Weather

396 
fxus66 kpdt 060524 aaa 
afdpdt 


Area forecast discussion...updated aviation discussion 
National Weather Service Pendleton or 
925 PM PST Monday Jan 5 2009 


Update...a few light showers over the Blue Mountains on radar with 
increasing middle and high clouds on satellite. Updated forecast to 
lower minimum temperatures in the Yakima Valley and lower Columbia 
Basin of Washington since cold air never mixed out of these areas 
this afternoon. Expect increasing precipitation later tonight as 
warm front lifts north over eastern Oregon and Washington. Did not 
adjust temperatures tomorrow afternoon...but do expect cold air to 
mix out in Tri-Cities and lower Yakima Valley...but not sure about 
upper Yakima Valley. Coonfield 


&& 


Aviation...06z tafs. A warm front will move into the region from 
the west lowering ceilings and bringing the onset of precipitation. 
Conditions will drop to MVFR by morning at nearly all taf sites with 
possible IFR conditions 10-18z. Winds will also increase in 
association with the warm frontal passage with southwest 15-20kt 
gusts 30-35kt. Conditions will return to VFR-mfr during the 
afternoon. 76 


&& 


Previous discussion... /issued 325 PM PST Monday Jan 5 2009/ 


Short term...tonight through Wednesday night...the area will be 
under a moist west to northwest flow through the short term period. 
Precipitation has tapered off today but another system will move 
into the area tonight for significant rain spreading across the area 
by tomorrow morning. Warmer air has moved into the area and 
temperatures will be warmer overnight but will remain near or just 
below freezing in the Columbia Basin and adjacent lower valleys. 
Upslope flow into the Blue Mountains will continue and snow will 
increase late this evening so have extended the Winter Storm Warning 
for the northern Blue Mountains of Oregon and northwest Blue 
Mountains in Washington through 3 PM tomorrow afternoon. As more 
warm air moves in with the warm front tomorrow...snow levels will 
rise to 5000 to 5500 feet and snow will change over to rain. Rain 
amounts tomorrow will be a tenth to a quarter of an inch in the 
lower elevations and up to three quarters of an inch in the 
mountains. Temperatures will rise to the 40s in the lower elevations 
and breezy to windy conditions can be expected in the afternoon. 
After that...a steady moist flow will continue to bring copious rain 
to the mountains Tuesday night through Wednesday with another one to 
two tenths in the lowland and up to an inch in the 
mountains...especially along the Cascade crest. Temperatures will 
remain above freezing nearly everywhere Tuesday night and rise to 
the middle 40s to lower 50s on Wednesday. Another shortwave will arrive 
Wednesday night for another burst of rain Wednesday night. Winds 
will remain breezy throughout the period. Perry 


Long term...Thursday through Monday...warm air advection will come 
to an end Thursday as a cold front moves through the region. This 
will lower snow levels and precipitation will return to snow in the 
higher elevations but also come to an end. Then a ridge of high 
pressure will build off the West Coast keeping the forecast area 
under a relative dry pattern. Could be some precipitation in the 
central Washington Cascades and areas northward but overall 
expecting light amounts. 


Hydrology...with the snow levels rising to around 7000 feet for 
Wednesday and Wednesday night and significant rain expected...we 
will see rapid rises on streams and rivers along the east slopes of 
the Washington Cascades and along the west facing slopes of the Blue 
Mountains. For Tuesday through Thursday...the east slopes of the 
Washington Cascades...6 to 7 inches of rain can be expected near the 
crest with lesser amounts eastward...with one-quarter to one-half 
inch expected in the Yakima Valley. Along the Blue Mountains...3 
inches of rain is expected in that period. Guidance shows the the 
Walla Walla and Umatilla rivers rising to flood stage Wednesday 
night and early Thursday. The mainstem Yakima and Naches rivers 
will see rapid rises...but are not expected to reach flood stage. 
Numerous small streams across central/southeast Washington and 
northeast Oregon will see rapid rises and we will monitor for 
possible advisories or warnings. Ml 


&& 


Preliminary point temps/pops... 
PDT 34 45 40 51 / 50 70 30 30 
alw 33 43 39 50 / 50 80 30 30 
psc 20 42 40 50 / 20 60 20 20 
ykm 16 37 32 45 / 20 50 20 20 
hri 34 45 41 50 / 20 60 20 20 
eln 25 36 32 41 / 20 60 30 30 
rdm 31 48 35 51 / 30 50 20 20 
lgd 29 39 35 43 / 60 80 40 50 
gcd 32 40 34 47 / 70 80 40 40 
dls 35 45 42 52 / 30 70 30 40 


&& 


PDT watches/warnings/advisories... 
or...Winter Storm Warning until 3 PM PST Tuesday for orz502. 


Washington...Winter Storm Warning until 3 PM PST Tuesday for waz030. 


&& 


$$ 


Ti:ygg 
for additional weather information, check our web site at... 
www.Weather.Gov/Pendleton 
76/76/76