Very Warm…Very dry. And a lot of sun to boot. That’s pretty much the forecast for the next week or so. A strong ridge of high pressure will take up residence over the west coast through the forecast period, kicking up our high temperatures into the mid-90s, but giving just enough stabilizing west flow to keep thunderstorms from developing. With summer officially starting Thursday morning, we will be in mid-summer form by that time.

Yesterday I mentioned the earth’s magnetic field will flip over and reverse every so often. There’s no real clear reason why the flipping occurs, although several theories have been proposed, all of which are hard to prove. And although the flipping seems to occur almost instantly from a geological perspective, it probably takes anywhere from a hundred to a few thousand years to complete. The last one happened 780,000 years ago… or “Pre-Geologists.”

Just how do we know that? We can thank molten lava. Basalts on the ocean floor, for example, contain a mineral called magnetite which, as its name implies, is magnetic. When rocks are in a molten state, the magnetite crystals align themselves with the earth’s magnetic field. When the lava hardens, the magnetite is stuck in that magnetic orientation. Analysis of sea floor basalts show alternating bands of north and south oriented magnetite crystals, showing the earth’s magnetic field made similar flips as the sea floor was extruded.

Mike can be reached at malger@ktvn.com

The weather over the next week can be summed up pretty distinctly…Hot and dry. A ridge of high pressure will strengthen boosting our Tuesday high temperature into the mid-80s, followed by the mid-90s from Wednesday through the end of the week. All that heat may allow some afternoon pop up cumulus clouds to build up, but overall the airmass looks quite stable, and at this time I don’t expect to see any storm development.

A while ago I mentioned that the earth’s magnetic field will flip over every so often, on average every quarter million years or so. Barbara wondered: “I don’t understand what it means for the magnetic poles to reverse. I know that our weather doesn’t suddenly turn from summer to winter as that is dependent on the inclination of the poles; but do all the compasses suddenly start pointing in the opposite direction?  If not, how do you know the poles have reversed?”

It’s not a physical flipping over of the earth… it just has to do with magnetic north switching with magnetic south. As you know, magnets have a north and south pole… for some reason over geologic time these flip for the earth’s magnetic field. More tomorrow.

A cooling trend will settle into the region as we head into the weekend. A cool low pressure center will drop down from the north, kicking up some brisk winds ahead of the cold front on Friday afternoon. High temperatures will fall slightly Friday afternoon to the upper 80s and continue to fall through the weekend, bottoming out on the mid to lower 70s on Sunday.

With respect to rain chances, it should stay dry through Saturday after which a slight chance of scattered showers arrives on Sunday through the middle of next week.

We’ve been talking about how far away would be affected by a 7.0 earthquake. It’s important to recognize the magnitude of an earthquake isn’t a measure of how far away it will be felt. It also depends on how you define “affected.” The Loma Prieta (a 6.9- earthquake 7.1 quake, depending on measurement type) in 1989 centered in the San Francisco area could be felt by some people over here in Reno, but we weren’t really affected. But a 7.0 quake can cause damage 100-150 miles away. The distance shrinks very rapidly as the magnitude drops.

While it likely won’t be a record day Wednesday, the high temperatures will certainly be mid-summer-plus as the ridge of high pressure maxes out over us. High temperatures will reach the mid-90s Wednesday and will slowly fall back as we go into the weekend , dropping to the low 90s Thursday, the upper 80s Friday and then into the low 80s and upper 70s over the weekend as a low pressure center backs its way into the region from the northeast. Depending on exactly where the low sets up, we could see an isolated shower or two late in the weekend, but generally speaking the outlook is dry.

Jill asks: “Can you explain to me the difference in “Isolated” and “Scattered” Thunderstorms in the weather forecasts?  I know what the 2 words mean but not how they apply to where thunderstorms are expected to appear.”

Actually, neither implies where they might occur, it only implies how likely it is you will see one. Isolated means you have about a 10-15% chance of getting under one, whereas scattered means about 20-50% of the region will have a thunderstorm. In addition, scattered suggests there will be several groups of showers going on at the same time, whereas isolated showers tend to be loners, with no or few neighbors.

We have jumped right into some mid-summer temperatures as we move into the first half of the week. Highs will reach the low 90s on Tuesday and climb into the mid-90s on Wednesday before a trough of low pressure drops close enough by the end of the work week to slide temperatures back to more seasonal realms. The airmass should stay quite stable throughout the week, so mostly sunny skies (with a few afternoon cumulus clouds) and dry conditions should prevail through the week. Winds could pick up by Friday enough to create a fire hazard.

Earlier I talked about the need to calibrate your barometer to correct it for your elevation. This is critical, because the value of knowing the air pressure is to see how it varies horizontally from one location to another. Those changes in pressure are very subtle when compared to changes in air pressure as you go up or down in elevation, so if you don’t correct for the elevation, you will get meaningless pressure information insofar as it having any meteorological value.

Our temperatures will take a quick dip this weekend, bringing in high winds, blowing dust and an increased fire danger.

Prior to that, sunny skies on Friday will be accompanied by very warm temperatures, topping out in the upper 80s in western Nevada valleys. A colder trough of low pressure will sweep past us to the north, and although it’s unlikely there will be any rainfall out of the system this far to the south, but the cold air up against the warm Friday airmass will create a strong pressure gradient, and winds will likely start building pretty strongly Saturday morning, and by the afternoon we could see valley gusts of 50 mph or higher. The airmass will be quite dry, so there is a Red Flag Warning in effect across all of western Nevada from 5 am to 11 pm Saturday. High temperatures will drop to the mid-70s on Saturday and stay there through Sunday, although Sunday is likely to be a little less windy than Saturday.

After the trough passes, the temperatures will quickly rebound, and should reach the low 90s by Tuesday.

We have a couple more warm and sunny days to finish off the work week before a trough of low pressure brings in a cool and breezy weekend. The high temperature on Thursday and Friday will be in the mid to upper 80s respectively, but late Friday the winds will start to pick up ahead of the trough, and by Saturday the temperatures will drop into the 70s with gusty winds that will create likely Red Flag Fire conditions. After the trough passes through on Monday, highs will return to the 80s for next week.

Yesterday I talked about the meteorological standard… the barometer, which measures air pressure. But why do we even care about this? By measuring the pressure of the air not only at different locations but also at different times, we can pin down where high and low pressure systems are located, and where they are moving. And with any single barometer, the exact pressure measured isn’t as important as the trend…whether rising or falling. A falling barometer indicated a low is moving in, a rising trend indicates a high building.

It’s also critical that any barometer is calibrated for its elevation. I’ll tell you why this is important tomorrow.