Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
902 am PST Monday Jan 26 2015
Synopsis...high pressure over the region and light surface flow
will result in widespread low clouds and fog this morning before
clearing. A weak front will dissipate over western Washington
Tuesday through early Wednesday. Another ridge will build over the
region Friday and Saturday giving dry and mild weather. The next
front brings a chance of rain back into the area Sunday and early
next week. Near or above temperatures are expected.
Short term...shallow dense fog covers much of the western Washington
lowlands this morning. Visibilities are 1/4 mile or less in spots.
But there are signs of clearing and the fog should lift and scatter
late this morning. A strong upper level ridge will bring another
sunny and warm day today with highs again in the 50s to lower 60s.
The upper level ridge will shift east tonight as a weak cold front
advances offshore. This front will bring more clouds and a few
showers to western Washington on Tuesday. This system looks pretty meager on
the infrared satellite and forecast quantitative precipitation forecast amounts are light...trace to few
hundredths. There will be some lingering moisture Tuesday night with
isolated showers mainly in the Cascades. Wednesday is looking drier as a
weak upper level ridge develops over western Washington. 33
Long term...high pressure aloft builds Thursday through Saturday
for a period of dry and mild weather. Inversions will likely result
in some morning low clouds and fog...otherwise mostly clear
afternoons. High temperatures will be above average in the low to
Long range models show the ridge breaking down Saturday night and
Sunday as a moist frontal system brings rain back into western Washington. A
trailing system lifts into b.C. Which may bring additional moisture
into western Washington beyond Sunday. There is a chance of rain early next week
and above average temperatures are likely. Mercer
Hydrology...flooding is not expected for the next 7 days.
Aviation...an upper level ridge is centered over Idaho today with
southwest flow aloft over western Washington. Flow will turn more
westerly Tuesday as a weak front moves into the region and
dissipates. Air mass stable and dry with areas of fog/stratus below
1000 feet this morning. Increasing clouds all levels tonight.
There is still fog at most terminals but a burst of southerly wind
early this morning lifted much of the fog into a stratus deck. Fog
and stratus is mainly over marine areas and land areas near the
water. The fog will dissipate later this morning giving sunny skies
over the majority of western Washington. Increasing high and middle
level clouds tonight.
Ksea...the terminal is on the edge of a fog patch and could slide in
and out of the fog until 18z or so. Sunny after that. Southerly wind
6-10 knots. High and middle clouds will form a ceiling sometime tonight
and the clouds will thicken and lower Tuesday. Chb
Marine...an approaching front has turned wind southerly this
morning and winds have increased to Small Craft Advisory strength on
the coast. An advisory is in effect on the coast today. The front is
weak so for now have limited winds elsewhere to 10-20 knots. There will
be a brief surge of westerly wind 10-20 knots in the Strait tonight and
Tuesday after the front passes.
Offshore flow will resume Wednesday and persist through Friday at
least. Another front will approach the area on Saturday. Chb
Washington....dense fog advisory in effect until 10 am PST this morning for
Pz...Small Craft Advisory coast.
You can see an illustrated version of this forecast discussion at