Area Forecast Discussion
Issued by NWS Portland, OR
Issued by NWS Portland, OR
052 FXUS66 KPQR 301658 AFDPQR Area Forecast Discussion National Weather Service Portland OR 958 AM PDT Thu May 30 2024 Updated aviation discussion. .SYNOPSIS..Warm and dry weather today with a slight warming trend through Friday. A weakening front pushes across the area on Saturday, which will result in a slight cooling trend but generally remaining dry. Then, a much wetter system associated with what remains of a tropical system is expected Sunday through Monday. Warm and dry weather returns for the middle of next week. && .SHORT TERM...Today through Saturday night...High pressure gradually builds across the region resulting in warm, dry weather along with northerly flow across the forecast area. This ridge of high pressure will be the dominant synoptic feature through Friday. Expect inland temperatures into the 70s today and upper 70s with some areas likely warming into the low 80s on Friday. Coastal locations and the Cascades will remain cooler with highs in the mid 50s to mid 60s. Saturday a pattern change is on deck as a broad upper level trough and associated surface, cold front brings slightly cooler temperatures as well as some very light precipitation to higher elevations. A larger, more robust system will start to impact the region Saturday night but the larger impacts are not expected until Sunday. /42 .LONG TERM...Sunday through Wednesday...On Sunday the remnants of Typhoon Ewiniar have been fully ingested into the models and are under the influence of the westerlies crossing the Pacific. The majority of ensemble guidance keeps us in slightly zonal flow or a slightly troughy as a shortwave trough can be seen in some models. As a result am leaning towards a cooler and wetter solution for Sunday and Monday. In addition to the trough, models are also showing the potential for a strong to moderate atmospheric river pointed towards the Pac NW. While that may sound ominous, we see many moderate to strong atmospheric rivers over the course of a winter season that bring only beneficial rains to the region. This appears most likely to do the same. Nonetheless, there are ~5% of the ensemble members that produce enough QPF at places like Astoria or Portland that we are not 100% out of the woods for potential impacts, particularly given many reservoirs are near their summertime full pool levels and do not have the flood control capacity that they do in the winter. At this time, storm total QPF values range from 1.00 to 1.25 inches within the Willamette Valley, 1.30-2.50 inches along the Coast and 1.25-3.50 inches for the Cascades. It will not be out of the question for higher elevations and area north of the Portland/Vancouver Metro area to receive accumulations towards the higher side of these ranges, with those areas that are north of the PDX/VUO areas and at a higher elevation could see upwards of 3.00 to 4.00 inches when all is said and done by Monday night. Tuesday and into the latter part of next week, cluster guidance does show a pattern change that will result in warmer and drier conditions with daytime highs in the 70s on Tuesday with temperatures likely climbing into the 80s by Thursday. /42 && .AVIATION...Prevailing VFR conditions across the area through the forecast period as high pressure builds bringing northerly winds aloft and at the surface. North winds increase after 18-21z Thursday with most locations around 10-12 kt. The southern Willamette Valley, including KEUG, will see winds 10-15 kt with gusts up to 25 kt, and coastal locations around and south of KTMK will see winds 15-20 kts with gusts to 30 kts. Winds decrease from 00-05Z Friday. PDX AND APPROACHES...Expect VFR conditions through the TAF period. North winds increasing to 10-12 kts through around 05Z Friday. Otherwise, expect light winds below 10 kts. -HEC && .MARINE...Weak high pressure will continue building across the northeast Pacific into Thursday, leading to increasing northerly winds across the waters. The strongest winds will be off the central coast of Oregon. For example, there is a >90% chance for wind gusts in excess of 20 kt across those waters this afternoon and tonight (most likely outcome for central/southern waters is gusts up to 25 kt). Most model guidance suggests winds will back off a bit for Friday, but there is still a high probability (>75% chance) wind gusts will peak above 20 kt across the waters off the central coast of Oregon. As a result, a Small Craft Advisory remains in effect for zones PZZ273, PZZ272, PZZ253, and PZZ252 Thursday into Friday morning. There is increasing agreement a more organized and stronger storm system will move into the northeast Pacific Sunday. This will bring a high probability (80-90% chance) for winds to turn southerly and wind gusts to at least climb into Small Craft Advisory thresholds of 25-30 kt. In addition, there is a 40-70% chance for at least a brief period of unusually late season Gale Force southerly wind gusts of 35 kt developing sometime late Sunday into Sunday night. Probabilities of this happening are highest off the far north Oregon and south Washington coasts than areas farther south towards Lane County. mh -TK/JH && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory from 3 PM this afternoon to 5 AM PDT Friday for PZZ252-272. Small Craft Advisory until 11 PM PDT Friday for PZZ253-273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland