National Weather Service New York NY
441am EDT Sat August 31 2024
Synopsis
A ridge of high pressure across the area today will continue to gradually weaken and give way to an approaching frontal system. The latter of which will move across the area tonight into Sunday morning. A secondary cold front will then pass through the area Sunday evening. Behind it, a large dome of high pressure over the Upper Midwest will then build east through the middle of next week, gradually moving offshore late next week.
Near Term - Through Tonight
Today will largely be dry with the area under the influence of a retreating surface high and an upper level ridge. Guidance continues to trend slower with the first frontal system that will move across the area tonight into Sunday morning. In addition, due to the slower timing and only weak instability to work with, CAMs also continue to trend toward a poorly organized convective event as showers and possible thunderstorms move into the area later this evening first across western portions of the Lower Hudson Valley. While there is modest large scale lift in the middle and upper layers, the ingredients are simply not there for strong and/or severe weather. In collaboration with SPC, the slight risk has been shifted well west of the forecast area. As for heavy rainfall concerns, PWATs (Precipitable Waters) increase to around 2 inches, so showers with some downpours will be possible during the overnight hours. Flooding concerns are mainly of the minor nuisance variety. WPC does have locations north and west of NYC under a marginal risk of excessive rainfall. Any flash flooding is expected to be isolated. Rainfall amounts are forecast to be under half an inch basin average. Localized higher amounts will be possible, especially north and west of the NYC metro.
Highs today will be near normal in the upper 70s to around 80. Due to cloud cover and increasing humidity, lows tonight will be on the warm side in the upper 60s to around 70. It will also become quite humid.
Short Term - Sunday Through Monday
Showers will likely linger in the morning hours Sunday, especially across LI and CT. The trend has been slower. Uncertainty then arises during the afternoon and early evening hours as a pre- frontal trough and cold front move across the area. Drier air advecting into the region could also be limiting factor if it mixes down in the low levels. However, this may be late enough with some of the 00Z guidance showing decent instability in the afternoon. Mid level flow is about 30kt. Storm Prediction Center does have the area in a marginal risk with the main threat being isolated damaging winds.
Highs on Sunday will in the upper 70s to lower 80s. This a slight nudge down due to the cloud cover persisting longer, which will be a factor in the amount of destabilization in the afternoon.
Cold front is forecast to move across the area the first half of Sunday night. Behind it, a northerly flow with much cooler, drier air coming in for the upcoming week. Highs on Monday will be in the 70s with dew points falling through the 50s.
Long Term - Monday Night Through Friday
High pressure will continue to build in behind the exiting front from the Great Lakes region Monday night and Tuesday, leaving a very sunny forecast for early next week. Overnight lows will drop into the middle 40s across the interior to upper 50s into the NYC metro area Monday night. Dewpoints drop into the 40s Monday night and remain there through Tuesday, reinforced by northwest flow.
Most model guidance brings the high pressure overhead Tuesday night into Wednesday morning, then gradually push it offshore Wednesday night into Thursday, and remaining offshore Friday. This will lead to a return flow from the south. This will mean continued sunny days before cloud cover increases Thursday night into Friday. Southerly winds will lead to increasing temperatures and dewpoints late next week. Highs will be in the mid 70s to low 80s by Friday.
Most global models try to develop a coastal low along the mid- Atlantic coast Friday and bring it near the forecast area Friday night into Saturday, but this is still very far out and the models do differ in strength, placement, and timing.
Marine
Winds and waves will remain below SCA (Small Craft Advisory) criteria through the middle of next week. Behind a cold frontal passage Sunday night, a large dome of high pressure builds east from the Upper Midwest and into the area through midweek. Pre- and post-frontal gusts Sunday into Monday could get near 20 kt.
Hydrology
Showers and possible thunderstorms tonight into Sunday morning look disorganized. The flood threat will be mainly of the minor nuisance variety. However, WPC maintains a marginal risk of excessive rainfall north and west of the NYC metro. This means there is the potential for isolated episodes of flash flooding.
Tides / Coastal Flooding
The risk threat has been adjusted downward today based several sources of guidance. Also, an easterly swell of 2-3 ft parallel to the coast should limit wave heigheights in the surf zone to 1-2 ft. Onshore flow will also become SE, but less than 10 kt. For Sunday, plan to go low at this time, but a southerly flow around 10 kt could bring the risk closer to moderate.
NOAA New York NY Office: Watches - Warnings - Advisories
CT...None. NY...None. NJ...None.
Marine
None.
