Scientific Forecaster Discussion
fxus61 kokx 180301
Area forecast discussion
National Weather Service New York New York
1101 PM EDT Thu Aug 17 2017
a warm front will approach tonight and move north through Friday
morning. A cold front approaches Friday, moving across the
region late Friday night. A frontal system will slowly pass
offshore on Saturday. High pressure will then build in through
the beginning of next week, followed by a midweek cold frontal
Near term /until 6 am Friday morning/...
updated to reflect stratus moving onshore of Long Island and a
dew point surge as the warm front draws closer to the area.
Precipitation forecast looks on track with a round of heavy rain
around rush hour possible. Previous discussion follows.
An area of low pressure will track east across the northern
Great Lakes tonight. A warm front associated with the system is
expected to approach this evening and lift north through the
local area overnight and into Friday morning. Showers and
possible thunderstorms will spread across the area overnight and
into Friday morning. Temperatures tonight will be in the upper
60s to lower 70s.
Short term /6 am Friday morning through Friday night/...
as a warm front moves north a strong southerly flow will usher
in behind, bringing an influx of moisture across the area.
Dewpoint will rise back into the 70s across the region along
with instability resulting in thunderstorms and heavy rain to
develop. There may be a break in the precipitation for a brief
time once the warm front lifts north, and until the cold front
nears later in the day. Storms will weaken and move into Long
Island and southern Connecticut by Friday night.
Temperatures on Friday will be in the upper 70s to lower 80s
with lows in the upper 60s to lower 70s.
There is a moderate risk of rip currents at NYC and Nassau
County ocean beaches.
Long term /Saturday through Thursday/...
the frontal boundary/sfc trof will slowly slide offshore on Sat.
Trends will need to be monitored for a slowing of this feature, as
the main upr trof which will force it ewd is still progged to be
over Ohio at 18z Sat. The slower the boundary exits, the slower shwrs
and especially clouds will exit. Based on the 12z data, areas along
and W of the Hudson dry, with the rest of the area low chances for
pcpn. Dry weather Sat ngt thru Mon ngt with high pres progged to
12z GFS timeheights indicate sunny skies on Mon with perhaps some
fair wx cu, particularly along the sea breeze front.
Chances for shwrs and tstms Tue thru Wed ahead of a cold frontal
passage. Best chances are Wed closest to the front attm, so as the
event draws closer pops may be eliminated for Tue.
A blend of the guidance and 2m data was used for temps thru the
period. The numbers will generally be abv average until the fropa
Aviation /03z Friday through Tuesday/...
a warm front approaches from the southwest tonight. A cold front
will approach from late Friday.
Stratus deck developed along the South Shore of Long Island
near kjfk and has spread to kewr/kisp. Unsure whether it remains
through the night as some hi-res guidance says yes, while others
say it sct out between 06z and 09z. Have tempo at kteb for now
as it's been having a tough time advecting inland.
Otherwise...VFR with deteriorating conditions around daybreak.
Friday will be very unsettled with the threat of showers and
scattered thunderstorms in the morning and then again with the
approaching cold front late in the afternoon. There is uncertainty
with improving conds in the warm sector after the warm fropa in
the morning, may be too optimistic in the NYC Metro. Gusty
winds and MVFR/IFR are possible with any heavier shower or
Light southerly winds overnight before increasing again 10 to
15 kt Friday. Gusts to 25 kt possible Friday afternoon across
much the region but especially along the coast.
Higher gusts possible with any thunderstorm.
Outlook for 00z Saturday through Tuesday...
Saturday night...MVFR or lower flight Cat possible in
showers/tstms with gusty winds possible during the evening.
Fog/stratus with MVFR or lower conds may linger through the
Sunday and Monday...VFR. Light northwest wind becoming SW by late
Sunday and Monday.
Tuesday...iso shra/tstms possible with MVFR or lower
a warm front approaches tonight and moves across the area
waters Friday morning. Southerly winds will increase ahead of an
approaching cold front Friday, resulting in 15 to 20 kt winds.
Seas may briefly build close to 5 feet Friday afternoon and into
Friday evening. Will hold off on a Small Craft Advisory for Friday afternoon and
evening given low confidence in widespread Small Craft Advisory conditions
There may be some lingering 5 ft seas on the ocean Sat as a
front passes E of the waters, but all areas are fcst to be blw
sca lvls by Sat ngt. Winds and seas are then progged to remain
blw sca lvls on all waters thru next Wed.
heavy rainfall is possible by morning as a warm front moves
northward through the region. Another round of heavy showers and
thunderstorms will be possible by evening with the cold frontal
passage. Rainfall accumulations are expected to be around a half
an inch to an inch, with locally higher amounts possible in
thunderstorms. At this time it remains difficult to pinpoint
where heavier showers and thunderstorms will develop. No
significant hydrologic impacts are expected, but some minor
urban flooding is possible.
Impacts from potential showers and thunderstorms Tuesday into
Wednesday are uncertain at this point, however at least minor
nuisance flooding will remain a possibility.