‘Omega Block’ to help bring rigorous system in the West this weekend
Computer weather models continue to show an “Omega Block” pattern setting up this weekend through early next week.
The “Omega Block” pattern refers to a buckling pattern in the movement of air in the atmosphere which resembles the Greek letter “Omega”, hence the name. There usually is a ridge in the upper air pattern with two troughs on both sides.
A classic "Omega Block" pattern is expected to develop late this week through at least early next week. Notice the upper-air flow resembles that of the Greek letter "Omega". This will bring cooler and more unsettled weather to parts of the western U.S.
The area under the ridge often features warm and dry weather while cooler and unsettled weather is found with the dips in the pattern. The far northwestern U.S. will be stuck in the cooler and more unsettled part of the pattern starting Friday and expanding farther south and east through the days after Friday.
The Southwest will see very warm weather towards the end of the week and the Rockies will get warmer weather over the weekend into early next week with the ridge passing over.
A rigorous upper-level low is expected to move into the Northwest Friday and then dive into the Southwest as it gets blocked by the “Omega” ridge.
This system will bring cooler air along with showery weather. The cooler pocket of air aloft will also bring instability and there will be some thunderstorms as well.
The Northwest U.S. will have to deal with this system Friday and Saturday while central and Southern California and the Southwest U.S. will deal with it Sunday to Tuesday and perhaps longer. This upper-level low will be cut off from the main flow and blocked by the ridge so it is possible it lingers past Tuesday.
A vigorous upper-level low will arrive in the Northwest Friday and dip southward as it is blocked by an Omega ridge. This will bring cooler and unsettled weather to the far West. Loop shown is GFS 500 mb height, wind and vorticity weekend into early next week.
Southern California will likely see showers and even a few thunderstorms Sunday and Monday.
Snow levels in the Sierra and Transverse Ranges will drop down to around 5,500 feet or so over the weekend with some fresh mountain snow likely.
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