075 FXUS66 KPQR 280328 AAA AFDPQR Area Forecast Discussion...Updated National Weather Service Portland OR 827 PM PDT Sat Apr 27 2024 .UPDATE...Only significant change this evening was to remove thunder from Sunday's forecast, as NBM thunder chances seem far too high given deterministic models showing a strong cap near 9-10 kft. Even if some updrafts over-achieve, the strong mid-level cap makes it hard to imagine cells growing tall enough to achieve the requisite charge separation for lightning. The coldest air aloft swings through quickly early Monday morning, but 500 mb temps may remain cold enough for deeper convection later in the day so will leave the thunder mentions in the forecast for Monday. Aviation discussion has also been updated below. Weagle && .SYNOPSIS...Front continues to bring rain this afternoon, transitioning into showery conditions that will continue through early next week. Wednesday and Thursday may have a break from showers, but expect a return of precipitation into next weekend. .SHORT TERM...(Today through Tuesday)...Fast moving front continues to move eastward, reaching the Cascades in the late afternoon. Rain will transition to showers behind the front, resulting in showers throughout the region by evening. Not much rain expected from this front today, with 0.25 to 0.50 inch (30-50% chance to exceed 0.5 inch) expected in the Coast Range and Cascades, northward of Newport and Mt Jefferson (Oregon Highway 20). Expect less rain across the coast and inland valleys, around 0.10 to 0.25 inch. Otherwise, similar 24 hour rainfall amounts for Monday and Tuesday, with Monday reaching farther south in the Coast Range and Cascades unlike today and Tuesday. Cooler air aloft will push inland tonight as the front passes, maintaining showers. This cooler air will steepen lapse rates and bring some instability through Tuesday for southwest Washington and northwest Oregon, as well as along the coast. As a result, any cloud breaks during the afternoon could provide enough warming to produce an isolated thunderstorm, most notably Monday through Tuesday, with less chances Sunday. Will keep a slight chance of isolated thunderstorms along the coast and for inland areas north of a Lincoln City to Salem line through Tuesday. Sunday night, another fast moving system will move southeastward into the region, bringing steady rain for a brief period before transitioning to showers. As this system passes by and brings cold air, snow levels of 4000-4500 feet will drop to 2000-2500 feet early Monday morning. As a result, 4-8 inches of 12 hour snowfall across the Cascades is expected through Monday morning. With chances around 50-60% of 12 hourly snowfall exceeding 6 inches Monday morning, as well as a late season drop of snow levels, a Winter Weather Advisory has been issued from 11PM Sunday to 11AM Monday for the Cascades. -JH .LONG TERM...(Wednesday through Friday)...Overall confidence is low to moderate as the pattern stays rather progressive into late next week. Deterministic and ensemble guidance continue to struggle to resolve the longitudinal placement of ridge/trough features going forward. Wednesday guidance has continued to trend a little drier nudging a larger scale upper-level low further north while a transient ridge glides over the region. Out of all the ensemble solutions available, this scenario is present in roughly 60% of them in addition to the latest deterministic ECMWF and GFS. Thursday and beyond, model uncertainty becomes truly significant with nearly a 50/50 split between maintaining a ridge feature overhead or bringing a potent trough into the region by Thursday and becoming most defined Friday. Current confidence in the forecast by Thursday is low. -JH/Schuldt && .AVIATION...A weak front will push across the area this evening with continued scattered showers bringing lowered visibilities and ceilings at times. Westerly flow aloft will persist through Sunday with southwesterly winds at the surface. Predominately IFR at the coast expected through at least 10-12Z, then gradual improvement to MVFR possible Sunday morning. Mix of MVFR and VFR inland tonight with CIGS bouncing between 2000-4000 ft through 08-10Z Sunday, then higher chances of becoming predominately VFR after 12Z Sunday. Notes: The ASOS at KTTD is only available via the dial in option. The AWOS at KMMV is still out of commission. There is no estimated time of repair. PDX AND APPROACHES...MVFR with cigs around 2500-3000 ft through 08Z Sunday, becoming predominately VFR 3500-4500 ft through Sunday evening. Light showers expected to persist through the period. Southwest winds around 10 kt for much of the period. /DH && .MARINE...Active weather is expected to continue this weekend into next week. A surface front is moving through the waters this afternoon and is expected to push inland by early evening. Winds remain elevated and southerly along and ahead of the front with gusts up to 30 kt, creating steep and choppy seas. A Small Craft Advisory remains in effect until this evening. Winds will shift westerly and decrease quickly behind the frontal passage this afternoon and evening with gusts below 20 kt. The next surface front will move through the waters late Sunday night into Monday morning. Winds will increase again with local gusts up to 20 to 25 kts. Seas will generally be 6 to 9 ft at 11 to 13 seconds through Monday. Another frontal system is forecast to move through the waters late Monday into Tuesday, producing elevated winds and seas in the low teens. -HEC && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory from 11 PM Sunday to 11 AM PDT Monday for ORZ126>128. WA...Winter Weather Advisory from 11 PM Sunday to 11 AM PDT Monday for WAZ211. PZ...None. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland