The large scale weather setup has not changed much in the past day. High pressure is still atop our area and is moving slowly eastward. The high pressure cell's center will slip to our east tomorrow, and our wind will blow from the south up the western side of the high pressure. The wind aloft will become southwesterly. The warmer southerly to southwesterly wind throughout the depth of the atmosphere will help to warm the air considerably. The humidity will also increase. Locally that noticeable change begins tomorrow and really revs up over the weekend. In response to a little more humidity clouds will be on the increase. Then there's the low pressure that was just off the coast of Washington yesterday. That system is headed southeastward and moving into the coast of Southwest Oregon and northern California and will continue its east to southeast motion across the Rocky Mountains and into the Plains. It will gain a little intensity over the Plains, but it will move mainly northeastward. A cold front will trail to its south and will move into our region with building humidity and warmth. The atmosphere could be primed for heavy rains in spots. The forecast position of the jet stream suggests heavy rain, as well. On average rainfall totals will be around half an inch, but localized spots could wind up with around an inch. Vertical wind shear profiles suggest ample turning in the wind direction with height, which would suggest a threat for tornadoes if the atmosphere was moderately unstable. Current stability forecasts are for only minimal instability, if any at all. Yesterday's model forecasts suggested a little more instability. The point here is there is a lot of time to monitor changes in how this system develops for our area. Severe thunderstorms capable of producing tornadoes are possible if that instability materializes, but slightly cooler temperatures could prevent this from happening. As minor as this may seem, it really can come down to one degree temperature difference, and this is an instance where one or two degrees of warmth can determine whether we see severe weather or just heavy rain.
TONIGHT: Clear and unseasonably cold. The low will be near 37, though the coldest locations could cool to 33-36. The wind will be calm.
TOMORROW: Mostly sunny and warmer. The high will be near 72. The wind will be from the south at 5-10 mph.
SATURDAY: Partly cloudy. The morning low will be near 45. The afternoon high will be near 74.
SUNDAY: Partly sunny with a slight chance for a shower. The morning low will be near 50. The afternoon high will be near 75. The rain chance is 20%.
MONDAY: Cloudy with heavy rain and a few thunderstorms. The morning low will be near 55. The afternoon high will be near 72. The rain chance is 70%.
TUESDAY: Sunny. The morning low will be near 42. The afternoon high will be near 61.
WEDNESDAY: Sunny. The morning low will be near 38. The afternoon high will be near 65.
THURSDAY: Mostly sunny. The morning low will be near 43. The afternoon high will be near 69.