Area Forecast Discussion National Weather Service Portland or 9:33 AM PDT Wednesday Jul 13 2016
Synopsis: — weak upper level high pressure builds through Thursday for seasonal weather. On Friday, an upper low over Southern British Columbia turns the flow more Northwesterly, for slightly cooler temperatures but continued dry conditions. Thereafter, the upper trough expands Southward through the Pacific Northwest for cooler conditions and a slowly increasing chance of showers and possible thunderstorms Sunday into early next week.
Update — forecast looks on track for today with zonal upper level flow and surface ridging nudging into the area. Should mean clearing skies and warm temperatures this afternoon. Only update to the forecast was for sky cover, to better reflect current conditions and dissipation through the morning hours. Late afternoon temperatures should be warm, but not hot, across the board, with middle to upper 60s along the coast and upper 70s to low 80s inland with rain. Bowen
Short-term: — (previous) today through Friday: upper level low amplitude ridging is starting to build over the region. A fair amount of scattered to mostly broken stratus remains over the inland areas while the coast and waters are seeing a much more mixed bag of conditions. Additionally, a weak and fast moving shortwave crossed 130W over the last couple hours and is bringing enough weak instability to produce isolated shower activity over the Northern waters. Models, including the hrrr, have zero hold on this feature and gut feeling is that the showers will not make it over the coast range. Will keep an eye on them and may need to update should they cross further inland this morning. Elsewhere along the coast the clearer skies are allowing some very low stratus to fill some of the river valleys. Otherwise, expect there will be enough breaks in the interior stratus to allow for a nominal breakup by middle day. There should be enough shallow mixing to produce spotty afternoon fair weather cumulus over the higher terrain. Additionally, a surface thermal trough will extend North along the coast and bring typical breezy afternoon and evening winds — perfect for kite flying. Also expect similar summertime Northerlies to develop up the willamette as well. Valley temperatures both days will generally hover from the upper 70s to the lower 80s — warmest Thursday.
Much drier air aloft will set up over the County warning area for Thursday and should result in a rather sunny and mainly fine day. Even expect there may be a rather large chunk of time where coast skies stay somewhat clear until the afternoon sea breeze draws clouds back to the immediate coastline. Thursday night will see a relatively compact upper low center cross Vancouver Island and settle over Northeast Washington by daybreak Friday. The attendant upper trough will also bring more of a Northwesterly flow aloft but still remain somewhat dry. Main impact appears to be the return of modest onshore flow and some light rain or more likely drizzle for the far Northwest CWA.
Long-term: — no changes. Previous discussion follows Friday night through Tuesday: only change was to introduce a slight chance of thunderstorms for a large portion of the area Sunday afternoon and evening as an upper tropopause fold will tie in with a lower level shortwave Sunday. Instability looks marginal for deep convection and this extra little punch may be enough of a trigger to overcome the weak middle level capping. Otherwise — no changes and the previous discussion follows. /jbonk
A high amplitude pattern develops over the Eastern Pacific and Western U. S. During the extended, with strong upper ridging around 150W and troughing along Western Canada, the Northeast Pacific, and the Pacific Northwest. The gefs demonstrates high confidence in this overall pattern developing this weekend and becoming well established Monday and Tuesday; although, members vary in terms of timing of shortwaves and precipitation amounts. Overall, quantitative precipitation forecast totals should be light (generally below 0.25 extended total) but notable for middle July. Consensus of the gefs is to hang on to the Western trough with slight retrogression by the middle of the week. Bright
Aviation: — coastal sites have joined inland sites with Visual Flight Rules conditions which will remain through the remainder of today.
KPortland and approaches — Visual Flight Rules ceilings through the day. /bentley
Marine: — North winds will increase over the coastal waters Wednesday as thermal low pressure strengthens in Northern California. Expect Small Craft Advisory threshold winds especially in the Central Oregon waters and parts of the Northern waters. The winds will likely spread North on Thursday. The gradient turns a bit more Westerly on Friday and winds may stay just below Small Craft Advisory thresholds.
