Marine Weather and Tide Forecast for Selma, OR

DISCUSSION
Once again high pressure is in control of the weather this evening, so clear skies are the rule area wide. Fires in eastern Douglas and Lane counties continue to burn, but late- day satellite imagery showed winds shifting around to the SW and the bulk of the thickest smoke was being lofted and carried off toward the NE into north-central Oregon.

The next frontal system headed in our direction looks pretty potent on satellite this evening, but we are expecting it to weaken as it moves onshore (especially down here). Right now, it extends southwestward from low pressure nearing the British Columbia coast (NW tip of Vancouver Island) and is still well offshore of the PacNW. The front will bring some light rain to our coastal areas on Friday, especially north of Cape Blanco. Some precip could also reach into portions of the Umpqua Basin, but the vast majority of the precipitation will occur to our north.
Areas that do get rain will probably only see a few hundredths, maybe up to a tenth of an inch. One reason we are expecting this front to weaken as it presses onshore is the persistent upper ridge to the south and the lack of jet support this far south.

Despite the high likelihood of a weakening front moving through SW Oregon and NorCal on Friday, one thing that won't be weak are the winds. Mid-level SW flow in advance of this front will strengthen as pressure gradients tighten and this will cause some breezy to windy conditions Friday afternoon/evening, strongest east of the Cascades. We have a wind advisory out for wind gusts exceeding 45 mph over there. Since relative humidity will also be quite low over there, we have heightened fire weather concerns and a Red Flag Warning is in effect. This afternoon's fire weather discussion (see below) spells out the specifics. Despite it being breezy too for portions of the Rogue/Illinois Valleys/Siskiyou Mtns and into the rest of NorCal, we don't think we'll need additional fire weather headlines. Humidity will be coming up in the valleys west of the Cascades. In NorCal, fire zones 280, 281, and 284, there might be a brief period of near critical fire weather with a combo of wind/low RH, but duration (too short- lived) should be the limiting factor there for additional products. Overall, temperatures on Friday will be cooler than they were today by about 5-15F. The largest downward trend in temps will be along the coast and in the Umpqua where cloud cover will be greatest. SE areas (Modoc) will see the least amount of cooling.

After Friday's front, high pressure will return with a warm, dry pattern returning this weekend into early next week. Another front probably fizzles at the coast Tuesday/Wednesday. Models do show another healthier front headed toward the area late next week, but it still isn't clear on just how much, if any precipitation we'll get from that. -Spilde



MARINE
Updated 800 PM PDT Thursday, October 3, 2024...A weak front is approaching and will moving across the waters tonight and Friday. Winds and seas have lowered below advisory conditions and will continue to gradually lower on Friday. Breezy to gusty north winds may return this weekend, but current model guidances keeps conditions below small craft advisory levels. Long period northwesterly swell will arrive in area waters on Monday morning.
This swell will increase surf heights into the middle of next week, but overall sea conditions look to remain below advisory levels.
-CC



PREV DISCUSSION
/Issued 431 PM PDT Thu Oct 3 2024/

Updated AVIATION Discussion

DISCUSSION...Surface analysis shows the thermal trough positioned along the south Oregon coast, with continued offshore flow.
Satellite image shows clear skies over the entire area.

Dry weather will continue through tonight.

A stronger upper trough will swing just north of the area Friday. At the same time a cold front will approach the coast late Friday morning, then push inland Friday afternoon. The best chance for precipitation should remain north of the Umpqua Divide and Coos County. Rainfall amounts will be light, with the highest amounts closer to the coast. Even it's not going to be a big rainmaker.

The bigger concern Friday will be moderate to strong winds east of the Cascades Friday afternoon and evening, with the strongest winds expected to be in Lake County. There's good agreement winds aloft at 700mb will be between 35-45 kts and even stronger at 600mb (between 50-60kts). A wind advisory remains in effect for the areas noted above, Please see NPWMFR for more details.

Dry weather returns Friday evening and is likely to continue this weekend into at least early next week, with warmer afternoon temperatures. The ensemble means (both ECMWF and GFS) show upper ridging building near or over the Pacific northwest, which will keep the storm track well north of the area.

