Area Forecast Discussion
Issued by NWS Portland, OR

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000 FXUS66 KPQR 252153 AFDPQR Area Forecast Discussion National Weather Service Portland OR 253 PM PDT Thu Apr 25 2019 .SYNOPSIS...Increasing west or northwesterly winds this evening will bring more clouds overnight tonight and cooler temperatures on Friday. We will continue to see cooler temperatures with a chance for a few showers Saturday. Sunday we will see high pressure return briefly, bringing back milder weather and sunnier skies for Sunday, and we`ll see a mix of sun and clouds early next week with fairly seasonable temperatures. && .SHORT TERM...Today through Sunday...A thermal trough is currently positioned over the Willamette Valley and I-5 corridor in SW Washington. As this trough progresses eastward, expect increasing westerly or northwesterly winds across the area, and an increase in cloud cover overnight tonight. Friday, clouds should clear back out late in the morning but temperatures will stay cooler due to onshore winds helping to keep temperatures down. Saturday a stronger upper-level trough swings down into Washington, helping to bring a fairly decent surge of marine stratus inland Saturday morning.This could also bring a few showers to SW Washington and far NW Oregon. Mainly north of Salem. Sunday, a shortwave ridge will move across the area, clearing skies and bringing temperatures back up closer to seasonal normals. -McCoy .LONG TERM...Sunday night through Thursday...Models are in general agreement large scale northerly flow will gradually become more northwesterly through the week. This should result in an increase in precipitation chances later in the week. Nonetheless, no major storm systems appear on tap and it appears any rainfall would be light if it were to occur. Expect high temperatures to generally top out near average for the date next week despite the northerly flow pattern. In the meantime, it should be noted that models are in decent agreement a shortwave trough dropping southward across the area on Monday could bring a period of modest east winds Sunday night before possibly a few showers occur over the higher terrain on Monday or Monday night. /Neuman && .AVIATION...Upper level high pressure currently across the area will begin to shift eastward today. An upper level trough moving eastward across the region late tonight should strengthen onshore pressure gradients enough to result in MVFR cigs pushing onto the Oregon coast and up a portion of the Columbia River. There remains some uncertainty in really how extensive these clouds will be, but expect at least some periods of MVFR conditions along the coast around ~12-18z Friday that could possibly push inland into the Portland metro taf sites. KPDX AND APPROACHES...Expect predominantly VFR conditions through 00z Saturday as onshore gradually increases across western Oregon. An upper level trough moving eastward across the region late tonight may strengthen onshore pressure gradients enough to result in MVFR cigs pushing up the Columbia River and impacting the terminal for several hours around 15-18z Friday, but confidence in this scenario remains relatively low. /Neuman && .MARINE...Northerly winds across the waters are hitting Small Craft Advisory criteria of 25 kt in spots, but are arguably not widespread at this point. As a result, we will keep the current Small Craft Advisories for winds in effect despite the marginal nature of the current winds. Gusty winds should transition to mainly our outer waters overnight so the inner waters were removed from the advisory once this evening passes. Seas are currently running in the 5 to 7 ft range this afternoon. As winds increase across our waters and upstream overnight, expect seas to build back into the 7 to 9 ft range. Dominant wave periods will lower back down into the 7 to 9 second range, which should put at least a chunk of the waters into our steep and square seas criteria for several hours later tonight and early Friday. As a result, Small Craft Advisories for Hazardous Seas were issued for all but the inner waters off the central Oregon coast. High pressure over the northeast Pacific and thermal low pressure over northern California will more or less continue through the weekend and maintain the current weather pattern in place. This should bring additional rounds of gusty northerly winds that will generally peak each afternoon and evening across the waters, particularly off the central Oregon coast. Additional rounds of especially steep and hazardous square seas will likely develop again late Saturday afternoon and evening. As an upper level storm system settles over the Pacific Northwest early next week, winds and seas should subside across the waters during the early to middle part of next week. /Neuman && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory for winds until 10 AM PDT Friday for Waters from Cape Shoalwater WA to Florence OR from 10 to 60 NM. Small Craft Advisory for hazardous seas from 9 PM this evening to 9 PM PDT Friday for Waters from Cape Shoalwater WA to Cascade Head OR from 10 to 60 NM. Small Craft Advisory for winds until 9 PM PDT this evening for Coastal Waters from Cape Shoalwater WA to Florence OR out 10 NM. Small Craft Advisory for hazardous seas from 11 PM this evening to 4 PM PDT Friday for Coastal waters from Cape Shoalwater WA to Cascade Head OR out 10 NM-Waters from Cascade Head to Florence OR from 10 to 60 NM. && $$ Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland This discussion is for Northwest Oregon and Southwest Washington from the Cascade crest to 60 nautical miles offshore. This area is commonly referred to as the forecast area.

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