Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
000
FXUS66 KSEW 051006
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
306 AM PDT Fri Jun 5 2020
.SYNOPSIS...Near seasonal temperatures expected today before a frontal
system brings a return of cooler and unsettled ("Juneuary")
weather for the weekend. An active pattern will remain in place
through the next week, with periods of showers possible through
much of next week.
&&
.SHORT TERM /TODAY THROUGH SUNDAY/...Quasi-zonal flow will transition
to southwesterly as an upper level flow moves southeastward along
the British Columbia coast today. A shortwave trough will round
the base of the trough later this morning and eject across the
Pacific Northwest this afternoon ahead of the approaching upper
low and an amplifying upper ridge over the Intermountain Basin.
The greatest shower chances will be in this corridor of mid-level
confluence south and east of the area this afternoon. By this
evening, additional shower activity is expected to develop in the
Cascades and Olympics as lift increases with the approach of the
upper low. The majority of the HREF hi-res ensemble members are
indicating a convergence zone developing across the north Puget
Sound Region Friday evening/Friday night and continuing into
Saturday morning. This is noteworthy in this case, as it will
limit any thunderstorm potential during the day as the upper low
moves inland during the day. Guidance is locked on the upper low
center to move inland across Oregon, which will keep thunder
chances in Western Washington confined to the Central Sound
southward, as upper level temperatures will be cool enough to
support thunder, forcing will be stronger and breaks in the clouds
will be more likely to help destabilize the atmosphere enough the
support thunder. A notable difference in this weekend`s setup is
that we will not have the bulk shear to support organized
convection like we did last Saturday - thus thunder and robust
updrafts capable of supporting small hail will likely be more
isolated in nature.
Unsettled weather will remain in place on Sunday, with thunder
chances remaining mostly confined south of the area. Nonetheless, an
isolated strike is not out of the question during the daytime hours
as the vort max associated with the low rounds the base of the
trough and lifts it northeastward. In the wake of this system, the
00Z operational GFS is hinting at a convergence zone developing
across the Puget Sound region once again, which will keep dreary
conditions in place Sunday afternoon/evening.
Temperatures will remain around seasonal levels this afternoon (mid
to upper 60s) before the cooldown for the weekend. Highs on Saturday
and Sunday will range from the upper 50s to low 60s with lows in the
mid 40s to low 50s.
.LONG TERM /MONDAY THROUGH THURSDAY/...Northwest flow will be in place
Monday morning in the wake of the weekend system. Upper level
heights will quickly rise as the next shortwave trough ejects
across Western Washington. While subtle disturbances will keep
POPs in the forecast, mainly for the higher terrain, this next
disturbance late Monday into Tuesday will be the next rain maker
for Western Washington and will usher in quasi-zonal flow once
again. This pattern will remain in place through the remainder of
the week, leaving the door open for additional upper level
disturbances to bring rain chances to Western Washington. Seasonal
temperatures will gradually return next week. Longer range
ensemble guidance is hinting at another potential deep trough over
the northwest by the end of the week/next weekend, but there
remains plenty of variance in individual members this far out.
Pullin
&&
.AVIATION...Southwesterly flow aloft as an upper level approaches
the Pacific Northwest. VFR high clouds across the area with a few
low clouds possible this morning along the coast. VFR for most
through this afternoon with mid clouds and light rain possible this
afternoon into this evening in spots. North winds this morning will
transition southerly this afternoon at 5 to 10 knots.
KSEA...VFR cigs with high clouds. Mid clouds late this afternoon
into this evening with light rain possible. Northerly winds will
transition southerly 5 to 10 knots into this afternoon.
JD
&&
.MARINE...A system will approach the area this afternoon for onshore
flow. Small Craft Advisory winds for the central and eastern
portions of the Strait of Juan de Fuca late this afternoon into
tonight with SCA winds for the northern inland waters Friday night.
Onshore flow into early next week as additional systems move through
the Pacific Northwest. Headlines expected at times into next week
with these fronts.
JD
&&
.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed
until then.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 5 AM PDT
Saturday for Central U.S. Waters Strait Of Juan De Fuca-
East Entrance U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory from 10 PM this evening to 5 AM PDT
Saturday for Northern Inland Waters Including The San Juan
Islands.
&&
$$
www.weather.gov/seattle
NWS SEW Office Area Forecast Discussion