Area Forecast Discussion
Issued by NWS Upton, NY

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402 FXUS61 KOKX 081229 AFDOKX Area Forecast Discussion National Weather Service New York NY 729 AM EST Sun Dec 8 2019 .SYNOPSIS... High pressure will pass east today. A warm front will approach late tonight into Monday, and lift through to the northeast Monday night. A cold front will approach on Tuesday and slowly passes east Tuesday night into Wednesday. Arctic high pressure will then follow later in the week before another potential storm system arrives next weekend. && .NEAR TERM /THROUGH TONIGHT/... Looking at a mostly sunny day today, with slowly increasing high clouds as the high moves east. High temps should be a shade warmer than a MOS blend, with lower 40s metro/coast and upper 30s inland, about 5 deg below avg. Mid level shortwave energy arrives beginning this evening, with chances for showers increasing from the south mainly after midnight. The 00Z NAM introduced showers this evening which looked too fast, so sided more with timing of other guidance with a start time past midnight. Early evening lows should be followed by steady or rising temps in deep layer WAA, with temps by daybreak ranging from the 30s well north/west, to the mid 40s NYC metro/most of Long Island, to the lower 50s ern Long Island. Precip arrives too late for any freezing rain issues in western Orange County where temps by daybreak may still be just below 32F. && .SHORT TERM /MONDAY THROUGH TUESDAY/... Should see rainfall with the approaching frontal sys in two primary waves. The first will come with the warm frontal approach/passage today tonight, then should a break in precip as we get into the warm sector late Mon night and Tue AM before precip with and mostly behind the approaching cold front arrives Tue afternoon/night. Model consensus is for axis of heavier precip with the warm front to be places farther east, more across Long Island and SE CT than areas to the west. Removed mention of thunder in most places as elevated instability should be minimal, though there does appear to be a window of opportunity for heavier showers and isolated thunder across eastern Long Island and coastal SE CT with warm fropa that may have to be watched for strong wind potential as well. Temps in the warm sector will be on the mild side, with widespread 50s for highs on Mon, even lower 60s across ern Long Island per consensus MOS. Temps should not fall much Mon night, the should be even milder on Tue, with lower 60s metro/Long Island/SE CT, and 55-60 elsewhere. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... As another shortwave rotates around the back side of the upper trough in central Canada, there are indications that rain moves just east, with additional rain/precip shield tracking northeast on the back side of the front Tuesday night into Wednesday due to upper level support. Assuming that does indeed occur, colder air will move in behind the front which will result in a transition from rain to snow, mix in between. This could result in light snow accumulations later Tuesday night into Wednesday, NW to SE. The upper trough weakens as it pivots east, and sfc high pressure builds in from the west late Wed, Wed night and Thursday. This will be the period of dry, but cold weather. Could be looking at the coldest air of the season, with temps struggling to reach or exceed freezing Thursday after a cold start to the day. Shortwave ridging moves east Thu night, with sfc high moving north and east of the area. Easterly flow then sets up, with dry conditions likely lingering into Friday. Thereafter, model spread grows, with latest run of the operational GFS quicker with southern shortwave`s movement east, which steers a sfc low out of the Gulf of Mexico and off the SE coast later Friday and Friday night, whereas Canadian and ECMWF are much slower with these features. Eventually, precip should move back in from the south by Saturday, but big difference in the upper level pattern are noted in the global models, with GFS phased with northern stream shortwave and southern stream. Canadian and ECMWF look much different (lack of phasing between the two), so plenty of time to iron out these details as the event draws near. Temps fall below normal after cold fropa into Thursday night, then moderate late in the week. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... VFR. High pressure will be over the terminals this morning, then passes offshore by afternoon. Light and variable winds becomes S by late morning and increase to around 10 kt with gusts 15-18kt by early afternoon. Some spots may be less frequent. Gusts are lost by early this evening. MVFR/IFR conditions develop late tonight into Monday morning as rain moves in ahead of an approaching warm front from the south. .OUTLOOK FOR 12Z MONDAY THROUGH THURSDAY... .Monday...MVFR/IFR in widespread rain. S G20-25kt, mainly at the coastal terminals during the afternoon/night, with a chance of LLWS. Slight chance thunder Monday afternoon/early evening at KISP and KGON. .Tuesday...MVFR or lower in showers, possibly changing to snow overnight. SW gusts around 20 kt possible. Winds shift to the NW with a cold frontal passage in the late afternoon/evening. .Wednesday...MVFR or lower in a chance of snow in the morning. W-NW G20-25kt possible. .Thursday...VFR. && .MARINE... High pressure over the waters this morning will give way to an approaching frontal system that will impact area through mid week. This will result in a strengthening southerly flow today through Monday night. Marginal SCA conditions are forecast on the ocean waters tonight with a short period where the winds fall off during the early morning to daybreak timeframe. Winds then quickly ramp back up by late Monday morning with the potential for gale gusts on the ocean waters by afternoon and SCA conditions elsewhere. These conditions will persist into Monday night. Thus, a gale watch has been issued for the ocean waters Monday afternoon and night. A SCA will likely be issued for the remaining waters later today. However, there is some uncertainty with the magnitude of the winds during this time due to a strengthening inversion across the waters, which will limit the high wind potential. Seas on the ocean are forecast to build 7 to 12 ft. Winds and seas will then diminish as a cold front approaches Tuesday, but remain above 5 ft on the ocean through at least Tuesday night. The front passes through the area Tuesday night with marginal SCA conditions possible Wednesday into Thursday morning in a W-NW flow. There is the potential for another storm system to impact the waters at the end of the week. && .HYDROLOGY... A significant long duration rainfall event is expected from late Sunday night into Wed. Event total QPF likely to range from 1.5-2.0 inches, locally 2-3 inches across eastern Long Island and southern CT. Heaviest rain should occur be Monday afternoon/eve. The long duration of the event should preclude widespread flooding. Nuisance/poor drainage flooding is the most likely outcome. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO35 (162.55 MHz) is still operating at reduced power. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Gale Watch from Monday afternoon through late Monday night for ANZ350-353-355. Small Craft Advisory from 5 PM this afternoon to 4 AM EST Monday for ANZ350-353-355. && $$ SYNOPSIS...Goodman/PW NEAR TERM...Goodman SHORT TERM...Goodman LONG TERM...Goodman/PW AVIATION...DW MARINE...DW HYDROLOGY...Goodman/PW EQUIPMENT...// is the U.S. government's official web portal to all federal, state and local government web resources and services.