Marine Weather and Tide Forecast for Seneca, OR
November 29, 2023 10:12 PM MST (05:12 UTC)
Sunrise 7:56AM Sunset 5:13PM Moonrise 7:04PM Moonset 10:51AM
Area Discussion for - Pendleton, OR
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FXUS66 KPDT 300431 AFDPDT
Area Forecast Discussion National Weather Service Pendleton OR 831 PM PST Wed Nov 29 2023
UPDATE
Current radar and infrared satellite imagery showing dry conditions under mostly cloudy skies as a stratus deck continues to linger across the area. This is in response to the upper level ridge that has been stalled over the Pacific Northwest over the last several days. However, a more active weather pattern is anticipated to arrive on Thursday as the antecedent upper level ridge departs to our southeast this evening. There is still a potential for freezing fog to develop overnight into Thursday morning, primarily along the Northern Blue Mountain foothills, Yakima Valley, Tri-Cities area, and the Hermiston/Boardman areas.
Coverage is expected to stay patchy in these areas, as the HRRR highlights a 30-50% and the NBM shows a 10-30% chance of visibilities of one mile or less. Due to the persistent cloud cover, morning low temperatures on Thursday will only drop into the mid to upper 20s.
Rain/snow chances will accumulate along the Cascades early Thursday before spilling onto the east slopes of the Cascades and into the Southern Blue Mountains through the morning and early afternoon. Precipitation chances become more widespread through the late afternoon and evening as the axis of the upper level trough passes over the area, followed by another shortwave Friday morning. Snow levels will be near the valley floor across the Lower Columbia Basin and between 2000-3500 feet south of the Gorge Thursday morning before slowly increasing to between 200-500 feet for the Lower Columbia Basin and 2500-4000 feet south of the Gorge by the evening. This will correlate to some light snow accumulations at lower elevations of the Basin, but amounts are expected to stay below 1 inch. Snow amounts in the mountains, primarily above 4500 feet, will reach 4-9 inches along the Oregon Cascades, 3-6 inches over the Washington Cascades, and 2-5 inches over the Northern Blue Mountains, with additional snowfall through Sunday as back-to-back systems drive through the Pacific Northwest. These sequential systems have warranted the issuance of various winter weather products, including a Winter Storm Warning over the upper slopes of the Washington Cascades beginning at 10 AM on Thursday, a Winter Weather Advisory along the east slopes of the Oregon Cascades also beginning a 10 AM Thursday, and a winter storm watch beginning late Thursday night/Friday morning that includes the Northern Blue Mountains and extends through Sunday afternoon for elevations above 4500 feet.
Minor edits to temperatures, precipitation chances, sky cover, and RH were conducted with this evening's forecast update to better account for current observations and recent guidance. 75
PREV DISCUSSION
/issued 301 PM PST Wed Nov 29 2023/
SHORT TERM
Tonight through Friday night
The pattern becomes very active and impactful over the next several days as a parade of weather disturbances take aim at the Pacific Northwest. With a cold airmass entrenched near the surface of Columbia Basin aided by our pesky low stratus and fog layer the past several days, widespread light snow is expected across the region with our first disturbance Thursday before the focus turns to heavy snowfall in the mountains over the weekend. Confidence is high enough in heavy snowfall for the east slopes of the Washington and Oregon Cascades, in addition to the Northern Blue mountains to issue several winter weather products. However, it’s worth highlighting the transition period Thursday night through Friday is marred by precipitation type uncertainty in the lower Columbia basin, Blue Mountain foothills, and peripheral valleys. If you plan on traveling through the interior Pacific Northwest late this week through the weekend be prepared for possible hazardous winter driving conditions, especially over the mountain passes.
