Scientific Forecaster Discussion
fxus61 kokx 181807
Area forecast discussion
National Weather Service New York New York
107 PM EST sun Feb 18 2018
high pressure builds over the area today, then slides offshore
into Monday. A warm front slowly approaches from the south into
Monday night, then lifts to the north early on Tuesday. A cold
front then approaches from the west into Wednesday, then sinks
to the south Wednesday evening. This front then stalls to the
south with waves of low pressure riding along it through the end
of next week, as high pressure builds across southeastern
Near term /until 6 PM this evening/...
forecast on track with just some minor adjustments to reflect
Otherwise, high pressure builds back into the region. Expect a
sunny afternoon. Highs will be in the lower 40s.
Short term /6 PM this evening through 6 PM Monday/...
given expected snow melt today, and temperatures falling below
freezing tonight across the lower Hudson Valley, S CT, most of
NE New Jersey (except areas adjacent to nyc) and most of Suffolk County,
there is the potential for black ice tonight on untreated
surfaces. Will address this threat in the severe weather potential statement.
Deep layered ridging, centered off the Florida coast, builds in
tonight and Monday. Tonight will be clear and dry as a result.
Increasing low level warm advection on Monday will result in
increasing cloud cover and a chance for some rain building into
the area mainly Monday afternoon (best chance over far west zones
where have low end likely pops). Lows tonight should run around
5 degrees below normal and highs on Monday around 5 degrees
above normal, mainly in the mid-upper 40s, except lower 40s in
the higher elevations to the north/west of NYC.
Long term /Monday night through Saturday/...
a deep layered ridge whose center progresses northwest to off the southeast
Seaboard through the middle of the week will be the main weather
player through then.
Continued low level warm advection Monday night into Tuesday
will likely bring rain to the region Monday evening, with pops
decreasing through the night as the 850 hpa warm front lifts to
the NE. Could see some patchy fog late Monday night over the
lower Hudson Valley as a result of abundant low level moisture
trapped in local valleys. The surface warm front lifts to the
north Tuesday morning, bringing the end to any lingering threat
of light rain to the region.
A passing shortwave Tuesday night over the top of the ridge
could bring some isolated showers (maybe even some patchy
drizzle - but not quite confident enough to forecast this yet)
to the area. Could also see patchy fog yet again over the lower
The region should be mainly dry on Wednesday as a 700 hpa
shortwave undercuts the ridge - however should see some mid-
level cloud cover as a result - and a slight chance of a shower
over far northwest zones.
Temperatures Tuesday and Wednesday will be well above normal
across the region. Highs Tuesday ranging from around 10 degrees
above normal over log island/coastal CT and coastal NYC where
cooler waters near by will serve as a limiting factor to around
20 degrees above normal inland. Depending on how much cloud
cover there is on Wednesday, it could be even warmer than
Tuesday, with highs possibly around record levels. Refer to the
climate section of the afd for details.
A passing northern stream shortwave flattens the ridge
Wednesday night, allowing a cold font to sink to the S, with
some passing showers.
The forecast becomes somewhat tricky for the remainder of next
week as it becomes dependent on how for to the S the cold front
sinks, which depends on the strength of high pressure building
across southeast Canada. Noting that the GFS typically does not handle
a pattern like this well, leaned towards the European model (ecmwf) and CMC
global for the remainder of the forecast. As a result, expect
unsettled weather during this time frame, with periods of off
and on precipitation - with exact timing determined by the
passing of shortwaves embedded in the flow aloft (very hard to
predict this far out). As a result, have limited pops to at most
chance Thursday-Saturday. Also with near seasonal temperatures
returning on Thursday-Friday, have the potential for some wintry
precipitation across mainly northern interior zones as well
(for now going with mainly a mix of rain and snow there). For
now it appears that Saturday could end up being a bit warmer
than Thursday and Friday, so no wintry mix then. This is all
still highly uncertain and there is the potential for
temperatures to end up a bit colder Thursday-Saturday then
Aviation /18z Sunday through Friday/...
high pressure builds in through this evening, then moves
West-northwest winds at 10 kt or less, becoming light and variable tonight.
Outlook for 18z Monday through Friday...
Mon...becoming MVFR to IFR with rain late aftn/early evening.
Tue...MVFR or IFR possible in the morning and again at night,
otherwise VFR with SW wind g20kt possible.
Wed...mostly VFR. Chance of showers with MVFR. SW wind g20kt
Thu...MVFR in rain.
Fri...chance MVFR in rain.
winds and seas have subsided below small craft levels.
Therefore, the Small Craft Advisory has been allowed to expire. Sub-advisory
conditions are expected on all waters through Tuesday. A
moderate SW flow on the ocean waters Tue night into Wed night
may result in advsy level seas on the ocean waters. An strong
sfc inversion should keep gusts below criteria. A cold front
moves through Wed night with winds becoming northerly and sub-
advsy conds returning through the remainder of the period.
even with the snow expected to melt rapidly, given less than 1
inch of liquid water equivalent in the snow, and no widespread
heavy rainfall to couple with the snow melt, no significant
hydrologic impacts are expected through at least the middle of
record highs for Wednesday February 21, 2018
j f Kennedy.........63/2002.........65......
NYC National oceanic and atmospheric administration weather radio station kwo-35 (162.55 mhz) is off the
air for an extended period of time.