Marine Weather and Tide Forecast for Seneca, OR
December 5, 2023 9:48 PM MST (04:48 UTC)
Sunrise 8:02AM Sunset 5:11PM Moonrise 12:27AM Moonset 1:50PM
Area Discussion for - Pendleton, OR
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FXUS66 KPDT 052217 AFDPDT
Area Forecast Discussion National Weather Service Pendleton OR 217 PM PST Tue Dec 5 2023
SHORT TERM
Today through Thursday...An atmospheric river continues to deliver a glancing blow to the northwest sector of our forecast area, providing for rain across the Washington Cascades and spilling over into the east slopes. Radar also shows some light returns across the WA Basin, however the bulk of meaningful rainfall continues to be in the Cascades. As this AR shifts eastward heading into Wednesday, the forecast area will see more widespread rainfall, breezy conditions, followed by a shift towards a colder pattern late Wednesday heading into Thursday. Snow levels remain very elevated at above 8000 ft this afternoon, but as the AR departs eastward and the flow aloft shifts more NW, snow levels will drop down toward the 2500-3500 ft range that is more typical of this time of year, and our mountain passes will start to see chances for snow rather than rain heading towards the end of the work week.
As far as ongoing concerns, a Wind Advisory remains in effect for the Ladd/Pyles Canyons until this evening. NAM pressure gradient forecasts the Meacham-Baker City gradient to remain elevated enough to support gusty conditions, however gusts for the Canyons have been right at or below advisory criteria most of the day. Will likely let the advisory run its course, even as pressure gradient forecasts suggest elevated winds through most of Wednesday. Winds will pick up across the forecast area Wednesday and Thursday as the AR moves eastward and we start to see the aforementioned shift in the upper- level winds, but no wind headlines are anticipated. These winds should also help scourge out the valley fog that is being reported this afternoon in the Kittitas Valley as well as in pockets of the Columbia River Gorge.
There had previously been hydro concerns given the heavy mountain snow we saw last week combined with the rapid rise in snow levels and rain-on-snow going on this week, but based on AHPS it looks as though only the Naches will eclipse bankfull, if any site does, limiting flooding concerns for our neck of the woods in contrast to the west side. Once this AR moves out of the PacNW, this next round of precip under colder weather may bring accumulating snow to our mountain passes, but thanks to this recent warmth, snow will initially struggle to accumulate. NBM probabilistic guidance does suggest around a 75% chance of 6 inches of snow falling at Snoqualmie Pass Thursday through Friday morning, however given the recent warmth, am only expecting a fraction of that even as snow levels crash over the coming days. Evans/74
LONG TERM
Friday through Tuesday...Overall the extended period begins in an active and progressive weather pattern as one trough exits the region on Friday quickly followed by another weather disturbance bringing low elevation rain and mountain snow Saturday into Sunday. As a result, the primary impact through the weekend will be focused on mountain snowfall over the weekend.
Otherwise, model uncertainty increases Sunday onward with the majority of guidance suggesting the development of at least some weak ridging feature towards Tuesday/Wednesday of next week.
Temperatures rise near to above normal by Sunday before falling back below normal early next week.
Both deterministic and ensemble guidance begin the period in good agreement as an upper-level trough which had passed through the Pacific Northwest the day prior begins to exit the region followed by a weak transitory ridge of high pressure approaching the coastline. Within the lingering northwesterly flow on Friday, models favor the continuation of post-frontal shower activity primarily pinned to the higher terrain features of the Cascades and eastern mountains – dry weather is likely for the lower Columbia Basin. The ridge axis off the coast then moves over the area Friday night into early Saturday morning while weakening in response to a substantial upper level shortwave slated to arrive Saturday. While snow levels start between roughly 2000-2500ft, strong warm air advection accompanying this disturbance facilities a rise to 4000-6000 feet north-to-south by the evening hours. The shortwave's axis passes overhead late Saturday and quickly exits to our east, allowing precipitation chances to taper off at lower elevations Sunday.
Still, snowfall accumulation for many of the pass locations through this event appears decent with the NBM projecting a 60-80% chance for the Cascade Passes to meet or exceed 8 inches of snowfall Saturday through Sunday – similar probabilities for the crests of the northern Blue Mountains and Wallowas as well.
