Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
924 am PDT Friday Jul 25 2014
Synopsis...high pressure aloft will prevail over the region
through this weekend for drier...sunnier...and warmer weather.
a weak upper ridge will prevail over the area today. A weak
disturbance passing to our north may set off a few showers over
the north coast...olympic range...and far north Cascades this
afternoon. Otherwise...look for partly sunny skies over the
County Warning Area today.
Heights will slowly rise tonight but the low level flow will
still be onshore. This may allow some stratus to redevelop over
the area but it should be more patchy in nature. The Four Corners
high will build northward into the northern rockies Saturday and Sunday with
500 mb heights above 5800 M over western Washington. This supports a dry and
warming trend with highs in the upper 70s to low 80s across the
interior lowlands on Saturday...warming to the low to middle 80s
Long term from the previous discussion...
global models continued to advertise a strong high pressure ridge
dominating the interior western U.S. Through much of next week. There
was some uncertainty as to how far west the ridge will shift and
this will affect where thermally induced low pressure develops.
Most models runs kept the ridge axis oriented northward over the Great
Basin which would keep lower pressure east of the Cascades and
allow for light onshore flow over western Washington. It will still be quite
warm...well into the 80s...but hot temperatures into the 90s may
be averted if the ridge axis remains farther east. The more
reliable European model (ecmwf) has varied from run to run...some putting the ridge
closer to our area so a period of even warmer weather is not out
of the question next week. High temperatures should be above
average regardless of the exact ridge position. Mercer
Aviation...weak upper level ridging and moderate westerly flow
aloft will persist over the region today. Low level onshore flow
will strengthen somewhat during the afternoon and evening hours
before relaxing late tonight.
The air mass over western Washington is stable. Lingering areas of
low level moisture remains everywhere except over parts of the
Strait and the central Puget Sound sound area as well as Whatcom County.
Ceilings currently 2-5k feet most areas...except local ceilings near 1k
around the kolm area. Lower clouds should lift and/or scatter out to
VFR levels by late morning...with clearing over much of the interior
during the afternoon.
Ksea...few-sct 2-45k clouds will linger this morning with more
clearing by the afternoon. Light winds will become northwesterly
during the afternoon.
Marine...onshore gradients and flow have relaxed this morning. A
typical pattern of high pressure over the coastal waters and lower
pressure inland will support onshore flow through early next week.
Expect strongest westerlies through the Strait...with Small Craft
Advisory level winds possible at times especially during the late
afternoon and evening hours. The current forecast reflects 10 to 20
knots westerlies this afternoon and nominal Small Craft Advisory winds
during the evening hours on Saturday and Sunday.
For the graphical afd...visit