textproduct: Portland

SYNOPSIS

A warming and drying trend is underway across southwest Washington and northwest Oregon as high pressure gradually builds inland. Temperatures will climb through the weekend and into early next week, with inland highs reaching the upper 80s to mid 90s Monday, Tuesday and Wednesday. Hot and dry weather is likely to persist through at least the middle of next week.

LONG TERM...Monday through Thursday

Ensemble guidance remains in strong agreement that the ridge will reach its greatest amplitude early next week, supporting the warmest temperatures of the forecast period. However, uncertainty for Tuesday and Wednesday have increased significantly. While Monday remains rather unscathed as daytime highs are still expected to be in the upper 80s to low 90s. The spread between the models and there ensembles really start to show come Tuesday and Wednesday. Starting at the top with the 500 mb WPC Clusters, Tuesday the clusters are split in this manner: Cluster 1 (30%), Cluster 2 and 3 (26%) and Cluster 4 (18%). Visually, there is very little difference between the clusters, however the biggest differences between the clusters is the location of an upper level low off the coast of California and the strength of The Great Basin High, with said clusters looking to favor The Great Basin system rather than the Pacific Low. Wednesday, looks even more uncertain with the Cluster percentage spread of 28%, 28%, 25% and 19%. In addition to the 500 mb spread, some ensemble models are bringing in some monsoonal moisture into the forecast Tuesday and Wednesday, which if that occurs, it could easily impact daytime highs. Said monsoonal moisture will be driven by the eastern Pacific low. The NBM is picking up on this potential as the high temperature spread for Tuesday and Wednesday has increased across the CWA with most areas showing an 8-12 degree F spread.

Current probabilistic guidance indicates a 25-45% chance of reaching 90 degrees across much of the interior lowlands on Monday afternoon, then a 50-75% chance on Tuesday and Wednesday afternoon. Additionally, there is a 20-40% chance of temperatures reaching 95 degrees on Tuesday and Wednesday, highest across the traditionally warmer valleys. While these temperatures are typical for mid to late July, several consecutive warm afternoons combined with limited overnight cooling will result in pockets of Moderate HeatRisk, particularly for those without adequate cooling or prolonged outdoor exposure. It should be noted that on Tuesday and Wednesday there is around a 15% chance for daytime highs around 98 degrees F. So, there is also the potential Major HeatRisk on Tuesday (15-30%) and Wednesday (10-25%). As Thursday rolls around, conditions looks to cool by a few degrees as a broad low (the low mentioned on Tuesday and Wednesday) looks to push eastward into the Pac NW. /42

AVIATION

Southwesterly flow aloft continues through 00Z Sunday as a slow-moving low pressure system lingers near Vancouver Island. Expect predominately VFR flight conditions through the TAF period. However, there is a 20-40% chance for ceilings around 2000-3000 ft over the Portland metro and northern Willamette Valley between 12-17Z Saturday, except around a 50% chance at KTTD. LIFR to IFR ceilings are expected to develop at the coast between 06-10Z Saturday (60-80% chance).

KPDX AND APPROACHES...Expect mainly VFR flight conditions through 18Z Saturday. However, there is a 20-40% chance for a brief period of MVFR ceilings around 2000-3000 ft between 12-17Z Saturday. Confidence in MVFR ceilings developing Saturday morning is not high enough to reflect in the TAF at this time. Light northwest winds are expected through Friday evening around 5-8 kt. -23

MARINE

A typical summertime pattern will remain in place through early next week with persistent north to northwest winds over the coastal waters. Winds will be strongest during the afternoon and evening hours each day, especially this weekend to the south of Cape Falcon. Expect wind gusts up to 25 kt over the central and southern waters this weekend, with seas becoming steep on Sunday due to a fresh northwest swell around 6-7 ft at 7-8 seconds. Between the increasing winds and steepening seas, conditions will become hazardous to small craft.

Steep seas early Monday are expected to become less steep through the day as northerly winds decrease. Seas and winds decrease even more on Tuesday, bringing benign conditions. -23

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory from 5 PM Saturday to 11 AM PDT Sunday for PZZ252-272-273.

Small Craft Advisory from 11 AM Saturday to 11 AM PDT Sunday for PZZ253.