Cape Shoalwater WA to Cascade Head OR out 10 NM Marine Forecast
|Tonight...N Wind 10 To 15 Kt With Gusts To 20 Kt. Wind Waves N 4 Ft At 4 Seconds. Sw Swell 1 Ft At 14 Seconds.|
|Wed...N Wind 10 To 15 Kt. Gusts To 20 Kt In The Afternoon. Wind Waves N 3 Ft At 5 Seconds. Sw Swell 1 Ft At 14 Seconds.|
|Wed Night...N Wind 15 To 20 Kt With Gusts To 25 Kt, Easing To 10 To 15 Kt With Gusts To 20 Kt After Midnight. Wind Waves N 4 Ft At 5 Seconds. Sw Swell 1 Ft At 13 Seconds.|
|Thu...N Wind 10 To 15 Kt With Gusts To 20 Kt, Rising To 15 To 20 Kt With Gusts To 25 Kt In The Afternoon. Wind Waves N 3 Ft At 5 Seconds. Sw Swell 1 Ft At 13 Seconds.|
|Thu Night...N Wind 15 To 20 Kt With Gusts To 25 Kt, Easing To 10 To 15 Kt With Gusts To 20 Kt After Midnight. Wind Waves N 4 Ft At 5 Seconds. Sw Swell 1 Ft At 13 Seconds.|
|Fri...N Wind 15 To 20 Kt With Gusts To 25 Kt. Wind Waves 4 Ft. Sw Swell 1 Ft.|
|Fri Night...N Wind 15 To 20 Kt With Gusts To 25 Kt. Wind Waves 5 Ft. Sw Swell 1 Ft.|
|Sat...Nw Wind 10 To 15 Kt. Wind Waves 4 Ft. W Swell 4 Ft.|
|Sun...Nw Wind 10 To 15 Kt. Wind Waves 4 Ft. W Swell 4 Ft.|
| Area Forecast Discussion|
National Weather Service Portland OR
325pm PDT Tuesday July 27 2021
Above normal temperatures continue through the forecast period as high pressure strengthens across the region. Temperatures are expected to warm through Wednesday with temperatures expected to peak on Friday. These hot temperatures and increasing monsoonal sourced moisture will bring periods of showers and potential thunderstorms primarily across the central Cascades and extending into the northern Cascades through the weekend and will likely continue into the start of next week.
Tonight through Saturday...An expansive high pressure system which started around the 4-Corners area now covers most of CONUS, with the center of the high now located close to the front range of the Rockies. As this high has expanded and shifted slightly to the west it has opened up the region to southerly flow along with a sizable vein of moist air from the desert southwest monsoon.
A number of shortwave vort maxes rotating northward around the high tonight and over the next few days, will bring a fair chance of some showers as well as thunderstorms to the Lane and Linn county Cascades. As these vort maxes embedded within the overall southerly flow move across the south/southeastern portions of the CWA there is the chance that showers and thunderstorms will manifest. While, the activity from last night/early this morning was active, a similar pattern could occur again tonight.
As the upper level ridge axis moves closer to our CWA, a thermally induced trough will set up along the crest of the Cascades starting Wednesday and continuing through at least Saturday. What this means for the area is that a warming trend will happen starting on Wednesday. Looking at model guidance to include the NBM has temperatures warming into the mid to upper 90s within the Willamette Valley, along the Columbia River Gorge and into the lower elevations of the Cascades. Thursday, with surface temperatures reaching the upper 90s for the areas mentioned above. Friday, temperatures continue to increase, as 850 mb temperatures increase towards 24C to 26C range across the CWA. These ranges will likely result in temperatures in the 97F to 100F, with the hottest temperatures along the I-5 corridor and into the Columbia River Gorge. Winds will also develop a more diurnal pattern throughout this time, as surface winds will be more onshore during the overnight hours and become calm with a north/northeasterly direction during the daytime.
Given that there will be a multi-period day of temperatures at or above the mid to upper 90s, an Excessive Heat Watch has been issued for The Willamette Valley, Foothills of The Cascades, areas along The Columbia River including the Columbia River Gorge and Hood River.
