Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 181746 AFDOKX Area Forecast Discussion National Weather Service New York NY 146 PM EDT Wed Apr 18 2018 .SYNOPSIS... An area of low pressure will approach from the west into this evening, then cross the area late tonight and Thursday morning. The low then quickly exits into the Canadian Maritimes through Thursday night. A trough of low pressure crosses the area on Friday. High pressure builds in from the west through Sunday night, then slowly sliding offshore Monday and Tuesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Adjusted temperatures down a few degrees based on latest trends. This is largely due to areas of clouds. Highs will top out in the lower to mid 50s. Steep low-level lapse rates will allow for instability stratocu this afternoon. This will result in varying amounts of cloud cover today Otherwise, gusty west flow will continue as another weak surface trough moves through the area, though flow will gradually decrease into the evening as a weak surface high builds. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... Cloud cover will gradually increase ahead of an approaching low pressure system, and with weak warm advection, temperatures will only fall into the upper 30s to mid 40s tonight, which is closer to climatological normals. Any precipitation will likely initially be light drizzle as the low levels begin to saturate in warm advection. Once a powerful vorticity maximum rotates around the broader trough into the area, deeper forcing for ascent should allow for steadier rainfall to develop, with the best chance on the northern periphery of the surface low. With a more continental trajectory of the mid-upper level flow, moisture will be somewhat limited aloft, especially in comparison to the previous system. Expect generally a half inch or less in accumulations. With cloud cover, rainfall and initially onshore flow, high temperatures will remain on the cool side, with highs in the upper 40s to mid 50s. The system departs by late afternoon and evening, with strong and gusty northwest flow developing on the back side. Given continued cyclonic flow, a few additional spotty showers will be possible into the evening. Cold advection into the night will allow temperatures to fall into the 30s. Should flow decrease sooner than forecast, a few sites to the north and west of NYC and across the pine barrens of Long Island may approach the freezing mark. && .LONG TERM /FRIDAY THROUGH TUESDAY/... The axis of the mean trough over the eastern U. S. slides offshore Friday, but the low levels should be sufficiently dry to keep things precipitation free. However, cannot 100 percent rule out a lingering shower early Friday morning over far eastern zones. Highs Friday should be around 5-10 degrees below normal. The region will be under NW flow aloft Friday night and Saturday, and with no shortwaves currently progged to embedded in the flow over the region, it should be dry. Lows Friday night and highs on Saturday should be around 5-10 degrees below normal. A northern stream 700-500 hPa trough moves across the area Saturday night and Sunday, followed by a northern stream shortwave trough Sunday night. However, with the best dynamics currently progged to the N and S of the area and relatively dry low levels, they should pass through dry. Deep layered ridging then builds in Monday through Tuesday with associated subsidence keeping things dry and allowing for minimal, if any cloud cover. Lows Saturday and Sunday night should run 5 to 10 degrees above normal while highs Sunday and temperatures Monday through Tuesday should run near to slightly below normal. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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A wave of low pressure approaches tonight, and passes over the region Thursday morning. VFR through midnight. Clouds thicken and lower overnight, falling to MVFR then eventually IFR by early Thursday morning. Ceilings will begin to improve back to VFR late in the 30 hour TAF sites. W winds around 15 KT with gusts 20-25 KT today. Winds then diminish early this evening becoming light and variable. Winds then become northwesterly by midday Thursday with gusts around 20-25kt. 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: Occasional gusts to 20 kt still possible from 22- 00z. KLGA TAF Comments: Occasional gusts to 20 kt still possible from 22- 00z. KEWR TAF Comments: Occasional gusts 16-19 kt still possible from 22- 00z. KTEB TAF Comments: Occasional gusts 16-19 kt still possible from 22- 00z. KHPN TAF Comments: Occasional gusts 16-19 kt still possible from 22-00z. KISP TAF Comments: Occasional gusts up to 20 kt still possible from 22-00z. .OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY... .Thursday-Thursday night...IFR/MVFR in rain Thursday, rain/snow showers THU night. NW winds G20-30KT Thursday afternoon. .Friday...VFR. NW winds G25-30KT. .Saturday-Monday...VFR.
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&& .MARINE... Gusty west flow very gradually decreases through the day. SCA conditions will gradually decrease from west to east, with ocean seas slower to subside. Conditions will then fall below SCA tonight as the pressure gradient continues to weaken over the area. Flow will remain weak into Thursday, but northwest winds will quickly strengthen into Thursday evening as the pressure gradient tightens. Winds may briefly gust to gale-force Thursday evening. Ocean seas build in response, with at least SCA level conditions expected into Thursday night. A moderate pressure gradient over the region should allow gusts to around 25-30 kt to continue over all waters on Friday and on the coastal ocean waters Friday night. The pressure gradient should relax over the waters this weekend, becoming light by Saturday night. As a result, sub Small Craft Advisory conditions are forecast over the waters around Long Island Saturday-Sunday night. && .HYDROLOGY... Rain amounts below a half inch are expected Wednesday night through Thursday evening with no hydrologic impacts anticipated. Dry weather follows thereafter. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off the air. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 4 PM EDT this afternoon for ANZ330- 340-345-355. Small Craft Advisory until 11 PM EDT this evening for ANZ350- 353. && $$ SYNOPSIS...MD/Maloit NEAR TERM...MD/Maloit/DW SHORT TERM...MD LONG TERM...Maloit AVIATION...BC MARINE...MD/Maloit HYDROLOGY...MD EQUIPMENT...

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