FXUS61 KOKX 181330

Area Forecast Discussion
National Weather Service New York NY
830 AM EST Sat Jan 18 2020

High pressure across the region gives way to a frontal system
that impacts the region this afternoon and tonight. Polar high
pressure building into the mid section of the country Sunday
will then move east and into the area by mid week. The high will
then remain in place through Friday.


A winter weather advisory remains in effect for most of the
region from 1000 AM today through 100 AM Sunday morning.

A mid deck of clouds across eastern Pennsylvania was seen on
radar and observations. These clouds will be moving into the
region a little quicker than forecast so increased sky cover
through this morning. Light snow was developing across western
Pennsylvania where thermal forcing was increasing. Temperatures
and dew points were increased, especially dew points across the
coastal areas as both were higher than forecast.

High pressure centered over New England into the mid Atlantic
was beginning to weaken and drift offshore early this morning.
The forecast timing and precipitation type and changeover remain
mainly consistent with the previous forecast, and model
guidance, with a slight delay with the ending across the far
eastern zones toward 09Z.

Warm advection light snow could begin as early as 16Z across
the western zones, and have chance and slight chance
probabilities. However the best forcing looks to be toward 18Z
as warm advection strengthens. Precipitation will remain all
snow through today. With a southerly onshore flow precipitation
begins to transition to a rain/snow mix then rain. The timing of
this transition may delayed dynamic cooling continues with wet
bulb temperatures still below freezing along the coast at 00Z.
Also, a low level jet will enhance lift and precipitation
continues as moderate to possibly briefly heavy. However,
another uncertainty is how quickly the lower levels warm, and
will be starting off a couple of degrees warm as temperatures
have fallen more slowly as high clouds have moved across the
region and a light northerly flow remains. So, still expect the
transition to begin 23Z to 00Z, especially the southeastern
zones and continue this evening. However, far northwestern
sections may not see a transition until late as the
precipitation is coming to an end late tonight. Also, with the
boundary layer warming a period of sleet will be possible with
the transition, and have this in the weather grids.

Precipitation amounts have been trended downward slightly and
Long Island coastal zones will be borderline with advisory level
snowfall. However, with the lower totals there is still
uncertainty with the timing of the transition to rain, so
decided to leave the advisory as posted.


Deep cyclonic flow will remain through Sunday as the center of
the low pulls east, and a weak trough remains back across the
Hudson Valley into southern New England. Models do indicate
enough moisture with the trough and have some precipitation as
energy continues to rotate through the longwave upper trough.
Think that a few flurries will be possible inland but will leave
out the mention at this time.


The northern branch of the polar jet will briefly visit the
northeast quarter of the nation next week with dry, and
unseasonably cold air. This will be a far cry from where we have
been this month with average temperatures at the official climate
sites round 10 degrees above normal. Central Park through the
first 16 days was fifth warmest all time.

After seasonable temperatures on Sunday, high temperatures
through midweek will be at or just below freezing. Additionally, a
gusty NW flow (up to 30 mph) on Sunday will gradually diminish
Sunday night into Monday as the high approaches and low pressure
departs across the north Atlantic.

For the second half of the week, the upper trough over the northeast
departs and will be replaced by a southern branch upper ridge.
The latter of which will be preceded by an upper low moving out
into the Central Plains on Thursday and into the mid Mississippi
Valley by Friday. This will allow for a gradual warmup with
temperatures returning to just above normal levels by next Friday.


A incoming low pressure system brings accumulating snow then
rain beginning late this afternoon into tonight.

VFR through the morning with NNW winds mostly under 10kt across
all terminals. Winds shift to the south as conditions
deteriorate rapidly in the afternoon with IFR conditions
expected to develop. LIFR is possible in periods of moderate
snow. IFR conditions are forecast to remain through the evening
improving to MVFR once the snow ends and rain begins during the
evening hours.

Forecast snow amounts: NYC and NE NJ terminals: 2-4 inches, LI
terminals: 1-3 inches, Lower Hudson Valley terminals: 3-5
inches, Southern CT terminals: 3-5 inches.

Light snow may begin an hour or two earlier than forecast in

.Saturday night...IFR with Snow changing to rain southeast to
northwest in evening, remaining snow well northwest. Dry conditions
return overnight with mostly MVFR conds.
.Sunday...VFR. W-WNW gusts near 25kt day into evening. Gusts
diminish late Sunday night.
.Monday-Wednesday...VFR, NW winds much of the period, N winds
Tuesday night into Wednesday.


No changes were made to winds and seas at this time.

Light north winds persist through the morning and afternoon

SCA conditions begin late Saturday evening ahead of the frontal
system. Strong south winds gusting 25-30 kts during the evening
and overnight hours switch west during the day Sunday but
remaining at SCA levels. Small craft conditions expand through
the Long Island Sound for most of the day Sunday. By the
overnight hours and into early Monday winds diminish below SCA
criteria and a northwest flow 10-15 kts develops over the marine

No hazards expected at this time for next week as a surface
high pressure system builds over the region. This will result in
light north winds of 5-10 kts with waves ranging 1-2 feet with
dry rain free conditions through Friday.


No hydrologic impacts are expected through Friday of next week.


NYC NOAA Weather Radio Station KWO35 (162.55 MHz) is still
operating at reduced power.


CT...Winter Weather Advisory until 1 AM EST Sunday for CTZ005>012.
NY...Winter Weather Advisory until 1 AM EST Sunday for NYZ067>075-
NJ...Winter Weather Advisory until 1 AM EST Sunday for NJZ002-004-
MARINE...Small Craft Advisory from 7 AM Sunday to 1 AM EST Monday for
     Small Craft Advisory from 7 PM this evening to 7 AM EST Monday
     for ANZ350-353-355.



NWS OKX Office Area Forecast Discussion