This event is NOT expected to produce anything near the extreme temperatures which happened in late June of this year. The synoptic set ups between these two events are significantly different. However, even though the current heat event is not likely to reach the caliber of the June event, precautions should still be taken.
Also, each afternoon from now through Saturday will bring at least a minimal convective threat along the central Cascades and extending into the northern Cascades by Saturday. Have included a thunderstorm mention each day although Wednesday and Friday may see potential storms remain well east of the crest. /42
Friday night through Monday...As mentioned in the short- term, the heat is currently forecast to continue Saturday, but uncertainty is high in how much surface heating the area will see given the potential for convective debris clouds to overspread the area Friday night/Saturday morning. The GFS and CMC bring convection across a large portion of our area Saturday evening into the overnight, while the ECMWF (European Centre for Medium-Range Weather Forecasts) keeps nearly the entire area dry. The highest chances for convection look to be over the Lane and Linn County Cascades, where the NBM has a slight chance for thunderstorms Saturday night through early Sunday morning. Therefore have added thunder to the forecast. However, confidence is moderate in that Thunderstorms will happen along the crest of the Cascades, but confidence is low on how widespread these storms could be.
Sunday we cool down a bit more, and currently high temperatures are forecast to be closer to normal for this time of year. NBM has an interquartile maxT range of 82-88F for Portland, which is still warm, but substantially less so than Thursday, Friday, and perhaps Saturday. Convection is possible again Sunday, but uncertainty is even higher. The highest chances again appear to be along the Cascades in Lane and Linn counties, where the NBM has thunderstorm chances around 15%. If there isn't prolific convective debris to limit radiational cooling, Sunday night could dip into the 50s in many locations, especially in valleys and in rural areas where there will be no urban heat island influence.
Cluster analysis shows uncertainty in the overall flow pattern by the end of the extended, with one solution suggesting a continuation of southerly flow, another suggesting zonal (i.e., westerly) flow, and others somewhere between the two. If the southerly flow regime favored by the GFS materializes, then chances for convection will continue through the end of the period. However, if the more zonal pattern favored by the ECMWF takes place, our area is both less likely to see convection and more likely to be cooler by the first part of next work week. Despite uncertainty in the upper-level pattern across our area, chances are high that early next week will be substantially less warm/hot than late this week. -Bumgardner
High pressure remains offshore with thermally induced low pressure over SW Oregon and NW California. This will bring the typical northerly wind pattern across the waters over the next several days. Winds should stay below SCA (Small Craft Advisory) criteria this evening although a few gusts may reach 25 kt, especially near the central Oregon coast. Seas are primarily wind-driven, with a small background swell. Northerly winds will increase Wednesday and Thu as the pressure gradient strengthens. There is an increasing chance for wind gusts to around 25 kt by Wednesday afternoon/evening, primarily for the coastal and southern waters. At the moment wind speeds on Thu appear to reach SCA (Small Craft Advisory) criteria more solidly across all waters. /DDH
Southerly flow into the area will bring hotter temperatures along with an increase in monsoon moisture on Thursday. These may set up terrain focused thunderstorms in the afternoon and evening, near the Cascade Crest in Lane and Linn counties, which may result in numerous fire starts as fuels continue to be critically dry. /Kriederman
.PQR WATCHES/WARNINGS/ADVISORIES... OR...Excessive Heat Watch from Thursday morning through Saturday evening for Cascade Foothills in Lane County-Central Columbia River Gorge-Central Willamette Valley-Greater Portland Metro Area-Lower Columbia-Northern Oregon Cascade Foothills-South Willamette Valley-Upper Hood River Valley- Western Columbia River Gorge.
Fire Weather Watch from Thursday afternoon through Thursday evening for Willamette National Forest.
WA...Excessive Heat Watch from Thursday morning through Saturday evening for Central Columbia River Gorge-Greater Vancouver Area-I-5 Corridor in Cowlitz County-South Washington Cascade Foothills-Western Columbia River Gorge.