Storms: Why N and W of a City?

Why is it that weathermen typically expect the N and W suburbs of a city to be hit hardest? At least in the Mid-Atlantic area, this is a typical statement…although there are exceptions. Even more puzzling, if one lives between two major cities, catching two local forecasts, one can be N of one city while being S of the other - such as in the Balt-Wash corridor. So then, this “N and W” becomes a quite relative and almost arbitrary statement.

Why would one local region consistently see more extreme weather? I am struggling to word this question, but maybe some other SDopers have made a similar observation and share my same question. Please help me rephrase, if necessary.

Lost in the storm,

  • Jinx

Just speculating, but I’m gonna guess that on the east coast of a funnel-shaped continent like North America, as you go north and/or west of a city, you’re likely to get into higher altitudes which are more prone to heavier snow.

The west coast doesn’t get snow storms in the same way of course.

Does your generalization hold true for interior cities? Probably not Buffalo or Erie. And I’m guessing it doesn’t hold true for Minneapolis or Bismarck either.

OK, but why should thunderstorms be more severe? WAG: You’re closer to the clouds at higher elevations? This would explain why frost is more wide-spread N and W…

Thanks for the “food for thought”.

  • Jinx

For winter weather, the predominant driving force is cold, high pressure air that forms in central Canada and expands toward the U.S. On the east coast of the U.S. this air approaches from the northwest and encounters warm moist air from the Atlantic Ocean. So the north and west parts of an urban area receive the first and most intense parts of the storm.

Incidentally, in Chicago, the southern parts, including Northwest Indiana, are often the hardest hit by snowstorms. I’m not a meteorologist, but I believe it has something to do with Lake Michigan.

I haven’t really noticed the N and W bias in storms. I have seen a lot of storms that dissipate or split up when they approach DC. I think it’s related to the terrain.

In DC and Baltimore, I’d expect storms to be more severe to the north and west only if the winds were coming from the east. That’s because the wind is running up the slopes of the Appalachian Mountains, contributing to the lift in the storm and triggering heavier rain or snow.

In winter, when there’s a cold front lying across the area, and warm, moist air comes in from the Atlantic, the same thing happens. Instead of running up the slope of the mountains, the warm air runs up the slope of a wedge of cold air at the front. We get narrow bands that might have a foot of snow, while a couple miles to either side people only get two or three inches. But the band could be north or south of the city.
One more thought. Bigger cities usually have a bubble of air over them that’s a couple degrees warmer than surrounding suburbs. This can enhance storms as the move over the city (typically coming from the north and west). Once the storm has dumped a bunch of precip, it will weaken.

Coastal Storms that hug the coast in winter have their heaviest precip, and coldest air due to counter clockwise rotation, in the north and west part of a storm.

Take Philly versus it’s suburbs in February. Cold air comes in from north as storm approaches. Philly is closer to the Ocean, so when the storm brings up some moisutre and warmer air, the temps in Philly are 32-33, while north and west it’s 29-30. Part of the event might be rain in Philly, keepiong totals down.

Additionally, even in cases where it’s an all snow event for the entire Philly area, Philly and points near the shore are going to be warmer. Let’s say it’s 26 degrees north and west, 30 in Philly and 31 in South Jersey. The lower the temp, the higher the snow piles up. Some of it is the chemistry of snow versus how cold it is.

Also, many storms hug the coast so closely that the heaviest precip band are north and west (again, low pressure rotating counter clockwise and this n/w area is where the wind comes from north/colder air, guranteeing more precip.

Sometimes, but not often, the storms stay off the coast and give the coastal area more snow. This past winter is a text book case of that. South Jersey and areas S and W of the city took harder hits.

Most news is based out of major cities, and it’s usually colder to the north, in almost (ALMOST - don’t pounce) all siutations. The NE and MID-Atlantic is usually like this.

Jinx, I suspect that the “north and west” phenomenon is limited to your region.

In metro Detroit, snowfall will tend to be heavier to the North and West due to the rising elevation of the glacial moraine that extends from Capac down to the Irish hills. In metro Cleveland, the worst winter weather falls to the Eastern suburbs due to the way that the winds come off Lake Erie and drag moist air up over the hills to the East.

On the other hand, both Detroit and Cleveland tend to see far more thunderstorm damage (and tornado threats) to the South and West, both because the prevailing summer storm winds are northeasterly and because the South and West suburbs lie on flatter land.

As noted in earlier responses, other cities also experience storms that differ from a “North and West” pattern.

Muskegon, MI and Erie, PA never have storms in the northwest suburbs.

And the eastern 'burbs of Milwaukee never get subjected to lawn watering restrictions, either.