Area Forecast Discussion
Issued by NWS Upton, NY

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923 FXUS61 KOKX 230539 AFDOKX Area Forecast Discussion National Weather Service New York NY 139 AM EDT Fri Mar 23 2018 .SYNOPSIS... High pressure builds from the west tonight. A series of low pressure troughs will move through Friday through Sunday, followed by high pressure building into New England from southeast Canada through Tuesday. A frontal system gradually approaches for the middle of the week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Forecast remains on track with only minor adjustments needed to reflect current temperature and dew point trends. Coastal low continues pulling away into the Canadian Maritimes tonight as high pressure gradually builds from the west. An area of cirrus moves through tonight resulting in partly cloudy skies with mid level clouds starting to increase towards daybreak as a shortwave associated with an upper level low track towards the area from the Great Lakes. Low temperatures tonight are expected to drop into the 20s and 30s due to the combination of partial radiational cooling and a fresh snowpack on the ground. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/... Persistent upper trough remains in place with a vigorous shortwave passing through in the afternoon and evening. Weak lift and limited moisture support the ongoing forecast of a slight chance of showers, with even the possibility of a few snow showers, mainly to the north and west. Drying conditions for Friday night will return as the shortwave exits to the east of the area and surface high pressure builds more into the region. High temperatures will remain below normal, only in the 40s. Lows Friday night will drop into the 20s for the outlying counties and in the low 30s around the NYC Metro area. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... The blocking pattern across the northern hemisphere will continue into next week with deterministic and ensemble means in general agreement. The pattern of a deep and anomalous upper trough extending down from southeast Canada will dominate through the weekend. The upper trough slides into the western Atlantic and will be replaced by significantly higher heights and ridging across the eastern States early next week Several shortwaves will rotate around the base of this upper trough on Saturday and Sunday with surface reflections indicated by weak low pressure troughs. The shortwave energy on Saturday is rather potent and model progs have the trough becoming a closed upper low and then shifting south and east of the area on Sunday. Each shortwave will assist in the resupply of unseasonably chilly air as the flow continues out of the north. While the atmosphere will be generally dry, the passing of the shortwave energy coinciding with weak low pressure troughs at the surface support a slight chance of rain or snow showers Saturday night through the first half of Sunday. Do not anticipate any significant precipitation, but a few locations could see a brief rain or snow shower. A strong surface high pressure around 1040 mb builds into New England from southeast Canada Sunday afternoon through Monday. The high settles over the area on Tuesday and should remain in control on Wednesday. A weak upper shortwave approaches Wednesday. The latest trend in the deterministic and ensemble models is for the upper trough that moved into the western Atlantic to cut-off and allow the ridge to remain in place aloft through the middle of the week. This may cause the approaching front to weaken, with limited precipitation across our area. Unseasonably cold temperatures with highs in the lower 40s this weekend will trend to near seasonable levels by Tuesday and possible slightly above normal for the middle of next week. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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A trough of low pressure pushes south through the area today. High pressure then builds down from southern Canada into tonight. VFR through the TAF period. Ceilings around 5000ft likely from around midday into the early evening hours. Cannot rule out some isolated snow/rain showers this afternoon. For now confidence in occurrence at any given terminal is low. With the best (but still low) chance at KGON, have introduced VCSH in the TAF late this afternoon. NW winds diminish to around or just below 10 KT early this morning. Winds increase a few knots by midday, with 15-20kt gusts probable late this afternoon/early this evening. Winds diminish to under 10kt out the NW-NNW this evening. .OUTLOOK FOR 06Z SATURDAY THROUGH TUESDAY... .Late tonight-Saturday...VFR. .Saturday night-Sunday...Most likely VFR. Very low chance of isolated rain/snow showers. N-NE winds G15-25KT possible. .Sunday night-Tuesday...VFR. NE winds G20-30kt possible Sunday night.
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&& .MARINE... SCA-level gusts will begin to subside as high pressure begins to build from the north tonight. Lingering swells will allow for ocean waters to remain at SCA levels through tonight, before subsiding Friday. Conditions remain below SCA levels Friday night. Sub-SCA conditions are forecast on Saturday. NE flow strengthens on Sunday into Sunday night with SCA winds anticipated on the ocean waters and possible the LI Bays and eastern LI Sound. Ocean seas will also build above 5 ft. The SCA conditions may continue on the ocean waters through early next week, mainly in seas on Tuesday. && .HYDROLOGY... Expect snow melt over the next week, as high temps reach into the 40s through most of the period, and 50s mid next week. No hydrologic problems are anticipated. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 AM EDT early this morning for ANZ350-353-355. && $$ SYNOPSIS...CB/DS NEAR TERM...MD/CB SHORT TERM...CB LONG TERM...DS AVIATION...Maloit MARINE...CB/DS HYDROLOGY...CB/DS EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.