Headed through early next week we’ll see the return of WNW flow aloft while snow levels drop back down to between 2000-4500 feet north-to-south on Monday and chances(20-40%) for light precipitation continue over the mountainous terrain. Some of the deterministic models, particularly the GFS and ECMWF, show a compact upper-level shortwave passing into Oregon either late Sunday or Monday which, should it occur, would increase precipitation and mountain snowfall concerns however this feature is largely “washed-out” when looking at ensembles leading to elevated uncertainty during this period.
Come Tuesday ensemble guidance continues to depict the development of a ridge over the far eastern Pacific leading to a trend towards drier conditions. That said, there’s still noteworthy uncertainty as to the longitudinal placement and amplification of this feature with only 37% of the total ensemble members favoring completely dry conditions for the region. The other 63% of ensemble members either have the ridge placed too far west and/or not amplified enough to prevent precipitation chances(15-30%) from persisting mainly over the higher terrain features. Schuldt/99
AVIATION
00Z TAFS...Conditions remain variable at YKM/DLS tonight through Wednesday with waves of light rain facilitating primarily MVFR to IFR visibility and ceilings. Other sites see VFR conditions hold in place, even if occasional light rain bleeds into PSC and ALW at times. Later on Wednesday this weather disturbance which has been mainly lurking NW finally pushes through the rest of the region with conditions trending to MVFR for ALW, PDT, and RDM/BDN late in the period although confidence the exact timing on this degradation is only moderate. Breezy winds at RDM quickly decrease this evening with winds remaining below 10-15 knots at all sites through the rest of the period. 99
PRELIMINARY POINT TEMPS/POPS
PDT 47 55 40 46 / 20 70 90 60 ALW 49 55 42 46 / 30 70 90 60 PSC 47 54 43 49 / 40 80 80 30 YKM 43 49 33 45 / 60 90 70 30 HRI 47 55 42 50 / 30 80 80 40 ELN 40 44 32 42 / 70 80 60 30 RDM 44 50 31 42 / 20 80 70 60 LGD 41 48 34 44 / 10 50 100 80 GCD 44 54 33 44 / 10 60 90 80 DLS 50 53 42 47 / 70 90 90 70
PDT WATCHES/WARNINGS/ADVISORIES
OR...Wind Advisory until 7 PM PST this evening for ORZ049.
WA...None.
Area Forecast Discussion National Weather Service Pendleton OR 217 PM PST Tue Dec 5 2023
SHORT TERM
Today through Thursday...An atmospheric river continues to deliver a glancing blow to the northwest sector of our forecast area, providing for rain across the Washington Cascades and spilling over into the east slopes. Radar also shows some light returns across the WA Basin, however the bulk of meaningful rainfall continues to be in the Cascades. As this AR shifts eastward heading into Wednesday, the forecast area will see more widespread rainfall, breezy conditions, followed by a shift towards a colder pattern late Wednesday heading into Thursday. Snow levels remain very elevated at above 8000 ft this afternoon, but as the AR departs eastward and the flow aloft shifts more NW, snow levels will drop down toward the 2500-3500 ft range that is more typical of this time of year, and our mountain passes will start to see chances for snow rather than rain heading towards the end of the work week.
As far as ongoing concerns, a Wind Advisory remains in effect for the Ladd/Pyles Canyons until this evening. NAM pressure gradient forecasts the Meacham-Baker City gradient to remain elevated enough to support gusty conditions, however gusts for the Canyons have been right at or below advisory criteria most of the day. Will likely let the advisory run its course, even as pressure gradient forecasts suggest elevated winds through most of Wednesday. Winds will pick up across the forecast area Wednesday and Thursday as the AR moves eastward and we start to see the aforementioned shift in the upper- level winds, but no wind headlines are anticipated. These winds should also help scourge out the valley fog that is being reported this afternoon in the Kittitas Valley as well as in pockets of the Columbia River Gorge.
