters. Also...latest guidance keeps 950 hpa winds below 25 knots.
As a result...have cancelled the Small Craft Advisory for the
coastal ocean waters that was in effect into this afternoon. Even
with the above...there should be gusts up to around 20kt this
morning over the coastal ocean waters.
Otherwise...a diminishing pressure gradient through Thursday
morning will keep winds and seas below small craft
thresholds...with winds 10 knots or less on all waters by tonight.
Winds should increase Thursday night...with tightening pressure
gradient ahead of the next system. For now do bring gusts up to
25-30kt on all waters Thursday afternoon. However...confidence in
this is not high enough to warrant issuing an Small Craft Advisory at this time.
There is some potential that a sufficient low level marine
inversion could form to preclude Small Craft Advisory wind gusts...with the best
chance for any 25-30 knots gusts on Thursday afternoon over New York
Harbor/west Long Island Sound/coastal ocean waters west of Fire Island
A prolonged period of Small Craft Advisory conditions probably will be setting up for
the ocean waters beginning Thursday afternoon...first via increasing
southerly flow Thursday afternoon into Friday ahead of a slow moving cold
front. The flow may weaken ahead of the front Friday night...but
leftover swells will still be hazardous during that time. Northwest to west
winds after cold frontal passage should reach Small Craft Advisory criteria on all
waters on Sat...then continue on the ocean Sat night into Sunday.
dry through Thursday.
There is potential for 3/4 to 1 inch of rain from late Thursday night
into early Sat morning.
Rivers and streams are expected to remain below bank full...but
increased river/stream flow across the lower Hudson Valley and
southern Connecticut will continue ice breakup and movement into
this weekend. Isolated ice jams are possible...which if they
occur...could result in localized flooding. Since ice jam flooding
is unpredictable and sudden...interests along ice covered rivers
should monitor National Weather Service forecasts for the latest information.
For details on specific area rivers and lakes...including
observed and forecast river stages and lake elevations...please
visit the advanced hydrologic prediction service /ahps/ graphs on
our web site.