Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 230225

Area Forecast Discussion
National Weather Service Pendleton OR
725 PM PDT SAT OCT 22 2016

.UPDATE...A southwest flow aloft persists over the forecast area
this evening with an upper ridge centered over the Rocky Mountains
and an upper trough off the coast. The low off the coast will sink
southward along the coast as the inland upper ridge slowly moves
east. This will result in the flow becoming more southerly during
the next few days which will slow the progression of weather systems
to move across the region. A weak disturbance may bring a chance of
showers over the Cascades, especially over Washington, late tonight
and Sunday morning. Elsewhere it will remain dry with just an
increase in clouds. As the upper low moves closer to the coast on
Monday another disturbance, which will be stronger, will move inland
crossing the Cascades Monday morning and then spreading
precipitation eastward over the rest of the CWA Monday afternoon and
Monday night. This next system has the potential to bring a couple
tenths of an inch of rain (with snow levels around 7000 feet) to the
CWA. After that an unsettled weather pattern will persist with a
long wave trough off the coast and weather disturbances rotating
around the trough and into the Pacific Northwest through most of the
rest of the coming week. 88


.AVIATION...06Z TAFs...VFR conditions will persist overnight and on
Monday. There may be a few light showers near KDLS late tonight and
early Sunday as a weak disturbances moves into the Cascades. There
is a low chance of patchy valley fog in the Lower Columbia Basin and
the Yakima Valley tonight...but temperature/dew point spread will be
greater and there will be a little more winds to keep conditions
better mixed than last night. Winds however will remain light and
under 15 kts through Sunday evening. 88


.PREV DISCUSSION... /issued 240 PM PDT SAT OCT 22 2016/

SHORT TERM...Tonight through Monday Night...Our area is currently on
the far western edge of a large broad ridge centered over the
Rockies and the Great Plains. An upper low and trough is located
offshore and is beginning to move ashore. Progress will be slow due
to the strength of the ridge but a weak disturbance will move ashore
and cloud cover will increase overnight. There will be a chance of
light showers along the Cascade Crest after midnight and Sunday
morning though the rest of the area will remain dry. On Sunday the
central low of the trough will move south from offshore of British
Columbia to offshore of Washington. This will turn the flow from the
southwest to more southerly and this will keep moisture and
disturbances hung up to our west. Fair and dry weather is expected
through Sunday evening though skies will be mostly cloudy. Sunday
night the low will move closer to the coast line as the ridge begins
to move east. A stronger disturbance will begin to cross the
Cascades late with a slight chance of showers along the Cascade
Crest. On Monday the disturbance will continue to slowly move into
the area with a chance of rain moving as far east as Yakima and
Ellensburg in the morning and then into the rest of the area on
Monday afternoon. Breezy southerly winds are expected Monday
afternoon, especially in the southern portion of the forecast area.
The disturbance will move through the area Monday night with a
chance of rain across the area though it will be tapering off in
Central Oregon overnight. Rainfall amounts appear to be about 1 to 2
tenths of an inch. Snow levels will be over 7000 feet, so snow will
be confined to the highest peaks. Temperatures will be in the 50s
and lower 60s on sunday then warm to mid 50s to mid 60s on Monday.

LONG TERM...Tuesday through Saturday.  Unsettled weather will
continue through much of the extended as several low pressure
systems move along the west coast.  On Tuesday a frontal boundary
will push east of the region with another system spreading rain
across the area Tuesday night and early Wednesday.  A frontal band
remains along the Cascades through Wednesday and then slowly pushes
east on Thursday as a shortwave moves north along the front.
Southerly flow will increase over the area late Friday and Saturday
as a low pressure area remains off shore of Washington and Oregon.
The models have the same basic ideas of the systems, but as there
are differences in timing and intensity will need some chance of
rain each day.  Temperatures will be near normal through most of the
period, but should be above normal with the strong southerly flow by
next Saturday.


PDT  41  58  45  64 /   0   0  10  20
ALW  47  60  51  65 /   0   0  10  20
PSC  45  59  48  63 /   0   0  10  20
YKM  41  58  44  59 /   0  10  10  30
HRI  41  59  45  64 /   0   0  10  20
ELN  41  55  43  55 /  10  20  10  40
RDM  34  60  41  58 /   0  10  10  30
LGD  40  62  47  63 /   0   0  10  20
GCD  43  62  47  61 /   0   0  10  20
DLS  45  61  47  60 /  10  20  10  40


.PDT Watches/Warnings/Advisories...


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