Radar — KOKX
Surface Analysis — Eastern U.S. (North)
Satellite
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Nearest monitored road: College Street (Primary)
Frost advisory issued for coastal ct, southern westchester, and eastern long island for tonight.
1) widespread frost expected outside of the nyc/nj metro area, with scattered freeze conditions possible, tonight into early sunday morning. Otherwise, dry and increasingly mild conditions should continue into mid mid next week.
2) the next chance of a wetting rain will be late next week.
.key message 1... The driest stretch of the year so far will persist in response to confluent NW upper flow this weekend, giving way to east coast upper ridging thru mid week. At the surface, modified canadian high pressure builds overhead through sunday, and then passes gradually offshore through mid week.
Widespread frost expected and freeze conditions possible across eastern long island, southern ct and southern westchester county tonight into early sunday morning under good radiational cooling conditions. The one caveat will be the northeastward progression of a cirrus deck over the ohio/tennessee rivers valleys associated with shearing central US shortwave, and to a lesser extent an upper jet streak aloft and a weak northern stream shortwave moving through northern new england. Although frost/freeze conditions are expected across areas to the north of this, the frost/freeze program has already ended for these interior areas. The frost/freeze program will end for suffolk, northern nassau, southern westchester, coastal connecticut, eastern bergen, eastern essex, eastern union sunday morning. Latest model trend is for a slower progression of the cirrus deck, giving more confidence in issuing a frost advisory for tonight. In addition, temps last night were colder than the deterministic and mos guidances, resulting in temps falling into the mid/upper 30S across the advisory area. With better radiational cooling conditions tonight would expect even cooler temps tonight.
For sunday, expect mostly sunny skies (although an increasing cirrus deck may filter sunshine), dry and seasonably cool. High temps will be slightly milder than those of sat, generally in the upper 50S/lower 60S.
Slightly milder temps for sunday night/early mon AM compared to tonight with light return flow developing. This does bring potential for patchy fog in addition to patchy frost conditions for outlying areas.
Conditions gradually moderate early to mid next week as heights rise aloft and high pressure slides offshore with return SW flow. High temps will incrementally rise through the 60S each day, to near 10 degrees above seasonable (upper 60S/lower 70S) by wed/thu. Similarly, overnight lows will rise from the 30S/40S mon morning to 50S/near 60 by thu morning (close to normal high temps for parts of the area this time of year).
.key message 2... General nwp/ai model agreement in NW pacific troughing slowly moving E-SE into the central conus through the early/mid next week, but then considerable spread (even more than 24 hr ago) on trough evolution as it moves towards the east coast late week/weekend. Sensitivity lying in evolution of NW pac trough and upstream aleutian trough, and possibly partial phasing with offshore SE US trough/closed low. Scenarios range from the central US trough remaining influenced by the northern stream and approaching as a closed low towards the NE/mid atlantic US east coast late week/weekend, or base of central US trough detaching from northern stream and drifting across the SE US, or variations in between.
There is general agreement on a frontal system and/or low pressure affecting the area late in the week into the weekend with a wetting rainfall, but with inherently low predictability on timing and sensible weather details this far out.
High pressure remains in control through the period.
VFR. NW winds 5-10 KT will become light N this evening into sunday morning, then back NW-W during the late morning and W-SW in the afternoon. Coastal terminals should see some sea breeze enhancement and/or winds backing a little more southerly in the afternoon.
...ny metro (kewr/klga/kjfk/kteb) taf uncertainty...
No unscheduled amd expected.
.outlook for 00Z monday through thursday...
Sunday night: patchy ground fog possible late at or near the long island/hudson valley/ct terminals, otherwise VFR.
Monday through wednesday: mainly VFR.
Thursday: chance of showers with MVFR or lower cond possible.
Detailed information, including hourly taf wind component forecasts, can be found at: https:/www.weather.gov/zny/N90
Sub-sca cond should continue on all waters through wed night as high pressure maintains a weak pressure gradient. Hazardous seas over 5 ft are possible on the ocean waters out 20 nm thu into thu night via increasing S-SE flow ahead of an approaching frontal system.