Smoke, heat, drought, excessive rain and cooler air: Examining the Lehigh Valley’s chaotic weather pattern

BETHLEHEM, Pa. – The Lehigh Valley is under a code orange air quality alert Friday, which means air pollution concentrations within the region may again be unhealthy for sensitive groups.

But it will likely be the final day of warnings from the state Department of Environmental Protection — for now — as the area looks to more tranquil weather and a big reduction in the smoke and haze in the days ahead.

• The Lehigh Valley is finally seeing the smoke and haze begin to clear, but is still under a code orange air quality alert Friday
• Smoke forecasts indicate big improvement in the coming days
• We're also in drought, but expecting some heavy rainfall by Monday

Here’s what to know about the upcoming weather pattern:

Clearing the air

As of Friday morning, Canada remained engulfed in flames in many areas.

But the National Weather Service said the upper-level low pressure system responsible for sending hazardous Canadian Wildfire smoke into the region “should finally start to see some movement today as it starts to retrograde west.”

Smoke forecasts indicate big improvements in the thickness of the smoke, with the highest concentrations of near surface smoke in Philadelphia metro area south.

But looking at the full air column, guidance still suggests plenty of smoke aloft that could lead to more hazy skies and altered sunrises and sunsets.

READ: The science behind the smoke: Here’s how Canadian wildfires are choking the Lehigh Valley’s residents

Pieces of energy also are sliding around the base of the low-pressure system and could bring showers and thunderstorms to the region this afternoon, the weather service forecast discussion said.

Drought

The latest map issued by the U.S. Drought Monitor on Thursday placed the majority of Pennsylvania — including most of the Lehigh Valley — in a moderate drought.

It’s the first stage of drought and a step up from the abnormally dry stage, and has been designated after May was particularly parched, with the Lehigh Valley recording less than a quarter-inch of rain (our second-driest May ever).

We’ve also had just a trace of rain so far this June, meaning rainfall hasn’t been measurable.

Speaking of rain…

All of Pennsylvania, as well as New York, New Jersey and Washington, D.C., fall under an excessive rainfall outlook early next week by the National Oceanic and Atmospheric Administration.

Lehigh Valley-based meteorologist Bobby Martrich of the Eastern PA Weather Authority said a half-inch to an inch of rain can be expected — not enough to eliminate rainfall deficits but “a step in the right direction."

“I think the excessive rainfall outlook is more tied to the fact that it’s so dry, so it may be hard to absorb initially,” he told LehighValleyNews.com on Thursday. “But the fact that it’s going [to rain] over at least 12 hours, if not more, is ideal.”

The government’s Weather Prediction Center said as a cold front moves into the Northeast and Mid-Atlantic, chances for heavy rain will develop as the cold front overtakes warm, moist air in the region on Monday.

Cooler, warmer, cooler

The weather service said Sunday “looks to be the warmest day for the foreseeable future” thanks to a south/southwesterly flow of air. It’s expected to increase dewpoints slightly, but the day shouldn’t be overly oppressive.

Temperatures look to get into the upper 80s, with some spots in Philly’s urban corridor even touching 90. But projected daytime highs are all over the place after, falling into the low 80s on Monday and Tuesday, and the 70s next Wednesday.