textproduct: Seattle/Tacoma

UPDATE

Middle and high level cloud cover over the area this evening. Satellite imagery shows upper level low well to the southwest still moving south. Low turning east Monday with precipitation chances showing up in the forecast Tuesday. Current forecast on track. No update this evening. Previous discussion below. Felton

SYNOPSIS

Mostly dry and warm weather will continue early this week. A low will track inland Tuesday and Wednesday with the next chance of precipitation for the region. Temperatures will also cool descent amount with this pattern change. The end of the week is favored to remain dry, with temperatures returning to mild.

SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/

An upper level ridge sits in the Idaho/Montana Rockies this afternoon, with an upper level low offshore. The ridge axis tilts northwest towards southern B.C.. Strong southerly flow ahead of the low will continue today into Monday. Temperatures have had no problem warming in this pattern, with several locations already hitting 70 and higher this afternoon. Winds remain light out of the north today, but will turn towards the south Monday afternoon ahead of the low moving ashore.

The flow will become split Monday into Tuesday as the low cuts off from the jet in southern Canada. The low will continue to dig southward towards California, with a trough expected to swing through as early as Tuesday from the in Canada (aided by some diffluence from the low to the south). Monday will continue the dry and warm pattern for one more day (high temperatures again reaching the low to mid 70s in the central/south sound). Moisture reaches the region by Tuesday with a 50-70% chance of rain (highest probabilities in the Cascades/Olympics and the Pacific Coast). There is also a 20% chance of thunder for the Cascades Tuesday afternoon (particularly along the crest). Precipitation amounts are expected to remain light overall, but the Cascades may see locally heavier precipitation with any convection that develops. Snow levels will be greater than 6,000 ft, leaving snow likely to just the volcanoes/high peaks in the mountains. Winds remain light for most on Tuesday, but the Cascades could see a few gusts to 20-25 mph from the west later in the day.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

The southern low will track inland towards the Rockies on Wednesday, with a trough from the Canada dipping southward Wednesday/Thursday. This keeps precipitation chances lingering Wednesday and into early Thursday. Wednesday will be the coolest day of the week, with most highs remaining below 60. Ensembles favor a dry and mild pattern returning late Thursday to finish off the work week, with some disagreement into how strong/long it will last into the weekend.

HPR

AVIATION

An upper level low will spin offshore tonight and Monday off OR/CA, with ongoing dry weather across western WA. The flow aloft is E to SE. VFR conditions prevail with a mix of mid and high level clouds. 33

KSEA...VFR through the period. N winds around 10 kt, becoming light NE this evening, then NW/N by 18Z Mon between 5-10 kt. 33/41

MARINE

Low pressure will spin offshore, off OR/CA, with light offshore over western WA tonight and Monday. The low will shift inland and weaken on Tuesday with onshore flow increasing. Highest winds will be through the Strait of Juan de Fuca. Onshore flow will continue through Thursday with high pressure over the NE Pacific. Offshore flow may develop toward the end of the week as a thermal trough forms along the coast. 33

HYDROLOGY

No river flooding in the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES

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