Seas are around 4 feet and will build to 6 feet as the Northerly winds increase today and Thursday, but probably stay below 10 ft. However seas will be choppy as periods hover 8 to 10 seconds. Into the weekend, seas will slowly fall back to the 4 to 6 foot range and remain there through at least early next week. Mh
Pqr
Puget Sound — Small Craft Advisory for winds from 2 pm this afternoon to 11 PM PDT this evening for coastal waters from cape shoalwater WA to Cascade head or out 10 nm.
Small Craft Advisory for winds from 2 pm this afternoon to 11 PM PDT Thursday for coastal waters from Cascade head or to florence or out 60 nm.
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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.
The Area Forecast Discussion is issued four times daily around 3AM, 9AM, 3PM, and 9PM.
A complete list of airport weather stations used for the METAR reporting system is at: http://adds.aviationweather.gov/metars/stations.txt . Regional airports weather station designations are at the bottom of this page.
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For Cloud levels (aka ceilings) in the untranslated discussion: Just add two zeros to the right to get the actual forecast cloud level in feet. So 030 is 3,000ft.
Acronyms
ACARS Aeronautical Radio Communications Addressing Reporting System
VFR Visual Flight Rules
Numerical Forecast Models Abbreviations
CMC Canadian Meteorological Centre
ECMWF European Centre for Medium-Range Weather Forecasts
GEM Global Environment Multiscale (CMC's short-range model)
GFDL Geophysical Fluid Dynamics Laboratory's Hurricane Model
GFS Global Forecast System (formerly known as the AVN and MRF)
MM5 Penn State University/National Center for Atmospheric Research's Mesoscale Model
NAM North American Mesoscale (formerly known as the Eta)
NGM Nested Grid Model
NOGAPS Navy Operational Global Atmospheric Prediction System
RUC Rapid Update Cycle Forecast Model
SREF Short Range Ensemble Forecasts
UKMET United Kingdom Meteorological Office
Washington Airports and other NWS stations
elevations in meters
N W elev
WA ARLINGTON MUNI KAWO 48 10N 122 10W 42
WA BELLINGHAM KBLI 48 48N 122 32W 50
WA WHATCOM (BLI) KHUH 48 57N 122 35W 26
WA BREMERTON NTNL KPWT 47 30N 122 45W 147
WA BURLINGTON/MT V KBVS 48 28N 122 25W 43
WA CHEHALIS CENTRAL KCLS 46 41N 122 59W 54
WA COLVILLE MUNICIP KCQV 48 32N 117 52W 572
WA DEER PARK KDEW 47 58N 117 26W 668
WA EASTSOUND/ORCAS KORS 48 42N 122 54W 8
WA ELLENSBURG KELN 47 02N 120 32W 519
WA EPHRATA KEPH 47 18N 119 31W 383
WA EVERETT KPAE 47 55N 122 17W 180
WA FAIRCHILD AFB KSKA 47 37N 117 39W 750
WA FORT LEWIS/GRAY KGRF 47 04N 122 34W 92
