Strong hair drier winds blowing from Sacramento Valley over the coastal range and through the gap towards the Pacific rewrote weather history of the Bay Area and surrounding region Friday, Saturday. An astonishing high of 106 degrees was recorded in Downtown San Francisco Friday surpassing the city’s all-time record high of 103 set in June 2000. Records date all the way back to 1874.
Why so hot in a typically cool part of California?

Credit: Tropical Tidbits
As seen in the 500mb height anomaly chart above, a powerful high pressure system over the region allowed strong heating throughout the region but the 594dm HP core positioned to the north put the Bay Area directly in line of a notable east to west flow from the Sacramento Valley to Pacific. Combination of hot sunshine from the high and more importantly the hair drier wind blowing towards the coast tipped thermometers over the edge.
Note highest anomalies are right up against the coast, helped by downslope compressional warming off coastal range…

Credit: Tropical Tidbits
Both Friday and Saturday hottest the hottest day in recorded history. Incredible said the NWS.
https://twitter.com/ggweather/status/903800269087141889?ref_src=twsrc%5Etfw&ref_url=https%3A%2F%2Fwww.washingtonpost.com%2Fnews%2Fcapital-weather-gang%2Fwp%2F2017%2F09%2F01%2Fsan-francisco-smashes-all-time-record-high-temperature-hits-106-degrees%2F
Friday
https://twitter.com/NWSBayArea/status/903789630088151041
https://twitter.com/SFmeteorologist/status/904029701156421632
https://twitter.com/NWSBayArea/status/903732022417469440
Exceptional heat affects transport.
https://twitter.com/Caltrain/status/903745286991949824
Saturday
https://twitter.com/NWSBayArea/status/904157400688680961
https://twitter.com/NWSBayArea/status/904126694088421378





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