Moisture associated with a system moving into northern california will move into the area today into thursday morning. Temperatures will be cool enough that precipitation late tonight and early thursday morning may fall as snow, or a rain- snow mix, on higher hills. Showers with low snow levels will continue for the rest of thursday into friday night as an upper low remains in the area. A brief dry spell over the weekend before the next system arrives later on monday into tuesday.
Satellite imagery shows moisture spreading north from a system moving into northern california only as far as southern oregon early this morning. Just some high clouds over western washington at 3 am/11z. Wide variety of temperatures with the cooler locations with little wind in the mid 20s and areas exposed to the northerly breeze in the mid 30s.
Moisture spreading up from the south will reach the area this afternoon with precipitation spreading from south to north over about the eastern 2/3rds of western washington. Before the moisture gets here just some high clouds this morning which could lead to a nice sunrise. Precipitation will be in the form of rain this afternoon. The increasing cloud cover will put a cap on the afternoon high temperatures with most places in the mid 40s.
Moisture thinning out over the area tonight into early thursday morning as the moisture continues to move north into british columbia. Surface gradients turning onshore with model koth-ksea gradients up to around plus 4 mb and kolm-kbli around 1.5 millibars by 12z thursday. Southwesterly winds increasing in the lower levels as well with the winds from just above the surface to 850 mb southwesterly 15 to 20 knots by 12z thursday. This will prevent the snow level dropping down to the surface. In general the snow level will be around 500 feet after midnight but as the snow level drops overnight the precipitation will be decreasing significantly so the chances for much accumulating snow overnight are not very high. A convergence zone could form near the east entrance to the strait of juan de fuca overnight but the zone will be weak and precipitation amounts with it will be light. Lows will be in the 30s.
Upper level low remaining over vancouver island on thursday with showers rotating around the low moving through western washington. Snow levels around 500 feet in the morning will rise to around 1000 feet in the afternoon. Air mass destabilizing a little in the afternoon creating more shower activity than the morning hours. Highs once again will be in the lower to mid 40s.
What is left of the upper level low drifting down over the area thursday night into friday keeping at least a chance of showers in the forecast. Snow levels will drop back down to around 500 feet late thursday night and early friday morning but the precipitation will be spotty and light. After morning lows in the upper 20s to mid 30s highs will be in the 40s.
Models in pretty good agreement over the weekend. Drying trend across western washington as what is left of the upper level low kicks out to the east and the flow aloft becomes north northeasterly. Surface gradients turn back offshore but not strong enough for any outflow winds over whatcom county. Gfs has a few lingering showers around saturday morning so have left a slight chance of showers in the forecast. Highs warming a little both days with a few low 50s both saturday and sunday.
Some differences in the model solutions remain on monday but even the faster timing of the gfs with the next system keeps precipitation west of puget sound during the day on monday. Have added some pops to the forecast for west of puget sound. System moving through the area monday night into tuesday. While this system will be on the cool side for march it will be warmer than what we have seen the last couple of weeks with snow levels up around 1500 feet. Upper level trough following the system later on tuesday with highs mostly in the 40s. Felton
River flooding is not expected for the next 7 days.
Wa...none. Pz...small craft advisory from 4 pm this afternoon to 4 am pst friday for coastal waters from cape flattery to james island 10 to 60 nm-coastal waters from james island to point grenville 10 to 60 nm-coastal waters from point grenville to cape shoalwater 10 to 60 nm.
small craft advisory from midnight tonight to 4 pm pst thursday for coastal waters from cape flattery to james island out 10 nm-west entrance u.s. Waters strait of juan de fuca.
small craft advisory from 4 pm this afternoon to 4 am pst thursday for central u.s. Waters strait of juan de fuca- east entrance u.s. Waters strait of juan de fuca-northern inland waters including the san juan islands.
Light offshore flow will become moderately onshore tonight as a surface trough along the coast shifts into the interior of western washington. Advisory strength winds are expected over the outer coastal waters and portions of the inland waters. Onshore flow will continue thursday then weaken friday as a surface ridge builds over the waters. Weak offshore flow is likely to return over the weekend as ridging builds east of the cascades. 27
Southwesterly flow continues aloft with an upper level low west of vancouver island. Light northerly sfc winds through the morning will transition to southerly during the afternoon. High clouds continue to increase through morning, lowering into the afternoon as a system pushes into oregon. Cigs generally vfr with mvfr cigs possible as precipitation moves into the area after 20z. precip mainly in the form of rain, developing around kolm by 19z, pushing north during the afternoon. Vfr/mvfr cigs into tonight through early thursday. Winds generally under 10 knots.
Ksea...vfr cigs to continue through mid-morning. Lowering cigs around midday with mvfr cigs by afternoon, continuing at times through tonight. Precip mainly in the form of rain. Northerly winds through late afternoon (23z-01z) before transitioning southerly. winds 7-12 knots this morning, becoming 4-10 knots during the afternoon. Jd