WA FRIDAY HARBOR KFHR 48 31N 123 02W 32
WA HANFORD KHMS 46 34N 119 35W 223
WA HOQUIAM KHQM 46 58N 123 56W 7
WA KELSO LONGVEIW KKLS 46 07N 122 54W 5
WA MOSES LAKE KMWH 47 12N 119 19W 362
WA OAK HARBOR AIRPA K76S 48 15N 122 40W 58
WA OLYMPIA KOLM 46 58N 122 54W 58
WA OMAK KOMK 48 28N 119 31W 395
WA PASCO KPSC 46 16N 119 07W 121
WA PORT ANGELES KCLM 48 07N 123 30W 85
WA PULLMAN/MOSCOW KPUW 46 45N 117 07W 773
WA PUYALLOP/THUN KPLU 47 06N 122 17W 164
WA QUILLAYUTE KUIL 47 56N 124 33W 54
WA RENTON KRNT 47 30N 122 13W 21
WA SEATTLE/BOEING KBFI 47 33N 122 19W 4
WA SEATTLE/METRO KSEA 47 27N 122 19W 136
WA SEATTLE/WFO KSEW 47 27N 122 18W 130
WA SEATTLE/ARTCC KZSE 47 17N 122 11W 99
WA SEATTLE/CAMANO I KATX 48 12N 122 30W 151
WA SHELTON KSHN 47 14N 123 08W 82
WA SPOKANE KOTX 47 41N 117 38W 727
WA SPOKANE/FELTS KSFF 47 41N 117 19W 609
WA SPOKANE/METRO KGEG 47 37N 117 32W 735
WA STAMPEDE PASS KSMP 47 17N 121 20W 1208
WA TACOMA KTIW 47 16N 122 35W 89
WA TACOMA/MC CHORD KTCM 47 07N 122 28W 98
WA TATOOSH/VOR KTOU 48 18N 124 38W 520
WA TOLEDO WINLOCK M KTDO 46 28N 122 47W 113
WA VANCOUVER KVUO 45 37N 122 39W 8
WA WALLA WALLA KALW 46 06N 118 17W 363
WA WENATCHEE KEAT 47 24N 120 12W 377
WA WHIDBEY IS. NAS KNUW 48 21N 122 39W 14
WA YAKIMA KYKM 46 34N 120 32W 324
WA BURLINGTON/MT V K75S 48 28N 122 25W 43
WA COLVILLE K63S 48 32N 117 52W 571
WA DEER PARK K07S 47 58N 117 26W 668
WA DESTRUCTION ISL 47 40N 124 31W 21
WA PORT ANGELES CG KNOW 48 08N 123 25W 4
WA SMITH ISLAND 48 19N 122 10W 15
WA PEARSON/VANCOUVR K60S 45 37N 122 39W 8
WA WEST POINT (LS) 47 40N 122 34W 3
BC ABBOTSFORD AIRPO CYXX 49 01N 122 22W 58
BC AGASSIZ (AUTO) CWZA 49 15N 121 46W 15
BC ENTRANCE IL AUTO CWEL 49 13N 123 47W 5
BC ESQUIMALT METOC CWPF 48 25N 123 25W 12
BC HOPE AIRPORT (MA CYHE 49 22N 121 28W 39
BC HOPE SLIDE CWKV 49 16N 121 13W 674
BC KELP REEFS CWZO 48 33N 123 14W 1
BC MALAHAT (AUTOB) CWKH 48 34N 123 34W 366
BC MERRY ISLAND CWMR 49 28N 123 55W 8
BC MT SICKER RADAR CXSI 48 51N 123 45W 1
BC NANAIMO AIRPORT CYCD 49 02N 123 52W 28
BC P. MEADOWS CS AU CWMM 49 12N 122 40W 5
BC RACE ROCKS AUTOB CWQK 48 17N 123 31W 5
BC SAND headS (LS) CWVF 49 06N 123 18W 1
BC SATURNA ISL (MAP CWEZ 48 46N 123 02W 7
BC SHERINGHAM AUTOB CWSP 48 22N 123 55W 21
BC SQUAMISH (AUTOB) CWSK 49 46N 123 10W 60
BC VANCOUVER (AUTOB CWHC 49 17N 123 07W 2
BC VANCOUVER INTL A CYVR 49 10N 123 10W 2
BC VIC. HARTLAND AU CWVV 48 31N 123 28W 49
BC VICTORIA (AUTOB) CWLM 48 25N 123 19W 70
BC VICTORIA HARBOUR CYWH 48 25N 123 23W 10
BC VICTORIA INTL AR CYYJ 48 38N 123 25W 19
BC VICTORIA UNIV CWYJ 48 28N 123 18W 39
BC W VANCOUVER AUTO CWWA 49 21N 123 10W 178
BC WHITE ROCK AUTOB CWWK 49 01N 122 46W 15