Joe’s Weather Blog: Starting To Dry Out Again (TUE-9/23)

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Good afternoon…after a near perfect weather day yesterday, while still very comfortable in the area this afternoon we are fighting a lot of clouds that have moved into the region. We should see more sunshine though this afternoon at times. Now the question is will there be any showers that creep into the region overnight?

Forecast:

Tonight: Mostly cloudy skies with a slight chance of some sprinkles or showers later this evening. I’m still wondering IF there is too much dry air in the bottom 10,000′ of the atmosphere though. Temperatures should not be as cool as this morning (52°). Readings will probably be closer to 60° or so. There may be some developing overnight showers, especially on the KS side, in the wee hours of the morning.

Tomorrow: Any shower or sprinkle activity should fade as the day moves along, but we’ll have a lot of clouds for awhile. Highs 70-75°

Thursday: More sunshine and milder weather with highs near 80°

Discussion:

Sort of a strange weather day, especially on the KS side as a persistent area of rain and showers continues to have a difficult time pushing eastwards. As it does so, not only is the forcing for the atmosphere weaker but also there is a very noticible dry layer of air below 10,000′ or so that is, in a sense, chewing up the moisture as it pushes east.

So let’s start today off with the sounding from the balloon launch this morning at the NWS in Topeka. As the balloon goes up, it takes temperature/moisture readings in the air that it goes through. These are plotted on a special chart called a skew-t chart.

 

The RED trace are the temperatures as the balloon goes up into the atmosphere and the GREEN is the dewpoint trace as the balloon ascends.

On this particular image…what I want to talk about is the large spread between the 2 trace lines below the 600 (in blue) number on the left side of the chart. That 600 represents 600 mbs or about 14,000′ up in the air (give or take). Notice how the RED/GREEN lines spread apart so much. That means that there is a LOT of dry air at that particular level. As a result whatever may fall from cloud bases above 14,000′ has a pretty decent chance of evaporating before reaching the ground.

What can happen is that as time moves along (hours typically) the dry air layer will slowly get saturated as more and more raindrops (or snowflakes in winter) fall through the layer of dry air. Eventually the drops fall through a mostly to saturated layer and reach the ground.

Overnight tonight the question is…is there enough saturation happening locally to allow that to happen?

I’m still not convinced…the afternoon satellite picture shows some significant breaks in the clouds around the KC area.

 

The model data, which can have a tough time forecasting the amount of time it takes to saturate the lower levels of the atmosphere shows the mid-level moisture nicely…but notice through time that the lower part of the atmosphere really never get’s that saturated at all.

 

The map above is one of my favorite ways of illustrating the moisture through the atmosphere. It also shows the wind fields and various other parameters as forecasted by the NAM model. The thing to look for is the various shades of GREEN in the top part of the image. Again notice that the bulk of the GREEN contouring is above 6-10,000′ or so through time.

Speaking of time…as usual 12Z is 7AM…18Z is 1PM…00Z is 7PM…06Z is 1AM.

The model though is trying to squeeze out some rain in there starting at 10PM tonight through 10AM tomorrow…

We’ll see about that…this dry air may be too much to overcome without a strong disturbance or anything really to counteract it.

I’ll insert the radar from the NWS in Pleasant Hill for your perusal.

 

The upper level dip in the flow that’s creating this minor concern is going to wallow around through the Plains for a few days. IF we’d have more moisture to work with, we’d be more favorably set up for additional decent rainfall…but that doesn’t appear to be in the cards at this point

One thing to be alert for is that in these scenarios there is a tendency overnight for the rain to actually increase in coverage. As the low level jet increases somewhat and the moisture moves northwards…you can see an uptick in the rain. Should this uptick occur near the Topeka area…in time our dry atmosphere would be overcome from the KC area westwards…so something to watch overnight.

At this point though I’m not too excited about any significant rain for the KC area, which we can actually use as it’s been pretty dry out there lately.

The pattern overall is sort of getting all jumbled up. There is not going to be a lot of upper level stuff blowing through our area for about a week or so. Their is a significant storm off the west coast though that may give the drought areas of N CA northwards some rain. Here is a water vapor loop of that storm…it means business as it’s packing near hurricane force winds with it!

 

Check out the wave heights that will be battering the PAC NW from this large fall storm…

 

This is a forecast for 8AM PDT on WED…the contours are in meters…there are some 7-8 meter waves forecasts…which would be 20-25+ feet. Add in various other factors and you can get 25-35′ waves out there. Here is a live web image of the surf effecting Oceanside, OR via www.oregonsurf.com which is due west of Portland, OR and int eh Tillamook Bay area…think cheese!

 

Should be an interesting place to be over the next few days…

This massive storm will wobble around off-shore for a few days then gradually weaken. A piece of the storm though will break off but odds are it really doesn’t effect our weather much aside from keeping us in more or less a southerly wind flow allowing temperatures to start the next month on the mild side.

Another storm is already moving into the Aleutian Islands and may offer better potential total/rain opportunity, but that is still 7+ days away from happening (of it even comes together for the KC area).

That’s it for today…let’s see if some can get any rain tomorrow AM. For those who have grass seed down…I’ll keep positive thoughts for you :)

Joe

 

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