There had previously been hydro concerns given the heavy mountain snow we saw last week combined with the rapid rise in snow levels and rain-on-snow going on this week, but based on AHPS it looks as though only the Naches will eclipse bankfull, if any site does, limiting flooding concerns for our neck of the woods in contrast to the west side. Once this AR moves out of the PacNW, this next round of precip under colder weather may bring accumulating snow to our mountain passes, but thanks to this recent warmth, snow will initially struggle to accumulate. NBM probabilistic guidance does suggest around a 75% chance of 6 inches of snow falling at Snoqualmie Pass Thursday through Friday morning, however given the recent warmth, am only expecting a fraction of that even as snow levels crash over the coming days. Evans/74
LONG TERM
Friday through Tuesday...Overall the extended period begins in an active and progressive weather pattern as one trough exits the region on Friday quickly followed by another weather disturbance bringing low elevation rain and mountain snow Saturday into Sunday. As a result, the primary impact through the weekend will be focused on mountain snowfall over the weekend.
Otherwise, model uncertainty increases Sunday onward with the majority of guidance suggesting the development of at least some weak ridging feature towards Tuesday/Wednesday of next week.
Temperatures rise near to above normal by Sunday before falling back below normal early next week.
Both deterministic and ensemble guidance begin the period in good agreement as an upper-level trough which had passed through the Pacific Northwest the day prior begins to exit the region followed by a weak transitory ridge of high pressure approaching the coastline. Within the lingering northwesterly flow on Friday, models favor the continuation of post-frontal shower activity primarily pinned to the higher terrain features of the Cascades and eastern mountains – dry weather is likely for the lower Columbia Basin. The ridge axis off the coast then moves over the area Friday night into early Saturday morning while weakening in response to a substantial upper level shortwave slated to arrive Saturday. While snow levels start between roughly 2000-2500ft, strong warm air advection accompanying this disturbance facilities a rise to 4000-6000 feet north-to-south by the evening hours. The shortwave's axis passes overhead late Saturday and quickly exits to our east, allowing precipitation chances to taper off at lower elevations Sunday.
Still, snowfall accumulation for many of the pass locations through this event appears decent with the NBM projecting a 60-80% chance for the Cascade Passes to meet or exceed 8 inches of snowfall Saturday through Sunday – similar probabilities for the crests of the northern Blue Mountains and Wallowas as well.
Headed through early next week we’ll see the return of WNW flow aloft while snow levels drop back down to between 2000-4500 feet north-to-south on Monday and chances(20-40%) for light precipitation continue over the mountainous terrain. Some of the deterministic models, particularly the GFS and ECMWF, show a compact upper-level shortwave passing into Oregon either late Sunday or Monday which, should it occur, would increase precipitation and mountain snowfall concerns however this feature is largely “washed-out” when looking at ensembles leading to elevated uncertainty during this period.
Come Tuesday ensemble guidance continues to depict the development of a ridge over the far eastern Pacific leading to a trend towards drier conditions. That said, there’s still noteworthy uncertainty as to the longitudinal placement and amplification of this feature with only 37% of the total ensemble members favoring completely dry conditions for the region. The other 63% of ensemble members either have the ridge placed too far west and/or not amplified enough to prevent precipitation chances(15-30%) from persisting mainly over the higher terrain features. Schuldt/99
AVIATION
00Z TAFS...Conditions remain variable at YKM/DLS tonight through Wednesday with waves of light rain facilitating primarily MVFR to IFR visibility and ceilings. Other sites see VFR conditions hold in place, even if occasional light rain bleeds into PSC and ALW at times. Later on Wednesday this weather disturbance which has been mainly lurking NW finally pushes through the rest of the region with conditions trending to MVFR for ALW, PDT, and RDM/BDN late in the period although confidence the exact timing on this degradation is only moderate. Breezy winds at RDM quickly decrease this evening with winds remaining below 10-15 knots at all sites through the rest of the period. 99
PRELIMINARY POINT TEMPS/POPS
PDT 47 55 40 46 / 20 70 90 60 ALW 49 55 42 46 / 30 70 90 60 PSC 47 54 43 49 / 40 80 80 30 YKM 43 49 33 45 / 60 90 70 30 HRI 47 55 42 50 / 30 80 80 40 ELN 40 44 32 42 / 70 80 60 30 RDM 44 50 31 42 / 20 80 70 60 LGD 41 48 34 44 / 10 50 100 80 GCD 44 54 33 44 / 10 60 90 80 DLS 50 53 42 47 / 70 90 90 70
PDT WATCHES/WARNINGS/ADVISORIES
OR...Wind Advisory until 7 PM PST this evening for ORZ049.
WA...None.
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