Florence to Cape Blanco OR from 10 to 60 NM Marine Forecast
|Tonight...N Wind 10 To 15 Kt. Wind Waves 3 Ft. Mixed Swell W 3 Ft At 10 Seconds And S 2 To 3 Ft At 15 Seconds.|
|Thu...N Wind 15 To 20 Kt. Wind Waves 3 To 4 Ft. Mixed Swell W 3 Ft At 10 Seconds And S 2 To 3 Ft At 15 Seconds.|
|Thu Night...N Wind 15 To 20 Kt. Wind Waves 4 To 6 Ft. Mixed Swell W 2 To 3 Ft At 12 Seconds And S 2 Ft At 15 Seconds.|
|Fri...N Wind 15 To 20 Kt. Wind Waves 3 To 5 Ft. Mixed Swell W 3 To 5 Ft And S 2 Ft.|
|Fri Night...N Wind 15 To 20 Kt...Easing To 10 Kt After Midnight. Wind Waves 3 To 5 Ft. Swell W 5 Ft.|
|Sat...N Wind 5 To 10 Kt...Backing To Nw In The Afternoon. Wind Waves 3 Ft In The Morning...Becoming 2 Ft Or Less. Swell W 5 Ft.|
|Sat Night...Nw Wind 5 To 15 Kt. Wind Waves 2 Ft Or Less. Swell W 5 Ft.|
|Sun...N Wind 15 Kt...Backing To Nw After Midnight. Wind Waves 3 Ft...Becoming 2 Ft Or Less. Swell W 4 To 5 Ft.|
|Mon...Sw Wind 10 To 15 Kt. Wind Waves 3 Ft. Swell W 6 Ft.|
| Area Forecast Discussion|
National Weather Service Medford OR
839pm PDT Wednesday Jun 23 2021
A few strong storms formed this afternoon, but overall the coverage was less than anticipated. This is especially true along the Cascade crest in northern Klamath County. To try and address why this happened we'l first turn to this afternoons sounding and compare it to yesterdays. There was more CIN, negative energy, in the environment, and 5 kts less shear today. The CIN indicates that there needed to be stronger forcing for storms than would have been needed yesterday. Commmon with high CIN values, there was more CAPE today than there was yesterday. Precipitable waters values were nearly the same as well, at 0.90" and 0.92" today and yesterday respectively. So, all things relatively square, other than the increased CIN, what today needed was a stronger forcing mechanism than yesterday. And that was lacking today.
In pouring through the latest four deterministic RAP runs, prior to convective initiation, the model data did not show a strong trigger except over the Siskiyou and Marble Mountains. A trigger, aside from orographics, was lacking along the Cascade crest and the east side. This is probably what limited the presence of thunderstorms. Although it's is worth highlighting that a sounding from Medford and a sounding from east of the Cascades would not have looked identical today, so there is some uncertainty as to why the east side did not see more activity.
Also want to note that this is the first instance where the SREF calibrated probability of 100+ lighting strikes busted. It showed a 6% chance for this occurrence, which seems to be the high even for other places in the CONUS, along the Cascades as a distinct bubble from the 4% over Siskiyou County, which came closer to verifying at 64 CG strikes thus far. This is a positive test case and a pragmatic reminder that this tool is contingent on thunderstorms forming in the first place. Having personally only used this tool for three events now, today was a positive learning experience for how best to make use of this tool.
In the short term future, stray storms that are very much isolated in nature, will remain possible for the next six hours or so. The latest RAP and GOES-17 mid-and-upper-level water vapor imagery show a wave moving through northern California now. This may be enough to support one or two more small storms during these late evening hours. In fact, two such cells can be observed on satellite trying to get going in northern Klamath and Lake Counties now, with a third in the works. Their storms tops are around 30 kft and are producing some lightning activity now. Can't rule out an isolated nocturnal thunderstorm tonight in eastern Klamath County and southern Lake county, so have retained them in the forecast.
