Area Forecast Discussion
Issued by NWS Portland, OR

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000 FXUS66 KPQR 231113 AFDPQR Area Forecast Discussion National Weather Service Portland OR 300 AM PST Wed Jan 23 2019 .SYNOPSIS...After some lingering light rain and drizzle today, high pressure building over the northeast Pacific will likely bring dry weather and mild temperatures into at least early next week. && .SHORT TERM...Today through Saturday...A shortwave trough moving across Washington state pushed a frontal rain band southeastward across the area overnight. This band of steadier rain has shifted southward into southwest Oregon where it will stall and dissipate in place over the next 12-24 hours. Farther north, very gentle isentropic lift along the 285K-290K surfaces will lead to areas of drizzle and light rain through at least this morning across the area. Thereafter, shortwave ridging slowly shifts towards the region, which should result in the area beginning to dry out late this afternoon and evening. Low clouds may be stubborn to dissipate entirely tonight, though. In areas that clear, areas of fog should develop quickly. Fog and low clouds should gradually clear Thursday and give way to high temperatures near to slightly above average for the date. Models then suggest a shortwave trough dropping southeastward across the Inland Northwest will likely bring a brief increase in clouds and winds to the higher terrain late Thursday. There is an outside chance of light rain across our far northern zones, but the bulk of the area will almost certainly remain dry. Shortwave ridging will then become more solidly entrenched across the Pacific Northwest Friday and Saturday. This should result in areas of valley morning fog and mild temperatures. Weak offshore flow on Saturday may result in the central Oregon coast and portions of the Coast Range and Cascade foothills warming well into the 60s on Saturday. Thinking morning low clouds and fog will keep temperatures from warming too much in the Willamette Valley, though. /Neuman .LONG TERM...Saturday night through Wednesday...Operational models and their ensembles are in good agreement a large ridge of high pressure will more or less continue across the northeast Pacific into early next week. This will produce a multi-day stretch of dry weather, initially mild temperatures, and areas of late night and morning valley fog. It should be noted that models are also coming into agreement a shortwave trough diving southward out of Canada will push cooler air into the Columbia Basin and turn the flow more solidly offshore Sunday night into Monday. At this point, models suggest a modest downslope wind event, but will need to monitor this in the coming days. Otherwise, operational models suggest it will remain dry through the middle of next week, but there are some ensemble members that suggest rain chances begin to increase. As a result, kept slight chance PoPs in the forecast for late Tuesday and Wednesday to account for the uncertainty. /Neuman && .AVIATION...A cold front moving onshore brought a band of steadier precipitation and gusty southerly winds through the region overnight. The rain band has now moved south into Lane County and will dissipate over the next couple of hours. Winds will also gradually subside over the next few hours. Expect widespread light rain to continue this morning, then become increasingly confined to the higher terrain this afternoon and tonight. The low level moisture that accompanied this front has brought steadily deteriorating conditions this morning, with current observations showing mainly IFR at the coast, with predominantly MVFR over the interior. Expect little change through the day, although cigs may lift a bit in the afternoon. The latest model soundings show that the low stratus may just persist through tonight. If any clearing does occur late today or tonight, it would almost certainly result in fog formation overnight. KPDX AND APPROACHES...Expect MVFR cigs through most of today. Light rain and gusty southerly winds should gradually decrease through the day. MVFR may end up persisting through tonight. However, if any scattering in the clouds occurs this evening, there is potential for IFR fog overnight into Thu morning. Pyle && .MARINE...A cold front moving through the waters will push onshore this morning. There are still some gusts around 35 kt being reported over the northern waters, so will hold on to the existing Gale Warning through 4 AM. Winds will subside fairly quickly behind the front and should be westerly at 15 kt or less by early this afternoon. High pressure will then begin to build over the waters tonight and remain in place through the rest of the week and much of the weekend. This will result in light winds for the next few days. Winds will become northerly and potentially gusty later in the weekend and into early next week. Seas will remain in the low to mid teens through most of tonight. A longer period swell will be arriving this morning that should push dominant periods to around 14 to 15 seconds. Seas will subside gradually tonight and should be back below 10 ft sometime on Thu morning. Then seas will remain in the 7 to 8 ft range through the rest of the week and into next weekend. Pyle && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Gale Warning until 4 AM PST early this morning for Coastal Waters from Cape Shoalwater WA to Cascade Head OR out 60 NM. Small Craft Advisory for winds until 7 AM PST this morning for Coastal Waters from Cascade Head OR to Florence OR out 60 NM. Small Craft Advisory for hazardous seas until 4 PM PST this afternoon for Coastal Waters from Cascade Head OR to Florence OR out 60 NM. Small Craft Advisory for Rough Columbia River Bar until 10 PM PST this evening. && $$ 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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