Scientific Forecaster Discussion
fxus61 kokx 270901 cca
Area forecast discussion...corrected
National Weather Service New York New York
401 am EST Mon Feb 27 2017
high pressure centered south of Long Island will continue to
drift out to sea today. A warm front will lift north of the area
on Tuesday. A cold front approaches on Wednesday, then crosses
the area Wednesday night. This returns cold, but seasonable
weather for the end of the week, with the chance for light snow
for early Friday. It's a dry weekend and warming up on Sunday.
Near term /through tonight/...
clear skies this morning will give way to rapidly increasing mid
and high clouds today. Based on satellite, the leading edge over
southwestern Pennsylvania gets here around 12-13z, with the
thickest stuff over the Ohio Valley arriving by noon. It should
be an overcast afternoon as a result. Subsidence today weakens
by 00z with some weak lift developing thereafter. At this point
however the deepest moisture will be exiting, so the forecast
has been kept dry right through tonight. Temperatures will
rebound quickly as the inversion breaks this morning. The Pine
Barrens on Long Island could be the big Winner, where
temperatures in the teens should shoot up around 20 degrees in a
matter of minutes as the inversion mixes out. The guidance was
in good agreement and reasonable based on temperatures aloft and
southwesterly flow, so a blend was used through the period.
Short term /Tuesday/...
the main question is whether it actually rains. The models
continue to back off, as they are just not supplying any
moisture to the region. With the Gulf of Mexico opening up,
there is a concern the models are not pumping enough moisture
into the flow. As a result, chances for precipitation have been
essentially been kept the same, with high chances by the end of
the day. With regard to temperatures, it will be mild again with
southerly flow. This temperature structure is likely to result
in enhanced sea breeze flow particularly across southern
portions of Queens and Nassau counties, as well as Brooklyn.
Long term /Tuesday night through Sunday/...
nwp appears fairly clustered and consistent with the overall
pattern, but not without lots of local forecast problems this
1. Tuesday - Wednesday. Warm air advection advection pattern will likely bring
light rain by late afternoon Tuesday there persists on and off into Wednesday
afternoon. We have likely pops, but expect these to go to categorical
as timing of precipitation becomes clearer.
There's lots of spread in the temperature guidance for Tuesday
and have gone with the cooler side (gfs) due to the onset of
precipitation and the extensive cloud cover. That being said, temps
should get well into the 60s by Wednesday away from the coast - of
course with a strong gradient at the coast. Advection fog also
becomes a forecast problem and can see repeat of a few days ago.
2. Wednesday aftn/eve. Instability is once again present along
with very strong shear in excess of 60 knots. Li's of -2 c and
total totals in the lower 50s are not to be ignored this time
of year as we saw Saturday night. Thus have included ts in the
forecast. No enhanced wording, but that may come as we get
3. Thursday. Windy with steady or slowly falling temps. Think
40 mph should do it for the winds, but we could get close to
Wind Advisory criteria.
4. Friday. Clipper system passes the region. Looking at the
gefs suggest much of the energy passes across up state and
across New England. Thus, keeping just a 30 pop for light snow.
The operation GFS is on the higher end of the quantitative precipitation forecast across the
okx forecast area.
On the other hand, the operational European model (ecmwf) is south of the area.
Temps are forecast slight below normal for Saturday, but rebound to
the lower 50s for Sunday.
Aviation /09z Monday through Friday/...
VFR through the taf period as high pressure off the mid
Atlantic coast moves east. High confidence in SW flow less
than 10 kt and increasing to 10-15g20kt by late morning and
into the afternoon.
..NY Metro enhanced aviation weather support...
Detailed information, including hourly taf wind component forecasts,
can be found at: http://www.Weather.Gov/zny/n90
Kjfk taf comments: start time of gusts may be off by +/- 2
Klga taf comments: start time of gusts may be off by +/- 2
Kewr taf comments: start time of gusts may be off by +/- 2
The afternoon kewr haze potential forecast is green...which
implies slant range visibility 7sm or greater outside of cloud.
Kteb taf comments: start time of gusts may be off by +/- 2
Khpn taf comments: start time of gusts may be off by +/- 2
Kisp taf comments: start time of gusts may be off by +/- 2
Outlook for 09z Tuesday through Friday...
late Monday night...VFR.
Tuesday...chance of light rain/MVFR conds.
Tuesday night-Wednesday morning...areas of fog with light rain
continuing. MVFR/IFR and possibly lower. Low level wind shear possible with SW
winds 45-55 kt at 2kft. SW winds g15-20kt Wednesday morning.
Wednesday afternoon-Wednesday night...showers and a chance of
thunderstorms. MVFR or lower possible. SW winds g20-30kt. Winds
become westerly late Wednesday night.
Thursday...VFR. West-west-northwest winds g20-25kt.
Friday...MVFR/IFR possible with a chance of light snow. West-northwest
southwest winds will produce Small Craft Advisory conditions on
the eastern two thirds of the ocean today and tonight.
Elsewhere, winds and waves are expected to remain just below
criteria at this time. For Tuesday, light flow will allow seas
on the ocean to remain below 5 feet.
The region will be in between the high pressure well offshore and
a low pressure area moving into the Midwest. The pressure
gradient gradually tightens through midweek with a strong cold
front eventually approaching from the west. The resulting
increasing SW flow will build seas to Small Craft Advisory range beginning Tuesday
night and continuing through midweek. Ahead and just behind the
cold front will be potentially the highest of winds, when gales
will be possible for the eastern waters and the ocean Wednesday
through Wednesday evening with otherwise Small Craft Advisory winds for all waters.
After this cold front moves across Wednesday night, there will be
gusty northwest flow and cold air advection. The ocean will likely
remain at Small Craft Advisory levels through the rest of the marine forecast
period through Friday. Small Craft Advisory level winds will persist Wednesday
night through Thursday and come to a brief lull below Small Craft Advisory Thursday
night before returning to around Small Craft Advisory levels Friday.
rainfall from Tuesday afternoon through Wednesday night should
run from 0.5 to 0.75 inches, with locally higher amounts
Release from Spring snow melt is occurring down the Connecticut
and Housatonic rivers.
Marine...Small Craft Advisory until 6 am EST Tuesday for anz350-353.