Looking out further into next week, there's some evidence suggesting the upper ridge shifting east with an upper troughing approaching the Pac NW towards the middle of next week. The flow aloft will be from the southwest and the operational models hint at a front approaching our area. However, the front will be nearly parallel to the upper flow. In this type of situation, the front will basically will have little or no southeastward progression into our area, therefore we will keep the forecast dry. There will be some cooling for the interior, but afternoon temperatures will still be above normal.

The combination of clusters, ensemble means (ECMWF and GFS), and operational models show more pronounced upper troughing over our area towards the end of next week, leading to an increased chance of precipitation and cooler temperatures. -Petrucelli

AVIATION
04/00Z TAFS
Generally clear skies and visibilities will continue to support VFR flight levels through the TAF period. A weak front will bring cloud cover and light showers over North Bend on Friday morning and afternoon. Additionally, the front will bring gusty southwesterly winds on Friday afternoon and evening to inland areas and especially east of the Cascades. These winds will continue into the next TAF period. -TAD

MARINE
Updated 200 PM PDT Thursday, October 3, 2024
Winds and seas will decrease this afternoon and evening as a thermal trough's influence decreases. An existing Small Craft Advisory for waters north of Cape Blanco and for Hazardous Seas south of Cape Blanco will remain in place through 5 PM tonight. While isolated areas of steep seas may be possible south of Cape Blanco in the hours following, another hazard product is not needed.

Seas are expected to remain below advisory levels through the forecast period. Northerly winds will increase over the weekend but will have little impact on local conditions. Long period northwesterly swell will arrive in area waters on Monday morning.
This swell will increase surf heights into the middle of next week, but overall sea conditions look to remain below advisory levels.
-TAD

FIRE WEATHER...An upper level trough with a cold front will bring strong, gusty west to southwest winds and low relative humidities tomorrow afternoon to southern Oregon and Northern California.
The tightest pressure gradients with this trough will be found east of the Cascades, and this is where there is an 80%-90% for gusts to reach 30 mph in the afternoon. The Fire Weather Watch for zones 624, 625 and 285 has been upgraded to a Red Flag Warning as sustained winds will reach 25-30 mph with RH values near and below 15%. The gusty conditions will be worst between 21Z Friday-03Z Saturday. The concern of needing a PDS (Particularly Dangerous Situation) on the east side was addressed, however it is not likely. Guidance is showing a 35-50% probability for gusts to reach 40 mph for 2 hours on far eastern zone 625 which will not meet the criteria.

Another area of concern was zones 621, 622 and 280 as minimum humidities Friday for the same issues, low RHs and strong winds.
However, the latest fire weather guidance show increased minimum humidities Friday. It's still not out of the question there could be brief periods of critical conditions Friday afternoon in Fire Zones 621, 622, and 280, but not being met. Therefore we'll hold off on issuing anything and let the evening shift take another look at this. However, we will headline this in the fire weather forecast.

Note: There is overall a 20-40% probability to see gusts reach over 20 mph in these locations. The highest probability for 20 mph gusts Friday is in eastern zone 280 between 21Z Friday and 00Z Saturday at 40-60%, so this is the main location that may need to have an additional review tonight for a fire weather product.

This front will also bring rain chances to the coast, mainly in Coos County but also northern Curry County and Douglas County starting tomorrow morning. However, as a line of rain moves inland it is expected to continue drying out, so less than a tenth of an inch is expected from tomorrow morning into the afternoon. A ridge will build this weekend which will continue a warm and dry trend with lighter winds. -Hermansen

MFR WATCHES/WARNINGS/ADVISORIES
OR...Red Flag Warning from 11 AM to 8 PM PDT Friday for ORZ624-625.

Wind Advisory from 2 PM to 8 PM PDT Friday for ORZ031.

CA...Red Flag Warning from 11 AM to 8 PM PDT Friday for CAZ285.

PACIFIC COASTAL WATERS...None.