Pattern Change.


Monday, November 8th 2010, 3:03 pm
By: News On 6


Pattern change. As Alan mentioned in his morning discussion, a major change in the wind pattern aloft is underway and those changes will eventually bring us a good shot at some badly needed rainfall later this week. However, between now and then it will be very warm and very windy which will maintain an enhanced fire danger situation. Fortunately, those strong southerly winds have finally started tapping into a little more moisture as you can see in the image to the right which shows how the dew point has changed over the last 24 hours. These higher moisture levels have already mitigated the fire danger somewhat by keeping us below the criteria for a red flag fire warning.

The pattern change aloft mentioned earlier will eventually bring a vigorous storm system through the southern Rockies and out into the Plains for later in the week. This system will then eject over us along about Friday and be replaced by a rather broad upper level trough to our west. This is a polar opposite of what the prevailing pattern has been like lately which had a rather strong ridge to our west. Typically, troughing to our west produces an unsettled pattern as systems will periodically cycle through that trough, some will amplify, and then eject eastward in our general direction. There are lots of details yet to be worked out, but the bottom line is that the latter part of this week and quite possibly much of the following week will be more unsettled than we have seen in quite some time.

As that system moves into the southern Rockies, it will maintain a very strong pressure gradient at the surface. This means our nighttime winds will not calm down much as the winds will still be on the order of 10-20 mph tonight, then back up to the 20-30+ range during the day Tuesday. By Wednesday, the system should be close enough for a few isolated showers/storms to be possible. Thursday will see a better chance of showers/storms along with mostly cloudy skies and continued southerly winds.

Friday still looks like our best chance of rain in quite some time. There are still some questions regarding the depth of the quality moisture, but the dynamics of the system will produce widespread lift along and ahead of a vigorous cold front. There are also some timing differences regarding whether the front arrives during the morning or later in the afternoon which will have a major impact on temperatures. But, those considerations aside, it still promises to be a very wet system with the potential of some locally intense storms.

That will be followed by cooler conditions for the coming weekend and then we will have to see how quickly systems reload and amplify as they swing through the trough to the west. So, stay tuned and check back for updates as the next week or two could be much more interesting.

Dick Faurot