Area Forecast Discussion
Issued by NWS Upton, NY

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KOKX 010522 AFDOKX Area Forecast Discussion National Weather Service New York NY 1222 AM EST Thu Dec 1 2016 .SYNOPSIS...
-- Changed Discussion --
A frontal system will move across the area early this morning, followed by high pressure later today. A series of weak troughs will pass through from Friday into Saturday. High pressure will briefly build in from Saturday night into Sunday. Then a low pressure system may impact the area Sunday night into Monday.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
-- Changed Discussion --
Warm front is beginning to move across Long Island with winds shifting to the south, and temperatures rising into the upper 50s. The warm front should continue lifting further north through the next few hours with the aid of a strong southerly LLJ and the associated developing surface low moving across north central NY. The warm front may hang up invof the Hudson River and across coastal CT. Flow here is a bit more NE and could help to slow the progression of the front. Where the warm front moves north, locally dense fog is possible, although it is a bit uncertain of the duration of any dense fog as southerly flow increases. For now, have issued an SPS across Long Island to account for locally dense fog potential. Temps will rise into the lower 60s after the warm front passage. Several bands of showers continue to move northward across Long Island and southern CT with another band moving across the Lower Hudson Valley, NE NJ and NYC. The actual cold front is also producing a narrow cold frontal rain band which can be seen on regional radar mosaic. Some gusty winds are possible with any heavier downpour and a rumble of thunder cannot be ruled out. Stronger cells could produce strong wind gusts via downward momentum transfer of SW H7-9 winds between 40-50 kt. The cold frontal rain band looks to progress across the area from west to east 08z- 10z time frame.
-- End Changed Discussion --
&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... Dry weather returns this time frame as upper low remains well to the north, and two surface lows will be located well to the north as well. Secondary low, that initially moves nearby as triple point low near the coast intensifies as it tracks toward the Canadian Maritimes. Fairly tight pressure gradient remains in place behind this system as high pressure builds well to the west. CAA is noted, but downslope flow and a lag in the cold air allows for above normal readings during the day per MOS and model blend. Winds persist Thursday night, which should preclude radiational cooling from occurring. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Forecast models in good agreement to end the week and start the weekend, with troughing over the region as a closed low north of the region lifts into southern Ontario/Quebec. Expect generally dry...cool...and breezy conditions Friday thru Sat in persistent deep WNW flow. A couple of weak shortwaves/surface troughs moving through the region may trigger some isolated sprinkles (and/or flurries nw of NYC) Fri afternoon through Sat. Conditions remain generally quiet with seasonable conditions heading into Sunday as high pressure builds over the region. There are significant differences in models Sunday night and Monday with the handling of the late weekend/early next week eastward evolution of a deep Western US trough. The main difference is whether the base of the trough closing off into Northern Mexico this weekend...travels with the parent northern stream shortwave or gets left behind. The implication being...a phased eastward moving trough would bring potential for a southern low and significant precip tracking up the east coast for Sun Night into early next week. Meanwhile...the latter detached scenario would just bring another weak trough through the region with perhaps some light precip. Either scenario is in play. Based on the complex interaction...may continue to see flip-flop of operation models and considerable spread in ensembles for this time frame for the next few days. As a result, this portion of the forecast will remain unchanged and with low chance POPs in the forecast. Dry weather is expected on Tuesday, with another low chance for rain on Wednesday as another weak low approaches. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
A warm front will slowly move northward across the region tonight followed shortly thereafter by a cold front overnight. Mainly IFR and lower conditions are occurring with some localized MVFR. The IFR and lower conditions should prevail though with intermittent rain showers and fog, locally dense. There will be some potential for showers and isolated thunderstorms ahead of the cold front going into the overnight period. Uncertainty though with timing and location of any thunderstorms. Eventually, conditions improve to VFR by Thursday morning and continue at VFR through the rest of the TAF period. Winds will initially be NE-E this evening ahead of the warm front, and then shift after the frontal passage to S-SW near midnight and shortly thereafter. KISP and KJFK already switching to more of S to SW flow. With that, gusts will become more frequent as well with winds overall increasing slightly. Winds further increase after a cold frontal passage, with winds shifting to a west wind. Wind gusts continue through much of the TAF period, mainly near 20-25 kt. Low level wind shear generally before 10Z will make for occasionally higher gusts than forecast, especially with any heavier showers or thunderstorms. Winds at 2kft will be near 50kt out of the SW for the low level wind shear. Timing of categorical changes could be 2-3 hours off from forecast. Wind shifts may also vary 1-2 hours from forecast. .OUTLOOK FOR 06Z FRIDAY THROUGH MONDAY... .Thursday night...VFR. West winds diminish late. .Friday...VFR. West gusts around 20 KT. .Saturday...VFR. NW gusts around 20 KT. .Sunday...VFR. .Monday...VFR...possibly lower at times depending on the track of low pressure to the south.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Warm front continues moving north of the ocean waters and should continue progressing through the rest of the waters in the next few hours. After warm fropa expect S-SW winds to increase to 15-25 kt with gusts 25-30 kt on all waters except NY Harbor, so SCA remains in effect. Patchy to areas of fog will likely continue to form into this with high dew point air advecting northward over mid 50 degree water should allow this fog to form. Extent of the fog remains in question however, and winds may hinder this development. Winds will shift around to the west early this morning as a cold front moves through. Expect these westerly winds to increase, and SCA conditions are anticipated across all waters this afternoon through tonight. Winds over the ocean waters remain elevated per WaveWatch and NWPS. SCA conditions for sea and wind gusts will remain likely on the ocean waters through Saturday in a tight gradient between Canadian Maritimes low and Central/Southern US high. On the non- ocean waters, marginal sca gusts possible during this period...particularly on Long Island Sound. With high pressure building back into the region Sat Night into Sun...a return to sub-SCA conditions would be expected. The sub- SCA conditions are expected into early next week.
-- End Changed Discussion --
&& .HYDROLOGY...
-- Changed Discussion --
Another 1/2 to 3/4 inch expected through early this morning as the frontal system works its way across the region. The main threat is urban and poor drainage flooding. No significant precipitation expected from Thu through Sunday. Potential for significant precip returns Sunday night into Monday, with low predictability in the details at this point.
-- End Changed Discussion --
&& .OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 AM EST Friday for ANZ330-335-338- 340-345-350-353-355.
-- End Changed Discussion --
&& $$ SYNOPSIS...BC/PW NEAR TERM...PW/DS SHORT TERM...PW LONG TERM...BC AVIATION...JM MARINE...BC/Goodman/PW HYDROLOGY...BC/PW

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.