Cape Shoalwater WA to Cape Lookout OR between 60 and 150 NM Offshore Forecast
|Today...N Winds 10 To 15 Kt, Becoming 10 To 20 Kt. Seas 3 To 5 Ft.|
|Tonight...N To Nw Winds 10 To 20 Kt. Seas 4 To 6 Ft.|
|Sun...N To Nw Winds 10 To 20 Kt. Seas 4 To 5 Ft.|
|Sun Night...N To Nw Winds 10 To 20 Kt, Becoming 10 To 15 Kt. Seas 4 To 5 Ft.|
|Mon...N To Nw Winds 5 To 15 Kt. Seas 3 To 4 Ft.|
|Mon Night...N To Nw Winds 10 To 20 Kt, Becoming N 10 To 15 Kt. Seas 3 To 5 Ft.|
|Tue...N Winds 10 To 15 Kt. Seas 4 To 5 Ft.|
|Tue Night...N Winds 5 To 15 Kt. Seas 3 To 4 Ft.|
|Wed...N Winds 5 To 15 Kt. Seas 3 To 4 Ft.|
|Wed Night...N Winds 10 To 20 Kt. Seas 3 To 5 Ft.|
| Area Forecast Discussion|
...UPDATED National Weather Service Portland OR
908am PDT Sat July 24 2021
...Updated for morning aviation weather... Synopsis
Slightly above normal temperatures and tranquil weather will continue the next couple days. A warming trend will begin by mid-week, with the potential for excessive heat again (though not as hot as the late June heatwave!) by the end of the work week. Convection will be possible in the Lane and Linn County Cascades multiple days this week, but exactly when is difficult to determine at this time.
Today through Monday night...This morning, 6.19 micron (upper level) water vapor imagery reveals the exiting upper low moving across eastern Manitoba/Nunavut and into the Hudson bay, and another broad upper trough sitting in the eastern Gulf of Alaska. South of these features, and northwest of a high pressure ridge centered in the Four Corners region, flow aloft remains largely zonal. Thus, our observable weather remains benign, with warm and breezy afternoons following chilly mornings for most locations across our CWA throughout the short term. Today is forecast to be the warmest day for most locations, with limited morning stratus around (except along the coast) to delay the onset of surface heating; highs should reach the 90s across most of the Willamette Valley. Tomorrow and Monday will both remain above normal, but slightly less so than today; highs both days should reach ~86-93F for most lowland locations, except along the coast where temperatures should peak only in the mid 60s to low 70s.
Tomorrow and Monday mornings, the depth of the marine layer should be similar to today - less than 1/2km (shallow), according to Bufkit soundings from the GFS and NAM - but we would not be surprised to learn drizzle has precipitated along the coast given some weak low level instability there. Since only two short term models (namely, the NAM and CMC) are suggesting it, it has not been added to the forecast at this time. Future shifts will determine whether or not it is warranted according to trends in the models as new iterations come in.
Parts of eastern/central Lane Co., along with much of the Cascades, are likely to see some haze as lofted smoke from the Jack Fire is pulled northeastward. However, the concentration of smoke aloft in our area - especially north of Lane and Linn counties - should remain low, with the sky still very visible. The GFS suggests convection is possible in these locations Monday afternoon/evening, but it is the outlier in the models at this time, so we have elected to leave that out of the forecast until convinced by more guidance. Bumgardner
Tuesday through Saturday...Cluster analysis suggests models are in conspicuous agreement in the upper level, synoptic- scale pattern throughout the long term period, with 500mb heigheights rising and becoming largely meridional across Oregon and Washington. Thus, confidence is reasonably high that temperatures will remain warmer than average throughout the period. Confidence is lower, however, in the timing and magnitude of any convective potential due to vast discrepancies between the deterministic models in the timing and placement of any shortwaves to initiate convection. The GFS suggests precipitation in the Lane and Linn Co. Cascades each day this week except Wednesday; the CMC brings precipitation to parts of the same area every day except Thursday; and the ECMWF (European Centre for Medium-Range Weather Forecasts) has rainfall in those locations only Tuesday night and Thursday. All of this is to say the guidance is perplexing and confidence is low, so the only timeframe during which rain showers have been mentioned for these areas is Tuesday evening - when all three models (and the NBM) suggest something at least skirting the eastern periphery of our CWA along the Cascade crest.
The potential for heat is another cause for concern during this period. Cluster analysis continues to suggest +3 to +9 decameter 500hPa height anomalies will overspread the area by Friday, which the NBM is suggesting to be the warmest/hottest day in the period. Thereafter, it is uncertain whether the ridge will be undercut by one/more disturbances moving north/northeastward along its periphery, near or just west of our area. Recent trends have been for a warmer Saturday and Sunday than what was forecast only 24 hours ago, which leads us to believe that (as has been the case in the past with heatwaves in this area) Friday may not be the hottest day afterall. For now, there is little reason to doubt the NBM at this time range, but it is important to know the potential for hot weather late next week and next weekend. NBM suggests the following chances for reaching the triple digits in PDX on Friday, Saturday, and Sunday, respectively: 30%, 20%, 20%. Meanwhile, the chances for exceeding 90F each day are 80%, 70%, and 60%. The signal in the models is considerably less significant/ominous than what it was preceding the late June heatwave, but still suggests it will be rather warm in the lowlands come next weekend. -Bumgardner
Little change in thinking for the coastal waters as high pressure well offshore and thermally induced troughing over SW OR/NW CA maintains a typical summertime northerly wind regime through much of the coming week. Low end Small Craft Advisory remains in place for the central waters this morning, with the expectation that those conditions will expand north of Cascade Head by early this afternoon as winds continue to trend upward and short period seas build to 4 to 6 ft in response. Expect this general pattern to remain in place through the next seven days as conditions continue to hover near low end advisory criteria with minor fluctuations in the pressure gradient. /CB
.PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory from noon today to 11pm PDT Sunday for coastal waters from Cape Shoalwater WA to Cascade Head OR out 60 NM.
Small Craft Advisory until 6am PDT Monday for coastal waters from Cascade Head OR to Florence OR out 60 NM.