Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 190242 AFDOKX Area Forecast Discussion National Weather Service New York NY 942 PM EST Thu Jan 18 2018 .SYNOPSIS...
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High pressure builds to the south overnight and Friday. Low pressure passes well to the north and east on Saturday. The low will send a back door cold front through the region Sunday into Sunday night. The front returns north as a warm front on Monday ahead of a strong cold front passage late Monday night into Tuesday. High pressure returns for the middle of the week.
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&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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High clouds from a shortwave, moving through the northern stream, were beginning t move into the northwestern zones as seen on the mid level water vapor loop. High and mid level clouds are expected across the northern tier in association of the shortwave. Updated the sky cover, winds, temperatures and dew points for current conditions and trends into Friday morning. The upper level disturbance moving out of the eastern Great Lakes passes to the north overnight. It will pass through dry with mid and upper level clouds. Another cold night with temperatures 5 to 10 degrees below normal in the teens to mid 20s.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Upper level trough swings out of the region early Friday with dry weather continuing as high pressure builds across the South. A west to southwest flow will advect in warmer temperatures with highs expected to be near normal, in the 30s to near 40. Temperatures fall into the 20s and low 30s Friday night under a mostly clear sky. && .LONG TERM /SATURDAY THROUGH THURSDAY/... A split flow pattern is progged across the eastern states this weekend with a developing storm system and upper trough over the west. The flow over the northeast will be mainly zonal with a relatively flat trough to our north. This pattern will yield above normal temperatures and dry conditions on Saturday as readings reach the upper 40s and lower 50s. It would not be surprising if highs end up a few degrees warmer than currently advertised. The flat trough to our north will have low pressure traversing across southeast Canada on Saturday into Saturday night. Trailing this low will be a back door cold front which should gradually sink southward Sunday into Sunday night as high pressure attempts to ridge down into New England. No precip is expected with this front, but temperatures should be held down a few degrees from those on Saturday. Highs on Sunday will be in the middle 40s for most locations. Upper jet stream pattern over the CONUS amplifies further Sunday into early next week as the storm system over the west translates into the central states by Monday. Upper ridge axis moves across the region late Sunday night into Monday as well. The frontal boundary to our south will gradually lift northward as a warm front on Monday with low level warm advection and the ridge axis sliding to the east. A warm nose should develop between about 750 and 900 mb as SW flow increases ahead of the approaching upper trough. Main concern with any precipitation will be for inland locations where surface temperatures are slow to rise above freezing. The magnitude of the warm advection and rising heights aloft would indicate any chance of snow is limited with PTYPE concerns in the form of light freezing rain or sleet. This appears to be confined to Monday morning across the interior. Warmer air continues to move in Monday afternoon and evening with temperatures getting into the upper 30s and lower 40s, changing any mixed precip to plain rain. There is divergence in model solutions Monday night into Tuesday on the amplitude of the upper trough as well as the location of the closed low and track of the surface low. Where confidence has increased is with the progression of the cold front. Highest chances for moderate to locally heavy rain continue to be late Monday night into Tuesday morning in association with the cold front and best dynamics from the upper trough becoming negatively tilted. Made some minor adjustments to PoP timing, with a decreasing trend Tuesday afternoon and evening as the front moves offshore. Highs on Tuesday should reach the upper 40s and lower 50s. Cooler air works back into the region for the middle of next week as high pressure takes over with temperatures near normal. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/...
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High pressure builds south of the region through Friday. VFR thru the TAF period. Winds decrease slightly thru the ngt and back to the w. W flow on Fri backs to the sw aft 23Z. .OUTLOOK FOR 00Z SATURDAY THROUGH TUESDAY... .Friday ngt...VFR. .Saturday...VFR. WSW winds G20-25KT. .Sunday...VFR. .Monday...Chance of MVFR or lower in -SHRA. S winds G20KT late day. .Tuesday...IFR in rain. LLWS. S winds G25KT morning, W winds G30- 35KT aftn.
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&& .MARINE...
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No further updates to the winds and seas at this time, with conditions remaining below SCA levels overnight and into early Friday afternoon. Buoy data across southern Long Island indicates that winds and seas have diminished to below SCA levels. With marginal conditions, occasional gusts to 25 kt, expected Friday afternoon into late Friday, and low confidence of occurrence will hold off on issuing another advisory at this time. SCA conditions are likely on the ocean waters on Saturday as a relatively strong pressure gradient develops between high pressure to the south and low pressure to the north. There is also a small chance for a few gale force gusts. Have elected to leave out of the HWO for now as confidence is low and they may end up only being occasional. A few SCA gusts are also possible on the near shore waters. More tranquil conditions are forecast on Sunday and Monday with winds and seas below SCA levels. Winds increase to SCA levels on late Monday night into Tuesday with a cold front passage.
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&& .HYDROLOGY... Dry through the weekend. A frontal system passing through late Monday night into Tuesday has the potential to bring around inch of rain. No significant hydrologic issues are anticipated at this time. && .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...None. && $$ SYNOPSIS...CB/DS NEAR TERM...CB/19 SHORT TERM...CB LONG TERM...DS AVIATION...12/JC MARINE...CB/DS/19 HYDROLOGY...CB/DS EQUIPMENT...

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