Colder Next Week…And How Does a Frost-Free Hose Bib Work?

We will finish the week (and Start the month) on a warmish note, with the Reno and Tahoe areas climbing up into the 50s with partly cloudy skies. A weak to moderate storm system will move into the region late Saturday afternoon, kicking up some brisk winds and giving us a slight chance of some showers late Saturday into Sunday morning. Those showers in the valley could turn to snow Sunday (although it is unlikely there will be valley accumulations), with the mountain passes likely to pick up a couple of inches during that same time frame. Things dry out late Monday for the rest of the week, but the cold air will stick around through Thursday.

Frost free hose bib

Yesterday I talked about frost free hose bibs. What makes a hose bib frost free? If you look at them before they are installed, you will notice the feed pipe is quite long…at least 6 inches but often a foot or longer (for colder climates.) The closing valve is seated all the way down at the end inside the foundation away from the outside end so that when it is shut off, there isn’t any water exposed to the cold air in the pipe, but is rather contained inside the structure. They are absolutely necessary in our cold winter climes.

 

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Weekend Storm Weakening…And Why You Should Disconnect Your Hoses

The mild weather will continue through the rest of the work week, and it is now beginning to look like the projected weekend storm will be weaker than the models had initially projected. For Thursday, sunshine in the morning will be replaced by a few afternoon clouds with mild high temperatures in the mid-50s…conditions that will essentially duplicate on Friday. A trough of low pressure late Saturday will start to kick up some winds and could bring some mainly mountain showers, but the latest computer models have weakened this storm significantly and now there is only a slight chance we will get any valley rain or snow. Temperatures will cool down to the 40s by the end of the weekend.

hose bib

I certainly hope that by now everybody has shut off and winterized their irrigation systems. But one thing that gets forgotten every now and then is to make sure that you disconnect your hoses from your hose bibs. The reason for this is that if the hose stays attached, water can stay in the nozzle of the hose bib, which can then freeze and crack, whereas if you disconnect the hoses, the water will drain out and have nothing in them to freeze.

 

Mild Week, Unsettled Weekend…And Where Is The Atmosphere’s Mid-Point?

This work week will be pretty non-descript, with mild afternoon highs in the 50s and overnight lows falling to below the freezing mark, but not dramatically below. The storm track will be far enough to the north so that we aren’t likely to see any precipitation through Friday, but not so far that we won’t see occasional cloudiness through the end of the work week. On Saturday, the ridge over us breaks down to allow a weak to moderate storm to come through the region, giving us a chance of rain showers late Saturday that could turn to some snowflakes by late Sunday.

Air pressure column

Yesterday I told you a one inch column of air to the top of the atmosphere would weigh about 14.7 pounds.  If you cut that column in half, how much would the bottom half weigh? About 7 ½ pounds, right? Nope. It would be somewhere around 14 ½ pounds. The actual answer depends in part on how you define the top of the atmosphere (for our purposes, we’ll ignore the thermosphere), but most is packed in the bottom. Because air compresses, most of the atmosphere’s mass is crammed into the lower 5%.

So just where is the “mass mid-point”? Out of an air column of about 105 miles high, half of all the air molecules are in the lower 3 ½ miles. The 500 millibar (half a bar) surface is located at about 18,000 feet, and is an important layer to watch when forecasting the weather.

500mb

 

Cool Week, Stormy Weekend?…And How Much Does Air Weigh?

While some cool weather will settle into the region for a while, we should stay dry through Friday, after which a weekend storm system could bring rain and snow showers all the way to the valley floor. In the short term, Tuesday should bring sunny skies with a high in the low 50s after a chilly start to the day in the 20s. As the week progresses, some cloudiness will come and go with similar temperatures, but on Saturday a cool storm system will pass through the region, with temperatures falling to the mid-40s by Sunday, which could turn Saturday rain into Sunday snow showers.

Balloon races

Air is pretty cool stuff. And while the term “lighter than air” gets bandied about a lot, it underscores the fact that air in fact does have mass. So how much does air weigh?

Air Weight

The easiest way to answer that is to look at air pressure. At sea level, the atmosphere has a pressure of about 14.7 pounds per square per inch. So what does that tell us about air’s weight? Applying fluid dynamics, that 14.7 psi means if you took a column of air one square inch in cross section from sea level to the top of the atmosphere, it would weigh in at 14.7 pounds. Another way of looking at it is to take the weight of a cubic foot of air. At standard temperature and pressure (zero degrees C and one atmosphere) a cubic foot of air would weigh about 1.3 ounces.

 

 

Thanksgiving Travel Curse Rears Its Ugly Head…

As we head into the Thanksgiving weekend, it looks like the old adage that we just have to have some kind of weather sometime over this particular holiday weekend will hold true. Saturday will be warm and dry, although the wind will likely pick up in the afternoon, gusting to the 30s by late in the day. High temperatures could reach 70 degrees…not that far from record level. That wind will increase in strength on Sunday (a High Wind Watch is in effect for that time period) and rain will move into the mountains, with some spillover rain to the valley late Sunday into Monday morning. Snow levels will start out very high (around 9,000’) Sunday, and will lower Sunday night to Lake Tahoe level, and could drop close to the valley floors on Monday, although accumulations aren’t expected until you get up about 1,000’ off the valley floor. Conditions will dry out after a good chance of rain and snow on Monday. Temperatures will fall to the mid-60s on Sunday and then all the way to the low 50s to upper 40s through most of next week.