Tonight into early Thursday morning marks the beginning of major pattern change as the high pressure responsible for the rather quiet and calm conditions vacates the region quickly followed by the arrival of the first in a series of shortwave troughs and frontal passages by Thursday afternoon onward. Precipitation will spread eastward as Thursday progresses through there remains some timing distances between models has to how quickly this occurs – the NAM and NAMNEST are by far the quickest bringing light snow or rain/snow mix to the region head of the main frontal band. But once the axis of the trough and accompanying front arrive late Thursday afternoon and evening confidence is high precipitation will be widespread. Since models indicate a weak warm-nose aloft with this initial disturbance doesn’t appear robust enough to thrust above freezing temperatures northward over the Columbia Basin, confidence is moderate to high precipitation will fall as primarily snow. HRRR probabilities for 0.5” of snow or more through Thursday night current sit around 50-90% for locations like Tri-Cities, Prosser, Pendleton, Walla Walla – highest for the latter two. That said, probabilities to exceed 2” for these same lower elevation areas are very low near 0-15% outside of Walla Walla(30-50%). With this in mind, a winter weather advisory likely isn’t needed for the lower Columbia Basin and Blue Mountain foothills at this time but light snow may still impact travel into Friday morning. Across the Cascades and eastern Mountains there will be little in the way of a break from snowfall Thursday through Friday and beyond as two shortwave features hit back to back initially. Thursday through Friday night, the NBM projects a 80-90% probability to exceed 12 inches of snowfall at most of the major Cascade Passes including Snoqualmie Pass, White Pass and Santiam Pass – near 40-60% for Blue Box, and the Tollgate area in the northern Blues. As a result several winter weather highlights were issued for the east slopes of the Washington and Oregon Cascades, and northern Blue Mountains.
As far as precipitation type is a concerned in the Columbia Basin Thursday night and Friday, there remains a slight chance(15-20%)
for pockets freezing rain to also develop across the Blue mountain foothills and Yakima/Kittitas valleys as the stratus layer erodes away, though confidence in timing and placement of this occurring is low before the warm air finally wins out at the surface by Friday night in conjunction with the passage of a second shortwave trough. Still, we’ll need to watch this period closely as models tend to mix out entrenched cold air right at the surface faster than actuality. At the very least, increasing west-southwesterly winds should held to expedite this process for the Blue Mountain foothills and far southern lower Columbia Basin Friday night with gusts increasing to 35-45mph come Saturday morning. Schuldt/99
LONG TERM
Saturday through Wednesday
Guidance is generally in good agreement on what looks to be an active and wet pattern to kick off December, starting with a warm front passage over the weekend before transitioning to a SW pattern by the end of the period. Snow concerns will gradually lessen over the course of the period as snow levels increase with warmer air building in through the weekend onward.
After predominately NW flow through the short term, warm air will start to nose in via a front starting overnight Friday into Saturday. This frontal passage will cause winds to pick up across the area, with NBM probabilistic guidance suggesting high probabilities (>70%) for wind gusts to eclipse 40 mph across much of the forecast area, save for the Kittitas/Yakima Valleys which will be more sheltered by the SW winds. Snow levels will start on the lower end at first, what with the cold NW flow prevailing ahead of the frontal passage, at around 2500-3500 ft for most areas, before increasing rapidly through the day Saturday as these gusty SW winds keep the boundary layer well-mixed and abundant with warmer Pacific air. This trend continues heading into late Sunday as the mid-level flow becomes more zonal behind the front, causing snow levels to bump up toward 4000-5000 ft by the start of the work week.
As far as precip is concerned, snow levels will be low enough to support snow for the first half of Saturday across our major mountain passes, before mixed precip transitions into rain Saturday afternoon onward. Ptype becomes a bit more of a challenge for the Yakima/Kittitas Valleys which will be more sheltered from the increase in winds, thus allowing the cold pool to persist longer, but deterministic guidance is offering wildly disparate values as to what temps in the Valleys will actually be, varying from upper 20s to mid 30s. NBM probabilistic was especially unhelpful, suggesting 80% chance for rain as ptype despite consistently depicting temps in the low 30s and upper 20s. Ended up favoring a snow forecast early for the two valleys, briefly transitioning into rain during the day, before receding back into snow heading into overnight Saturday into Sunday, however confidence in ptype is low (20%) due to model disparities. Fortunately, QPF looks to be light, with NBM probabilistic suggesting about a 40-45% chance of liquid precip over 0.1, so even if snow falls, amounts should generally be less than an inch. Forecast confidence in ptype elsewhere is much higher, with elevations below 2000 ft receiving rain all weekend long (confidence 60-70%) and elevations above 4500 ft receiving primarily snow (confidence 50-60%).