Beyond this, the upper low driving this unsettled weather will begin to return to where it came from to our south. This will shift the area of greatest instability further south and focus storms mainly in northern California. Limited isolated storm potential will still exist in extreme southern Klamath and Lake County. A good description of the uncertainty with these storms was provided in the FireWx section of the previous discussion and here, "Signals are a bit mixed in the models, with some models hitting the Modoc area harder than Siskiyou County and others doing the opposite. Activity also looks as if it could be briefly scattered across southern Lake and Klamath counties. However, some waves of subsidence from building high pressure from the north will be pushing over the area increasing through the day, and this is expected to diminish the vertical extent and general ascent with time. Therefore, we expect convection on Thursday to begin early and then end earlier than normal. With PWATs (Precipitable Waters) up around 1 inch, it's quite possible that the activity will morph into more of an area of rainfall in some areas during the evening. -BTL"
And finally, on the weather heading into this weekend from the previous discussion, "As we head into the weekend an Upper level high builds just to the north of the region with an upper low well to the south of us. This blocking pattern will bring near record to record temperatures into the region this weekend. The models remain in near universal agreement in very hot temperatures for all but the coastal areas, and temperatures are very likely to be hotter than they were last weekend. Sunday is the day of highest concern as it's forecast to be the warmest. In fact, we're expecting extreme heat risk Sunday in Medford given the latest forecast of 111 degrees for a high and an overnight low that is not expected to drop below 70 degrees. The Excessive Heat Watch has been updated to a warning, and is in effect from Saturday through Tuesday, although with the often stubborn Rex Block pattern, a duration of this event past Tuesday is possible, but confidence is not high enough to extend the warning past Thursday at this time. -Sven"
Updated 800pm PDT Wednesday, 23 June 2021...North winds have begun to increase, mainly south of Cape Blanco with steepening seas. A Small Craft Advisory recently began, roughly beyond 3 nm from shore. The advisory level winds and steep seas will spread nearer shore tonight before spreading northward on Thursday as a thermal trough continues to build northward. These conditions will persist through Friday before the thermal trough expands so far north (into Washington State) that our steep seas and gusty winds subside this weekend. Moderate winds and seas are expected during the weekend with southerly winds developing late Sunday, possibly continuing into Tuesday. On Tuesday, models are beginning to show an incoming northwest swell that could generate conditions hazardous to small craft, but confidence is low in the extended forecast. -DW/Keene
Updated 400pm PDT Tuesday 22 Jun 2021... Thunderstorm activity today is still expected to be more isolated than it was over the last couple of days, overall, but scattered activity is expected over and near the Marble and Siskiyou Mountains, possibly the Cascades near and north of Crater Lake, and possibly across much of the East Side into this evening. Confidence in significant activity along and east of the Cascades is not high in activity becoming greater than isolated for this evening, however. While most storms will produce rainfall that could be wetting in thunderstorm cores, significant lightning on dry fuels is expected, and isolated dry storms are possible.
Models hang onto some instability and moisture sufficient for showers and thunderstorms tonight into the morning over and near the Upper Klamath Basin. While there's no clear trigger to realize the potential, we've kept a slight chance of showers and thunderstorms in for that area overnight into the morning hours.
The low will move southward Thursday focusing scattered thunderstorm activity over Northern California. Signals are a bit mixed in the models, with some models hitting the Modoc area harder than Siskiyou County and others doing the opposite. Activity also looks as if it could be briefly scattered across southern Lake and Klamath counties. However, some waves of subsidence from building high pressure from the north will be pushing over the area increasing through the day, and this is expected to diminish the vertical extent and general ascent with time. Therefore, we expect convection on Thursday to begin early and then end earlier than normal. With PWATs (Precipitable Waters) up around 1 inch, it's quite possible that the activity will morph into more of an area of rainfall in some areas during the evening. Still, given the recent dryness and the heat on the way and the expectations of scattered lightning in NorCal Thursday, the Fire Wx Watch has been upgraded to a Red Flag Warning.
Very hot and dry conditions are expected Friday through Monday with record high temperatures very likely Saturday through Monday. Record high temperatures are very likely next weekend and all time June records will be threatened. There is about a 25% probability that even all-time record high temperatures could be threatened on or about Sunday/Monday. ~BTL
.MFR WATCHES/WARNINGS/ADVISORIES... OR...Excessive Heat Warning from 11am Saturday to 11pm PDT Tuesday for ORZ023>031. Red Flag Warning until 11pm PDT this evening for ORZ623>625. Red Flag Warning until 11pm PDT this evening for ORZ621.
CA...Excessive Heat Warning from 11am Saturday to 11pm PDT Tuesday for CAZ080>085. Red Flag Warning until 11pm PDT this evening for CAZ280>282-284-285. Red Flag Warning until 11pm PDT this evening for CAZ280.
Pacific Coastal Waters...Small Craft Advisory until 11pm PDT Friday for PZZ350-356-370-376.