Dry offshore flow will continue through tuesday night. Moisture associated with a system moving into california will lift into the area later wednesday through thursday morning. Temperatures will be cool enough that precipitation wednesday night into thursday morning may fall as snow, or a rain-snow mix, on higher hills. Showers with low snow levels will continue later thursday into friday as an upper low moves across the area. Drying is expected next weekend with temperatures remaining below normal.
Cold high pressure extending from the interior of british columbia into eastern washington is combining with lower pressure offshore to give dry easterly flow across the region. Skies are clear, dewpoint temperatures are low, and diurnal temperature ranges are high with maximum temperatures today mainly in the lower to mid 40s. with dewpoint temperatures well below 20, temperatures will fall rapidly after sunset and lows will fall into the upper teens to 20s. Conditions will likely not change much tuesday into tuesday night from what we are seeing today.
Forecast challenges increase wednesday through thursday as moisture moves into the area. Models continue to have some difficulty handling upper lows and their interaction over the eastern pacific during this period. One upper low off se alaska drops southward interacting with the upper low now off central vancouver island. It lifts the nearby low northeastward and takes its place a bit farther west. At the same time, the northern stream lows interact with a large and moist low now centered near 32n 141w lifting moisture northeastward into the pacific northwest. The gfs and canadian solutions tend to be more progressive with the moisture lifting it into eastern washington and oregon and only swiping western washington with light precipitation amounts. The ecmwf lifts the moisture more into western washington and gives upward of 0.5 inches of liquid equivalent precipitation to the area. The gfs has trended toward the ecmwf, and the ecmwf has trended a bit wetter from its earlier solutions.
Both the gfs and ecmwf are rather cold with precipitation beginning as a brief period of rain before wet-bulb cooling occurs due to the very dry air mass in place -and precipitation turns to snow. Snow quickly turns to rain in the gfs while the ecmwf lowers 1000-850 mb thicknesses to about 1293m and 925mb temperatures to about -2. Both models show pressure gradients becoming increasingly onshore. Snowfall with strengthening onshore flow below 1000 ft elevation is really hard to get without really cold air in place.
At this time the forecast will show a rain snow mix for lower elevations and wet snow at elevations above about 500 feet. The most likely scenario would be for any accumulations to be brief and less than an inch, not on roadways, temperatures a couple degrees above freezing, and precipitation turning back to rain thursday morning as temperatures rise toward the mid 40s. If temperatures are slightly higher than forecast, precipitation in the lowlands would likely be all rain. If slightly colder than forecast, 2-3 inches of wet snow could cause a slushy accumulation on roadways above 200 ft or so during the thursday morning commute.
The mountains will likely see less than advisory amounts of snowfall with this system. Albrecht
Showers on friday will decrease as an upper low moves eastward across the area. Snow levels will be low and some higher hills in the lowlands could see brief accumulations friday morning.
Offshore flow and drying is likely over the weekend behind the departing upper low. However today`s ecmwf rotates a piece of the departing upper low back into the area for a chance of more precipitation. Will follow the non ecmwf blend at this time and await another run before making changes to the weekend forecast. rain chances may increase after about monday and temperatures will start to return to closer to normal for early march (if we are lucky). Albrecht
River flooding is not expected for the next 7 days.
Wa...none. Pz...none.
Offshore flow and northerly will continue through tuesday, but should remain below advisory levels. Marine advisories are not likely tonight through tuesday as gradients and winds remain weak.
Winds will turn onshore wednesday as a trough along the coast moves inland. West winds forecast in the strait wednesday night could approach advisory levels. Onshore wind will taper thursday and friday. Offshore flow will resume saturday. Chb
An upper level low will remain near vancouver island tonight and tuesday. Flow aloft will remain southwesterly tonight and tuesday. The air mass is dry and stable; vfr conditions are forecast through tuesday. Surface flow is generally northeasterly with high pressure over central british columbia. Breezy conditions around kbli.
Ksea...vfr conditions with nearly clear skies. Northerly wind 5-12 kt. Chb