Hints of Autumn appearing in numerical solutions
Thursday, August 13, 2015
Our weather for the next week looks to begin with the persistent summer monsoon having upper-level flow generally from the south or southwest around a Great Basin ridge. The week will end with a series of cool fronts that veer the flow to the west.
The weather through Saturday should be typical of the summer with warm days and the chance for afternoon storms. A storm currently off the coast of northern California will move mostly north of our area late Saturday quickly followed by another wave of cooler air early Sunday that will keep temperatures cooler than normal on Sunday. Additionally, these weak fronts will flatten the Great Basin ridge and may invigorate our typical afternoon storms for the weekend.
Concurrently, a seasonably strong storm moving southward this weekend along the West Coast from the Gulf of Alaska will turn our winds back to the southwest by Monday, warming temperatures to normal and continuing the chance of afternoon storms.
As this storm crosses the coast and begins to move eastward across the Great Basin on Tuesday, significantly drier air will move into the area by Tuesday or Wednesday, followed by a mostly dry frontal passage Thursday or Friday. This storm should lead to noticeably cooler temperatures by the end of the work week, and these cool temperatures will be reinforced by next weekend as another Pacific Northwest wave moves over the region.
There is considerable model uncertainty for next weekend and after that as the American GFS forecasts a building ridge in the Gulf of Alaska while the European ECMWF shows much less, if any, ridging. Incidentally, the Gulf of Alaska ridge is a typical feature of an El Nino event, and I’ve found that while the American GFS may be early in predicting pattern changes, the model often is correct in forecasting an eventual pattern change. It will be interesting to see how that forecast evolves over the next few weeks.
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