Weather with Bill Evans

National Weather Service New York NY Tuesday July 15, 2025 A weak front sags south of the area this morning, but remains nearby through Wednesday as a Bermuda high remains anchored well offshore. The boundary will lift north Wednesday Night, with a trough moving through Thursday and then a cold front moves through Thursday Night into Friday. This front remains just south of the area through the weekend while high pressure attempts to build. Another cold front moves through late Sunday night into early Monday morning. Shortwave trough axis slowly slides east this morning, with weak surface trough sagging south as well. Lingering shower activity, slight chance of thunder, across NYC/NJ metro, LI and S CT early this morning expected to push se of the region by mid to late morning. With shortwave upper ridging building in, and mid-level drying, only an isolated shra/tsra threat in the aft/eve along seabreeze boundary and higher terrain. Seasonable temps (mid to upper 80s) and humid conditions (lower 70 Tds) continue today into tonight. Tds could end up being a bit lower than forecast across interior based on mid-level drying and weak offshore flow. This yields heat indices in the lower 90s to around 95F across much of the region today. After collab with neighboring offices have held off on heat advisory for today with only marginal coverage of 95 HI for NYC and pts N&W, where Tds could end up slightly lower than NBM deterministic. Patchy stratus/fog development possible tonight/Wed Am in the moist and weak flow environment. Shortwave ridging surface/aloft slides east during the day on Wednesday, with a southern plains shortwave approaching the region Wed eve and crossing the area Wed Night. At the surface weak high pressure on Wed will give way to an approaching warm front Wed eve, pushing north of the region Wed Night into Thu AM. A warm advective SW flow establishes around Bermuda high with likelihood for start of a mid to late week heat wave. Between morning stratus and aft/eve convection a period of partial clearing likely to lift widespread daytime temps in the upper 80s to lower 90s, and Tds in the mid 70s. Widespread heat indices in the upper 90s to lower 100s F likely. Potential for 105F heat indices appears low and sparse. Scattered late day into overnight convection likely with passage of southern shortwave and warm front. Isolated severe threat and localized flash flood threat late Wed aft/eve for NYC and points west in a moderately unstable and moist airmass. Convective intensity should diminish overnight as it translates east, but locally strong tsra and minor flood threat would still exist with moistening profiles and marginal elevated instability. Tri-State region is likely under an active zonal upper flow on Thursday and in the midst of hot and very humid airmass on Thursday on the periphery of Bermuda ridging and ahead of approaching trough axis. With active flow aloft, convective debris and timing/placement of pre-frontal trough axis and convective initiation will be forecast challenges for amount of sunshine. With that said, 850mb temps will be approaching 19c, and with even limited sunshine supporting mixing to that level, temps in the upper 80s and lower 90s are likely, with Tds potentially pooling into the mid to upper 70s. This would yield widespread heat indices of 100 to around 105F, presenting a low to moderate potential for extreme heat watch/warning level. Potential for aft/eve convection once again, with isolated severe threat and localized flash flood threat Thu aft/eve for much of the area in a moderately unstable and moist airmass. Have stuck close to NBM deterministic T and Tds for Wed and Thu based on convection and cloud cover timing challenges. NBM deterministic also lies within a fairly tight 25 to 25^th NBM ensemble range for much of the area, outside of LI. A slow moving cold front moves through on Friday, continuing chances for showers and thunderstorms. The front remains south of the area Saturday and much of Sunday before another front approaches Sunday and moves through late Sunday night into early Monday morning. With weak high pressure building in, much of the area will be dry for Saturday, though an isolated shower or thunderstorm cannot be ruled out mainly N and W of NYC. Another cold front approaches for Sunday, giving the area better chances for showers and thunderstorms late Sunday through the beginning of next week with the front remaining nearby. While nothing remarkable for mid July, temperatures Fri likely top the upper 80s to lower 90s for most, and with dew points forecast at least into the upper 60s and lower 70s, heat indices should achieve mid to upper 90s. One caveat may be the unsettled pattern, with showers and thunderstorms possible each afternoon through late week with nearby frontal boundaries, though the overall severe risk appears low. However, deep layer moisture should keep PWATs near or above 2 inches, and with it, the potential for higher rainfall rates with any convective activity. Sub-SCA conditions through Thursday in a weak pressure regime, although ocean seas will likely build to 3 to 4 ft late Wed into Thu with persistent 15 to 20 kt S/SW flow, possibly around 5 ft by Thu Night. Marginal SCA gusts possible Wed late aft/eve and more likely Thu aft/eve with coastal jet formation. A return to sub-SCA for Friday likely with offshore flow and subsiding S swell in wake of cold frontal passage. Sub SCA conds continue into the weekend with weak pressure gradient. Otherwise, afternoon/evening showers/tstms through the period could produce locally higher winds/seas at times. Water levels expected to continue to recede below minor flood levels across flashy NE NJ river basin this morning. Localized flash flood potential from scattered aft/eve convection Wed thru Fri. The rip current risk is low today, with a mix of 1 ft SE swell with 2 ft s wind waves. After a low risk rip current risk to start on Wednesday likely increases to moderate in the aft/eve with strengthening S flow and building 2 to 3 ft S wind waves.