Ptype confidence increases even further after the weekend as the pattern turns warmer. Guidance agrees in the start of the work week seeing ridging, however if the IVT forecast via the GEFS is anything to go by, this ridging looks to be dirty in nature, offering continued PoPs for our area, primarily in the mountains, with NBM suggesting PoPs in the 40-50% range, with 80-90% across the Washington Cascades. Snow levels look to rise well above 5000 ft during the day Monday onward, however, so snow at pass level is not really a concern. Towards the tail end of the period, ensemble clustering hints toward a shift in the upper-level pattern, suggesting SW flow that would introduce more widespread PoPs across the CWA, again primarily in the form of rain as snow levels remain above 5000 ft. Will have to keep an eye on hydrologic concerns given this quick transition from snow to rain in the mountains. Evans/74
AVIATION
00z TAFs
Low clouds will continue to make for at least MVFR conditions for all sites save for BDN/RDM, which will see bkn- ovc cigs around 4-8 kft through the period. Elsewhere, ovc cigs remain at around 1-2 kft, with some variation in cigs/vsby possible overnight, however confidence in exact timing / magnitude of change is very low. Starting Thursday afternoon, light snow will move into the area and impact all sites, however any precip during the day Thursday is expected to be on the lighter end, with aviation impacts limited mainly to continued low cigs. Evans/74
PRELIMINARY POINT TEMPS/POPS
PDT 25 31 27 40 / 10 30 80 80 ALW 26 31 28 39 / 10 30 70 80 PSC 28 33 28 40 / 10 20 60 50 YKM 27 34 27 34 / 0 30 30 60 HRI 28 34 29 41 / 10 30 70 60 ELN 26 33 26 36 / 0 30 30 50 RDM 24 39 26 43 / 10 60 60 60 LGD 23 39 27 39 / 10 40 70 80 GCD 24 39 24 41 / 10 60 90 80 DLS 31 37 32 44 / 10 70 80 90
PDT WATCHES/WARNINGS/ADVISORIES
OR...Air Stagnation Advisory until 11 AM PST Thursday for ORZ041-044- 050-505>508-510-511.
Winter Storm Watch from Friday morning through Sunday morning for ORZ502.
Winter Weather Advisory from 10 AM Thursday to 4 AM PST Friday for ORZ509.
Winter Storm Watch from late Thursday night through Saturday afternoon for ORZ509.
WA...Air Stagnation Advisory until 11 AM PST Thursday for WAZ024- 026>029.
Winter Storm Watch from Friday morning through Sunday morning for WAZ030.
Winter Storm Warning from 10 AM Thursday to 10 AM PST Sunday for WAZ522.
Area Forecast Discussion National Weather Service Pendleton OR 831 PM PST Wed Nov 29 2023
UPDATE
Current radar and infrared satellite imagery showing dry conditions under mostly cloudy skies as a stratus deck continues to linger across the area. This is in response to the upper level ridge that has been stalled over the Pacific Northwest over the last several days. However, a more active weather pattern is anticipated to arrive on Thursday as the antecedent upper level ridge departs to our southeast this evening. There is still a potential for freezing fog to develop overnight into Thursday morning, primarily along the Northern Blue Mountain foothills, Yakima Valley, Tri-Cities area, and the Hermiston/Boardman areas.
Coverage is expected to stay patchy in these areas, as the HRRR highlights a 30-50% and the NBM shows a 10-30% chance of visibilities of one mile or less. Due to the persistent cloud cover, morning low temperatures on Thursday will only drop into the mid to upper 20s.
Rain/snow chances will accumulate along the Cascades early Thursday before spilling onto the east slopes of the Cascades and into the Southern Blue Mountains through the morning and early afternoon. Precipitation chances become more widespread through the late afternoon and evening as the axis of the upper level trough passes over the area, followed by another shortwave Friday morning. Snow levels will be near the valley floor across the Lower Columbia Basin and between 2000-3500 feet south of the Gorge Thursday morning before slowly increasing to between 200-500 feet for the Lower Columbia Basin and 2500-4000 feet south of the Gorge by the evening. This will correlate to some light snow accumulations at lower elevations of the Basin, but amounts are expected to stay below 1 inch. Snow amounts in the mountains, primarily above 4500 feet, will reach 4-9 inches along the Oregon Cascades, 3-6 inches over the Washington Cascades, and 2-5 inches over the Northern Blue Mountains, with additional snowfall through Sunday as back-to-back systems drive through the Pacific Northwest. These sequential systems have warranted the issuance of various winter weather products, including a Winter Storm Warning over the upper slopes of the Washington Cascades beginning at 10 AM on Thursday, a Winter Weather Advisory along the east slopes of the Oregon Cascades also beginning a 10 AM Thursday, and a winter storm watch beginning late Thursday night/Friday morning that includes the Northern Blue Mountains and extends through Sunday afternoon for elevations above 4500 feet.
