Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
245 PM PST Thursday Feb 11 2016
Synopsis...rain will increase across the area tonight. A weak cold
front will move east across the area Friday morning. An upper level
trough will produce showers Friday afternoon through Saturday
morning. A pair of warm fronts will bring rain Saturday afternoon
through Sunday evening. West flow aloft will maintain an active
weather pattern into early next week.
Short term...radar shows light rain all over the place though it
has been pretty light...only a trace to a few hundredths in most
places. Rain rates will increase tonight as a warm front moves
northeast across the area. By 18z Friday a cold front is on the
coast. It will move east through western Washington during the day
Friday with showers in its wake late Friday through Saturday
morning. Highs on Friday will be in the middle 50s. The snow level will
be 6000 feet or higher until the cold front passes.
An upper trough moves by Friday night giving showers. Saturday
morning looks relatively dry except for mountain showers. The snow
level will dip to 3000-4000 feet Friday night and Saturday. The next
system will arrive Saturday afternoon on the coast and rain will
spread inland as the snow level rises back to 6000 feet or so
Saturday night. Rain will fall at times through Sunday night. Highs
Saturday will be around 50 but temperatures will rise to the middle
and upper 50s on Sunday. Burke
Long term...all models move the conveyor belt of moisture north on
Sunday night and Monday though they differ in the details such as
how fast and how far north. There is some chance that heavy rain
could continue over the Olympics and north Cascades for awhile.
Recent model trends have been toward less wet solutions for
Washington with most of the precipitation in Canada. On Tuesday
models bring the now less energetic front back south through
Washington. The GFS is slower and wetter with this transition. For
now have mostly chance probability of precipitation for Monday and Tuesday except for the
The GFS and Euro are truly at odds Wednesday and Thursday. They
differ in the broad pattern as well as the details. Have kept broad
brush chance probability of precipitation in the forecast. Burke
Hydrology...river flooding is unlikely through Saturday. There is
some potential for heavy rain over the Olympics and north Cascades
beginning Saturday night which could cause the Skokomish River and
possibly a few rivers in the north Cascades to flood early next week.
Aviation...moist SW flow aloft. The air mass is stable. A warm
front sits from the northern coast of Oregon northwest to a 985 mb low
centered near 51n 141w. This front will lift NE across the region
this evening.. the cold front associated with this system will move
east across the area Friday morning.
Offshore flow associated with the approaching warm front continues
to give mainly VFR ceilings to the interior. Areas of MVFR to IFR
ceilings and visibilities in -ra are now occurring over the olympic
peninsula and in the south interior from about kgrf and kolm
southward. Conditions will gradually deteriorate to MVFR in the
interior this evening as rain spreads NE with the warm front.
Ksea...p6sm -ra ovc050 will deteriorate to 4-5sm -ra bkn025 ovc040
about 02z as a warm front approaches from the SW. Improvement to VFR
can be expected after 18z Friday behind a cold front and as flow aloft
interacts with the Olympics giving clearing at times around the
terminal. Wind NE 4-6 knots will become southeasterly about 06z then southerly 8-12kt
about 15z-18z Friday. Albrecht
Marine...a warm front extending from the northwest Oregon coast to
a 985 mb low near 51n 141w will lift NE through the waters this
evening. A trailing cold front will move east across the waters
Friday morning. Small craft advisories remain in effect for the
coast and the West Entrance to the Strait and will soon start at the
East Entrance and in the northern inland waters. Small Craft
Advisory conditions will spread into Admiralty Inlet about 10 PM
The frontal system will move inland Friday morning and then onshore
flow will follow Friday afternoon or evening into Sat morning. Small
Craft Advisory south flow is likely over Puget Sound sound and Hood Canal
Friday night and Saturday morning as flow aloft interacts with the
Olympics and a mesoscale low forms over the NE olympic peninsula.
A series of frontal systems will give Small Craft Advisory
conditions to most of the waters Sat night through early next week.
Pz...Small Craft Advisory until 9 PM PST Friday for coastal waters
from Cape Flattery to James Island 10 to 60 nm-coastal
waters from Cape Flattery to James Island out 10 nm-coastal
waters from James Island to Point Grenville 10 to 60 nm-
coastal waters from James Island to Point Grenville out 10
nm-coastal waters from Point Grenville to Cape Shoalwater
10 to 60 nm-coastal waters from Point Grenville to Cape
Shoalwater out 10 nm-West Entrance U.S. Waters Strait of
Juan Delaware fuca.
Small Craft Advisory for rough bar until 9 PM PST Friday for
Grays Harbor bar.
Small Craft Advisory until 9 am PST Friday for East Entrance
U.S. Waters Strait of Juan Delaware fuca-northern inland waters
including the San Juan Islands.
Small Craft Advisory from 11 PM this evening to 9 am PST Friday
for Admiralty Inlet.
An illustrated version of this forecast discussion can be seen at