Area forecast discussion
National Weather Service Pendleton or
449 am PDT Sat may 25 2013...updated
Updated wording in the aviation discussion
Short term...today through Memorial Day. The Pacific northwest will remain
under a broad upper trough with a series of waves bringing scattered
to numerous showers. Two upper low centers are currently
pinwheeling around each other...one located over southern Alberta
and another near 47n/130w. Our forecast area will be located
between these two low pressure centers today...therefore the chance
of showers today is only about 10-30 percent with the best
probability along the east slopes of the Washington Cascades.
Precipitation chances increase tonight as the low over the eastern
Pacific ejects towards the Oregon coast. By sunrise on
Sunday...widespread rain is expected along the east slopes of the
Oregon Cascades and as far east as Paulina. Precipitation will
spread eastward during the day...mainly affecting our Oregon zones.
Rainfall amounts up to 0.25 of an inch are expected...and some areas
in the Oregon mountains could see up to 0.5 of an inch. Will keep
the slight chance of thunderstorms over our eastern zones Sunday
aftn/eve. Due to the amount of cloud cover on Sunday...confidence is
not high enough to increase from slight chance to chance of
thunderstorms. Showers will taper off from the west after the
passage of the upper level trough Sunday night. Another shortwave
trough is prognosticated to swing across Oregon and southern Washington on
Memorial Day...bringing another round of scattered to numerous
showers. Once again...the best chance of precipitation on Memorial
Day will be along the east slopes of the Oregon Cascades and most of
central Oregon. Wister
Long term...Monday night through Saturday...the next upstream
weather system is forecast to move into the Pacific northwest as a
negative tilt trough by both the GFS and European model (ecmwf) Monday night. This
system will bring a surge of moisture that will pivot around the
base of the trough from western Oregon/Washington east-northeast
across the eastern areas of the Pacific northwest. As a result there
should be a pretty good chance of precipitation over the entire County Warning Area
Monday night into Tuesday along with cooler temperatures again.
However snow levels will remain high enough to negate any winter
weather concerns over the mountain passes in the County Warning Area with snow
levels up around 6500-7500 thousand feet mean sea level. Precipitation along
the areas east of the Cascades will see some decrease in due to
downslope winds off the Cascades by Tuesday night. There will be an
overall decrease in precipitation from Wednesday Onward as the
weather system stretches and weakens. However an overall trough
pattern will remain over the forecast area through Friday with
mainly mountain showers continuing. A drier northwest flow will then
develop by Saturday with improving conditions and the beginning of a
warming trend in time for the weekend. The atmosphere will be too
stable throughout the extended period for any thunderstorm threat. 88
&&
Aviation...12z tafs...VFR conditions will prevail through the next
24 hours. There will be a break in the weather today with dry
conditions at all taf sites. Then another weather system will move
into the area tonight with increasing chances of showers at all taf
sites...especially krdm...kbdn and kdls. Winds will be light and
under 10 kts this morning but will increase to 10-15 kts this
afternoon and early evening. Winds will diminish to less than 10 kts
again by 06z tonight at most taf sites. 88
&&
Preliminary point temps/pops...
PDT 67 47 65 47 / 10 20 60 20
alw 69 51 68 51 / 10 20 50 30
psc 72 48 73 50 / 10 10 40 20
ykm 67 47 69 49 / 20 20 40 20
hri 71 48 70 51 / 0 20 50 20
eln 65 45 67 46 / 20 20 40 20
rdm 65 40 62 40 / 10 60 80 10
lgd 65 41 64 41 / 10 20 50 40
gcd 65 43 63 40 / 10 30 60 30
dls 69 50 68 51 / 10 30 70 10
&&
PDT watches/warnings/advisories...
or...none.
Washington...none.
&&
Threat index
today : green
Sunday : green
Monday : green
Green: none or limited need for watches, warnings, or advisories.
Yellow: a few watches, warnings, or advisories possible or in effect.
Red: numerous watches, warnings, or advisories possible or in effect.
For additional weather information, check our web site at...
www.Weather.Gov/Pendleton
$$
85/88/88