Minor edits to temperatures, precipitation chances, sky cover, and RH were conducted with this evening's forecast update to better account for current observations and recent guidance. 75
PREV DISCUSSION
/issued 301 PM PST Wed Nov 29 2023/
SHORT TERM
Tonight through Friday night
The pattern becomes very active and impactful over the next several days as a parade of weather disturbances take aim at the Pacific Northwest. With a cold airmass entrenched near the surface of Columbia Basin aided by our pesky low stratus and fog layer the past several days, widespread light snow is expected across the region with our first disturbance Thursday before the focus turns to heavy snowfall in the mountains over the weekend. Confidence is high enough in heavy snowfall for the east slopes of the Washington and Oregon Cascades, in addition to the Northern Blue mountains to issue several winter weather products. However, it’s worth highlighting the transition period Thursday night through Friday is marred by precipitation type uncertainty in the lower Columbia basin, Blue Mountain foothills, and peripheral valleys. If you plan on traveling through the interior Pacific Northwest late this week through the weekend be prepared for possible hazardous winter driving conditions, especially over the mountain passes.
Tonight into early Thursday morning marks the beginning of major pattern change as the high pressure responsible for the rather quiet and calm conditions vacates the region quickly followed by the arrival of the first in a series of shortwave troughs and frontal passages by Thursday afternoon onward. Precipitation will spread eastward as Thursday progresses through there remains some timing distances between models has to how quickly this occurs – the NAM and NAMNEST are by far the quickest bringing light snow or rain/snow mix to the region head of the main frontal band. But once the axis of the trough and accompanying front arrive late Thursday afternoon and evening confidence is high precipitation will be widespread. Since models indicate a weak warm-nose aloft with this initial disturbance doesn’t appear robust enough to thrust above freezing temperatures northward over the Columbia Basin, confidence is moderate to high precipitation will fall as primarily snow. HRRR probabilities for 0.5” of snow or more through Thursday night current sit around 50-90% for locations like Tri-Cities, Prosser, Pendleton, Walla Walla – highest for the latter two. That said, probabilities to exceed 2” for these same lower elevation areas are very low near 0-15% outside of Walla Walla(30-50%). With this in mind, a winter weather advisory likely isn’t needed for the lower Columbia Basin and Blue Mountain foothills at this time but light snow may still impact travel into Friday morning. Across the Cascades and eastern Mountains there will be little in the way of a break from snowfall Thursday through Friday and beyond as two shortwave features hit back to back initially. Thursday through Friday night, the NBM projects a 80-90% probability to exceed 12 inches of snowfall at most of the major Cascade Passes including Snoqualmie Pass, White Pass and Santiam Pass – near 40-60% for Blue Box, and the Tollgate area in the northern Blues. As a result several winter weather highlights were issued for the east slopes of the Washington and Oregon Cascades, and northern Blue Mountains.
As far as precipitation type is a concerned in the Columbia Basin Thursday night and Friday, there remains a slight chance(15-20%)
for pockets freezing rain to also develop across the Blue mountain foothills and Yakima/Kittitas valleys as the stratus layer erodes away, though confidence in timing and placement of this occurring is low before the warm air finally wins out at the surface by Friday night in conjunction with the passage of a second shortwave trough. Still, we’ll need to watch this period closely as models tend to mix out entrenched cold air right at the surface faster than actuality. At the very least, increasing west-southwesterly winds should held to expedite this process for the Blue Mountain foothills and far southern lower Columbia Basin Friday night with gusts increasing to 35-45mph come Saturday morning. Schuldt/99
LONG TERM
Saturday through Wednesday
Guidance is generally in good agreement on what looks to be an active and wet pattern to kick off December, starting with a warm front passage over the weekend before transitioning to a SW pattern by the end of the period. Snow concerns will gradually lessen over the course of the period as snow levels increase with warmer air building in through the weekend onward.
