23Z F 6 May 2011 Forecast Discussion

We finally got some west winds just before noon, and winds have continued from the west this afternoon. However, it appears we may have a break in west wind on the flats this evening as one short-wave trough aloft is passing on to the east. There is a weak surface wind shift from NW to N in SE WY attm, and I think it likely that this will hold together this evening as it moves south down I-25, to arrive on the flats mid-late this evening. Even before this we may see slackening of the wind as the incident solar radiation at the surface diminishes, partly due to the persistent cloud cover. So, I anticipate the nighttime hours after, say, 11pm MDT will see light winds.

This evening's cool push is much less substantial than the one that came down on Wednesday, and I expect that if it makes it down this far, it will rapidly be mixed out on Saturday unless cloud cover is more opaque than I anticipate. Accordingly, I look for a deep mixed layer, with sufficient vertical mixing of momentum to allow breezy conditions, to develop by late morning Saturday. As the flow aloft is going to be backing into the SW over the next 36h or so, winds are likely to be more from the W = SW Saturday afternoon than they have been this afternoon. There is a possibility that such conditions could repeat Sunday as well.

Peak gust probabilities on M2 ...... > 15m/s ............ > 25m/s

00-06z 7 May: ................................ 50% ............... near 0%

06-12z 7 May: ................................. 20% ............... near 0%

12-18z 7 May: .................................. 30% ............... near 0%

18-24z 7 May: ................................. 40% ............... near 0%