Area Forecast Discussion National Weather Service Seattle WA 300 PM PST Thursday Dec 17 2009
Synopsis: — a weather system will spread rain from the coast to inland areas tonight. Showers will taper Friday with dry weather likely Saturday. Another system will bring rainy and cooler weather from Saturday night through Monday. A chance of rain will continue into next week.
Short term: — next weather system is arriving more or less on schedule. Rain began on the coast this afternoon and will spread inland tonight. Have high precipitation probabilites for the period 06z 18z everywhere. Showers should diminish considerably Friday afternoon but the chance of showers will continue into Friday evening.
GFS and NAM both show dry weather Sunday and have made the forecast dry — even in the mountains. A system moves into Southern Oregon late Saturday but should not bring any rain to Washington until Saturday night. There will be clouds Saturday — especially in the South — but have left the forecast mostly cloudy with a few partly sunnies in the North part.
Rain that develops Saturday night will inaugurate a wet period that will last into Tuesday. There will be rain at times in the lowlands. Both the GFS and Euro bring a deep upper low from the Gulf of Alaska Southeast toward the Pacific Northwest. Temperatures will fall — with Highs near 50 on Friday falling to more like 45 on Sunday. Lows will fall mainly into the 30s. Burke
Long-term: — the upper low is forecast to move East through Southern British Columbia about Tuesday. High precipitation probabilites will last through Tuesday as the low spawns showers. Temperatures will also be on the cool side with Highs 40-45 and Lows 35-40. There does not appear to be any threat of much colder temperatures as both the GFS and Euro keep arctic air far to the North — and periods of onshore flow keep the marine influence strong over Western Washington. There could be a snow shower or two in the lowlands at night but in the main the precipitation type will be rain.
Dry weather looks likely Wednesday and possibly Thursday but kept chance precipitation probabilites going for now. Burke
Hydrology — skokomish river is receding after getting within a few inches of flood stage last night. The river could spike upward again Friday in response to the rain tonight — but flooding seems unlikely. There was probably an extra push last night from melting snow in the upper valley — and that source of water is now gone. No other rivers seem likely to do much over the next 10 days. There is no huge weather system bringing warm rain.
No flooding is expected on the green river. Burke
Aviation: — an upper level high pressure ridge over WA will flatten tonight as a front brushes by overnight and Friday morning. In advance of the front — low level offshore flow will increase and keep low clouds to a minimum — except on portions of the Olympic peninsula. The front will slowly move onshore late tonight and reach the Cascades on Friday morning. Rain and lowering ceilings were already spreading onto the coast but will take much of tonight to finally reach Puget Sound and the Cascades. Rain and showers should taper off on Friday afternoon — but a turn to onshore flow will keep ceilings mainly in IFR ranges on Friday and Friday night.
SeaTac — ceilings will remain in the 040-050 range as low level offshore flow limits clouds below that level. Frontal Passage at sea will occur in the 09z 12z time frame — accompanied by rain and lowering ceilings. Prevailing IFR ceilings expected on Friday with a turn to onshore flow and lots of low level moisture. E Southeast wind 4-8 knots — becoming Southwest around 09z tonight. Haner
Marine — the approach of a weakening front will bring an increase in East Southeast gradients through this evening with small craft winds for all but the Central Strait and Puget Sound tonight. The front should pass Western WA overnight — followed by a turn to onshore flow on Friday. In the wake of the front — surface high pressure will build into the interior of B. C. On Saturday and Saturday night. This will bring a turn back to offshore flow over Western WA. Another warm front will lift Northeast across the forecast area on Sunday.
Westerly swells will generally run in the 10-15 feet range over the coastal waters through Saturday morning. Haner
SEW
WA — none.
Puget Sound — Northern inland waters. Small Craft Advisory for rough bar conditions Grays Harbor.
Weather. Gov/Seattle
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.
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