The (extra) Peculiar Winds Forecast Around the Las Vegas Valley | Jan 13 2016
The Background
Winds around the Las Vegas Valley are a frequent...and usually the dominant forecast concern. The terrain around here does funny things to winds. Under weak synoptic flow...the terrain is the primary driver of winds (upslope/upvalley during the day...and drainage/downslope at night). Often times, these terrain interactions can really throw some curveballs under stronger synoptic forcing...depending quite a bit on stability. During the summer months, mixing often plays a role in bringing breezy southwest winds into the valley (as opposed to typical light diurnal easterlies).The Scenario
Here we can see a similar scenario, with widespread southwest winds spreading over the valley...but not quite in the valley yet. In central parts of the valley, more typical lighter easterly winds are found. A quick glance at a sounding and forecast PBL height time series show that mixing is indeed the issue here. Unidirectional westerly flow aloft would certainly support southwest winds, but a stout inversion and clouds are creating conditions where the PBL is struggling to mix up to even 1kft AGL in the valley. This is often a forecast challenge to determine how far across the valley these southwest winds will push.
