National Weather Service (2024)

Area Forecast Discussion
Issued by NWS Portland, OR

-- Highlight Changed Discussion --

-- Discussion containing changed information from previous version are highlighted. --150FXUS66 KPQR 281006AFDPQRArea Forecast DiscussionNational Weather Service Portland OR305 AM PDT Sun Jul 28 2024.SYNOPSIS...
-- Changed Discussion --
See Also
National Weather Service
Another pleasant day on tap across the region, withmorning clouds and afternoon sunshine, though clouds will last longeralong the coast. Front arrives late tonight into Monday, with coolerair and even spotty light rain or showers. By Wed, high pressurebuilds over the western USA, bringing warmer temperatures back westof the Cascades to start August.
-- End Changed Discussion --&&.DISCUSSION...
-- Changed Discussion --
(Today through Saturday)...Key Messages: 1) Increasing onshore flow tonight into Monday, with cooler temperatures and more clouds for Monday. 2) Areas of light precipitation on Monday into Tuesday, but little if any rain expected to south/east of Salem. 3) Warming trend for later this week, with inland highs into the lower to middle 90s.Not much change in the pattern today, as still under dominance ofnorthwest flow aloft. Upper dry low that was over the region onSaturday, and brought high level smoke and haze into the area, is nowwell east of the Cascades. As such, will see little if any smoke/hazealoft today, except closer to the fires in the Cascades. Main storytoday will be the wait for the breakup of the marine stratus. Suspectwill see inland stratus gradually break up and give way to sunnyskies by later this morning. But, likely to take longer for cloudsalong the coast to break apart. Will trend forecasts as such. Withthe clouds, will lean bit closer to MAV guidance, with inland highsin the upper 70s to lower 80s today.NOAA satellite imagery showing weather system over the Gulf ofAlaska this am. Models in fairly decent agreement in this systemdropping into southwest British Columbia and the Pac NW on Monday.As is approaches, will see increasing onshore flow, with marineclouds spreading across much of the interior tonight. Bit of lift asthe front approaches may be sufficient to produce areas of drizzlealong the coast and into the coastal mtns. Will add this to forecast.Models show the frontal system gradually pushing inland on Monday.With the strong onshore flow, and good deal of clouds, will seetemperatures much cooler for Monday. Will follow closer to MAVguidance, and keep inland temperatures in the lower to middle 70s,though could get closer to 80 far areas in far south WillametteValley, such as Eugene and Cottage Grove. This as the clouds may notbe as solid as they will be farther north around Portland and Salem.Big question still centered around whether or not this front willremain intact enough to produce precipitation. Does appear will berain at times along the coast, Coast Range and Willapa Hills, andeven as far inland as the south Washington Cascades/foothills. Bestestimates would put 0.10 to 0.20 of an inch for those areas, thoughcould get 0.25 to 0.35 inch across south Washington coast into theWillapa Hills. But, rest of the area looks to stay in few drops tomaybe as much as 0.05 inch. That said, suspect no rain to scattereddrops may be more the case for areas to south and east of Albany(which would be Linn and eastern Lane counties, right where some rainwould be helpful). Even though will not have much rain in that area,at least higher humidity and cooler temperatures will help.Another weakening system will arrive on Tuesday, but likely to seeeven less potential for rain. Will keep some mention of light rainshowers, but rainfall will be rather meager at best. Bit warmer, butstill looks that temperatures in the 70s inland (60s along coast).Will transition from cooler trough pattern of Monday/Tuesday to abuilding ridge for Wednesday and beyond. Models and their ensemblesare in good agreement showing high pressure ridge building across thewestern USA, enough such will push warmer air mass back into westernOregon/Washington for later this week. Overall, appears inlandtemperatures will be in the 80s to lower 90s on WED, then in lower tomiddle 90s for THU through SAT, and likely into early the followingweek. But, at this time, do not see any indication that this will beas hot as the early July heat. At least appears to have some reliefat night, with lows 55 to 65./Rockey
-- End Changed Discussion --&&.AVIATION...
-- Changed Discussion --
Marine stratus continues to affect the coast, withMVFR cigs expected at least through the rest of Sunday night. Highres model guidance is trending towards coastal marine stratusclearing to VFR around 22z, with 70% confidence, but with moreclouds streaming in from a system pushing in, there could be achance that coastal stratus never clears throughout Sunday,remaining MVFR for the duration of the TAF period.Inland, VFR conditions dominate throughout the period. Theexception is that marine stratus is pushing down the ColumbiaRiver, and a brief period of MVFR is expected at terminals nearthe Columbia (KPDX, KTTD) between 12z-18z. Model guidance putsconfidence at 80% for MVFR conditions during this period. Windswill generally remain light and northwesterly, with winds expectedto top out at 10 kt.It should be noted that wildfires burning in the Central ORCascades (east of KEUG) as well as within the Columbia River Gorge(east of KPDX and KTTD) could result in some slant rangevisibility issues at times as smoke/haze spreads east of theCascades. However, predominately west to east flow should mitigatethese impacts.PDX AND APPROACHES...VFR with mostly clear skies expected through12Z Sunday. MVFR returns with 80% confidence between 12-18z due tomarine stratus coming up the Columbia River. Predominantlynorthwest winds around 4-6 kt. /JLiu
-- End Changed Discussion --&&.MARINE...
-- Changed Discussion --
High pressure offshore weakens as an area of lowerpressure drops south from the Gulf of Alaska on Sunday. Northwestwinds around 10 throughout the period, shifting west to southweston Sunday. A weak front will move across the coastal waters onMonday with southerly winds peaking around 15-20 kt. Seas expectedto remain around 3 to 5 ft through early next week.
-- End Changed Discussion --&&.PQR WATCHES/WARNINGS/ADVISORIES...OR...None.WA...None.PZ...None.&&$$www.weather.gov/portlandInteract with us via social media:www.facebook.com/NWSPortlandx.com/NWSPortland