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Area Forecast Discussion (AFD)

Issued by Pendleton, OR (PDT)

FXUS66 KPDT 191539

Area Forecast Discussion
National Weather Service Pendleton OR
839 AM PDT Fri Apr 19 2019

.SHORT TERM...A cold front now approaching the Olympic Peninsula
will push its way to the WA Cascades around noon today, across
southeast WA and north central OR between noon and 4 PM, then the
remainder of the forecast area late this afternoon and early
evening. There are couple of weather concerns associated with the
approaching front, mainly the thunderstorm threat. Based on the 
MLCAPES between 600-900 J/kg and 35-40 knots of bulk shear, some 
storms could be strong with heavy rain and dime-size hail. 
Currently, skies are mostly sunny throughout eastern OR which will
aid in surface heating late in the day. Fortunately, storm motion
will be around 15-20 knots so the heavy showers that may occur 
with thunderstorms will be relatively short lived. Winds will 
increase ahead and behind the front with gusts to 25-30 mph--not 
strong but those deciding to do agricultural burning may be caught
by surprise by the sudden wind shift and gusts. 

The front is moving slower than previously anticipated, and the
forecast was updated to reflect the later timing of precipitation.
QPF amounts were also adjusted to go higher in the Blues and
Wallowas this evening. In general, the front will bring up to 
0.25 inch of rain (locally heavier underneath showers or 
thunderstorms) but the Blues and Wallowas could receive 0.25-0.5

The upper level trough and cold front will move east Saturday with
clearing skies from the north. Sunday is looking great for 
outdoor activities and Easter egg hunting. Skies will be mostly 
sunny with highs in the mid-50s to mid-60s for most of the 
forecast. The Lower Columbia Basin and Eastern Columbia River 
Gorge will be around 70 on Sunday. Wister


.PREV DISCUSSION... /issued 458 AM PDT Fri Apr 19 2019/ 

LONG TERM...Monday through Friday...Monday through Tuesday night a 
ridge will be over the area and fair and dry weather is expected 
aside from a slight chance of upslope showers along the Washington 
Cascade crest. There will be partly cloudy skies Monday night 
through Tuesday night as a disturbance approaches the coast but only 
makes slow progress. By Wednesday the ECMWF and Canadian models show 
a weak system and trough crossing the area and flattening the ridge 
to the south while the ECMWF has the disturbance fizzle out and 
maintains a ridge. Have leaned towards the GFS and have a chance of 
showers in the mountains Wednesday afternoon along with a slight 
chance of thunderstorms in the eastern Oregon mountains. The lower 
elevations will have a slight chance of showers with the Columbia 
Basin remaining dry. Showers will taper off overnight. Models 
continue to disagree Thursday and Thursday night with the GFS and 
Canadian continuing to have a trough over the area and the ECMWF 
having a ridge. Have kept a slight chance of showers in the 
mountains with the lower elevations dry. On Friday, the GFS 
continues to have a weak trough over the area while the ECMWF has a 
system and trough moving through the area. Have kept a middle ground 
with a slight chance of showers mainly in the mountains. 
Temperatures Monday through Wednesday will be in the mid 60s to mid 
70s then for Thursday and Friday will be in the 60s and lower 70s in 
the lower elevations and in the 50s and lower 60s in the mountains. 

AVIATION...12Z TAFs...A cold front and trough approaching the area 
will bring increasing mid and upper level clouds today. Showers are 
expected this afternoon and tonight. There will also be a chance of 
thunderstorms this afternoon and evening over central Oregon and the 
eastern Oregon mountains, potentially affecting KRDM and KBDN. Did 
not feel the chances of thunder were strong enough to mention in the 
TAFs for KRDM and KBDN but the likeliest times would be 21Z-02z. 
After 00Z, ceilings will be 3500-8000 feet with occasional MVFR 
conditions possible. West to northwest winds will increase to 10 to 
20 kts with higher gusts this afternoon from 20Z-03Z but otherwise 
winds will be less than 12 kts. Perry


PDT  72  46  62  37 /  20  60  10  10 
ALW  74  48  64  39 /  20  50  10  10 
PSC  76  49  69  39 /  20  20  10  10 
YKM  71  44  67  38 /  20  10  10   0 
HRI  75  49  68  39 /  20  30  10  10 
ELN  63  40  63  36 /  30  10  10   0 
RDM  70  43  56  32 /  40  60  50  10 
LGD  71  45  55  35 /  60  80  50  20 
GCD  74  45  53  35 /  60  80  70  30 
DLS  68  47  67  40 /  20  30  10  10