455
FXUS61 KOKX 042028
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
428 PM EDT Sun May 4 2025

.SYNOPSIS...
-- Changed Discussion --
A frontal boundary across the Lower Hudson Valley into central New England will settle south tonight to near the coast as high pressure builds southeast out of eastern Canada. At the same time, low pressure will be cutoff over the Tennessee and Ohio Valleys. The system will then pass through on Wednesday. Another upper level disturbance may impact the area late in the week. High pressure west of the region will then attempt to build into the weekend.
-- End Changed Discussion --
&& .NEAR TERM /THROUGH MONDAY/...
-- Changed Discussion --
A cutoff upper level low will meander across the Tennessee and Ohio Valleys through Tuesday, while upper level ridging builds across eastern Canada. This keeps the area in close proximity to a frontal zone with a deep-layered southerly flow aloft. To the east of the upper low, a warm conveyor belt will send showers and embedded thunderstorms north off the ocean and into the area. In addition, SE to E winds will enhance orographic lift across CT, in particular areas of western CT.The latter of which though remains uncertain as timing and location of the bands may change in coming days. These look to be narrow corridors of moderate to heavy showers with a slight chance of thunderstorms. There is no deep convection with marginal instability and PWAT values of 1.25 to 1.50". Upper air soundings are generally moist adiabatic with deep-layered lift. SPC HREF shows very low probabilities of >1"/hour and >3"/3 hours. FFG values are around 2 inches/1-hour and 3 inches/3-hour. These are unlikely to be achieved. Also, river and stream flow is low. Thus, dry antecedent conditions and lack of deep convection should limit any flooding to primarily minor nuisance. However, CAMs do show bullseyes across the area with some of the convection, so isolated flash flooding is a possibility. WPC has the area under a marginal risk the next couple of days. This rain will not be constant as the bands reorganize and setup over different locations. Greatest uncertainty with this forecast is not whether there will be bands of moderate to heavy rain, but rather the location. The initial thought is much of the lift will be collocated with the LLJ which shifts east tonight and then back to the west on Monday. This is likely do to the building high out of southeast Canada forcing the gradient to vary across the area. The activity over western areas this evening is forecast to gradually translate east overnight and then back to western portions on Monday. It will remain mild with the cloud cover and onshore flow with lows in the mid 50s to around 60. Blended in CONSALL with NBM to get values a bit cooler with the rain on Monday with highs in the lower to mid 60s.
-- End Changed Discussion --
&& .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
-- Changed Discussion --
Much of the area will continue to see showers/isolated thunderstorms into Tuesday. Once again, there is some uncertainty with the location of the LLJ and the heavier bands. Rainfall amounts will likely need adjustments through in subsequent forecasts. The upper low will begin to edge eastward along with the deeper moisture and lift. Much of the area is expected to see 2 to 3 inches of rain through the entirety of the event. The upper end of the amounts are currently forecast to be across western LI and into SW CT. This of course may vary due to the aforementioned uncertainty. Lows Tuesday night will remain above normal in the mid and upper 50s. However, highs due to the cloud cover will be closer to normal in the 60s.
-- End Changed Discussion --
&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
Overall improving conditions to begin the period as any organized or prolonged precipitation comes to an end. However, with an upper level low still lingering into Wednesday, look for diurnally driven pop-up showers and possibly a few isolated thunderstorms mainly during the afternoon and early evening hours on most days throughout the work week. The first upper level low pulls away late Wed / Wed night, but to only be followed by another upper level disturbance later Thursday and possibly into a good portion of Friday. Global NWP guidance indicates more uncertainty with the 2nd upper level low / disturbance late in the week. Some of the global guidance eventually kicks the upper level disturbance away into the weekend. However, some guidance suggest that the system gets completely closed off, and possibly cut off from the westerlies. The second solution appears to be less likely at this time, but cannot be discounted. Have chosen to keep next weekend dry, but this could change if the 2nd solution emerges more in subsequent NWP cycles. Temperatures will average near normal Tuesday night through late Thursday. Temperatures then may fall a bit below normal into Friday, before likely recovering to normal or slightly above seasonable levels into the weekend.
-- End Changed Discussion --
&& .AVIATION /19Z SUNDAY THROUGH FRIDAY/... Frontal boundary remains stationary across the region tonight. As a result showers will continue to develop and gradually make their way farther east within the region through tonight. MVFR conditions persist through this evening with the chance of rain showers. Higher chance of IFR and localized LIFR conditions expected tonight and into Monday. Southerly winds become more easterly tonight. Wind speeds vary from near 5 kts to near 15 kts. Some gusts can be expected between 20-25 kt at times although this is not expected to be widespread. Wind speeds tonight lower to less than 10 kts, then increase again Monday. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... Amendments likely to refine timing of showers and thunderstorms. .OUTLOOK FOR 18Z MONDAY THROUGH FRIDAY... Monday: Showers likely with MVFR or lower expected. A chance of tstms mainly at night. E winds G15-20kt. Tuesday: Showers with MVFR or lower expected. A chance of thunderstorms. SE winds G15-20kt day into early eve possible. Wednesday: Chance of MVFR or lower with a slight chance of showers/thunderstorms. Thursday: VFR. Friday: VFR with slight chance of showers. Detailed information, including hourly TAF wind component forecasts, can be found at: https:/www.weather.gov/zny/n90 && .MARINE...
-- Changed Discussion --
Expecting all waters to remain below SCA through Monday morning. Marginal SCA conditions are possible on the ocean waters Monday into Tuesday with E/SE winds and seas building close to 5 ft. NWPS guidance was used based on forecast winds. However, NBM and Wavewatch were around 5 ft. Stayed with the lower guidance at this time. Ocean seas gradually subside below small craft criteria Tuesday night with as ocean seas settle in at around 4 ft through Thursday. Marginal small craft conditions are possible towards later Thursday night, especially out on the ocean as the winds become more northerly.
-- End Changed Discussion --
&& .HYDROLOGY...
-- Changed Discussion --
Total rainfall forecast through Tuesday evening is 1.5 to 3.5 inches. Locally higher amounts will be possible. There is a marginal risk for excessive rainfall (localized flash flooding). This will be a long duration event and current thinking is that any flooding will be more of the minor nuisance variety. See the Near Term section above for more details on reasoning. Predominantly dry conditions return with mainly diurnally driven widely scattered shower / thundershower activity towards mid and late week. Thus there are no hydrologic concerns for the mid and late week.
-- End Changed Discussion --
&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JE/DW NEAR TERM...DW SHORT TERM...DW LONG TERM...JE AVIATION...20 MARINE...JE/DW HYDROLOGY...JE/DW