 

Time to Dry Out…And Some Impressive Rain Totals

After receiving more than a month’s worth of precipitation in less than 24 hours, things will begin to calm down and clear up as we head into the weekend. After some scattered showers into early Friday morning, our skies will break up in the Reno area with a few snow showers left up in the mountains through Friday morning. A chilly high in the 40s on Friday for Reno will warm to the 50s on Saturday with sunny skies coming back. Saturday will start off cold with valley lows dropping to the mid-20s at the warmest, with some of the outlying valleys possible cooling to the teens. Saturday’s sunshine will give way to some clouds on Sunday, and then a series of weak storms that could send an isolated shower or two our way, but doesn’t appear to have any major storms in it before the end of Thanksgiving weekend.

snow totals

If you are wondering, some of the rainfall totals were very impressive, ranging from over 6 inches at Blue Canyon to nearly an inch at the Reno Airport (probably the driest spot around.) Some places in the valley (both Lakeview and Cold Springs) had 24 hour totals that haven’t been seen for 30 years. High up in the mountains, some areas piled up over three feet of snow, a boon to early opening plans.

 

 

Flood Advisories and High Mountain Snow

An Atmospheric River will bring significant rain and high mountain snow to the region through Thursday. An Areal Flood Watch is in effect through Thursday, and will mostly affect the smaller creeks and drainages. Snow levels will be quite high, only lowering to about the 7,500’ elevation Thursday. By Early Friday morning, that snow level will probably fall to the Lake Tahoe elevation (around 6,200’), but by that time the heaviest precipitation will have passed on to the south.

Total snowfall amounts will of course depend on the elevation. Above 8,000’, snowfall totals could exceed several feet, while it is unlikely there will be more than trace accumulations at the lake itself.

Rainfall

As for rainfall totals, there is a possibility some valley locations will accumulate an inch or more of rainfall, with significantly more on the west side of the valley expected than on the east side.

Once Friday arrives, temperatures will cool to the upper 40s as the skies partially clear. Saturday should be dry and partly sunny, but expect a hard freeze (with lows in the upper teens to twenties) Saturday morning.

 

Strongest Storm So Far This Season…

Another strong and windy winter storm is setting up to move through the region Wednesday and Thursday. Initially in the valley, strong winds (valley gusts could exceed 60 mph in some areas and a High Wind Warning is in place starting 10 am Wednesday) will limit how much rainfall we get due to a strong rain shadow, but late in the day as the front passes through we should get some spillover rain here in the valley as the winds back off a bit and extra moisture from an Atmospheric River gets pumped into the system. Snow levels in the mountains will start out at about 7,000’ and will likely rise through the day Wednesday to 8,000’ or higher before falling back down to Lake Tahoe level by Thursday. A Winter Storm Warning is in effect from Wednesday afternoon through late Thursday night.

With the input of the Atmospheric River, total precipitation amounts are likely to be very impressive. Several inches of water will fall in the form of rain and snow on the crests, and snowfall totals could range from an inch or so at the lake to two to three feet above the 8,000 foot level.

 Watches-Warnings

 

On Again, Off Again Pattern Setting Up

It’s an up and down weather story this week. Tuesday will put us in between storm systems with partly cloudy skies and mild temperatures near 60 in Reno. A stronger storm system is moving into the region Wednesday, kicking up gusty winds and bringing some mountain rain and snow with valley rain. The mountains will catch enough, with snow levels that will lower to below pass level, so that a Winter Storm Watch has been posted for the mountains from Wednesday afternoon through Thursday. The winds will once again create a significant rain shadow for the valley, but there should be some spillover Wednesday afternoon into Thursday, especially on the west side of the valley. Temperatures will start out at about 60 degrees on Tuesday and will drop just a few degrees to the upper 50s on Wednesday before falling to the lower 50s through the end of the work week.

The weekend should clear out with a dry Saturday (with mild high temperatures near 60) before another weak to moderate storm system moves through the area late Sunday.

 

Sunny Saturday, More Storms to Come…and What Are Those Weather Stations? (Conc.)

The weather will clear up in time for the weekend, with mild temperatures and mostly sunny skies on Saturday. The afternoon high should top out at about 60 degrees with light winds. Late Sunday, winds will start to pick up ahead of another storm system similar to the last one to come through the region. On Monday, clouds will accompany gusty winds with mainly mountain rain and snow (snow level will likely be about 8,000’), although there is a chance of a little spillover on the west side of the valley. After another break on Tuesday, another storm moves through on Wednesday into Thursday.

Road Weather Station RWS200

Yesterday, Roger wondered about the Road Weather Information Systems along the highways between Gardnerville and Reno. I was actually the consulting meteorologist on the project when it started back in the 90. They employ a full weather station along with road sensors that measure pavement temperatures and other things like if water or ice is present. It’s a big help to road crews as winter storms approach to let them know when they should put de-icing substances on the roads, and can save them (and us) a ton of time, resources and grief.

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