Area Forecast Discussion
Issued by NWS Pendleton, OR

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972
FXUS66 KPDT 150920
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
220 AM PDT Sun Sep 15 2019

.SHORT TERM...Today through Tuesday...Two low pressure systems
will be the focus of the short term weather, bringing rain and
unseasonably cool temperatures as well as locally breezy winds.
Before the arrival of the first system today, one concern will be
fire weather related over southeast Oregon. Winds will increase
today, and the relative humidity lowering again into the teens
this afternoon poses concerns for fire spread for any new and
existing fires. Southwest winds aloft will increase and a thermal
trough will set up near the Lower Treasure Valley. Winds gusting
to 20-30 mph are expected for areas in and around the John Day
Basin and Baker County, affecting fire weather zone 642.
Conditions may not warrant a Red Flag Warning but will highlight
breezy winds and low humidity in the Fire Weather Forecast.

The center of the first low is just north of Vancouver Island
tracking south-southeast. The upper level flow has backed to the
southwest and a slow moving cold front is sagging south across
western WA. Rain has developed along the Olympic Peninsula that
will spread southeast along the east slopes of the WA and northern
OR Cascades this morning, as far east as Yakima and The Dalles by
noon today. As the offshore trough deepens, the upper flow will
back more to the south. The cold front will nose inland, and
precipitation will increase along the remainder of the OR Cascades
but not much farther east. Thoughts remain the same that areas
east of Prosser, Bickleton, Arlington, and Redmond will be dry and
under partly cloudy to mostly sunny skies today. Winds will be
locally breezy, especially along ridgetops.  The front will
approach the Cascade Range early Monday morning, and rain will
increase from the west overnight. On Monday, the front and the
parent upper level trough will gradually travel across WA/OR with
showers and isolated thunderstorms. Instability is not impressive
but the cold air aloft (H5 temps down to -22C) could bring a few
CG strikes and small hail. Snow levels will lower to around 7000
feet, therefore some of the higher mountain peaks will have light
accumulations of snow.

Showers will taper off Monday night with decreasing clouds and
chilly overnight lows. Some of the colder mountain valleys such as
Bear Valley, Ukiah, and LaPine will be near to below freezing. The
next low on Tuesday is taking a similar track as the first one,
traveling south along the BC coast. Another round of widespread
precipitation will occur Tuesday across WA/OR. Afternoon
temperatures will be about 10 degrees below seasonal average with
highs in the 60s to lower 70s and snow levels around 6500 feet.
Wister

.LONG TERM...Tuesday night through Saturday. A low pressure system
over the pacnw will spin moisture into the region that will produce
clouds and showers across the two state area Tuesday night and
Wednesday. As the system moves away...showers will linger especially
over the area mountains into Thursday. Another quick moving system
is expected that will keep the unsettled weather through Friday.
Conditions should slowly improve this weekend as a ridge of high
pressure builds into the two state area along with slightly warmer
temps.

&&

.AVIATION...vfr conditions will persist until a weather system
lowers ceilings and rain chances increase at tafs sites kykm and
kdls after 18z followed by taf sites krdm and kbdn after 22z.
Ceilings could approach lcl mvfr especially in showers.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  76  53  67  48 /   0  30  50  10
ALW  79  55  69  50 /   0  20  50  20
PSC  79  58  73  54 /   0  40  30  10
YKM  68  50  72  46 /  40  50  20  10
HRI  77  57  73  52 /   0  40  40  10
ELN  66  49  71  46 /  60  50  20  10
RDM  75  46  65  40 /  20  70  50  20
LGD  83  50  62  43 /   0  20  70  30
GCD  82  49  61  43 /   0  30  70  20
DLS  67  53  72  51 /  50  60  20  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

85/97/97



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