Heat Wave Expected this Week

Discussion: The upper levels are setting the stage for a heat wave. Once the current weak trough moves away, the upper jet is going to push N of NJ for a period (Tues-Sat) which will correlate with higher geopotential heights across the region, evident at 500mb analysis. This will allow for hot and tropical conditions to build beneath the jet for all of NJ during said timeframe. For surface conditions this should produce hazy, hot, and humid conditions but mostly rain/storm free. In this kind of setup, the troposphere expands as it heats up and actually inhibits lifting by way of a capping inversion. Air cannot rise unless there is cooler air above it. In a capping inversion, the air aloft is warmer than the air beneath it…so it traps the surface air at the lower levels. NJ will be in a slow-moving warm sector with no synoptic triggers for thunderstorms. There could be meso triggers however. A sea breeze front that aggressively wedges in off the ocean could provide enough lift to break the capping inversion (break the cap). Once this happens, air mass thunderstorms can form and then create additional meso fronts via outflow boundaries which can create adjacent storm cells as original air mass cells collapse. We call these pulsers on radar. If this happens, no one should be surprised. But I still think most will just see a hazy, hot, and humid few days. The primary safety hazard this week will be heat and how hot the humidity will make the heat feel. I recommend everyone stays as cool and hydrated as your situation allows. The heat wave should break after this coming Saturday with a cooler end to the weekend (Sunday) lasting into next week.

There seems to be a lot of confusion about thunderstorm predictions. For the past month or so we’ve been in an unsettled pattern with hit-or-miss thunderstorm potential any day. There seems to be people who have locked into a definite “it will storm or it won’t storm” mentality. This doesn’t work this way folks. There are no widespread synoptic systems involved where that kind of prediction can be better made. All of the storms so far have been isolated breakouts that are impossible to pinpoint in a geographic forecast. So when we say mostly sunny with a chance of isolated pop-up thunderstorms, you should not feel betrayed by the forecast. It’s exactly what it is…hit or miss. This coming week and heat wave will be even more hit-or-miss meaning most of the state should appreciate blue sky while a few areas see pop-up storms in the ridiculous storm fuel environment we’ll be in.

Monday (July 24) high temperatures, as of right now – Monday, 7/24 2pm), are leveling off in the low-to-mid 80s for most NJ locations. Humidity has returned and skies are mostly cloudy (sun poking through here and there). Isolated showers and thunderstorms are possible through evening hours. Winds are light out of the S/SW. Overnight lows should range from mid-60s to lower-70s from NNJ elevations to SNJ coasts.

Tuesday (July 25) high temperatures should reach the mid-to-upper 80s for most NJ locations. Skies should be mixed with sun and clouds with a humid feel. Showers and thunderstorms are possible during afternoon-evening hours with severe potential on the table. Winds should be light out of the S/SW. Overnight lows should range from 60-70 from NNJ elevations to SNJ coasts.

Wednesday (July 26) high temperatures should exceed 90 for most NJ locations away from the ocean. Coastal areas should hang in the mid-to-upper 90s prior to any sea breeze activity. Skies should be mostly sunny but hot and humid. Not seeing much storm activity though with this setup, isolated pop-ups are always possible. Winds should be light out of the W/SW. Overnight lows should stay above 70 statewide.

Thursday (July 27) high temperatures should reach or exceed 90 statewide. Perhaps upper-80s for immediate coasts but possibly closer to 100 for interior/95 locations. Skies should be mostly sunny with a hot and humid feel. Overall/widespread there should be little storm activity. But again, isolated pop-ups are always possible in this setup, especially if sea breeze comes off the ocean more aggressively. Winds should be light out of the S/SW. Overnight lows should stay just above 70 again statewide.

Friday (July 28) high temperatures should again reach or exceed 90 statewide. Skies should be mixed with sun and clouds with the same storm caveat as Wednesday and Thursday…most see a rain-free day. A very few could see pop-ups. Winds should be light-to-breezy out of the SW. Overnight lows should stay near or just above 70 statewide.

An early look at the weekend indicates the heat wave lasting another day (for Saturday) followed by a slight back-off in temperatures for Sunday. Monday and next week then look even cooler with highs in the upper-70s/80s. Standard caveat for daily pop-up showers and thunderstorms despite no widespread organized weather systems outside of a frontal passage. For this week, please stay as cool and hydrated as your situation allows for. Have a great week and please be safe! JC

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Jonathan Carr

Jonathan Carr (JC) is the founder and sole operator of Weather NJ, New Jersey’s largest independent weather reporting agency. Since 2010, Jonathan has provided weather safety and forecasting services for New Jersey and immediate surrounding areas through the web and social media. Originally branded as Severe NJ Weather (before 2014), Weather NJ is proud to bring you accurate and responsible discussions ahead of high-stakes weather scenarios that impact the garden state. All Weather. All New Jersey.™