Showers and a convergence zone will weaken today and give way to a dry and warmer period of weather through much of wednesday. A weak frontal system will bring spotty areas of light showers to the area thursday before better troughing aloft brings a better chance for scattered showers friday and into the weekend. Another quick break in the showery weather appears likely early next week.
Troughing encompasses much of the western us early this morning, with two areas of closed low pressure embedded within, one passing over w wa and the other moving across the mt/alberta border. On both the upstream and downstream sides of the broad trough exist ridging, of which the downstream ridge continues to bring hot conditions to locations east of the rockies. Near the surface, high pressure continues to influence w wa/or while weak troughing remains over e wa/or, while a cyclone develops over the central plains and high pressure dominates the se.
Yet another active morning on regional radar as widespread showers continue to push from the offshore waters of wa across the olympic peninsula and across the sw interior. Another convergence zone developed earlier monday and continues to affect mainly eastern clallam, island county, and snohomish county. This activity is largely the result of enhanced pva from the passing shortwave trough mentioned in the previous paragraph.
For today, the shortwave trough will pull e/se of the local area later this morning, carrying the brunt of the favorable dynamics for vertical motion along with it. Most of the shower activity will begin to diminish in coverage and intensity towards and through the morning commute. The convergence zone may hang on slightly longer than the shower activity but is also expected to weaken and dissipate through the morning. Some snow is possible at stevens pass early this morning as snow levels linger around or below 4500ft, but no accumulation is expected.
Mostly dry conditions are expected this afternoon and evening, with perhaps the exception of some lingering showers near the cascades. A shortwave ridge will quickly begin to move into the area from off the pacific, yielding sinking air and generally tranquil conditions. The ridge will largely be driven by the deepening of another large scale trough over the open ocean as a shortwave trough digs south from the center of trough/low over the gulf of alaska. Some patchy morning fog may develop in spots wednesday morning (mainly low-lying areas) with dry conditions continuing. Cloud cover will be quickly increasing from the west early wednesday in response to deepening troughing over the pacific.
By wednesday evening, the shortwave trough primarily responsible for the amplification of the pacific trough will round the base of the trough and eject up the eastern flank of the trough, helping to push a sfc frontal system towards w wa. Meager moisture transport in the vicinity of the front will make for nothing more than areas of light precip through wednesday night and into thursday morning. Some locations may not receive any rainfall from this system. As the parent trough pulls north late thursday, precip will also lift north, bringing a dry end to the short term period.
The long term forecast period will begin dry on friday despite a fairly high amplitude trough noted just offshore. As the trough becomes further amplified just offshore on friday, the next shortwave will eject northward towards w wa. Latest trends in model guidance are suggesting a later arrival of the precip with this wave from the south, which could make for an overall drier day on friday should this trend continue.
A later arrival of precip will make for increased rain chances friday night and through much of saturday. At this point generally expecting scattered showers during this time period. Residual troughing may then keep scattered showers in the forecast for sunday as well, although it`s worth mentioning neither day looks like a washout.
Another transient ridge may be in the cards for early next week ahead of yet, you probably guessed it, another trough over the gulf of alaska.
The daily hydrology discussion has ended until the start of the next rainy season; it will only be updated as needed until then.
Wa...none. Pz...small craft advisory until 2 am pdt wednesday for central u.s. waters strait of juan de fuca-east entrance u.s. Waters strait of juan de fuca.
Westerlies along the central and eastern strait of juan de fuca will continue to yield small craft advisory winds through much of the day today, before easing late tonight into wednesday. Overall, expect onshore flow to gradually ease into midweek as high pressure builds over the northeastern pacific. Low pressure will then move into the area waters later in the week for a more active pattern and the potential for an uptick in onshore flow again by the weekend.
Seas will hover between 4 to 6 feet today, before subsiding to 2 to 4 feet near midweek. Seas are then anticipated to build towards 4 to 6 feet again late in the week as low pressure moves across the region. 14
An upper level trough will exit the region today as upper level ridging starts to build in from the west. Radar early this morning shows scattered shower activity across western washington-with a pscz located primarily over snohomish county at this hour. Conditions across most area terminals are mvfr in showers to vfr for terminals outside of showers. Latest hi-res guidance hints at the pscz dropping southward into king and pierce counties, so could see a brief wind shift to the north and reduced ceilings and visibilities for inland terminals east of the sound. Most likely timing of the pscz dropping southward would be between 11-14z. Overall shower activity should come to an end by 18z for a gradual improvement in conditions towards vfr for most area terminals by the afternoon. Onshore flow will continue in the low levels.
Ksea...current conditions are mvfr with ceilings generally hovering between 1000-2000 ft. Pscz dropping southward into king county could yield brief northerly winds at the terminal (primarily between 11-14z) and a further drop to ceilings and visibilities. Overall improvement towards vfr conditions by the afternoon. Winds from the south, generally persisting at 8 to 13 kts, easing to below 10 kts by this afternoon. 14