Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 082057 AFDOKX Area Forecast Discussion National Weather Service New York NY 357 PM EST Mon Mar 8 2021 .SYNOPSIS...
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A ridge of high pressure builds in through this evening. Then, a warm front will move across tonight. A cold front will move across Tuesday morning into early Tuesday afternoon. Strong high pressure then builds in from the west Tuesday afternoon through Tuesday night. High pressure shifts to the east on Wednesday as a slow moving frontal system approaches the area. The front slowly moves through the area Friday and Saturday before high pressure takes hold on Sunday. Another frontal system looks to approach from the west early next week.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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Winds decrease going into this evening and before clouds increase, optimal radiational cooling will lead to surface temperatures dropping rapidly during the evening hours. Then, clouds increase with a warm front passage and low level SW winds will increase late tonight. Warmer arrives in the 950mb to 850mb layer late evening into overnight and the surface will follow this tendency but at a slower rate. The warm layer in the 950 to 850mb layer is forecast to reach 4 to 5 degrees C, easily allowing for the melting aloft and surface precipitation type to either be rain or freezing rain. Winds will have a large amount of westerly flow from lower to upper levels, keeping conditions mainly dry with the warm frontal passage. However, some forcing aloft with small area of positive vorticity advection at 500mb along with some 700mb omega will present a possibility for some sparse coverage of very light rain or very light freezing rain depending on the surface temperature. Some mesoscale models and a few SREF members also indicate light precipitation across a few parts of the region late tonight into early Tuesday. GFS and ECMWF 12Z runs indicate a few small 0.01 inch areas of precip across parts of Southern Connecticut and Eastern Long Island. The national blend of models was used for forecast lows tonight and the forecast hourly temperatures become steady going into overnight and eventually rise going into early Tuesday morning.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
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Slight chance of some lingering light rain across parts of Southeast Connecticut and Eastern Long Island between 6 and 8am Tuesday. After Tuesday 8-9am, expecting any precipitation to move south of Long Island with otherwise dry conditions. A cold front will move northwest to southeast across the region Tuesday morning into early Tuesday afternoon. Initial cold air advection behind the cold front will allow for an increase in vertical mixing depth and gusty winds, likely peaking in the late morning before low level winds decrease for Tuesday afternoon. For the high temperatures forecast on Tuesday, used a blend of mixing down from 900mb using NAM12 temperatures along with a consensus of MOS and went one degree higher. The resulting forecast highs are mainly in the mid 50s to near 60. These are relatively higher towards the coastline where there will be more downslope flow. A strong area of high pressure builds in from the west Tuesday afternoon into Tuesday night. Strong subsidence will provide for mostly clear sky conditions and a further decrease in winds as the overall pressure gradient decreases. Forecast lows convey a more vast range as radiational cooling will be optimal. The forecast lows range from the lower 20s for parts of the interior and the Pine Barrens of Long Island to lower 40s for parts of NYC.
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&& .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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High pressure positioned over the area begins to move offshore late Wednesday and winds become primarily southerly. With clear skies, and dry conditions, temperatures will rise into the middle and upper 50s for much of the area, about 5-10 degrees above average. A low pressure system over the Upper Midwest and southern Canada will allow the pressure gradient to tighten over the area with high pressure remaining just offshore. This will allow for a strengthening S/SW flow over much of the area with temperatures remaining above average through much of the middle and end of the week. The S/SW flow will bring in more moisture as well allowing for skies to be partly to mostly cloudy at times. High temperatures on Thursday and Friday will be in the upper 50s for Eastern LI and SE coastal CT with the rest of the region rising into the middle and potentially upper 60s during the afternoon each day. This will be anywhere from 10-15 degrees above average and a nice preview of Spring. As the cold front approaches the area on Friday, a chance of rain showers will be possible with a relatively moist and warm airmass ahead of the front. There is some disagreement as to how far the cold front can move through the area on Friday night and Saturday. The GFS pushes the cold front completely through the area by Saturday with a primarily NE flow and dry conditions. The CMC and ECMWF both slow the front down and allow for another wave to ride along the front and bring the potential for more rain during the day on Saturday. As of now, slight chance PoPs are in place due to the uncertainty. Either way, temperatures looks to drop back down to seasonable, generally in the upper 40s and low 50s. A strong high pressure system looks to move into the area on Sunday and into the beginning of next week with the next frontal system approaching the area sometime in the late Monday to Tuesday timeframe.
