ITHACA, N.Y. — As we prepare to enter the second half of 2020, we’ll be starting things off on a hot and rather humid note. There’s nothing particularly alarming in the early summer forecast for this week, with only pop-up showers and thunderstorms on Tuesday and Wednesday to break the largely pattern of the past few weeks. Forecast models are suggesting it will be a hot, rainless but muggy Independence Day weekend, so stock up on the cold drinks and popsicles now.
Your Weekly Weather
Some pop-up showers and storms have rumbled across Tompkins County this morning and early afternoon, and you can attribute that to an upper-level low pressure system. Being further up in the atmosphere without a low-level component means its surface effects are limited, but since air is drawn into areas of low pressure and the air in the core of upper-level low is colder, it enhances atmospheric instability. The upper-level low helps draw heated surface air upward on convective currents (updrafts), meaning that warm, moist surface air gets a boost when rising up and condensing into clouds, showers and thunderstorms depending on the energy of the local atmosphere – and on warm summer days, there’s plenty of energy to tap into.
Since this upper-level low has broken away from the fast flow of the jet stream, it’s going to slowly meander over Eastern New England for the next couple of days. While it will wander far enough east to provide a dry day on Monday, it will retrograde enough on Tuesday and Wednesday to help set off some scattered showers and thunderstorms across the Southern Tier, especially areas east of Ithaca. On the temperature side, expect highs and lows to track near or a little above normal – upper-level lows usually won’t impact surface temperatures much without a near-surface counterpart (the pairing of the two varieties is known as a “stacked low“).
For the rest of your Sunday, expect skies to steadily clear out, leaving only a few passing clouds by sunset. Highs will top out in the mid 80s, but with this morning’s showers and storm it does feel muggy, so it’s not the most pleasant of Sunday evenings. Sunday night will be partly cloudy with a few isolated showers and thunderstorms east of Ithaca, petering out with the loss of daytime heating. Lows will be in the low 60s.
Monday will be a dry day as the low shifts eastward, and it’ll be a warm, rather sticky day with partly cloudy skies and highs in the mid 60s and a dewpoint in the mid to upper 60s. Monday night will be partly cloudy with a low in the low 60s.
Tuesday will see that retrograding low reintroduce the possibility of showers and thunderstorms, especially in the afternoon and evening hours, roughly 2-8 PM. Don’t expect a washout, but with the humid, moisture-laden air, anything that does perk up will have the potential to cause some heavy downpours as it taps into that ambient water vapor. The atmosphere will allow for some strong thunderstorms, but at this point it’s not looking like the dynamics will be favor to severe storm development (but still, always take precaution when you hear thunder, because lightning is occurring – “when thunder roars, go indoors“). Apart from the pop-up storms, it will be partly cloudy with a high in the low 80s. Tuesday night will see the convective activity die back with the loss of daytime heating, and it will be mostly cloudy overnight Tuesday into Wednesday morning, with a low in the low 60s.
Wednesday will be much the same, with pop-up rain showers and thunderstorms primarily in the afternoon and evening hours, with mostly cloudy skies otherwise and a high in the low 80s. Wednesday night will see storms wind down in the late evening, followed by dry condition with mostly cloudy skies and a low in the low 60s.
Thursday will see the upper-level low finally shunted southeastward over the Atlantic as it weakens and a ridge of high pressure builds into the region. This will allow for drier conditions, but the ridge will be built northward by deep southwesterly flow – which is quite hot and quite humid (without the low, though, the air aloft stays stable and prevents development of thunderstorms). A few clouds will bubble up, but otherwise plan for mostly sunny skies and a high in the low 90s, though it may feel more like the mid to upper 90s with a dewpoint forecast to be in the upper 60s. If you’ve been giving the air conditioning or fans a rest, they’re going to be back on in full force by Thursday. Thursday night will be mostly clear, warm, and humid, with lows in the mid 60s.
Friday will be another hot and humid day as the ridge holds in place over the Southern Tier – the maximum amplitude actually looks to be over the Upper Midwest, but this a fairly expansive ridge of moist, hot air. Expect a humid day with partly cloudy skies and a high in the upper 80s to around 90 °F. Friday night will be mild and dry with partly cloudy skies and a low in the low to mid 60s.
For your 4th of July holiday weekend, expect a hot and dry day and warm and dry evening. Highs will be in the mid to upper 80s both Saturday and Sunday with partly cloudy skies. Lows overnight will be in the low 60s.
Looking ahead into the second week of July, we should be on the lookout for a potentially major heat wave. Models are latching onto the idea of a very hot and moist airmass in place for several days in the second week of July, which could potentially result in the issuance of heat advisories and warnings. The long-term pattern shows that temperatures are likely to continue to be hotter than normal throughout much of next month, with drier than normal conditions to go with that abnormal heat. Given the dry June we’ve had, that could potentially make us vulnerable to drought conditions and brushfires, so we’ll want to keep a close eye on soil moisture and water levels as we head through the next couple of weeks.