textproduct: Seattle/Tacoma

SYNOPSIS

Upper level low southwest of Haida Gwaii this morning will slowly move southeast reaching Western Washington Saturday. Upper level disturbance spinning out of the low moving through today. Low moves east Saturday night with a temporary upper level ridge Sunday. Another upper trough will hang out over the area the first part of next week for more showers and cool temperatures. Possible strong upper level ridge beginning to build Thursday.

SHORT TERM /TODAY THROUGH SUNDAY/

Upper level low just southwest of Haida Gwaii this morning will slowly move southeast ending up off the northern tip of Vancouver Island later this afternoon. Upper level shortwave spinning out of the low moving through for another showery day. Can't rule out a thunderstorm later this afternoon into the early evening hours. Temperatures will not warm up much from the current readings with highs near 60.

Upper level low continuing to move southeast ending up over Western Washington Saturday afternoon. Showers tonight through Saturday. With the low on top of the area Saturday afternoon air mass becomes even more unstable. Models have been consistent with the stability indexes indicating a chance of thunderstorms ( lifted indexes below 0, convective temperatures below highs, solid lapse rates and 300 to 600 J/KG of CAPE ). Small hail also possible with 500 mb temperatures below -25C. Snow levels down to near 4500 feet making for a cold wet day in the upper elevations. Lows tonight in the 40s. Highs Saturday only in the mid 50s to lower 60s. The record low maximum for Seattle Saturday is 52 degrees. We are not going to break that record. The forecast high of 58 degrees would be the 3rd coldest June 6th in the last 40 years.

Upper level low weakening and moving off to the east Saturday night. Shower activity coming to an end quickly with just a chance of showers in the Cascades by midnight. A little bit of clearing combined with the remnants of the cool air mass will produce some chilly for this time of year lows Sunday morning. The colder locations will get into the upper 30s while the remainder of the area will be in the lower to mid 40s.

A little break in the action Sunday with a temporary upper level ridge moving through the area. Plenty of low level moisture hanging around in the morning with high clouds in the afternoon. Even with a little bit of sunshine highs will still be below normal, in the lower to mid 60s. Felton

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/

Extended models have been consistent in bringing an upper level trough into Western Washington the first part of next week. The inconsistency comes in the timing of the trough vacating the area. Each run has been slowing down the departure with the current runs keeping the trough over Western Washington into Wednesday. Showers and cool forecast through the middle of next week.

Upper level ridge building offshore Thursday with drying northerly flow aloft clearing skies. Highs getting back to normal Thursday, mid 60s to lower 70s.

Note...the current 8-10 day solutions on both the GFS and ECMWF are showing the development of a strong upper level ridge. It should be noted that if we actually got the weather predicted in the 240 hour progs we would have a lot wilder weather here in Western Washington. Having said that if this current solution works out we could be looking at the first 90 degree day of the year in Seattle the weekend after next. Stay tuned. Felton

AVIATION

A weak frontal system will move across the western Washington at the surface, bringing scattered shower activity to the area throughout the day and isolated chances for thunderstorms this afternoon and evening in its wake. Confidence in the extent of thunderstorm coverage remains too low for inclusion in any single TAF site at this time. Ceilings will gradually lower area-wide throughout the day, but look to largely remain VFR across the interior terminals. The exception would be some brief reductions in ceilings and visibilities in any heavier shower or isolated thunderstorm activity. Winds will remain out of the S/SW today, persisting at 4-8 kt this morning but will increase to 8-12 kt by this afternoon. Gusts to 20 kt will be possible for the interior terminals of Puget Sound through the afternoon and evening hours.

KSEA...Gusty south to southwesterly winds will continue throughout the majority of the morning and afternoon hours. Locally, gusts could increase in the event of a heavier shower or nearby thunderstorm moving in/near the terminal. Confidence is still too low to include TS in the TAF at this point, but conditions will be monitored for inclusion if necessary. VFR cigs expected today, with a decrease to MVFR likely tomorrow morning generally after 12Z.

14/21

FIRE WEATHER

ERCs will respond to the increase in moisture over the next several days, especially in the fine fuels. Today and more so Saturday will feature area wide chances for thunderstorms, but model PWAT values indicate the storms will contain adequate QPF. The pattern turns warmer and drier the end of next week and looks to remain that way beyond the middle of the month. Favorable fire weather conditions will increase as the pattern remains in place. Felton

SEW WATCHES/WARNINGS/ADVISORIES

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