Sunny 4th of July Forecast… And Leave the Fireworks to the Pros


Now that we are entering July, temperatures in the 90s are to be more expecte4d, and it looks like they will be in that realm for the next week at least. A broad and strong ridge of high pressure has a little dent in its top due to a low pressure trough up in British Columbia. That is a very stable pattern for us down here in western Nevada, and sunny skies will result, with high temperatures topping out near 90 degrees Tuesday and on the 4th of July Wednesday. That trough will also result in some fairly aggressive west to southwest winds in the afternoons, gusting to 30 mph on Tuesday, and perhaps relaxing slightly on Wednesday afternoon.

As the trough rotates through midweek, the temperatures will start to climb, reaching the mid to upper 90s by the time the weekend arrives, with sunshine throughout.


Speaking of the 4th, those afternoon breezes will create some ticklish fire conditions, and it is a good time to be reminded that all personal fireworks are illegal in Washoe County (and in most of Nevada.)  It’s definitely not worth the fines if you are caught, or worse yet, start a wildfire, where you will be on the hook for all the costs of putting it out.




In a Word, Hot…And How Do We Know The Earth’s Magnetic Field Reverses?


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.

pole reversal

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.



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Hot Week Ahead… And How Do The Earth’s Poles Reverse?


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.

pole reversal

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.


Cool and Damp Father’s Day?… And How To Compare Earthquakes


A low pressure center will drop into the region over Father’s Day weekend, cooling us down, kicking up some blustery winds, and giving us a chance of some showers on Sunday. For Saturday, the skies will remain mostly sunny, and temperatures will be only slightly cooler than Friday’s. But the colder air moving in will boost the afternoon winds across western Nevada, with gusts well into the 30s. By Father’s Day Sunday, high temperatures will plummet to the low 70s, and the core of the low will be nearly on top of us, which will create enough instability and dynamics to produce scattered rain showers.

Earthquake Energy Chart

We’ve been talking about earthquakes of differing magnitudes. Here’s another way to compare one earthquake to another of differing magnitudes: The earthquake magnitude scale is logarithmic. That means (in this case) that a 7.0 earthquake releases about 30 times the energy than a 6.0 quake, which in turn releases 30 times the energy of the 5.0 earthquake. So a 7.0 earthquake has nearly 1,000 times the energy release that a 5.0 quake has.



Cooling and Breezy… And How Far Away Will a 7.0 Earthquake Have an Affect


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.

Earthquake 1

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.

Earthquake Energy Chart


Starting to Cool Down… And How Far Away Will a 7.0 Earthquake Be Felt?


It looks like the temperature has peaked, and now as the ridge of high pressure slowly weakens, the temperatures will reflect that. Skies should stay sunny through Saturday as the high temperature drops to the low 90s on Thursday, the upper 80s on Friday, near 80 degrees on Saturday and then drop to the mid-70s on Sunday. As the colder air moves in, afternoon winds will be pretty strong, with Friday afternoon gusts to 30 mph or more. A trough of low pressure will back in from the northeast over the weekend, and the cool pool of air associated with it could produce isolated showers starting on Sunday.

Earthquake 2

It has been a while since we have had a major earthquake here in western Nevada, but we certainly live in an area that could have one. Jessica asks:  “How far away will a 7.0 earthquake effect, versus a 6.0 and 5.0? Thanks for any input you have.”

It’s hard to put into real precise terms, because the distance felt depends on several factors, including direction of the fault movement and the rock it is passing through, as well as the depth of the hypocenter and the surrounding geology. I’ll have more on this tomorrow.

Hot Wednesday, Cooler Weekend… And What’s the Difference Between Isolated and Scattered?


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.

Thunderstorm Sierra

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.


Hot Start To Summer Vacation… And Why Calibrate Barometers?


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.

Barometer 2

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.


Red Flag Fire Warning Saturday


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.



Fire Danger This Weekend…And Why Is A Barometer Important?


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.

Barometer 2

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.

Surface analysis

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