National Weather Service Area Forecast Discussion for Long Beach, WA USA
000 fxus66 kpqr 021825 afdpqr Area Forecast Discussion National Weather Service Portland, OR oregon 1025 am pst fri dec 2 2016 .synopsis...a warm front off the pacific will approach the coast today, and move inland at the end of the day. a cold front from the nw will follow fri night, moving se through the area. another front will move south into the pacific nw sat night and sun, ushering in a colder air mass for early next week that originated in the arctic. there is the potential for low elevation snow down to the valley floor on monday. another system is expected to move through later next week, which bears watching with the potential for significant impacts later next week. && .short term...today through sunday... rain is starting to pick up along the coast this morning associated with isentropic upglide ahead of the warm front. will see rain spread southeastward across the area today. snow levels are currently around 3000 feet according to the troutdale wind profiler, but should be rising with the approach of the warm front. snow levels are expected to rise above the passes, so bulk of the precipitation should fall as rain on the passes. the trailing cold front moves onto the coast this evening, turning rain over to showers. drying at mid-levels, however, should limit qpf overnight tonight with this system. snow levels will fall back down to 3000 to 4000 feet behind the front tonight, but limited qpf should keep accumulations below advisory criteria. moisture generally limited to low levels early sat, with forecast soundings suggesting shallow low level instability best across the north part of the forecast area. coupled with a weak onshore flow, will keep a low pop in across most of the forecast area sat. sat night sees a westerly flow aloft with sagging upper heights. models agree on a sharp but slow moving front sagging south through sw wa into nw or sat night. moisture cross sections show the slow moving system picking up deeper moisture sat night and sun. westerly flow ahead of this system increases modestly to 20 kt at 850 mb, which paired with the deeper moisture increases moisture transport. with good moisture transport and additional dynamic lift associated with the front will go with categorical pops. with cooling air mass expect to see a good shot of snow down to passes in the northern cascades saturday night into sunday. qpf amounts in the cascades on sunday suggest locations above 5000 feet could see a foot or more of snow. snow accumulations on the passes could reach 5 to 10 inches impacting travel through the cascades. a high surf advisory is in effect for the coast for saturday morning as large swell out of the northwest is expected to build seas to around 20 to 24 feet by early saturday morning. -mccoy .long term...sunday night through thursday...sunday night we will start to see significant cool air moving into the region, with our first chance for significant snow in the cascade foothills starting sunday night. by monday morning, models show wet-bulb zero heights getting down below 1000 feet. this coupled with 850 temperatures around -5c to -6c, means the potential for accumulating snow down to at least 1000 feet monday morning with a secondary shortwave expected to move across the region on monday. could see drying behind the front overnight sunday night which would help temperatures wet-bulb down monday morning for a chance of snow down to the valley floor. paved surfaces may be too warm for much accumulation, but can`t rule out an inch which would impact the monday morning commute in valley locations from salem northward. south of salem may start as more of a mix of rain and snow. midday, snow levels should come up a bit allowing precipitation to turn to rain right around the valley floor, but could continue to see accumulating snow down to 1000 feet. precipitation turns back to showers monday night with another brief period where we may see snow all the way down to the valley floor, but drying behind the front should limit qpf monday night. tuesday will be the coldest morning so far this year, with temperatures generally down below freezing everywhere except along the coast. will generally remain fairly cold through the day, with temperatures in inland valley locations possibly not getting out of the 30s. in addition to cooler temperatures, will also see easterly winds start to increase tuesday evening, particularly in and near the columbia gorge, which could make it feel even colder tuesday night. forecast later next week gets a little more uncertain with another system expected to move across the area sometime between wednesday night and friday night. this could be another high impact event, especially with the earlier scenario which could overrun cold air trapped in the valley for a freezing rain scenario. the later scenarios may be a less impactful cold rain event. stay tuned to the forecast for later next week as well. -mccoy && .aviation...mostly vfr conditions this morning will deteriorate to mvfr this afternoon with the more persistent rain. higher terrain will be obscured in clouds and rain this afternoon through this evening. winds will shift from the south to the southwest between 00 and 03z for the coast, and between 03 and 06z for the willamette valley. rain will turn to showers late tonight and 2500 to 2000 feet cigs should settle into the interior valleys early saturday. there may be enough mixing with showers saturday morning to result in vfr cigs for the coast. except newport may see fog if there is any clearing overnight. kpdx and approaches...vfr conditions today will deteriorate to mvfr late this afternoon with more persistent rain. light winds will shift from the south to the southwest between 03 to 06z. cigs will likely lower to around 2000 feet late tonight into early saturday morning. tj && .marine...a frontal system is generating gusts up to 25 kt this morning, and will increase to around 30 kt this afternoon and evening. seas will be between 11 and 13 ft today before a larger swell builds late tonight. large seas are being observed at the buoys far offshore this morning. as of 8 am, buoy 46004 (~540 miles away) currently reports 33 ft at 17 seconds, buoy 46036 (~420 miles away) has 19 ft at 14 seconds, and buoy 46005 has 15 ft at 12 seconds. these seas will decay to around 20 to 24 ft at 17 seconds when they reach the wa and or coast early saturday morning which is quite a bit higher than the 06z enp forecast. buy more in on observations than models and have increased seas saturday morning. seas in the columbia river bar will build to around 20 ft with the ebb this evening then remain above 17 ft until the next ebb early saturday morning where seas will be around 24 ft with larger breakers. tj && .pqr watches/warnings/advisories... or...high surf advisory from 2 am to noon pst saturday for central oregon coast-north oregon coast. wa...high surf advisory from 2 am to noon pst saturday for south washington coast. pz...small craft advisory for winds until 6 pm pst this evening for coastal waters from cape shoalwater wa to florence or out 60 nm. small craft advisory for hazardous seas until 4 pm pst tuesday for coastal waters from cape shoalwater wa to florence or out 60 nm. small craft advisory for rough columbia river bar until 6 pm pst saturday. && $$ interact with us via social media: www.facebook.com/nwsportland www.twitter.com/nwsportland this discussion is for northwest oregon and southwest washington from the cascade crest to 60 nautical miles offshore. the area is commonly referred to as the forecast area.
Information courtesy of the National Weather Service - NWS Portland...
Issuing Weather Forecast Discussion Homepage