With heat and humidity building Wednesday, Western New York faces a very muggy Thursday with scattered and occasional thunderstorms increasing in the afternoon and early evening. Mid-level winds, abundant moisture and an approaching cold front may trigger a few strong to severe thunderstorms, with possible damaging gusts. The Storm Prediction Center has Western New York at "slight"/15% risk for severe thunderstorms.
After Wednesday’s upper 80s, Thursday’s lower 80s may sound more comfortable. However, dew points will be flirting with an oppressive 70, much like late last week on the 4th and 6th. It will feel steamy. That steam is likely to get organized into spotty downpours, a few of which may be torrential. This is in addition to the severe storm threat. In high-resolution models, here are projected rainfall totals through Thursday night.
A southwest flow off relatively cooler Lake Erie should stabilize the atmosphere a bit closer to the lake, as you can see heavier amounts are just inland. That same modest stabilizing effect may also lessen the risk of severe storms closer to the lake, including the immediate metro area, with risk being somewhat higher inland. This same model depicts such a tendency.
This is not to say “nothing by the lake,” but only to lay out an approximate risk assessment.
Temperatures return briefly to the upper 70s on Friday with moderate humidity. Dew points may edge up a bit on Saturday, and then drop back to the comfortable 50s on Sunday. With a weak cold front passing Saturday night, a few overnight lighter showers may show up, ahead of our third consecutive gorgeous Sunday. All in all, it will be a fine weekend.
Heat will begin to rebuild by next Tuesday with temps heading into the upper 80s along with increasing humidity at least for Tuesday and Wednesday, and probably beyond.
In the upper levels of the atmosphere, model ensembles are showing persistently above average barometric pressures over our region, with a hot ridge of high pressure just off to our west. This will allow temperatures at the surface to run above average for most of the time even into the latter part of the month.
This is the part of an outlook where I sometimes get smart-aleck comments, like, “It’s July. It’s warm. Why is this news?” The main point here is “above average” means warmer than the usual warmth. It doesn’t mean records are going to be falling by the wayside. What is somewhat unusual will be the persistence of this hot ridge, with no lasting cooldowns for a couple of weeks. The eastern Great Lakes don’t typically experience such persistent very warm to hot spells. There are hints in the ensembles the hot ridge will shift to the far west very late in July, which would allow a cooler northwest flow in the Great Lakes.
The probabilities for above-average temperatures remain high for most days in the Climate Prediction Center outlooks through the next two weeks.
The somewhat lower probabilities over a large swath of the south are associated with the precipitation that will be coming with the tropical development in the northern Gulf of Mexico. The flood potential near the lower Mississippi, including New Orleans, is worrisome. River levels are already at record levels, and flash flooding began in New Orleans on Wednesday even ahead of more organization for this system. Here is a track range (the entire cone, not the center line) in a preliminary outlook from the National Hurricane Center, found in this interactive map.
While most model tracks take the center west of New Orleans, that still leaves the New Orleans metro area at high risk for torrential rains and possible modest storm surge, being east of the system center. Here are estimates for rainfall totals from what may become Tropical Storm Barry.
With some serious flooding already in place, some of the ingredients are in place for flooding to become locally disastrous over the next few days. The above average Gulf temperatures will be lending extra evaporative moisture to this system, enhancing the threat.
Some remnant moisture — not a tropical storm — may eventually move toward the Great Lakes next week, but that remains speculative.