Dangerous Smoke & Severe Weather Discussion

The Great Lakes, Ohio Valley, Mid-Atlantic, and Northeast are facing a rare double threat today as two significant weather hazards occur simultaneously. The day will begin with thick wildfire smoke, resulting in poor to hazardous air quality across many locations. Then, as the atmosphere becomes increasingly unstable, severe thunderstorms will develop and move through the same areas, bringing the potential for damaging wind gusts, large hail, torrential rainfall, and isolated tornadoes.

This combination of hazardous smoke and severe weather is relatively uncommon. While severe thunderstorms are capable of temporarily improving air quality by mixing the atmosphere and washing some of the smoke out with rainfall, they can also create rapidly changing conditions. Strong thunderstorm outflow winds may push dense smoke into areas that had previously seen improving conditions, causing visibility and air quality to fluctuate dramatically within a short period.

There is hope that today’s thunderstorms will provide at least temporary relief from the thickest smoke as the cold front pushes eastward. However, the latest forecast guidance suggests that improvement will be short-lived. Behind the front, another surge of dense smoke is expected to spread south into Michigan before expanding across Ohio, Indiana, Pennsylvania, Maryland, and New Jersey by tomorrow afternoon.

As cooler air settles in behind the front, the atmosphere will become more favorable for surface-level smoke. Rather than remaining elevated, fine particulate matter is expected to mix down to ground level, particularly across Michigan and Ohio, where air quality could once again deteriorate into unhealthy or hazardous categories.

Looking into early next week, the overall weather pattern continues to favor repeated rounds of smoke across the Great Lakes, Ohio Valley, Appalachians, Mid-Atlantic, and Northeast. Persistent northwesterly winds aloft will continue transporting smoke from the large wildfire complexes burning across central Canada, meaning communities that have already experienced poor air quality are likely to see additional episodes.

There is, however, some encouraging news. Forecast models indicate that periods of rainfall may develop over portions of the Canadian wildfire regions during the next one to two weeks. While these rains are unlikely to extinguish the largest fires, they could help reduce fire intensity in some areas, limit the production of new smoke, and provide localized improvements. The extent of that relief will depend on how widespread and persistent the rainfall becomes. Until then, smoke intrusions are expected to remain an ongoing concern across much of the eastern United States.

Residents should continue monitoring local Air Quality Index (AQI) forecasts and be prepared for rapidly changing conditions today. In areas affected by heavy smoke, limit prolonged outdoor activities, keep windows closed, use HEPA air filtration when possible, and wear a properly fitted N95 respirator if extended time outdoors is necessary. At the same time, stay alert for severe weather warnings, as thunderstorms capable of damaging winds, hail, and tornadoes may develop with little notice.

Surface pop this morning shows low pressure over eastern Canada with a cold front that extends down through the Appalachians. That cold front is not going to produce very much in the way of any significant chilly weather, just cool things off a little bit. Another cold front coming through the plains will produce severe weather today from the Midwest into the southern plains. A dry line across western Texas will be the focal point for severe thunderstorms developing. Supercell thunderstorms can produce large hail damage and winds and even some tornado activity across parts of Kansas, Oklahoma and western Texas this afternoon. The western part of the country is okay with some sunshine and warm weather.

The current storm has under achieved snow amounts and basically that was due to the coldness and dry air that the snow developed in. The size of the snowflakes really mattered in this storm and because they were smaller, the amounts were not as much as I expected. You can see on the chart below how temperature and saturation impact the size of snow dendrils.

The pattern remains such that a powerful storm should develop along the East Coast. I know the models have been going all over the place with the storm, showing it as a 965mb storm with 20-30 inches of snow, to a suppressed weaker storm across the South. With the NAO negative i.e. blocking pattern along with the +PNA and -AO should all lead to a pattern where a storm intensifies along the East Coast, History has shown that the models doe poorly until 5 days from the storm when they start showing the true magnitude of what can happen. If by Tuesday afternoon, the storm is not shown on the GFS and ECMWF, then is not coming and just light snow and ice will impact areas from Texas to Virginia. Below is an image of what could happen this weekend.