Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

FXUS66 KPDT 190231

Area Forecast Discussion
National Weather Service Pendleton OR
731 PM PDT Fri Aug 18 2017

.UPDATE...A dry westerly flow will be over the area for the next 
few days. An area of high clouds will move across the northern
portion of the forecast area through the late evening hours.
Otherwise mostly clear skies are expected tonight. Some smoke will
continue in central Oregon...mainly Deschutes and Crook 
Counties...from local fires. Low temperatures tonight will be 
mostly in the 50s with 40s in the mountains. A few 30s can be 
expected in the colder mountain valleys. Will update the cloud 
cover grids for Monday based on the latest NAM. A look at the RH 
fields suggests that there will be little if any cloud cover for 
Monday at eclipse time. 78


.AVIATION...06Z TAFS...VFR conditions are forecast to continue 
through the next 24 hours at all taf sites. Skies will remain 
mostly clear but there will be some smoke concerns impacting KRDM 
and KBDN due to local fires which could impact visibility and 
produce a smoke layer. However so far this evening there have been
no restrictions to VSBYS at either site. Winds will be mostly 5-15
kt but 10-20 kt at KDLS...with some higher gusts mainly after 18Z


.PREV DISCUSSION... /issued 310 PM PDT Fri Aug 18 2017/ 

SHORT TERM...Tonight through Monday...The Pacific Northwest remains 
in a flat westerly flow between and upper low in northern British 
Columbia and high pressure in the Pacific off of northern 
california. Satellite imagery shows a weak cold front about to move 
ashore on the Olympic Peninsula though a band of cirrus ahead of the 
front is moving through the Columbia Basin. Models are all showing a 
few light showers along the Washington Cascade crest this evening so 
have added a slight chance of rain showers near Snoqualmie Pass. Do 
not anticipate anything more than barely measurable rain. The front 
has also tightened up pressure gradients along the Cascades and 
winds are increasing in the Columbia Gorge and Kittitas Valley where 
20 to 25 mph winds are expected through early evening before 
decreasing overnight. The rest of the area will have 5 to 15 mph 
winds late this afternoon and evening. Smoke from wildfires in 
Central Oregon continue this afternoon and have carried through 
areas of smoke for the next couple of days from Redmond southward to 
La Pine. This weekend, the low to our north develops a trough over 
our area with a more northwesterly flow. Do not foresee any 
precipitation or even much in the way of clouds as moisture is 
lacking. Winds will pick up again Saturday afternoon in the Columbia 
Gorge and Kittitas Valley to 15 to 20 mph with the rest of the area 
mainly below 10 mph. By Sunday night the trough will be moving east 
into the Rockies and the offshore ridge will begin building over the 
area. Monday for the eclipse, skies should be clear though if fires 
remain active, smoke could cause some reduction in visibility in 
Central Oregon around Bend and perhaps north to Madras and east to 
John Day, but light winds and reduced instability aloft suggest 
fires will be less active over the next few days. Temperatures on 
Saturday and Sunday will be a few degrees cooler than today due to 
the trough with mid 70s to mid 80s across the region. Have trended 
night time lows for tonight through Sunday night cooler to match 
recent low temperatures being cooler than forecast. This yielded 
lows in the 50s in the Columbia basin and in the upper 30s and 40s 
elsewhere. On Monday with the ridge expanding over the area, highs 
will be 4 or 5 degrees warmer with mid 80s to lower 90s in the 
Columbia Basin and generally in the 80s elsewhere. Perry

LONG TERM...Monday night through Friday...An upper level ridge will 
migrate across the region Monday night and Tuesday. The ridge will 
move east of the area Tuesday night and Wednesday as an upper level 
trough approaches the coast. This will turn the flow more southerly 
across eastern Oregon and allow some moisture to advect into the 
region leading to the potential for some showers and thunderstorms 
from central Oregon to northeast Oregon Wednesday afternoon and 
overnight. The upper level trough will then sweep into southern 
British Columbia on Thursday pushing a dry cold front through the 
area with increased winds thus turning cooler Thursday and Friday. 


FIRE WEATHER...A combination of dry and marginally unstable 
conditions (Haines in the 5 category), poor to moderate recoveries, 
and a thermal trough brought active fire behavior to the large fires 
in central Oregon last night.  Conditions were not expected to 
change today, so Red Flag Warnings were posted along the east slopes 
of the Oregon Cascades and central and north central Oregon. In 
addition, gusty winds this afternoon and evening associated with a 
weak but dry cold front as well as RHs in the single digits and 
teens will continue through sunset. The Haines will improve to a low 
category of 4 tonight, and the humidity recoveries will not be as 
low as what was observed last night. Temperatures will be slightly 
cooler, RH's slightly higher, and winds lighter over the weekend 
which is good news for Monday's big event. No major fire weather 
concerns are anticipated on Monday as well, but it should be 
stressed that the dry conditions will continue and it doesn't take a 
lot of wind for a big problem for any new fires. Wister


PDT  58  83  54  83 /   0   0   0   0 
ALW  62  85  59  84 /   0   0   0   0 
PSC  59  87  55  86 /   0   0   0   0 
YKM  56  87  56  86 /   0   0   0   0 
HRI  59  86  56  86 /   0   0   0   0 
ELN  59  83  55  84 /   0   0   0   0 
RDM  47  84  44  84 /   0   0   0   0 
LGD  51  81  48  82 /   0   0   0   0 
GCD  50  84  48  83 /   0   0   0   0 
DLS  61  84  60  86 /   0   0   0   0 


OR...Red Flag Warning until 10 PM PDT this evening for ORZ610-611-


National Weather Service Glossary of Abbreviations