This morning the short wave at 500 mb that will impact the Southwest on Monday and Tuesday next week is embedded somewhere within a very complex pattern over the northern Pacific. The above graphic is this morning's 500 mb analysis from the NWS NAM model, showing an elongated cyclone stretching east to west along about 45 to 50 degrees latitude, north of a strong, zonal height gradient. By 84-hours (below - valid at 5 pm MST Monday 8 April) the NAM morning forecast indicates that a strong split in the 500 mb flow has occurred west of Canada, as a substantial short wave and closed low dug from the Pacific system into the Southwest. Maximum vorticity at this time is forecast within a filament from northwestern New Mexico westward across southern Arizona. If this forecast verifies, we'll have experienced a strong frontal passage across the metro Tucson area sometime Monday morning.
The 96-hour spaghetti chart for 500 mb (also valid 5 pm Monday) above shows largest spread (i.e., highest uncertainty) over North America extending from the southern California coast northeastward to Hudson's Bay. However, the local NWS has already made deterministic, point forecasts of winds and gusts they expect on next Monday - see weather cartoon below. I don't think that I recall seeing such strong winds, including gust speeds, forecast so far out in time for southeast Arizona. Will continue to monitor the evolution of this interesting system.
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