After predominately NW flow through the short term, warm air will start to nose in via a front starting overnight Friday into Saturday. This frontal passage will cause winds to pick up across the area, with NBM probabilistic guidance suggesting high probabilities (>70%) for wind gusts to eclipse 40 mph across much of the forecast area, save for the Kittitas/Yakima Valleys which will be more sheltered by the SW winds. Snow levels will start on the lower end at first, what with the cold NW flow prevailing ahead of the frontal passage, at around 2500-3500 ft for most areas, before increasing rapidly through the day Saturday as these gusty SW winds keep the boundary layer well-mixed and abundant with warmer Pacific air. This trend continues heading into late Sunday as the mid-level flow becomes more zonal behind the front, causing snow levels to bump up toward 4000-5000 ft by the start of the work week.
As far as precip is concerned, snow levels will be low enough to support snow for the first half of Saturday across our major mountain passes, before mixed precip transitions into rain Saturday afternoon onward. Ptype becomes a bit more of a challenge for the Yakima/Kittitas Valleys which will be more sheltered from the increase in winds, thus allowing the cold pool to persist longer, but deterministic guidance is offering wildly disparate values as to what temps in the Valleys will actually be, varying from upper 20s to mid 30s. NBM probabilistic was especially unhelpful, suggesting 80% chance for rain as ptype despite consistently depicting temps in the low 30s and upper 20s. Ended up favoring a snow forecast early for the two valleys, briefly transitioning into rain during the day, before receding back into snow heading into overnight Saturday into Sunday, however confidence in ptype is low (20%) due to model disparities. Fortunately, QPF looks to be light, with NBM probabilistic suggesting about a 40-45% chance of liquid precip over 0.1, so even if snow falls, amounts should generally be less than an inch. Forecast confidence in ptype elsewhere is much higher, with elevations below 2000 ft receiving rain all weekend long (confidence 60-70%) and elevations above 4500 ft receiving primarily snow (confidence 50-60%).
Ptype confidence increases even further after the weekend as the pattern turns warmer. Guidance agrees in the start of the work week seeing ridging, however if the IVT forecast via the GEFS is anything to go by, this ridging looks to be dirty in nature, offering continued PoPs for our area, primarily in the mountains, with NBM suggesting PoPs in the 40-50% range, with 80-90% across the Washington Cascades. Snow levels look to rise well above 5000 ft during the day Monday onward, however, so snow at pass level is not really a concern. Towards the tail end of the period, ensemble clustering hints toward a shift in the upper-level pattern, suggesting SW flow that would introduce more widespread PoPs across the CWA, again primarily in the form of rain as snow levels remain above 5000 ft. Will have to keep an eye on hydrologic concerns given this quick transition from snow to rain in the mountains. Evans/74
AVIATION
00z TAFs
Low clouds will continue to make for at least MVFR conditions for all sites save for BDN/RDM, which will see bkn- ovc cigs around 4-8 kft through the period. Elsewhere, ovc cigs remain at around 1-2 kft, with some variation in cigs/vsby possible overnight, however confidence in exact timing / magnitude of change is very low. Starting Thursday afternoon, light snow will move into the area and impact all sites, however any precip during the day Thursday is expected to be on the lighter end, with aviation impacts limited mainly to continued low cigs. Evans/74
PRELIMINARY POINT TEMPS/POPS
PDT 25 31 27 40 / 10 30 80 80 ALW 26 31 28 39 / 10 30 70 80 PSC 28 33 28 40 / 10 20 60 50 YKM 27 34 27 34 / 0 30 30 60 HRI 28 34 29 41 / 10 30 70 60 ELN 26 33 26 36 / 0 30 30 50 RDM 24 39 26 43 / 10 60 60 60 LGD 23 39 27 39 / 10 40 70 80 GCD 24 39 24 41 / 10 60 90 80 DLS 31 37 32 44 / 10 70 80 90
PDT WATCHES/WARNINGS/ADVISORIES
OR...Air Stagnation Advisory until 11 AM PST Thursday for ORZ041-044- 050-505>508-510-511.
Winter Storm Watch from Friday morning through Sunday morning for ORZ502.
Winter Weather Advisory from 10 AM Thursday to 4 AM PST Friday for ORZ509.
Winter Storm Watch from late Thursday night through Saturday afternoon for ORZ509.
WA...Air Stagnation Advisory until 11 AM PST Thursday for WAZ024- 026>029.
Winter Storm Watch from Friday morning through Sunday morning for WAZ030.
Winter Storm Warning from 10 AM Thursday to 10 AM PST Sunday for WAZ522.
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