textproduct: Seattle/Tacoma

SYNOPSIS

High pressure will rebuild over the region in wake of a front that moved through western Washington yesterday. A few areas of fog will be likely next couple mornings as conditions dry out from recent rains. A weaker front will bring a slight chance of showers to the far north interior and Olympic coast Thursday and Friday. This upcoming weekend and early next week remain dry, as the ridge axis shifts through with warmer temperatures.

SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/

Pattern overhead remains fairly zonal with the jet stream over southern Canada. A broad ridge will pass overhead today, with high pressure down at the surface centered over southeast British Columbia. Conditions have dried out for the remainder of today with most cloud coverage cleared on satellite (except for a few areas of low clouds in the north interior and higher alto or stratocumulus clouds elsewhere). The morning cloud coverage and fog subtracts a degree or two for high temperatures going into the afternoon, as they will peak in the upper 50s to low 60s. Mid and high level clouds will fill in tonight/Thursday morning ahead of a weak warm front that will pass through next couple of days. The cloud coverage will likely limit the fog development to the valley areas next couple of mornings, with overnight temperatures ranging from the low to upper 40s. There is a 30-40% chance of showers in the north interior and northwest Olympic coast Thursday and early Friday. Remaining areas will stay dry. Temperatures will slowly warm up Thursday and Friday, with highs approaching 70 in the Puget Sound/south interior, and lows increasing into the upper 40s/low 50s.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Ensemble guidance remains locked on an amplifying upper level ridge passing over the region over the weekend. This will likely result in surface high pressure continuing to build over the weekend with an offshore pattern, and temperatures warming up into the mid 70s (approaching 80 in a couple valley areas in the Cascades). With low temperatures around 50 during the weekend, the HeatRisk will remain yellow (minor) with this pattern. As the ridge moves east of the region early next week, temperatures will decrease back into the mid 60s with lows remaining around 50. Conditions will remain dry through the long term forecast period.

HPR

AVIATION

Widespread VFR conditions with some high level clouds spreading into the area from the west-northwest. VFR conditions are expected overnight, with a similar - albeit less widespread scenario of MVFR to IFR conditions with fog and areas of low stratus Thursday morning. High resolution ensemble guidance (LAMP) indicating the best odds in the most sheltered locations particularly south of Puget Sound (KOLM). Northwesterly winds 7-9 kts will east late evening becoming northeast at many locations.

KSEA...VFR conditions will persist overnight with some scattered to broken ceilings above 15 kft moving into the area overnight. Uncalibrated probabilities from LAMP for MVFR or lower conditions remains around 3% Thursday morning. Northwest winds 8 or 9 kts will east and veer to the northeast at 5 kts or less overnight.

MARINE

High pressure will rebuild over the waters through the end of the week, with a weak front moving through Thursday and Friday. A thermal trough will build along the coast this weekend with a brief period of offshore flow over the waters. Once the ridge shifts eastward early next week, onshore flow return. The only potential for hazardous winds (with gusts greater than 20 kt) is the Strait of Juan de Fuca on Monday into Tuesday with the initial push of onshore flow. This remains a 50-60% likelihood this far out.

Seas will remain at 3-6 ft through the forecast period.

HPR

FIRE WEATHER

Conditions will remain mostly dry going through the end of the week into next week (except for a slight chance of showers in the north interior/Cascades and northwest Olympics). An upper level ridge and thermal trough pattern will build going into the weekend across the region. This will turn the flow pattern to light offshore. While critical fire weather conditions are not expected, a few Cascade Valley areas may see relative humidity values dip to as low as 30% as temperatures warm into the upper 70s to near 80 this weekend. Onshore flow will return early next week as the ridge shifts eastward.

HPR

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...None.