114 FXUS66 KPQR 061640 AAA AFDPQR Area Forecast Discussion National Weather Service Portland OR 939 AM PDT Mon Sep 6 2021 .SYNOPSIS...Warm and dry weather will continue early in the week as upper level ridging builds across the Pacific Northwest. A series of weak storm systems will bring cooler temperatures and a chance for some light rain beginning Tuesday night. && .SHORT TERM...Today through Wednesday...Water vapor satellite imagery early this morning shows a shortwave ridge over the Great Basin with a cutoff upper level low pressure off the California coast. In addition, a large shortwave trough is located south of the Gulf of Alaska. Models are in good agreement the aforementioned shortwave ridge over the Great Basin will build northwestward into the Pacific Northwest over the next 24 hours. This will result in temperatures warming well into the 80s this afternoon for inland valleys with temperatures warming further Tuesday and likely topping out near 90F on Tuesday. Onshore flow should keep the coast cool. Models remain in good agreement the cutoff upper level low pressure off the California coast will eject northeastward across the Pacific Northwest Tuesday night. This should result in clouds and some elevated convection pushing from southwest to northeast across the area Tuesday night. Between any showers moving at a fairly rapid clip and drier air below 700mb, rainfall amounts should generally remain light. In addition, the best PVA, jet support and height falls has shifted slightly farther north and west in the models over the past 24 hours. As a result, the best chances for any showers growing into thunderstorms may actually be offshore vs. over southwest Washington and northwest Oregon Tuesday night. Nonetheless, there is still enough elevated MUCAPE in the NAM that have opted to maintain a mention of thunder across our northern zones Tuesday night. This will likely be expanded or contracted in the next 12-24 hours as we enter the CAM's time domain. The aforementioned shortwave trough currently south of the Gulf of Alaska will continue to slowly slide eastward towards the Pacific Northwest Wednesday. It appears it will likely remain far enough offshore that high temperatures will once again be able to climb into the 80s for the interior valleys Wednesday while the coast remains considerably cooler. /Neuman && .LONG TERM...Wednesday night through Sunday...Models and their ensembles are in broad agreement shortwave troughing over the eastern Pacific midweek will transition across the Pacific Northwest Thursday through Sunday. However, there are enough differences between various models and their ensembles on exactly how it will evolve that there remains quite a bit of uncertainty on when exactly inland high temperatures will cool from the 80s into the 70s. A weak front associated with the aforementioned shortwave trough will likely push towards the region late Thursday or Friday, but rain chances in any given 6 hour period remain rather small during this time period and mentionable rain is largely confined to just our far north coast at this time. An additional front that will develop as a shortwave trough currently near the Kamchatka Peninsula moves eastward late in the week will push towards the region over the weekend. Again, there are enough differences in the models and their ensembles that NBM PoPs remain generally below mentionable thresholds at this point for the weekend across most of the CWA. The bad news bottom line is that there is very little sign of a major soaking rain in the next 7 days. The good news bottom line is that there is very little sign of a major east wind event in the next 7 days. /Neuman && .AVIATION...Low level stratus is breaking up along the coast faster than expected and should reach stable VFR criteria by 18Z. Ridging to the southwest will keep all inland sites in VFR criteria throughout the day with gusty northerly winds in the afternoon. Strongest winds will be in the central and southern Willamette Valley as well as along the central Oregon coast with wind gusts around 20 kt. Winds will weaken overnight with scattered high clouds inland. The 12Z HREF shows LIFR ceilings around 003 ft advecting south along the SW Washington coast around 06Z Tues and making its way to KONP by 10Z. According to the HREF there is a 50% chance that KAST will drop down to 1/4 SM by 12Z with the LAMP guidance in agreement. Expect LIFR conditions along the coast through the night and into the end of the TAF period. For detailed regional Pac NW aviation weather information, go online to: https://weather.gov/zse KPDX AND APPROACHES...VFR conditions are expected over the TAF period. Expect northerly winds in the afternoon around 10 kt weakening into the overnight hours. -BMuhlestein && .MARINE...Current observations over the coastal waters are weaker than expected this morning with gusts at buoy 089 around 4 kt and buoy 050 around 12 kt as of 9 AM this morning. Have changed the timing of the Small Craft Advisory to start at 2 PM this afternoon as afternoon winds are still expected to meet criteria. Seas have been hovering around the 7 ft range with a period of 10 to 11 seconds. Winds expected to ease to 10-15 kt with gusts up to 20 kt through Tuesday. Winds will ease further becoming onshore by Wednesday. This wind shift is due to a weak low that appears to be making its way north from the offshore waters west of California. Models are showing the lows strong southwesterly winds staying west of 60 nm but it could shift east bringing strong winds Thursday. Seas will build slightly from the passing of the low with the potential for seas to be around 10 ft. At this time little impact is expected. -BMuhlestein && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory from 2 PM this afternoon to 7 AM PDT Tuesday for coastal waters from Cape Shoalwater WA to Florence OR from 10 to 60 NM. Small Craft Advisory from 2 PM this afternoon to 2 AM PDT Tuesday for coastal waters from Cape Shoalwater WA to Florence OR out 10 NM. && && $$