. There is a weak upper level short wave evident on wave vapor imagery
lifting Northeast through Oregon and will clip Southeast WA tonight. While this system is triggering convection over the Oregon Cascades models insist the Southwest flow will keep the central/N Cascades under a stable regime and also shunt moisture off to the East of our area
. Because the ridge axis is centered so far inland over the great basin and Northern rockies — varying degrees of onshore flow will will develop over Western WA through the weekend. The main thermally induced trough remains East of the Cascades and should prohibit any offshore flow pattern from developing West of the Cascades. Regardless — upper heights above 5880+ meters will support high temperatures into the 80s Thursday through the weekend. Thursday should be the warmest day as the ridge temporarily strengthens over the area
. Highs could reach the upper 80s or even close to 90 in a couple interior locations around the far South Sound and interior. Late night and morning clouds will intrude further inland each morning beginning late Thursday night/Friday morning. The increased
influence will help moderate daytime Highs by a few degrees — but still remaining above average. The air mass becomes weakly unstable starting Friday — especially over the Cascades and Olympics. Models today have backed off on the scope of potential thunderstorm activity across Western WA and show the drier Southwest flow pattern dominating the overall pattern. However — weakness at 500 millibars develops just offshore steering systems Northward through the interior Pacific Northwest. A slight increase in moisture and lift over the mountains could trigger a few thunderstorms. After struggling with this potential the past couple days it seems best to at least mention the chance for the mountains. .
Long-term: — the weakness in the ridge will move off into B. C. On Sunday. A few isolated thunderstorms could still probability of precipitation over the Northern Cascades but the air mass over the mountains should begin to stabilize. Both the GFS/ECMWF agree on a period of ridging Monday through at least Tuesday. This should maintain the warm and dry weather pattern with less morning clouds. By middle week some models start to show stronger Westerly or Southwest flow aloft over Western WA with low level onshore flow. This is still probably a dry pattern but could produce renewed marine clouds and backing off of high temperatures. Highs in the 80s early to middle week may struggle to reach the upper 70s — or near average — for this time of year. Mercer
. This will give light Southwest flow aloft to the area
through Thursday night. At the surface — a ridge of high pressure centered over the offshore waters along 130w combined with thermally induced low pressure East of the Cascades will give light low level onshore flow. The onshore flow is expected to be a little weaker tonight than it was Tuesday night. While patches of fog and low stratus remain in the Strait of Juan de fuca this afternoon
— moisture has evaporated over the remainder of the area. A weak short wave ridge moving Northeast across the area late tonight into Thursday should keep any fog and stratus late tonight into Thursday morning confined to the coastal areas and possibly into the Chehalis Gap and Strait of Juan de Fuca. Elsewhere expect good Visual Flight Rules conditions under clear skies. Albrecht sea — expect clear skies through Thursday. North to Northwest winds 8-11 knots will become Northeast 5-7 knots after 04z then will diminish overnight. Albrecht
will result in light onshore flow through Thursday. Expect small craft advisory conditions through the Central and Eastern portions of the Strait of Juan de Fuca late this afternoon and tonight. The surface ridge along 130w has weakened a bit today — so expect North to Northwest winds along the coastal zones to remain just below Small Craft Advisory criteria through tonight. Destruction island is blowing around 25 knots this afternoon from the Northwest — but that site is elevated and the air mass is quite stable — so the momentum is not expected to impact the sea surface. Small Craft Advisory conditions are expected over portions of the coastal zones and through the Strait late Thursday afternoon and Thursday night. While Northwesterly flow may decrease somewhat over the coastal zones on Friday as pressure gradients become more Westerly — Small Craft Advisory conditions are expected through the Strait of Juan de Fuca and there is a slight chance of Gale conditions around the Central Strait Friday evening for a few hours. Albrecht
Puget Sound — visit http://www. Weather. Gov/seattle/gafd/latest_webafd.html
The Area Forecast Discussion is issued four times daily around 3AM, 9AM, 3PM, and 9PM.
The original form of the discussion, in all CAPS can be found at http://www.srh.noaa.gov/data/SEW/AFDSEW or With hyperlinks to Jargon http://www.wrh.noaa.gov/total_forecast/getprod.php?prod=XXXAFDSEW&wfo=sew&dict=no&version=0
Another form with hyperlinks to images referenced in the discussion can be found at: http://www.wrh.noaa.gov/sew/gafd/latest_webafd.html
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.
For a Glossary of jargon used in these discussions see this link
NWS Glossary lookup. You can either type in the word you are looking for in the box below or browse by letter.
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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
To learn about cloud types see this article with pictures
Under normal conditions, a 1000 mb height is near the surface (sea level - 400 ft),
standard sea level pressure is 1013.25 mb at 15C°
By looking up current pressure and temperature, we can calculate what the standard mb height levels are today.
Standard sea level pressure is 1013.25 mb at 15C° — also known as a standard atmosphere.
Most of the time,
1000 mb is near the surface (sea level - 400 ft) (In really deep low pressure, Sea level pressure can drop well below 990mb.)
850 mb is near 1,500 meters (5,000 ft),
700 mb is near 3,000 meters (10,000 ft),
500 mb is near 5,500 meters (18,000 ft),
300 mb is near 9,300 meters (30,000 ft).
*Note: When 500mb heights are said to be "rising to 540" it means 5400m above sea level. (height above zero geopotential meters.)
But, confusingly, when discussing 850mb heights, the convention is to omit the leading 1, so that 850mb heights of "540 dam" are actually 1540 meters above sea level.
(What committee came up with all this? I guess we have to remember that bits used to be very expensive.)
Just remember that when (constant pressure) heights rise it means that the pressure on the surface is rising too. More on heights and how they are reported: http://www.theweatherprediction.com/basic/obs/
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.
Alternate Weather Jargon glossaries:
NWS official glossary -- Very complete except for idiosyncratic forecasters Or use above form.
Contractions only from NOAA
METAR interpretation http://weather.cod.edu/notes/metar.html
NOAA's official abbreviations http://weather.cod.edu/notes/abrv.html
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