Area Forecast Discussion
Issued by NWS Portland, OR
Issued by NWS Portland, OR
552 FXUS66 KPQR 100354 AAA AFDPQR Area Forecast Discussion National Weather Service Portland OR 854 PM PDT Thu May 9 2024 .SYNOPSIS...A large eastward tilted ridge of high pressure will remain overhead through early this weekend, bringing dry weather and rapidly warming temperatures. Inland valley temperatures are expected to reach the mid to upper 80s Friday and Saturday - could see some record breaking highs in urban areas. Saturday night into Sunday, winds will shift from offshore to onshore flow, bringing cool yet still above seasonal norm temperatures into early next week. && .SHORT TERM...Now through Saturday...Ridge continues to build and tilt eastward into our region, maintaining clear skies. Today and tomorrow, as the ridge further tilts and moves inland, offshore flow will increase over the PNW. Temperatures begin to warm today (up to low 80s inland), with a rapid increase into tomorrow as offshore flow and ridge strengthening continues. As a result, Friday and Saturday are expected to be the warmest days this week. With these aforementioned favorable conditions, there is high confidence (90-95%) that inland valley temperatures will exceed 85 degrees F on Friday and Saturday. There is a 50-60% chance for temperatures to exceed 90 degrees F on Friday and Saturday, however it looks to be mostly focused on the Portland/Vancouver Metro and areas surrounding. Other inland urban areas, such as Salem/Corvallis/Eugene, have a 10-20% chance to exceed 90 degrees F on Friday and Saturday. There is more uncertainty for temperatures at the coast, as some model guidance is suggesting that the ridge will shift inland Saturday, leading to onshore flow moderating and cooling temperatures. As a result, expect upper 70s to low 80s Friday with a 50-70% chance to exceed 80 degrees F, decreasing to upper 60s to low 70s on Saturday. With such unseasonably warm temperatures for early Spring and coming out of cold weather, there is no doubt people will visit rivers, lakes, and the ocean for SW Washington and NW Oregon this weekend. It is important to remember that rivers and lakes remain dangerously cold with water temperatures mainly in the 40s. Such temperatures can easily cause cold water shock for those without proper cold water gear, resulting in an involuntary gasp of air that can lead to drowning. Be sure to bring a life vest and be extremely cautious around rivers, especially with snowmelt causing cold and swift currents! -JH .LONG TERM...Sunday through Wednesday...Widespread cooling is expected Sunday as the upper-level shortwave trough moves towards the coast, weakening the inverted thermal trough overhead and pushing it eastward. As this trough gets pushed eastward over the Cascades, widespread westerly onshore flow will return, bringing more widespread cooling (cooling to low 70s by Monday). The marine layer will likely remain too shallow for much in the way of morning cloudiness inland through Sunday, but the upper ridge may weaken enough for some low clouds to push into the inland valleys for a few hours Monday morning. Cannot rule out patchy light drizzle at the north coast Monday morning as well, especially given the weak upper-level shortwave progressing overhead providing some added support just north of our CWA. WPC cluster analysis is beginning to move more towards a solution favoring ridging re-developing by the middle of next week. Around 80% of ensemble members display relatively strong ridging by Wednesday next week, allowing temperatures to climb back into the low to mid 70s. Still around a 20% chance of another trough developing, which would bring more seasonable temperatures and light rain showers back to the area. -JH/Schuldt && .AVIATION...High pressure remains over the region, with dry northerly flow aloft and VFR conditions. North/Northeasterly winds through the TAF period across the airspace. PDX AND APPROACHES...High pressure will maintain VFR with mostly clear skies. && .MARINE...No big changes, as strong high pressure remains anchored offshore. Meanwhile, thermal trough will hug the south Oregon coast, building northward later today into tonight. With this pattern, will maintain gusty northerly winds on the waters, with gusts 20 to 25 kt today north of Cascade Head, and gusts 25 to 30 kt to the south. As thermal trough builds north later today into tonight, will see winds near shore relax back below 20 kt. Gusty winds will continue offshore well into overnight hours. Thermal trough will push the tighter pressure gradient farther offshore later tonight and Fri, as the thermal trough expands northward along the north Oregon coast. This will push the gusty north winds farther offshore, with lighter east to northeast winds on most of the coast waters, especially nearshore. But, with the thermal trough shifting back to the Coast Range Fri evening, will see wind flip back to north or northwest Fri evening. Seas mostly 5 to 8 ft today into tonight, with the higher seas more choppy as being dominated by the gusty winds. Seas stay at 5 to 6 ft into Sat. Thermal trough will shift much farther inland on Sat and Sun, with north to northwest winds returning to the coastal waters. Will not be as strong, but generally gusts 20 to 25 kt at times in the afternoons and early evenings. Seas mostly 6 to 8 ft. && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory from 5 AM to 9 AM PDT Friday for PZZ210. Small Craft Advisory until 11 PM PDT this evening for PZZ251>253-271. Small Craft Advisory until 5 AM PDT Friday for PZZ272-273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland