Area Forecast Discussion
Issued by NWS Portland, OR

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000 FXUS66 KPQR 250420 AAA AFDPQR Area Forecast Discussion...UPDATED National Weather Service Portland OR 919 PM PDT Sun Mar 24 2019 Updated Aviation and Marine sections .SYNOPSIS...High pressure briefly brings dry and mild weather today across southwest Washington and northwest Oregon. Weather turns cooler and wetter starting Monday as an upper-level trough settles over the northeastern Pacific and Pacific Northwest. && .SHORT TERM...Today through Wednesday...A shortwave ridge is passing over the area today, causing this clear sunny weather this afternoon, as well as the morning fog this morning. This will be short lived, however. A broad unstable air mass off the West Coast can be seen on satellite, and this is the broad upper-level trough that will be settling itself off the coast of Washington and Oregon through most of this week. This negatively tilted trough will bring the first shortwave up from the southwest late tonight into Monday. This means rain and some mountain snow at higher elevations. The warm front lifts north, spreading rain across the area Monday morning, with stratiform rain turning to showers behind the warm front as the unstable air mass moves into northwest Oregon and southwest Washington. Expect showers to stat to taper off Monday night, but won`t completely clear out on Tuesday. Any showers on Tuesday should stay confined mainly to the Coast and Coast Range. Offshore flow increases late Tuesday night into Wednesday as the low pressure center associated with the base of this upper-level trough moves closer to southwest Oregon and starts to approach from the southwest. Wednesday should stay mostly dry as the low stays south of our area, but Lane County may get clipped by some precipitation on the north side of the low. We will also see gusty east winds develop through the Columbia River Gorge on Wednesday as the pressure gradient increases across the Cascades. -McCoy .LONG TERM...Wednesday night through Sunday...Operational models and their ensembles suggest a large upper level trough over the eastern Pacific will continue cool and showery weather over the region during the second half of the work week. Expect shower activity to generally be at a minimum during the nighttime hours and to peak each day during the afternoon and early evening hours. Thursday definitely looks to be the wettest day in the extended forecast. While shower chances certainly appear to exist on Friday, coverage and intensity should be considerably less than Thursday. Both the EPS and GEFS ensemble means suggest shortwave ridging will shift across the region over the weekend, but the GEFS is admittedly a bit faster. As a result, went with a blend of the solutions, which trended PoPs and sky cover downward and temperatures upwards Saturday. PoPs were trended closer to climo on Sunday when timing differences in the shortwave ridge axis shifting across the region could result in additional wet weather moving back into the region. /Neuman && .AVIATION...VFR conditions with increasing high clouds this evening as an occluded front approaches from the southwest. The front will swing south to north across the region Monday. Expect rain to begin around 13-15Z Mon in the KONP-KEUG area then reach KAST-K4S2 by 18-20Z Mon. MVFR conditions are expected with the front, around 19-21Z KONP-KEUG and 22Z Mon-01z Tue KAST-KPDX. VFR should return after frontal passage, but may still see spots of MVFR cigs through Mon evening. KPDX AND APPROACHES...VFR expected to continue through 21Z Mon, then increasing chances for MVFR cigs as the occluded front moves through. Right now think best time for MVFR conditions will be around 00Z-03Z Tue time frame.East wind develops at the west end of the Gorge, including KTTD, tonight and strengthens overnight into Mon morning with gusts 25-35 kt. /mh Weishaar && .MARINE...Wind speeds primarily 15 kt or less through 07Z Mon. Another splitting front along 130W longitude this afternoon pivots northeast overnight and Mon morning. The bulk of the energy will be over the N California and S Oregon waters. There is the potential for southerly gusts to 25 kt over the southwest portion of PZZ275 and easterly gusts to 25 kt over the north waters late tonight through Mon morning. Due to the localized nature of these gusts om the easterly winds, will not issue an advisory. However with greater potential for south to southwest gusts to 25 kt Mon through Mon night over all zones, have issued an advisory. Wind speeds diminish later Mon evening and Tue through late week under generally weak surface gradients. Wave heights expected to get just above 10 ft late tonight through Mon night and will issue a small craft advisory for hazardous seas with the afternoon forecast. Although total wave heights may fluctuate at or just below 10 ft, the potential roughness due to mixed swell supports an advisory. Seas hover in the 6 to 8 foot range Tue through the end of next week. /mh Weishaar && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory for winds from 11 AM to 10 PM PDT Monday for Coastal Waters from Cape Shoalwater WA to Florence OR out 60 NM. Small Craft Advisory for hazardous seas from 5 AM Monday to 5 AM PDT Tuesday for Coastal Waters from Cape Shoalwater WA to Florence OR out 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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