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&& .AVIATION /21Z MONDAY THROUGH SATURDAY/...
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High pressure builds offshore, giving way to a weak frontal system approaching from the west. The warm front moves through the area tonight, followed by a cold front Tuesday morning. Mainly VFR. Brief MVFR possible overnight in spotty light rain. WNW winds 5-10 kt will back around to the SSW this evening, then back around to the WNW at 10-15kt G15-20kt Tuesday morning. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... Winds mainly left of 310 magnetic this afternoon. A few gusts 15-17kt. .OUTLOOK FOR 21Z TUESDAY THROUGH SATURDAY... .Tuesday Afternoon...VFR. NW G15-20kt in the afternoon. .Wednesday...VFR. .Wednesday Night...MVFR or lower in stratus possible for coastal terminals. .Thursday...MVFR or lower AM coastal terminals, then VFR. S-SW gusts 15-20 kt. .Friday...Mainly VFR. Chance of showers. S-SW gusts 20-25 kt, becoming W-NW late afternoon/evening. .Saturday...Mainly VFR. Low Chance of AM showers. NW G15-20kt. Detailed information, including hourly TAF wind component forecasts, can be found at: http:/www.weather.gov/zny/n90
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&& .MARINE...
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Small craft advisory in effect from 07Z Tuesday until 18Z Tuesday for the ocean east of Fire Island Inlet out 20 nm. Conditions on the waters will be initially below SCA criteria going into this evening. Then, after a warm front passage and ahead of a cold front, SW winds will be increasing and the boundary layer will increasing as well. This will be enough for gusts of 20-25 kt to develop mainly on the ocean east of Fire Island Inlet. Other waters will stay below that SCA wind gust threshold of 25 kt. The gusts near 25 kt on the ocean east of Fire Island Inlet continue into Tuesday before all waters are below SCA thresholds after 18Z. Tranquil conditions expected for Tuesday afternoon into Tuesday night with conditions getting well below SCA thresholds. Any remaining wind gusts diminish Tuesday night. OCean seas are forecast to be mainly 2 ft for Tuesday night. Sub-SCA conditions on all waters on Wednesday and Wednesday night with high pressure overhead. Increasing S/SW flow on Thursday will bring SCA conditions on the ocean waters with gusts 25-30kts and waves 5-7ft. Gusts for non- ocean waters look to remain just below SCA Thursday and into Friday. SCA conditions on the ocean continue through much of the end of the week and into the weekend with conditions dropping below SCA by Saturday afternoon. Gusts remain marginal for the ocean through the beginning of next week. Ocean seas looks to build again near SCA criteria Sunday afternoon.
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&& .FIRE WEATHER...
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There has been mainly dry conditions going back to late last week. The forecast for Tuesday has forecast low level relative humidity of around 30 to 35 percent and gusts up to near 20 mph. These are almost conducive for enhanced spread of any brush fires if any were to occur. With these limiting factors plus some residual snow cover across parts of the interior, held off on any special weather statement issuance for the time being. The potential for any enhanced spread of any brush fires would increase if dewpoints trend lower than forecast Tuesday or if gusts increase closer to 25 mph or greater.
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&& .HYDROLOGY... No hydrologic concerns are expected. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 2 AM to 1 PM EST Tuesday for ANZ350- 353.
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&& $$ SYNOPSIS...JM NEAR TERM...JM SHORT TERM...JM LONG TERM...MW AVIATION...DW MARINE...JM/MW FIRE WEATHER... HYDROLOGY...JM/MW

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