Area Forecast Discussion
Issued by NWS Portland, OR
Issued by NWS Portland, OR
845 FXUS66 KPQR 232116 AFDPQR Area Forecast Discussion National Weather Service Portland OR 215 PM PDT Sun Jun 23 2024 .SYNOPSIS...Dry on Monday as a transient shortwave ridge will bring a brief warmup across the region Monday and Tuesday. An upper level trough brings relatively cooler temperatures for the middle of the week along with periodic chances for rain showers. Warm and dry conditions return for next weekend. && .SHORT TERM...Tonight through Wednesday Night...Cooler and moister conditions today will give way to dry conditions Monday as an upper level ridge develops over the region through Tuesday. So, for the start of this week, look for daytime highs in the upper 70s to upper 80s for inland locations, mid 70s to mid 80s for the Cascades and low 60s to low 70s for the coast, with the warmest day expected on Tuesday. On Tuesday there remains around a 25% probability for daytime highs to creep into the low 90s and around a 5% probability to see daytime highs in the mid 90s for inland locations. As the upper level ridge develops, a weak, thermally induced low will result in increasing, northerly winds for the Willamette Valley, with gusts up to 20 mph possible on Monday. High resolution and deterministic models do show that the aforementioned upper level will quickly push eastward as the next system from the Gulf of Alaska brings another round of cooler, near seasonal temperatures for Wednesday with high temps in the mid to upper 70s for inland locations, low 60 to low 70s for the Cascades and mid 50s to mid 60s for the coast. This trough will also bring increasing chances for rain showers for the majority of the CWA. Overall timing of this precipitation is still under review, but at this time, conditions are looking to be moderate PoPs, but low QPF. Still, have moderate confidence in most locations seeing some measurable precipitation by early Thursday morning. It should be noted that the system on Wednesday is resulting in favorable flow pattern for thunderstorm development along the Cascades with around a 5-10% probability at this time. /42 && .LONG TERM...THURSDAY THROUGH SUNDAY...A shortwave trough continues pushing through the area on Thursday, bringing cooler temperatures and some light rainfall. Daytime highs will fall to the low 70s for inland areas. Rainfall looks light during daytime hours, with even high end scenarios (10% chance) showing rainfall around 0.25", and only in the northern areas (southeast WA). Rain should end around evening-time as the trough moves out of the area, after which the night looks dry and cool. Friday sees zonal flow, with no chance for precipitation. Temperatures begin to warm again, with a 30-40% chance of temperatures above 80 in the Willamette Valley. WPC Cluster Analysis shows continued trending towards some kind of ridging developing over the weekend, but not much certainty yet regarding timing or exact location. Expect warmer temperatures and generally drier conditions. /JLiu && .AVIATION...Moderate to strong onshore flow continues, with mostly VFR (CIGS 3500 to 5000 ft). Clouds are more solid over the coastal mtns and west slopes of the Cascades, thanks to decent upslope flow. Clouds will gradually break apart through rest of today into this evening. As low level flow turns north to northeasterly tonight, clouds will clear, mainly on coast from Tillamook southward, and inland to south and east of Portland. Brief morning clouds on Monday am on coast from Tillamook northward and inland from Portland northward through Cowlitz Valley. These should give way to mostly clear skies by 17Z. PDX AND APPROACHES...VFR with broken clouds at 4500 to 5000 ft into early evening, but these will gradually give way to mostly clear skies by 03Z. While suspect will remain VFR through Mon, there is a 40% chance will broken MVFR (CIGS 2500 to 3000 ft) reform 10Z to 16Z, mainly to east and north of PDX. /Rockey && .MARINE...High pressure will expand across the waters through Monday, while thermal low pressure strengthens over far northwest Calif into far sw Oregon. This will tighten the northerly pressure gradient on Monday, enough to allow north winds to pop 20 to 25 kt gusts Mon afternoon into Mon evening. But, this mainly over the waters off the west central Oregon coast. As such, will put up Small Craft Advisory for said conditions. Otherwise, not much change in the pattern for early this week, as high pressure remains anchored off the Pac NW. Low pressure will arrive mid-week, with a weakening front arriving. This will bring return of unsettled weather, with return of west to southwest winds, but still mostly 15 kt or less. /Rockey && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory from 2 PM Monday to midnight PDT Monday night for PZZ253-273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland