National Weather Service Area Forecast Discussion for Long Beach, WA USA
fxus66 kpqr 051021 afdpqr fxus66 kpqr ddhhmm afdpqr Area Forecast Discussion National Weather Service Portland, OR 221 am pst thu dec 5 2013 .synopsis...a cold air mass will remain over the forecast area for the next few days. an upper level disturbance will dive south along the oregon coast late thursday night and friday. this system will bring areas of snow to the oregon coast and inland areas south of salem. a much colder air mass settles over the region friday night and saturday. a slow moderation will occur sunday through early next week...followed by a transition to milder and wetter conditions the latter half of next week. this transition could start icy for many inland areas later tue into wed with cold air in place. && .short term...thursday through saturday...temperatures early this morning running from around 2 to 6 degrees colder compared to the same time last night. a few low temperature records have already fallen as of 10z. kvuo and keug have already set record lows...and the 21f at khio has tied the 1972 record for the date. not much change today...at least through the afternoon hours. short-wave feature near 55n 128w at 10z will continue to slide s today. gfs cross-section along the oregon and washington border shows mid and high clouds reaching the nrn part of the forecast area by 18z. model depicts lowering cigs 18z to 00z fri...but still above 8000 feet along the n oregon and s wa coast. main short-term concern is the snow potential late tonight and fri. models have come into general agreement regarding the low track. however...still some differences on qpf areas. it appears the latest model runs are a bit slower with the onset of precip. have trimmed pops in the 06z-12z fri time frame. the nam...which has shown the most qpf the past few runs...shows some changes in the 06z run. it now has the surface low a bit further offshore fri morning...with no qpf inland even at 15z. it focuses the qpf and dynamics over swrn oregon late fri morning and in the afternoon. taken at face value...much of our forecast area would get shut out. the 00z 4km wrf-gfs shows the coast and coast range areas getting a little snow between 12z and 15z fri...then spreading southeast after 15z. it gives the s willamette valley 2-4 inches by 00z sat...highest amounts toward cottage grove. unfortunately for kpdx/kvuo metro snow fans...the 4km wrf-gfs shows little to nothing due to low-level offshore flow. confidence is moderate to high that areas south of ksle will need an advisory fri. could even get close to warning amounts in the far south. agree with previous shifts that the line of measurable snow (more than a dusting) will be near tillamook to salem to santiam pass. areas to the north likely to get just flurries...with little to no accumulation. however...a couple exceptions include the n oregon coast range and areas such as forest grove...vernonia where low-level east flow results in up-slope into the east slopes of the coast range. south of the aforementioned line...accumulations are highly like with the best snowfall potential s of a newport to albany line. any slight deviation in the low trajectory will have a big impact on snowfall details. the low exits into nrn california fri evening...followed by much colder nely low-level flow. fri night will be the coldest night in quite awhile. the 00z ecmwf shows 850 mb temps near -15c at kpdx 12z sat...while the gfs is just slightly warmer at -13c. increasing offshore gradients fri night and sat will result in extremely cold wind chills in east-wind prone areas. sat highs will struggle to get out of the 20s for many inland areas. current sps explains the wind-chill details quite well. it appears a slow moderation begins sun...with 850 mb temps in the -7 to -10c range. weishaar .long term...saturday night through wednesday... the past couple of days the models have been trending toward keeping the cold and dry arctic air mass in place over the region over the weekend and into early next week. it now looks like a good bet that we will remain dry until the middle of next week...with very cold overnight lows continuing on sat through mon nights. the models are beginning to zero in on a moist and mild system approaching the pac nw around midweek. it appears that this system may bring the potential for some heavy rain to the area...with some indications that there may be connections to subtropical moisture. however...with the very cold air mass in place ahead of this system...will need to continue to monitor for the potential that precipitation will start out as freezing rain or ice in spots. the best chances for this scenario would be in the columbia river gorge and in valleys spots with within the cascade foothills. at any rate...this system will likely bring an end to the very cold weather...ushering in a more typical winter time pattern. pyle && .aviation...high pressure and increasing offshore flow should lead to vfr conditions for all taf sites through 06z friday. there is a chance a few riverside locations in the central and southern willamette valley and along the columbia river could see some river fog develop early this morning due to relatively warmer river water encountering the very cold ambient air. expect increasing mid level clouds ahead of a low pressure system dropping down the coast through the afternoon and evening. kpdx and approaches...increasing offshore flow should produce vfr conditions at the terminal through 06z friday. kmd && .marine...wave conditions look to remain fairly benign through the middle of next week. there is an area of low pressure that drops down the coast later tonight into friday. with strong high pressure inland...expect offshore winds to increase...particularly across the outer waters. gusts to 25 kt seem like a decent possibility during this time. there may be a few gusts in the nearshore waters...but predominantly confined to coastal gaps. a stronger low pressure system may impact the region towards the middle of next week...possibly bringing gale force winds to the waters. kmd && .pqr watches/warnings/advisories... or...none. wa...none. pz...none. && $$ more weather information online at.. http://weather.gov/portland interact with us via social media www.facebook.com/us.nationalweatherservice.portland.gov 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...
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