Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 241341 AFDOKX Area Forecast Discussion National Weather Service New York NY 941 AM EDT Tue Apr 24 2018 .SYNOPSIS... Offshore high pressure today will eventually give way to approaching low pressure from the south. The low continues to move closer to the region tonight into Wednesday and eventually the low center moves right across the area Wednesday night. Low pressure lifts to the north on Thursday. High pressure briefly builds, then gives way to a wave of low pressure late Friday and Friday night. A cold front moves through Saturday followed by high pressure Sunday and Monday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... The upper level jet stays north of the region with some upper level ridging. The surface high pressure will remain offshore and slowly move farther offshore during today. There will be some sun for the first half of the day but clouds will increase, lower and thicken during the afternoon. The pressure gradient will remain weak, keeping the onshore flow weak. Therefore used a warmer blend for temperatures with the ECS/MAV guidance. Expecting another day in the lower 60s near the coast and more in the mid to upper 60s away from the coast. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... Surface low pressure slowly approaches from the Southeast US. There will be multiple trough approaching from the west in the upper levels and even some signs of phasing between the northern and southern branches of the upper jet. Expect most rain tonight through Wednesday with it tapering off Wednesday night as the low moves overhead Wednesday night and eventually north of the region late Wednesday night. Most substantial increase in isentropic lift occurs right after 00Z Wed. Most rain falls Tue night through Wed morning with a max of omega conveyed by models around the 12Z hour. This will also coincide with the approach of the southerly low level jet. NAM is remarkably farther west with this compared to the GFS and other models such as the Canadian and ECMWF. Depth of lift as diagnosed by omega decreases Wednesday afternoon. Steady rain will become lighter and may have some breaks from time to time. Thunderstorm potential will be isolated due to presence of some low level instability off the Atlantic feed of moisture. Also related to the Atlantic feed of moisture will be the precipitable waters, which are forecast to reach 1 to 1.3 inches Wednesday morning into early Wednesday afternoon. After that, the precipitable waters decrease, with values closer to 1 inch through the evening. Further drop of precipitable water to below half inch by early Thursday. Ample low level moisture will be present as well Wednesday into Wednesday evening. The steadier rainfall during the day will be accompanied by fog but kept coverage patchy. There will be a period of time Wednesday evening with the center of the low passing overhead. The less forcing will make for lighter rain and light winds will keep moisture abundant considering the earlier rainfall. Expecting areas of fog to develop Wednesday evening and then become more patchy overnight when winds become more westerly behind the low. Used a consensus of raw temperatures for the short term and to minimize diurnal temperature ranges. && .LONG TERM /THURSDAY THROUGH MONDAY/... During the Thursday through Saturday time frame, features to watch include departing shortwave over the northeast, southern stream shortwave traversing across the southeast states ahead of vigorous northern stream shortwave that moves out of the upper midwest toward the east coast by Saturday. The southern stream shortwave will lift northeast as the downstream trough amplifies, with deep SW flow setting up. During the late Friday time frame, showers ahead of this shortwave and sfc low are possible, but differences in the models continue, with non GFS solutions pushing most of the precip just SE of the area. Will maintain chance Pops with higher probabilities SE zones due to the uncertainty. Prior to that, generally dry weather is expected Thursday, Thursday night and into early Friday. Any lingering rain ends Thursday morning. During the Saturday night through Monday timeframe, upper trough pushes east, and there is the potential for additional showers late Saturday into Saturday night, although probabilities do not appear to be high at this time. Greater likelihood would be NW of the area as trough closes off north of the Great Lakes region. Upper trough lingers Sunday but gives way to building ridge as sfc high builds by Monday. Temperatures remain right around seasonal norms, with Sunday perhaps a few degrees cooler behind the cold front. Temperatures warm early next week. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/...
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High pres will continue to move off the coast today. Low pres approaches from the sw tngt. Southerly flow 10 KT or less this morning, backs to SE after 16Z, then backs to ESE aft 18z, and to the e aft 00z. Speeds generally around 10kt or less until aft 00z, then a gradual increase can be expected, especially at the coasts. Gusts to around 20kt on Wed. VFR through 00z, with cond lowering to IFR or lower overnight as rain develops. There is a low chc for tstms aft 12z Wed. 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: No unscheduled amendments are expected. The afternoon KJFK haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KLGA TAF Comments: No unscheduled amendments are expected. The afternoon KLGA haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KEWR TAF Comments: No unscheduled amendments are expected. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: No unscheduled amendments are expected. KHPN TAF Comments: No unscheduled amendments are expected. KISP TAF Comments: No unscheduled amendments are expected. .OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY... .Wednesday...Rain with IFR/LIFR conds. Isolated thunderstorm possible. SE winds 15-20, gusting 25-30 KT. .Thursday...Shower possible with conditions becoming VFR. .Friday-Saturday...Mainly VFR. Chance of showers late Friday into Saturday.
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&& .MARINE... The weak pressure gradient will keep conditions well below SCA thresholds today. Tonight, with the continuance of onshore flow, expecting ocean seas to eventually build to 5 ft. With the approach of the low level jet, expecting wind gusts of 25-30 kt as the pressure gradient deepens between an approaching area of low pressure and offshore high. Expecting this to result in widespread SCA wind gusts for all waters Wednesday morning and then just remaining on the ocean due to primarily ocean seas from residual swell for Wednesday afternoon into Wednesday night. Expecting non-ocean waters to return to mainly below SCA conditions for Wednesday afternoon into Wednesday night. Low pressure passes further to the north Thursday, with high pressure briefly building behind through Thursday night. Gusty westerly winds Thursday, around 20 kt, diminish as the high builds. However, lingering rough ocean seas persist before slowly subsiding Friday and Saturday. There is a chance seas away from the coast linger close to 5 ft through Friday. A wave of low pressure passes Friday, and a cold front approaches Saturday. Winds however will remain below 25 kt, sub SCA. && .HYDROLOGY... A widespread 0.9 to 1.6 inches of rain is likely Tuesday Night into Wednesday, with heaviest amounts favored across NYC metro, NE NJ, Lower Hudson Valley, and SW CT. Heavy rain will be possible at times and this would potentially cause minor urban and poor drainage flooding, especially if the higher end of rainfall ranges are realized. Expecting the bulk of the rain to fall between 2am and 2pm Wednesday. && .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 from 6 AM to noon EDT Wednesday for ANZ330-335-338-340-345. Small Craft Advisory from 8 PM this evening to 6 AM EDT Thursday for ANZ350-353-355. && $$ SYNOPSIS...JM NEAR TERM...JM SHORT TERM...JM LONG TERM...PW AVIATION...JMC/MET MARINE...JM/PW HYDROLOGY...JM/PW EQUIPMENT...

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