National Weather Service Area Forecast Discussion for Long Beach, WA USA
000 fxus66 kpqr 251608 afdpqr Area Forecast Discussion National Weather Service Portland, OR oregon 908 am pdt tue oct 25 2016 .synopsis...deep low pressure below 980 mb centered well off southern vancouver island and the northern washington coast will gradually weaken and move north through wednesday. a second low closer to 990 mb is forecast to move north off the oregon coast late tonight and wednesday for gusty coastal winds and more rain at times before weakening as it makes landfall on vancouver island wednesday night. another disturbance is expected thursday. another low is expected to send surges of moisture into the forecast area this weekend. && .update...shower bands rotating around a large low offshore of the british columbia coast will continue showers across nw oregon and sw washington this morning. a line of thunderstorms were embedded in these showers over the waters off of south washington and north oregon early this morning. radar showed some rotation with these cells as they moved north into the north washington waters. these storms have mostly stayed over the waters, but there have been a few isolated thunderstorms making it to the immediate coast, before quickly weakening. satellite and radar imagery shows another weaker line of thunderstorms approaching the central oregon waters, and have added isolated thunderstorms for the central oregon coast and coastal waters through this morning. satellite imagery shows the next low developing offshore of north california. this low has a lot of moisture with it as satellite derived precipitable water shows a bullseye of 2.2 inch precipitable water values near the forming low center. there is an extended swath of 1.5 inch precipitable waters just south of the forming low. gfs modeled precipitable water is forecasting the general moisture around 1.5 inches, but does not show the locally higher amounts around the low center. we will watch these values as the low continues to develop and moves towards the pacific northwest this afternoon. the observed moisture on satellite has increased the forecast confidence that this low will produce a warm front that will move across nw oregon and sw washington overnight tonight into early wed morning. the front is rather quick moving which will prevent the rainfall totals from being excessively high. however with the high moisture content, expect the rain to be heavy at times, and high rain rates may challenge small streams and drains, especially if they are clogged with leaves. the highest rain totals will be over the higher terrain of the coast range, and modeled 850mb south winds around 70 kt will likely enhance orographic lift. can expect around 1 to 2 inches of rain for the coast range, and washington cascades tonight through wed morning, and 0.5 to 0.75 inch elsewhere. the winds will gust along the immediate coast wednesday morning impacting the beaches and headland and higher terrain of the coast range the most with gusts up to 50 mph. east winds will increase in the gorge tonight where gusts around 45 mph can be expected through wed morning. east portland areas near the columbia gorge entrance will also have breezy east winds tonight and wed morning with gusts around 35 or 40 mph. tj previous short term from 403 am this morning...today through thursday...a deep low likely below 980 mb was centered off vancouver island and the north washington coast outside 130w early this morning and will slowly weaken as it moves northwest into the gulf of alaska today and tonight. the associated cold front moved east of the forecast area overnight and we are under south to southwest flow aloft with a few showers around. the best coverage of showers early this morning has been over the coastal waters and near the coast, and the langley hill national weather service doppler radar showed several storms earlier with rotating updrafts for which we issued special marine warnings. that activity seems to have eased a bit now. will keep a chance of thunder along the coast through the morning per lifted index forecasts. there is another comma cloud beginning to develop this morning out around 37n/138w that the models develop into a low around 990 mb that moves north along the oregon coast just inside 130w late tonight and wednesday. the coastal gradient remains rather easterly again with this storm and that may prevent high winds from developing, but still expect some winds along the coast again. the strongest winds will be over the coastal waters. the associated moist warm front with pws pushing 1.5 inches accompanied by 850 mb inflow winds of 60 to 70 kt will lift north through our forecast area late tonight and wednesday morning with pretty substantial rains. the rains will not likely last long enough for any river flooding, though local ponding of water is possible. the surface low weakens as it makes landfall into vancouver island wednesday night. the associated cold front lingers over southwest washington and northwest oregon into early thursday for decent rain continuing before letting up on thursday. one more upper level disturbance will move through on thursday and finally push the front east of the forecast area later in the day. tolleson .long term...no changes. previous discussion follows... thursday night through monday...wet weather pattern looks to continue into this weekend, with another trough dropping out of the gulf of alaska thursday into friday. may get a brief break from the rain friday morning as shortwave ridging builds up ahead of the next surface low that comes up from the southwest. this low looks fairly weak, bottoming out in the high 990s to right around 1000 mb. heavier rain will impact southwest oregon, but should be more moderate as it moves farther north into northwest oregon and southwest washington. showers should linger across the area saturday night through sunday morning before another weak system comes up the same track as the last low, along the track of the south side of the upper-level trough sitting off the coast of washington and oregon. this one looks fairly weak as well, only bringing moderate rainfall to our area sunday evening through monday morning. this second surface low is more associated with the upper-level trough, which shifts onshore sunday night into monday, though another upper-level trough appears to come in and take its place off the coast of washington and oregon for on-and-off rainy weather to continue into early next week. -mccoy && .aviation...predominately vfr today and tonight. scattered showers will continue across the forecast area this morning, with isolated thunderstorms possible along the coast mainly in the morning through 19z. another low pressure system will spread rain across the region tonight, with brief period of mvfr cigs and vsbys possible. gusty south to southeast winds possible through this afternoon. kpdx and approaches...predominately vfr. isolated showers today, with rain returning after 06z. gusty southeast winds possible through 00z. && .marine...low pres center near 49n 133w will continue to weaken and drift nw today. wind over the southern waters have generally subsided below gale strength, so will drop the warning there with the morning forecast. over the northern waters both buoy 46029 and garibaldi still indicating gale force gusts, so that warning will be allowed to continue through expiration midday. seas were down in the upper teens this morning at 46029 and 46050, and should continue to subside slowly today as both winds and sw swell diminish. another weaker low will move north off the oregon and washington coast late tonight through wed night, likely near 129w to 130w. while not as intense, the low still appears strong enough to warrant the gale watch for the outer waters wed. late in the week looks a little calmer on the coastal waters with a weak frontal system approaching the waters fri. && .pqr watches/warnings/advisories... or...none. wa...none. pz...gale watch from wednesday morning through wednesday evening for waters from cape shoalwater wa to florence or from 10 to 60 nm. gale warning until noon pdt today for coastal waters from cape shoalwater wa to cascade head or out 60 nm. small craft advisory for rough columbia river bar until 6 am pdt wednesday. && $$ 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...
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