Windy today, higher elevation thunderstorms Saturday – Wednesday

May 11, 2018 – Wind Advisory from 10 AM this morning to 6 PM PDT this evening. Period of windy conditions today. Temperatures remaining slightly above normal. Showers and thunderstorm chances mountains through the middle of next week.

Discussion

Upper low now centered over northeast Oregon will drop southeast into the Great Basin today. Surface high pressure pushing in behind over the Pacific Northwest will create a tight northerly gradient over the north state which when combined with upper level northerly flow will bring breezy north winds. Northerly winds already starting to pick up over the northern Sacramento valley with current wind speeds in the mid teens. Winds are expected to pick up above wind advisory criteria throughout the Sacramento valley by late morning as surface gradients increase to above 12 mb from Sacramento to Medford. Shortwave dropping down backside of low may bring a few showers over the northern Sierra. Cooler air will filter into the area bringing a decrease in daytime highs today but maximum temperatures should remain a bit above normal. Winds will stay breezy during the evening hours but will be on the decrease.

Upper low remains over the Great Basin through early next week. Shortwaves rotating around the low will bring a threat of showers over the Sierra Cascade range Saturday. Stability progs indicate enough instability for a slight threat of thunderstorms as well.Only minor changes are expected in the weather pattern Sunday and Monday with upper low expected to only move slightly. This should mean only slight changes with high temperatures and afternoon/evening Sierra crest thunderstorm threat Saturday through Monday.

Extended discussion (Tuesday through Friday)

An upper level low centered over the Great Basin weakens, and exits the area on Tuesday, only to replaced by a Pacific upper low. Afternoon/evening thunderstorms are expected to continue over the mountains and foothills at least through Friday, and potentially through the weekend. The core of the low is expected to move inland late Thursday into Friday. Below normal temperatures are expected by mid week due to synoptic cooling and cloud cover. Valley temperatures remaining in the 70s are forecast for Thursday. This blocking pattern is showing few signs of ending any time soon.