Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 211125 AFDOKX Area Forecast Discussion National Weather Service New York NY 725 AM EDT Tue Mar 21 2017 .SYNOPSIS... A weak cold front will move across this morning, followed by a stronger cold front tonight. High pressure moves into the Great Lakes Wednesday and then closer to the local region Wednesday night. High pressure builds Thursday, and passes to the east Friday. A cold front sags south toward the area this weekend. Low pressure approaches the region early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Other than some slight adjustments with temperatures and dewpoints over the next few hours, the rest of the forecast remains on track. Quasi-zonal flow aloft with an approaching WNW-ESE upper level jet streak today will help steer surface features to the SE. A weak cold front passes southeast this morning. A stronger cold front approaches from the NW late today. The weak cold front is difficult to discern with an overall weak pressure gradient across the region. The colder temperatures aloft are apparent from model fields to move in this morning. The frontal passage is mainly dry with any precipitation being light rain confined towards the SW portions of the region. Behind this weak front, a more westerly flow develops and will allow for vertical daytime mixing. This will have less marine influence. Very mild temperatures are expected. Used a blend of bias corrected ARW and NMM with some further manual adjustments. The range for max temperatures will be well into the 50s, higher 50s within the NYC Metro Area.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
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The jet stream dives south of the region late tonight and stays south of the region through Wednesday night. A deep upper level trough swings through the region late tonight into early Wednesday with a high positive vorticity advection tendency. The trough axis moves east of the region Wednesday afternoon with a ridge starting to build in Wednesday night. A stronger cold front will be moving across tonight. The overall westerly flow through the atmosphere will make for a dry frontal passage. However, strong deformation is evident in the model fields in the low to mid levels behind this front. Strong cold air advection will occur. Northwest gusty flow eventually develops late tonight and through Wednesday and Wednesday evening. The flow backs from NW in the lower levels to W in the mid levels, presenting backing of winds. Much colder temperatures will result. Upper 20s to lower 30s are expected for lows tonight while highs Wed will be about 20-25 degrees colder than the previous day. Even colder lows Wed night are forecast, with a general range of 8 to 20 degrees. The wind chills will become quite conspicuous Wednesday night when the cold airmass in place will still have gusty NW winds. The combination Wednesday night of NW winds of 15 to 20 mph with temperatures in the single digits to low 20s will make for apparent temperatures (wind chills) getting close to zero to slightly below zero in some locations.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/... Dry weather Thursday, then unsettled through the weekend and into early next week. High pressure/ridge provides plenty of sunshine Thursday. Then upper shortwave approaches Friday as ridge flattens across the northeast. Further west, split upper flow with ridge located in southern Canada, and mid west trough sets the stage for sfc high pressure building to the north from central Canada, with a frontal boundary approaching from the NW. Some light precipitation may ride along this frontal boundary Friday, Friday night and into Saturday, as the high builds to the north. The front sags south toward the area Saturday per GGem, GFS and EC. Spotty rain possible with the front, although lift and moisture is lacking for widespread coverage. The trough makes eastward progress, with sfc low approaching the area Sunday into Monday. Increasing moisture and lift will likely result in increasing coverage for rain, or rain/snow mix interior during that time. Cold temperatures Thursday are expected as the Canadian high pressure builds. Then temperatures warm closer to, but just short of normal Friday as the high passes and southerly flow sets up. Temperatures over the weekend will depend on exact placement of backdoor front. Saturday readings may rise to above normal levels ahead of the front, but likely settle back below normal thereafter as northeasterly flow sets up, assuming front does pass just to the south, which appears likely at this time. && .AVIATION /11Z TUESDAY THROUGH SATURDAY/...
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A weak cold front will move across this morning. Light northwest winds will continue through the morning push before turning more westerly this afternoon. Clouds scatter out after 18Z. VFR through the TAF period. 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 expected. KLGA TAF Comments: No unscheduled amendments expected. KEWR TAF Comments: No unscheduled amendments 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 expected. KHPN TAF Comments: No unscheduled amendments expected. KISP TAF Comments: No unscheduled amendments expected. .OUTLOOK FOR 00z TUESDAY THROUGH Saturday... Tuesday night-Thursday..VFR. NW gusts 20-25 kt possible on Wednesday. .Friday...Chance of sub-VFR cigs. .Saturday...Mainly VFR.
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&& .MARINE...
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Sub SCA today and through much of tonight. Then gales develop as a result of cold air advection over relatively warmer sea surface temperatures Wednesday into Wednesday evening. Think the top of the mixed layer will be realized in terms of Bufkit soundings wind gusts. Gale warnings are in place for all waters 10Z Wed through 06Z Thu. Winds will diminish Thursday as high pressure builds. Seas subside during this time. By Friday, the center of the high passes to the east, and increasing southerly flow will result in building seas. A cold front approaches the waters from the north Saturday. Winds begin to diminish as the front nears, allowing seas to subside once again.
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&& .FIRE WEATHER...
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For Wednesday, there will be very breezy conditions with a NW flow of 15 to 25 mph with gusts 35 to 40 mph. This will help dry out the low levels of the atmosphere with dewpoints falling well into the single digits, with resulting relative humidity dropping to between 20 and 30 percent for much of the area. The two parameters of gusty winds and dry low levels will enhance the spreading of any brushfire but temperatures are very cold so this will be a limiting factor.
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&& .HYDROLOGY... No hydrologic problems expected through this week. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Gale Warning from 6 AM Wednesday to 2 AM EDT Thursday for ANZ330-335-338-340-345-350-353-355. && $$ SYNOPSIS...JM/PW NEAR TERM...JM SHORT TERM...JM LONG TERM...PW AVIATION...CB MARINE...JM/PW FIRE WEATHER...JM HYDROLOGY...JM

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