884 
FXUS66 KPDT 091753 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
1053 AM PDT Mon Apr 9 2018

Updated AVIATION discussion

.UPDATE...An upper level ridge will move through WA and OR today.
This will bring a sunny and warm day after a cold start. I 
updated forecast to reduce cloud cover this morning based on 
satellite. Variable high cloudiness and fair weather CU will 
produce partly cloudy skies this afternoon. Minor changes to 
temperatures were also made. Rest of forecast on track. Coonfield

&&

.AVIATION...18Z TAFs...VFR conditions and light winds through the 
next 24 hours. Cirrus 20-30kft will increase in coverage through the 
day ahead of the next system arriving Tuesday. Stratiform rain 
spreads east of the Cascades to TAF sites beginning along with 
lowering CIGS down to 040-060 AGL. Marginal Wind Shear within 2k 
feet AGL possible by 12Z Tuesday at KBDN and KRDM as winds above the 
surface increase through Tuesday morning, although not confident 
enough to add Low Level Wind Shear (LLWS) at this time. Will look at 
potential for LLWS at KRDM and KBDN for the 00Z TAF issuance 
this afternoon.  Polan 

&&

.PREVIOUS DISCUSSIONS... /issued 258 AM PDT Mon Apr 9 2018/ 

SHORT TERM...Today through Tuesday night...The Pacific Northwest 
will be under a transitory upper level ridge today and tonight. Thus 
will see dry and warmer conditions across the area through tonight. 
There is plenty of moisture aloft so will see partly cloudy skies 
with varying amounts of high cloudiness. Winds will be relatively 
light today. Will see an increase in winds overnight from central 
Oregon east and northeast across the interior mountains. Also should 
see winds become breezy to windy across the south end of the Grande 
Ronde valley and at the foot of Blue mountain foothills. The 
increase in winds will be in response to increasing pressure 
gradients due to the approach of the next Pacific system. This next 
system will bring varying chances of rain to the region by Tuesday 
morning. Snow levels will be between 6600 and 7800 feet Tuesday 
morning. This next system's cold front should be through the region 
by Tuesday afternoon. Thus will see varying coverages of showers 
Tuesday afternoon and evening with the highest coverages over the 
eastern mountain zones. Snow levels will fall Tuesday afternoon and 
evening, though they will remain above 4200 feet at the lowest 
Tuesday evening. Winds will increase to breezy across the Columbia 
Basin and adjacent valleys, as well as the Gorge, behind the cold 
front. These winds will decrease during the mid and late evening. 
Showers will decrease to a few lingering mountain showers late 
Tuesday night. Meanwhile snow levels will continue to fall 
overnight, but snow accumulations will be very limited and light. 90 

LONG TERM...Wednesday morning through Monday night...An active 
weather pattern with breezy conditions and periods of rain will 
continue through early next week as a pair of North Pacific lows 
transit the region. The wettest day still appears to be Wednesday 
afternoon/evening as a plume of subtropical moisture gets caught up 
in the southwesterly flow associated with a trough rotating around 
the first of the lows mentioned above. In the last few runs 
operational models have trended a little more progressive with this 
feature with upper level flow becoming westerly and cutting off this 
moisture feed by late Wednesday night. Have reduced total 
accumulations slightly to accommodate this change, but still expect 
up to .25 inches of rain in the lower elevations and .3 to .4 inches 
in the mountains by early Thursday. There is still some potential 
for some late season winter impacts in the passes during the day 
Thursday with snow levels falling to 2500 to 3500 feet, but it 
remains uncertain exactly how much moisture will be left to work 
with. Any mountain showers will taper off by Friday evening as weak 
ridging builds into the region for the first half of the weekend 
with the next system arriving Sunday afternoon. Peck 

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  64  43  61  40 /   0   0  30  10 
ALW  66  46  63  41 /   0   0  30  10 
PSC  67  42  66  39 /   0   0  20  10 
YKM  67  42  64  37 /   0   0  40  10 
HRI  67  43  65  38 /   0   0  20  10 
ELN  63  41  59  36 /   0   0  50  10 
RDM  67  42  60  34 /   0   0  30  10 
LGD  59  41  59  36 /   0   0  70  30 
GCD  61  45  58  38 /   0   0  60  30 
DLS  67  45  63  40 /   0   0  50  20 

&&

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

$$

76/99/90/74