Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
240 am PDT Wednesday Jul 1 2015
Synopsis...high pressure aloft will remain over the Pacific
northwest into early next week for hot and dry weather.
Short term...an upper ridge will be over the Pacific northwest
through Friday. Temperatures will remain well above normal. Other
than some morning clouds near the coast...skies will be generally
clear each day. MOS guidance indicates Thursday will be the warmest
day for most areas. The European model (ecmwf) 850 mb temperatures peak on Thursday
as well but the GFS is actually warmest today and both models show
the weakest onshore flow today versus Thursday. Either way...the
next three days will continue the recent stretch of very warm
weather for western Washington. Schneider
Long term...the upper ridge over the area will retrograde offshore
this weekend and early next week. Heights will initially remain high
and models indicate a thermal trough developing along the coast for
low level offshore flow. This could result in even warmer
temperatures with lower to middle 90s possible by Sunday for parts of
It looks like there will be some cooling early next week as low
level onshore flow increases again and upper heights gradually lower
across the region. Temperatures will still be a little above normal
however and there is no precipitation expected through next
Aviation...westerly flow aloft will continue over western
Washington today with a small upper ridge moving over the area this
afternoon. The flow will back to southwest tonight as a weak upper
trough moves over southern Vancouver Island. Weak low level onshore
flow will continue. The air mass will remain dry except for a
shallow surface-based marine layer.
There is little to no marine stratus over the forecast area
early this morning. Areas of stratus could develop along the
coast during the next few hours and then dissipate by midday...with
the pattern repeating itself again tonight and Thursday morning.
Otherwise skies should be generally clear.
Ksea...northerly wind 6-12 knots today...becoming north to northeast
4-8 knots tonight. Skies should remain generally clear. Mcdonnal
Marine...gale force westerlies that developed in the central Strait
of Juan Delaware fuca and East Entrance Strait Tuesday evening eased
overnight. Relatively weak onshore flow will continue through
Friday...with high pressure well offshore and lower pressure east
of the Cascades. The result should be Small Craft Advisory northwest
winds over the outer coastal waters...and marginal Small Craft
Advisory westerlies in the central and east Strait during the
A thermally induced trough of low pressure will develop over western
Washington this weekend...and winds should be 20 knots or less.
Pz...Small Craft Advisory outer coastal waters...central and east
Strait of Juan Delaware fuca.
You can see an illustrated version of this forecast discussion at
www.Weather.Gov/Seattle/gafd/latest_webafd.Html - temporarily out of
service but should return by the end of this week.