Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 240200 AFDOKX Area Forecast Discussion National Weather Service New York NY 1000 PM EDT Sun Sep 23 2018 .SYNOPSIS... High pressure building across Quebec on Monday will reach the Maritimes Monday night, allowing a warm front to approach the Tri- State Region from the south. The warm front slowly moves northward through the area Tuesday into Tuesday night, followed by a cold frontal passage Wednesday night. High pressure then builds to the north through late week, while a series of weak lows move along a stalled frontal boundary to the south of the area. A stronger area of high pressure builds from the west through the weekend. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Light showers or sprinkles reside just to the south. Mid lvl front remains just s of the cwa, with light rain and sprinkles confined to the ocean s of LI as a result. This frontal zone will be suppressed swd overnight as the pressure rises across the area. Some erosion of the clouds noted, with mainly high level cloudiness to contend with overnight, although pesky stratus still hugs the coast. Temps have been slow to fall and much of the modeling is showing mainly clr skies late tngt. Clearing would allow for a quick but significant drop in temps. Because of this, the coldest blend of MOS has not been used, but the warmest NBM and raw consensus was not used either. The Superblend was in the middle, and was used for the fcst, but this was nudged down a degree or two. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... A strong high approaching 1040 will be invof Quebec City Mon mrng. The influence of the high will keep the cwa dry for most if not all of the day. A second shot of thick cirrus, as well as some low clouds advecting in on increasing ely flow, should produce a mostly cloudy late mrng and aftn. Mid lvl moisture transport increases Mon ngt, with a theta-e ridge building in rapidly. This will result in rain developing and spreading nwd across the cwa late Mon and Mon ngt. The pres gradient will be increasing due to the strong high to the n and the approaching warm front to the s. Winds will respond, with increasing flow thru the day and ngt. Gusts to 30 mph can be expected, particularly along the coasts, from late in the day thru the overnight. A blend of the guidance was used for temps. There is a high rip current risk on Mon. && .LONG TERM /TUESDAY THROUGH SUNDAY/... The main concern for the extended will be the potential for heavy rainfall, especially Tuesday with the warm frontal passage as instability begins to increase, aiding in the potential for convective downpours. With antecedent high pressure centered offshore, there will be a prolonged period for moisture advection, both from Atlantic and Gulf regions as wind profiles veer with height. PWAT values will quickly increase with the warm frontal passage to around 1.75-2.00 inch, which per SPC sounding climatology is close to maximum values for time of year. The best chance for any heavy rainfall will be with and following the warm frontal passage, particularly as instability increases across the area. Additionally, despite warm temperatures aloft, there will be instability concentrated below roughly 500 mb, and with strong veering winds with height as the front moves through (0-3km SRH around 200-350 m2/s2), there will be potential for brief low topped supercells capable of damaging winds. Rainfall may become more periodic into Tuesday night and Wednesday in the warm sector as broad height falls and cooling temperatures aloft increase deep layer instability across the area. At the moment, SPC has much of our forecast area in a 15% outlook for severe wind potential due to the low CAPE but high shear environment. The greatest potential for any severe weather and, once again heavy rainfall will be Wednesday night as a short wave and attendant cold front move through. However, broad southwest flow aloft will remain as a western Atlantic high begins to retrograde, and a phased upper low lingers across central Canada into the Great Lakes. As a result, the forward progression of the cold front will significantly slow, with the front expected to stall across the south and potential for us to remain in a humid and somewhat unsettled period into at least Thursday. By late week, flow aloft becomes more northwesterly, with increasing confluence allowing a surface high to strengthen and build into the area for the weekend, with a return to a cooler and much drier fall- like air mass. High temperatures in general will be within a few degrees of climatological normals with the exception of Wednesday as we remain in the warm sector following the warm frontal passage. Low temperatures initially will be 10 to 15 degrees above normal, before returning to within around 5 degrees above normal for late week with the passage of the cold front. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... A frontal boundary will remain nearly stationary across the Mid Atlantic states through Monday, while Canadian high pressure gradually build into New England. A frontal system will approach Monday night. Lingering MVFR ceilings should erode or settle south overnight. As such, VFR cigs are expected, with redevelopment of MVFR cigs likely late Monday morning into Monday afternoon. E/NE winds below 10 kt, strengthening to 10 to 15 kt during morning push. E/NE winds of 15 to 20 kt with gusts to 25 kt likely developing Monday morning for coastal terminals. These gusts continue in the afternoon as winds veer slightly to the E. .OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY... .Monday night-Tuesday...Periods of rain/showers with IFR or lower. E wind gusts of 25-30 kt, becoming SE Tue. .Tuesday night-Wednesday...Showers and isolated tstms possible with MVFR or lower at times. Southerly winds. .Thursday...Mainly VFR. .Friday...MVFR with rain possible. && .MARINE... Winds and seas will remain well below SCA thresholds overnight, then increase to solid SCA levels Monday and Monday night. Winds remain strong from the east then southeast as a warm front passes through the waters on Tuesday. At least SCA conditions will exist on all waters, with the potential for gale-force gusts on the ocean waters early in the day. Winds gradually decrease into Wednesday, though a few gusts to near SCA-levels will remain possible before the cold frontal passage Wednesday night. Even though winds decrease further into Thursday, ocean seas will remain elevated before gradually falling below SCA levels Thursday night into Friday as the pressure gradient relaxes. && .HYDROLOGY... No hydrologic impacts are expected thru Mon. A frontal system will bring locally heavy rainfall and the potential for localized flooding Monday night into Wednesday night. At the moment, the greatest potential for any impacts is expected to be Tuesday with the warm frontal passage. Storm total accumulations are expected to range from around an inch to three inches over the course of three days. && .TIDES/COASTAL FLOODING... Minor coastal flooding possible during the times of high tide Monday night and Tuesday morning in response to a strengthening easterly flow ahead of an approaching low pressure system. Surges of around 1 1/2 to 1 3/4 ft, and locally up to 2 1/4 ft, are needed for minor flooding. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...High Rip Current Risk from 6 AM EDT Monday through Monday evening for NYZ075-080-081-178-179. NJ...None. MARINE...Small Craft Advisory from 6 AM Monday to 6 AM EDT Tuesday for ANZ330-335-338-340-345-350-353-355. && $$ SYNOPSIS...JMC/MD NEAR TERM...JMC/PW SHORT TERM...JMC LONG TERM...MD AVIATION...PW MARINE...JMC/MD/PW HYDROLOGY...JMC/MD TIDES/COASTAL FLOODING... EQUIPMENT...

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