Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
252 PM PDT Tuesday Jun 2 2015
Synopsis...low pressure aloft will remain over the region through
Wednesday for continued unsettled conditions. High pressure
aloft will slowly build over the area from the west on Thursday.
Look for high pressure aloft to prevail over the region Friday
through this weekend. This will result in dry and rather warm
a weak upper level trough will remain over the region through
Wednesday. Anticipate scattered showers across the County Warning Area...more
numerous in the afternoon. The risk of showers will markedly
decrease Wednesday night as the air mass undergoes stabilization.
Thursday will be a transition day. An upper level ridge centered
offshore will slowly build into the County Warning Area from the west during the
day. It should be dry across much of the area but cannot rule out
a few light showers over the mountains in the afternoon. Increased
sunshine will translate to some warming...with daytime temperatures
forecast to climb above normal.
Look for an upper ridge to prevail over the Pacific northwest on
Friday for dry...sunnier weather and above normal temperatures.
anticipate an upper ridge to remain over the region this weekend.
This combined with light northerly low level flow will result in
rather warm conditions. The medium range solutions generally
agreed that the upper ridge will flatten on Monday...thereby allowing
the tail end of an upper level trough to approach the area. This
would also serve to initiate a marine push. Consequently...most
areas on Monday should be 7-10 degrees cooler than on Sunday.
Additional cooling will occur on Tuesday due to continued strong
onshore flow and the presence of a weak upper level trough.
Note...there were two major flies in the forecast ointment in the
form of hurricanes Andres and Blanca off the coast of Mexico. The
release of latent heat from these hurricanes could result in the
upper level ridge over the County Warning Area this weekend to end up stronger
and to hang around longer than what the models were advertising.
Aviation...a broad upper trough will be over the region through
Wednesday with low level onshore flow. Air mass moist and slightly
unstable. Low clouds will prevail with some improvement expected
Ksea...low clouds should fill back in tonight...then lift and
perhaps scatter Wednesday afternoon. Southerly wind 5 to 10 knots.
Marine...onshore flow will prevail for the next several days with
high pressure offshore and lower pressure inland. Expect Small Craft
Advisory west winds in the Strait of Juan Delaware fuca most afternoons
and evenings. There will also likely be some Small Craft Advisory
northwest winds over parts of the coastal waters later this week.
You can see an illustrated version of this forecast discussion at