Damaging Winds and Extreme Fire Weather Danger through early Monday, Critical Fire Weather Concerns Tue & Wed

October 27, 2019 – A strong wind event today into early Monday will result in extreme fire weather danger. Enhanced fire weather concerns possible again by the middle of next week. Dry through the extended forecast. Near or below average temperatures through mid week then a little above normal temperatures by the end of the week. High Wind Warning in effect until 11 PM this evening, Red Flag Warning in effect until 11 AM Monday.

Discussion

Upper trough dropping into the central Great Basin this morning with upper trough axis currently dropping southward through Northern California. Surface high pressure pushing in to the Pacific Northwest producing a tight gradient across the north state. Current surface gradient from MFR to SAC about 16 mb at this time and climbing. Gusty north winds have developed over most of the north state with peak wind gusts at the higher elevations of the coast range topping 50 mph. Therefore will keep wind warning currently in place going this morning.

Winds keeping overnight humidity recovery quite low, as expected, so Red Flag warning will remain in place as well. Daytime highs today in the wake of the trough axis will take a significant drop dropping from several degrees above normal on Saturday to near or a little below normal this afternoon. Tight surface gradient forecast to continue through the night weakening slowly then should take a fairly significant drop off Monday afternoon bringing decreasing winds. Daytime highs stay right around normal on Monday as high pressure pushes in over the west coast.

Another upper trough will be dropping southward out of Canada and into the northern Great Basin on Tuesday. By Tuesday afternoon, surface gradient tightens enough to bring the start of another round of moderately strong north winds to the CWA. Low RH values will mean that another Fire Weather product will likely be needed. Airmass cooling behind the trough axis will bring a little cooling again Tuesday and Wednesday. Surface gradients drop off again by Wednesday afternoon with decreased winds by the evening hours.

Extended Discussion (Thursday through Sunday)

Second system over the Northwest Territories (N of Great Slave Lk at 0130 PDT) that reinforces the Wrn States trof and brings more Nly wind to Norcal Tue/Wed will be lifting NEwd into the Central/ Nrn Plains States Thu and Fri, and then reinforcing the Hudson Bay low (lobe of the Polar Vortex) this coming weekend. This negative height anomaly will allow for amplified ridging and a positive height anomaly along the W Coast relaxing pressure gradients and providing a warming trend. On Thu max temps will be near to slightly above normal (except a little cooler than normal over the W Slope Sierra) then warming to several degrees above normal Fri thru Sun, except over 10 deg above normal over the Nrn portion of the CWA. The dry air mass over Norcal will be subject to good radiational cooling especially in the NE Mtn zones where mins will drop into the teens and 20s, and mid 30s and 40s in the Valley. Might have some thin spots of patchy frost in the wind sheltered/low lying areas in the Vly, but the dry air mass will preclude widespread frost.