Kevin Myatt is The Roanoke Times' weather columnist.

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Enjoy the unseasonably cool air that will be filtering in from the northwest this weekend and into next week. It may be followed by our hottest air mass of the season building in from the same direction.

We're used to the idea that cool air comes into our region from the north or northwest and warm air moves in from the south or southwest. That is usually how it works.

That's what's happening this weekend, after a strong cold front for this time of year moved through the region Friday. Cool air from Canada will drop our high temperatures into the 70s and low 80s the next couple of days, while our lows will be in the 50s to near 60.

This may well be our coolest weekend until fall breezes blow sometime after Labor Day.

But on the back end of this cool snap, which may linger through much of next week in a sluggish atmospheric pattern, high pressure that has been scorching the West much of the summer will finally be nudged eastward.

The high is expected to build gradually eastward over the northern half of the country, eventually into the eastern U.S. So the hot high-pressure system may build over us from the northwest, or at least the west, rather than from the southwest.

There could be some days in the upcoming week when temperatures in the Dakotas or the upper Midwest exceed those in Texas, where east winds on the south side of the clockwise-rotating high will sweep in more Gulf moisture and cooling precipitation.

This is really not as unusual as it sounds for mid- to late July. If the heat dome happens to become established farther north, it can be hotter near the Canadian border than it is near the Mexican border.

By a week from now, we will probably have high temperatures around 90 again. If the high sets up shop right over us for an extended period of time after that, we could soar well into the 90s for many days the following week. It's too early to say whether or not we could challenge 100, a mark Roanoke hasn't hit in eight years.

The one thing that will be safe to say is that rainfall in the upcoming pattern is likely to be sparse at best.

Anytime we get air masses moving in from the northwest, be it hot or cold, they are mostly dry. Just look at a map and see how far it is to an ocean in that direction.

In this case, we also will have few if any fronts or upper-level disturbances moving through, as they will be blocked by the building dome of high pressure over the northern U.S.

So all we will be left with is whatever afternoon showers and thunderstorms daytime heating and our mountainous terrain can cook up. This weekend's air mass may be so cool high in the atmosphere that any amount of heating at the surface will trigger some potent afternoon thunderstorms, but they will be few and far between.

We had just enough rain here and there during the past week to prevent the drought area from expanding. Moderate drought now reaches into the western parts of the New River Valley with severe drought over the far southwest corner of the state. But if the expected upcoming pattern comes to fruition, the drought would expand.

There is one thing that could throw a wrench in all this, and that's a tropical system. We are hitting the time of year when we would expect those to form with more frequency and intensity. A tropical system could short-circuit next week's cool snap by bringing in steaminess, or it could disrupt any heat wave that follows with moisture and clouds.

We'll keep our eyes out to the southeast for something that could interrupt our weather coming from the northwest.

For the record on 100-degree weather

While on the subject of hot weather, I want to set the record straight on a couple of statistics about 100-degree weather in Roanoke that have appeared in recent Weather Journal columns and were printed incorrectly once each.

Since weather records began in 1948, we have had 38 days at or above 100 degrees at Roanoke Regional Airport. And our hottest temperature on record was 105 degrees on Aug. 21, 1983.

I'm not sure we'll add to the 38 days and I strongly doubt we'll challenge the 105 this summer, but for the record, that's where we stand.