Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 230413 AFDOKX Area Forecast Discussion National Weather Service New York NY 1213 AM EDT Thu Mar 23 2017 .SYNOPSIS... High pressure builds in tonight from the Great Lakes, moving more into the region on Thursday. The high moves offshore Thursday night. A warm front passes Friday, followed by a cold front Saturday. The front will wobble across the area on Sunday before lifting back north on Monday as a warm front. Additional areas of low pressure may impact the area starting late Monday. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Just some minor adjustments made based on latest observations, with temperatures a bit cooler than forecast. An unseasonably cold airmass across the region will result in overnight lows some 15 to 20 degrees below normal. This combined with gusty NW winds will result in wind chills in the single digits to lower teens. Surface pressure gradients remain up through most of the night, however, the general theme is for gradually diminishing winds. Some record lows may get reached or tied tonight, see the climate section below. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/... Surface high pressure will slide southeast from the Great Lakes Thursday morning toward the Delmarva Peninsula by Thursday afternoon. This will result in a clear sky with northwest winds shutting off by the late morning and winds turning to the west to southwest by the afternoon which will push readings back to near 40 in The City with lower 40s in urban sections of Northeastern NJ and the 30s elsewhere. Ample sunshine will help take the edge off the early spring chill. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... The good news is the really cold weather is on the way out, however, so is seeing the sun during much of the extended as an unsettled weather pattern sets up. A warm front will lift north across the area Thursday night into Friday morning in advance of an area of low pressure ejecting out of the southern Plains. As the Plains low gets closer an increase in moisture will take place and spread light precipitation into the area on Friday morning - possibly as early as 5 to 8 AM. Given temps will be near to below freezing especially inland in the normal Klondike spots of Orange, Putnam, Passaic and CT, there will be the risk for frozen precipitation before temperatures gradually rise above freezing with the passage of the warm front. Forecast model soundings all show a warm nose or warm layer aloft with shallow cold air so the risk for a variety of frozen precipitation exists. Across North Jersey and the Lower Hudson Valley, frozen precipitation may start as snow but quickly go to sleet or more likely freezing rain as the warm layer aloft surges in. Model soundings look a little better for a bit more in the way of snow across interior CT, where at Danbury snow may last a little longer before mixing with sleet and/or freezing rain for a bit before transitioning to all rain. Either way, QPF amounts are mainly a tenth of an inch or less so this will not be a big event but perhaps just enough to create some slick spots on roads if it lasts long enough. If precip is slower to arrive, then p-type will be more likely just rain as temps will warm up by later in the morning. However, this short lived cold snap will chill any road surfaces allowing for even a light amount of precip to get slick except in spots where a hefty salt still sits on the roads. By Friday night, the warm front should push far enough north that most of area dries out except for inland CT where some light rain may linger. The southern Plains low advances east on Saturday toward St. Louis. Our area should be in the warm sector, though still see a decent amount of clouds. Depending on if we get any sun, temps may crack 60 especially from The City on west. Southerly flow off the chilly waters will hold max temps down on The Island, CT and southern parts of Brooklyn and Queens into the 50s. The warm front to our north will start to get shoved back south by later in the day in response to a surface high pressure over eastern Canada. Model consensus is there as to a backdoor cold front moving toward the area Saturday evening and thus we showed an increase up in PoPs in that time frame from east to west across CT and Long Island. Also given the marine push, I added in patchy fog as we may end up seeing more drizzle at times than actual light rain. Temps will slowly fall through the night. Inland we may see a little frozen precipitation if colder air seeps in better than expected. Sunday the main issue is where does the front stall out. The ECMWF on the 00Z operational run was warmer by about 10 degrees in spots than the 12Z operational GFS. For now I played temps in between but suspect from The City on east the cooler scenario will win on out but there is certainly some bust potential with temps. In many spots readings may hold steady or even fall through the day depending on what the front decides to do. We kept in a chance of rain through the day as the approaching low from the west and the front overhead should keep enough lift in place to keep things wet most of the time. Beyond Sunday waves of low pressure are expected to impact the area with a frontal boundary near or north of the area. The first wave should pull east by Monday morning but model agreement was poor after this with timing and the track of the lows. Given the pattern, frozen precipitation may be possible at times well inland especially at night where any cold air is trapped. If the frontal boundary hangs up further south then frozen precipitation is possible further toward the coast. Most likely though the flow aloft is west to southwest, so I have favored a warmer forecast. I bumped up temps a bit over the previous forecast based on a blend of the operational GFS and ECMWF. There could be some breaks in rain at times, but this far out exact timing of features is difficult. && .AVIATION /04Z THURSDAY THROUGH MONDAY/... VFR through the TAF period with mainly clear sky. NW winds 15-20KT with gusts 25KT will slowly diminish overnight. Winds will pick up again for a few hours late morning and early afternoon Thursday, then likely drop off late in the afternoon as high pressure settles across the area. .OUTLOOK FOR 00Z FRIDAY THROUGH MONDAY... .Thursday night...VFR with winds becoming light. .Friday...MVFR possible. Chance of SHRA. SW winds G25KT. .Saturday...Mainly VFR. Chance of mid-late afternoon MVFR in CIGs and -SHRA. .Saturday night and Sunday...MVFR/IFR conds in rain. E-SE winds G20-25KT. .Monday...MVFR conds possible in showers. && .MARINE...
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Gale warnings were converted to SCAs earlier as wind gusts are below 35 KT. The SCA will expire near daybreak for the Harbor, Bays, and Sound, and then by late morning for the ocean. Freezing spray was kept in for later tonight into the morning especially for the ocean waters and eastern end of The Sound. High pressure moves across the waters tonight, and passes well to the east Friday. Winds diminish during this time, but begin to increase from the SW later Friday into Friday night. A cold front approaches from the north Saturday, and settles near or just south of the waters Saturday night into Sunday. Winds diminish, and turn toward the E/NE. Speeds increase yet again Sunday as high pressure builds well to the north.
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&& .HYDROLOGY... Unsettled weather from this weekend through early next week may result in an inch or more of precipitation. However, this would occur over a prolonged period and would be intermittent, so no hydrologic concerns are anticipated. Snowpack melt in interior sections will continue at a slow rate through Thursday with most areas likely loosing any significant snowpack by Saturday as temperatures rise to above normal readings and lows even remain above freezing. && .CLIMATE... The following are record low temperatures for Thursday March 23, 2017 along with the forecast low temperatures. Record Low Temperature Forecast Low Temperature ---------------------- ------------------------ Central Park........12 (1875) 20 LaGuardia...........20 (1959) 22 Kennedy.............20 (1959) 20 Islip...............15 (2004) 18 Newark..............13 (1934) 19 Bridgeport..........19 (2004) 17 && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 AM EDT early this morning for ANZ330-335-338-340-345. Small Craft Advisory until 11 AM EDT this morning for ANZ350- 353-355.
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&& $$ SYNOPSIS...DW/CS NEAR TERM...PW SHORT TERM...CS LONG TERM...PW/CS AVIATION... MARINE...DW/CS HYDROLOGY...CS CLIMATE...

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