Scientific Forecaster Discussion
fxus61 kokx 270236
Area forecast discussion
National Weather Service New York New York
1036 PM EDT Fri may 26 2017
low pressure departs the New England coast tonight as weak high
pressure settles over the region. A weak wave of low pressure
passes to the south Saturday into Saturday night. A series a weak
waves of low pressure or troughs will move through the northeast
Sunday through Thursday. A cold front is expected to move
through the region Friday.
Near term /until 6 am Saturday morning/...
forecast is on track. Minor adjustments made to winds/T/TD based
on latest obs/trends.
Heights aloft will continue to rise tonight as low pressure
continues to depart the New England coast. Clouds will dissipate
somewhat, but there is enough low level moisture for at least partly
cloudy skies overnight.
Lows will range from the lower 50s inland to the middle and upper
50s near the coast.
Short term /6 am Saturday morning through Saturday night/...
main concern for Saturday is with a convectively induced shortwave
that is currently located over the upper Mississippi River valley.
Models have not been handling this energy very well as depicted with
dprog/dt at 500 mb. However, it appears they are beginning to handle
this feature better with just some timing differences overall. The
shortwave is forecast to quickly traverse through the Ohio Valley
tonight and then towards the region on Saturday. Prefer to follow a
blend of the NAM, 3-km NAM and ECMWF, which brings the shortwave
offshore late afternoon and early evening. The GFS, gefs, and CMC
are a bit slower and do not bring it offshore until overnight
Saturday. Have elected to go with slight chance pops, mainly
for the western half of the area, as better lift and moisture
appears to pass to the south of the region.
Otherwise, mostly cloudy skies are expected with high temperatures
around 70 in NYC and middle and upper 60s elsewhere.
Clouds gradually decrease Saturday night as ridging builds aloft.
Lows will be near normal.
Long term /Sunday through Friday/...
with a delay in the timing of the northern stream longwave
trough and the shortwave rotating through the base of the trough
have delayed the probabilities of showers until late in the day
sunday; and mainly across the far west and southwest zones.
Aloft, an upper ridge axis will still be west of the region at
12z Sunday with heights rising until the afternoon. At the
surface a weak high will be moving off the coast. Then as the
shortwave moves into the region probabilities increase Sunday
night into Monday. At the surface the will be weak forcing as a
weak cold front moves into the region. A thermal ridge also
moves into the area Monday afternoon. Monday may be one of the
warmer days of next week. With weak surface based instability,
and increasing aloft along with increasing cape will have
thunderstorms Monday afternoon into the evening. There is still
some uncertainty with the timing of the upper trough and
shortwave for Sunday and Monday.
The closed upper low and longwave trough will be slow to move
east through the week as a series of shortwaves rotate through
the trough, while at the surface weak lows, or troughs move
through the area. There remains a lot of uncertainty with the
timing and placement of the systems through the upcoming week.
And, there will be a prolonged period of unsettled weather. Will
carry slight chance to low chance probabilities through the
week, although there may be periods of dry weather.
Aviation /02z Saturday through Wednesday/...
low pressure near Nova Scotia will move slowly east tonight through
Saturday. Weak high pressure builds into the terminals Saturday.
VFR. A few isolated showers are possible Saturday afternoon from the
NYC terminals and west and south, with VFR conditions.
Northwest wind diminish late tonight and remain less than 10 knots into
Saturday morning. Sea breezes develop Saturday afternoon.
Outlook for 00z Sunday through Wednesday...
Saturday night...MVFR to IFR in stratus and fog.
Sunday...improving to VFR.
Sunday night-Monday...MVFR/IFR likely in showers. Thunderstorms
possible Monday afternoon.
Tuesday-Wednesday...VFR. Slight chance of showers and
southerly swell continues on the ocean waters through tonight.
Seas will subside overnight as the swell diminishes. 5 ft seas could
linger east of Moriches Inlet through Saturday morning, so have
extended the Small Craft Advisory to account for this. Otherwise, sub-Small Craft Advisory conditions
are forecast on the waters through Saturday night.
A weak surface pressure gradient force will be across the
forecast waters Sunday through Wednesday as a series of weak
lows or troughs move through the waters with low pressure
remaining north of the Great Lakes into Tuesday night. The lows
then moves slowly east through Friday. Winds and seas will
remain below Small Craft Advisory levels Sunday through
no hydrologic impacts into early next week.
the combination of high astronomical tides and a southerly swell
will keep water levels within striking distance of minor
coastal flood benchmarks for potentially several high tide
cycles through this weekend into early next week for the more
vulnerable locations. The new moon was yesterday and tide
levels will gradually begin to lower this weekend. However, the
swell will likely inhibit water levels from receding much in the
South Shore back bays of western Long Island today with a minor
coastal food episode likely during the higher of the two tide
cycles this evening. Thus, a coastal flood advisory has been
issued for southern Queens and southern Nassau counties. A
statement is also in effect for isolated minor coastal flooding
across lower New York Harbor. Elsewhere, the coastlines adjacent
to western Long Island Sound could also come close tonight, but
confidence is low at this time.
CT...coastal flood advisory from midnight Saturday night to 3 am
EDT Sunday for ctz009.
New York...coastal flood advisory from midnight Saturday night to 3 am
EDT Sunday for nyz071.
Coastal flood advisory until 1 am EDT Saturday for nyz178-179.
Coastal flood advisory from 9 PM Saturday to 2 am EDT Sunday
Marine...Small Craft Advisory for hazardous seas until 6 am EDT
Saturday for anz353-355.
Small Craft Advisory for hazardous seas until 11 am EDT
Saturday for anz350.