Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

FXUS66 KPDT 291730

Area Forecast Discussion
National Weather Service Pendleton OR
1030 AM PDT Wed Mar 29 2017

Updated aviation discussion

.SHORT TERM...Today through Friday...A wet and windy period is 
expected over the next 24 to 36 hours as a system and trough crosses 
the area. The warm front with the system is over the area and rain 
has begun in most locations. This afternoon and tonight the cold 
front will follow the warm front and move through the area. Rain 
will be likely across the area through tonight, perhaps a little 
less so in the Columbia basin and Yakima and Kittitas valleys. Rain 
amounts will be significant with up to 1.5 inches in the mountains, 
up to an inch in Union and Wallowa counties, up to 2/3 of an inch in 
the Blue Mountain foothills and up to half an inch elsewhere. Snow 
levels will be high, so snow will be confined to above above 7000 
feet. The abundant rainfall will lead to river rises and hydrology 
concerns will have to be monitored carefully. Right now the John Day 
River at Service Creek and the Grande Ronde at Troy are expected to 
reach flood stage and several others are expected to be above 
bankfull. On Thursday a trough will cross the area with a chance of 
rain and snow in the mountains and a slight chance of rain in the 
lower elevations. Snow levels will be down to 3500 feet due to the 
colder air coming in with the trough. Rain amounts will be much 
light with less than a tenth of an inch in the lower elevations and 
up to a quarter inch in the mountains. Rain will taper off Thursday 
evening and end overnight. Winds will be another concern today and 
especially on Thursday. Pressure gradients are tightening up and 
much of the area will have southwest winds of 10 to 20 mph today 
with 15 to 25 mph in the Southern Grande Ronde Valley. Winds will 
decrease overnight but pressure gradients will be even stronger on 
Thursday with much of the area having west to northwest winds of 15 
to 25 mph. The Columbia Gorge and the Kittitas and Southern Grande 
Ronde Valleys look to be borderline for a wind advisory. Do not have 
enough confidence to put one out this early but anticipate that 
advisories might be needed for those areas. Friday an offshore ridge 
will build over the area for a sunny and dry day. Temperatures will 
be in the 50s as the warm front crosses the area today. Tomorrow 
highs will be in the mid 50s to lower 60s in the Columbia Basin with 
40s and lower 50s elsewhere. Friday will be in the upper 50s to mid 
60s with upper 40s to mid 50s in the mountains. Lows tonight will be 
in the mid 30s to mid 40s due to the heavy cloud cover but will drop 
to the mid 30s to around 40 with mid 20s to lower 30s in the 
mountains Thursday night. Perry

.LONG TERM...Friday night through Wednesday.  The extended starts 
off mainly dry as a ridge of high pressure moves across the area 
Friday night.  A weak frontal band is shown by the models to move 
south into Oregon on Saturday with some showers by late day. The 
unsettled weather returns by Sunday as a trough of low pressure is 
expected to move through Sunday with lingering showers over the 
eastern portions of the forecast area on Monday. Models are then 
diverging with the GFS dropping a low into southern Canada, while 
the ECMWF has a stronger ridge on Tuesday.  They do however come 
back into more agreement with a large low pressure area off the west 
coast which will keep the unsettled weather through mid week. 
Temperatures will be near to slightly below normal. 93  


.AVIATION...18z tafs. VFR conditions are generally expected with 
light rain for some sites through this afternoon. There may be some 
MVFR with the heavier showers and ceilings 050-070 with visibility 
lowering to 4-6SM at times. Winds will be 10-20kt. 


PDT  56  41  53  35 /  90  80  40  20 
ALW  57  45  54  40 /  90  80  50  20 
PSC  58  44  60  38 /  70  40  20   0 
YKM  60  39  61  35 /  60  30  20   0 
HRI  57  43  58  37 /  70  60  30  10 
ELN  54  37  52  34 /  70  40  20   0 
RDM  59  37  51  26 /  60  70  30  10 
LGD  55  40  51  36 /  90  90  70  30 
GCD  59  39  50  33 /  80 100  80  20 
DLS  57  44  58  40 /  80  60  20  10 



National Weather Service Glossary of Abbreviations