Area Forecast Discussion
Issued by NWS Portland, OR
Issued by NWS Portland, OR
719 FXUS66 KPQR 041732 AAA AFDPQR Area Forecast Discussion...UPDATE National Weather Service Portland OR 1032 AM PDT Fri Jul 4 2025 Updated Aviation discussion .SYNOPSIS...Onshore flow continues as a series of short wave, upper level troughs move over the area tonight through Friday. This will increase mixing and bring some moist air into the region. As a result of this pattern there is a slight chance (15-20%) of rain showers late tonight through Friday afternoon along the Cascades. Could see isolated thunderstorms over the ridges through the same time period. Warming and drying trends return for the weekend and persist through at least the middle of the upcoming week. && .SHORT TERM...Now through Monday...The previously advertised shortwave upper level troughs are moving over the area with the first one exiting the forecast area this morning. The second shortwave will pass over eastern Oregon later this morning. High resolution simulated reflectivity shows the next batch of showers arriving right around sunrise then exiting in the afternoon. Showers will remain right over the Cascades. There continues to be a slight chance (less than 20%) for thunderstorms over the highest elevations of the Willamette Natl Forest late this afternoon as the moisture meets peak daytime heating. Any thunder storms would be far and few between. Temperatures will be similar to Thursday with highs in the 70s throughout much of the area, and in the lower 60s along the coast. Skies will be mostly cloudy to the north and clear in the south. Saturday through Sunday will encounter a gradual warm up as high pressure builds, and a low aloft forms over northern California. This low has shifted further south than previous model runs which will reduce the intensity of the ridging pattern overall. Winds aloft will start to become north to northwesterly through the weekend. -Muessle .LONG TERM...Monday through Thursday...The upper level low will push inland over northern California on Monday which will enhance the developing ridge. There continues to be some disagreement in global models on where this low will park. If the deterministic GFS rings true, high temperatures on Monday- Wednesday will be cooler than if the deterministic ECMWF manifests. These scenarios can easily be observed in the 850 mb temperatures on Monday and Tuesday where they range from 16-20 deg C. Because of this, there remains a bit of uncertainty in the temperature forecast. Lets dive into the numbers of some of the warmest areas: On Monday, the 25th-75th percentile (most likely range) high temperatures range from 88-92 deg F in the Willamette Valley and a similar spread in the Upper Hood River Valley. The southern Willamette Valley around Eugene and Cottage Grove are trending warmer due to more of a northeasterly flow. On Tuesday, the 25th-75th percentile max temperatures range from 90-95 deg F in the Willamette Valley, and 91-98 deg F in Hood River. The coast will see very little variation each day. Overall, the spread isn`t too far to recognize that Monday and Tuesday will be hot with a Moderate HeatRisk for many areas. For those susceptible to heat, take precautions. Transitioning into Wednesday there has been a shift from previous forecasts. The low will move into Idaho increasing northwesterly flow and bringing in cooler air. 500 mb ensemble heights show one cluster with well above normal temperatures, two with near normal, and one with below normal. While the forecast once showed temperatures in the 90s for many valley locations, the NBM has backed off and has brought in highs into the 80s. With that said, there is still a 25% chance that highs will exceed 90 degrees F in the Willamette Valley. Will continue to monitor this as the pattern continues to resolve. Minimal change on Thursday. -Muessle && .AVIATION...An area of low pressure aloft moves over NW Oregon through this evening before shifting east of the Cascades by Saturday morning. Southeasterly flow aloft will maintain high cirrus through this afternoon from convection east of the Cascades today. Predominately VFR conditions expected inland through at 12z Sat. Marine stratus along the northern coast this morning will likely (60% chance) persist through much of today, with potential breaks in the clouds and possible (40% chance) improvement to VFR between 20-02z. Then, marine stratus expected to surge back onshore tonight with MVFR cigs after 02z Sat. PDX AND APPROACHES...VFR with broken high clouds expected through much of tonight. There is a 20-30% chance of MVFR stratus pushing up the Columbia River after 12z Saturday morning. Northwest winds expected to increase this afternoon to around 10 kt. /DH && .MARINE...Persistent surface high pressure offshore will support continued north to northwest winds across the waters. Diurnal gusts will reach 10-15 kt north of Cape Falcon and 15-20 kt from Cape Falcon to Florence both Friday and Saturday afternoon, easing to around 10 kt each night while seas continue at 3-6 ft through the weekend. Sunday into early next week, strengthening surface high pressure will see winds increase to 20-25 kt and seas build to 5-8 ft. -Picard && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && .MARINE...Persistent surface high pressure offshore will support continued north to northwest winds across the waters. Diurnal gusts will reach 10-15 kt north of Cape Falcon and 15-20 kt from Cape Falcon to Florence both Friday and Saturday afternoon, easing to around 10 kt each night while seas continue at 3-6 ft through the weekend. Sunday into early next week, strengthening surface high pressure will see winds increase to 20-25 kt and seas build to 5-8 ft. -Picard && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland