The center of a deep upper level low pressure system will dive down into California today which will destabilize our atmosphere this afternoon along with surface heating. Northcentral Washington today can expect mostly cloudy skies, a light west breeze and a 60% chance of showers and afternoon t-storms with highs later on in the upper 60’s to lower 70’s. There will be an enhanced risk for flash flooding on burn scars over north-central Washington. In particular, burn scars in the east slopes of the northern Cascades will be at most risk. Confidence is high for thunderstorms in this area as that shortwave disturbance will moving in during peak heating and steering flow will be weak. The Cougar Creek burn scar is a particular concern above Ardenvoir as it burned extremely hot in 2018 and won`t take much more than 0.30-0.50 inches of rain in 30-60 minutes for fast flowing runoff into drainages and in particular into the Mad River that feeds down into the town of Ardenvoir. Other burn scars that are still considered higher probabilities for flash flooding with heavy rain will be a concern as well, such as Wolverine, Uno Peak, Crescent Mountain and the Carlton Complex. We will be issuing a Flash Flood Watch for this threat that will cover the afternoon and early evening hours. Concerns for flash flooding are less across the Okanogan Highlands eastward as storms will be moving faster.
Not as much instability on Tuesday with partly cloudy skies, a 30% chance for showers and highs around 70 degrees.
By Wednesday, the upper trough of low pressure weakens and lifts north allowing the precipitation threat to ease but allowing some windy conditions in its wake. Across Northcentral Washington, partly cloudy skies for Wednesday with a northwest wind 10-20 mph with gusts possibly to 26 mph.
A broad, upper level trough will remain over the region on Thursday with partly cloudy skies, a 30% chance of showers with afternoon highs cooler, in the mid 60’s.
Weather improves across Northcentral Washington on Friday and into the weekend with partly cloudy skies Friday and highs in the upper 60’s. Partly cloudy to mostly sunny skies on Saturday and Sunday with highs on Saturday in the mid 70’s and into the upper 70’s on Sunday.