Wet Wednesday And Thursday

8/17 Tuesday 1:30 pm

Smoke is not going to be an issue for the next 48 hours. I will resume the smoke forecast when conditions warrant.

For today, I can’t rule out some afternoon convection, but conditions are far less favorable than they have been over the last few days.

We have a storm system approaching that’s going to affect our weather for the next couple of days. Unlike the monsoonal flow or afternoon convection, this is an actual storm that will be enhanced by convection and instability. A trough of low pressure will be dropping down from the northwest into the Great Basin to our west, through Utah, and clip Southwest Colorado as it moves northeast across the state.

This is unique in that, if I remember correctly, this is only the second time we have had this happen this summer. It is a much easier storm to predict. We know it is going to happen, we just don’t know what exact path it will take-therefore we don’t know exactly who is going to get the heaviest rainfall. For the last few days, the models have been favoring the western portions of the forecast area. The GFS model tends to move these systems out too quickly. The Euro model tends to dig them in too deeply west of the forecast area. That explanation may sound familiar because I talk about these model biases all winter long.

The rain should move in by Wednesday afternoon from west to east. We should have rain continuing through the evening and throughout the night. Showers will return or continue during the day on Thursday. Showers should come to an end very early Friday morning. Drier air will work in and we will return to convective afternoon showers through the weekend.

Experience tells me the Euro is usually best at picking the storm path (minus that bias). It is not always correct, but it is usually closer than the GFS.

Here is the Euro’s depiction of how everything transpires. This is in 3-hour increments beginning at 9 am Wednesday through 9 am Friday morning. The darker the green tones, the heavier the rain. You may notice a little blue mixed in there occasionally, that is snow at the highest elevations.

It would not surprise me if we get one more revision to a later arrival of the precipitation tomorrow. As you may remember, that happens a lot with these approaching systems.

All said and done, here is what the Euro is showing for totals by Friday morning.


The WPC model (below) is a blended US NOAA model, it is heavier-weighted with the lower GFS totals.

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