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Area Forecast Discussion (AFD)

Issued by Pendleton, OR (PDT)

FXUS66 KPDT 190353

Area Forecast Discussion
National Weather Service Pendleton OR
853 PM PDT Thu Apr 18 2019

Based on the latest radar as well as high resolution model data,
made some adjustments to pops for tonight into the first part of 
Friday. The ridge seems to be holding on longer than originally 
thought, so lowered pops in our western areas during this time. 
They weren't much during the early part of Friday, but cut them 
back, especially in the SW portion of our area. Otherwise, just 
made adjustments to temps and sky cover.


.PREV DISCUSSION... /issued 200 PM PDT Thu Apr 18 2019/ 

SHORT TERM...Tonight through Sunday...A ridge of high pressure will 
continue over the region overnight and into Friday. Then an upper 
level trough off the coast will begin moving into the region pushing 
a cold front into the area. Precipitation will increase along the 
crest of the Cascades late tonight and Friday then spread into 
eastern portion of the forecast area Friday afternoon. The Basin and 
east slopes of the Cascades will be rain shadowed by the Cascades so 
not expecting much precipitation in these areas but will experience 
some increasing breezy westerly winds Friday afternoon through 
evening. Will also see a slight chance of Thunderstorms mainly over 
Grant and Wallowa counties Friday afternoon and evening. A closed 
low pressure system forms at the tail end of the front off the 
southwest coast of Oregon Friday night and then moves into northern 
California Saturday. This process will stall the cold front over 
eastern Oregon From Wallowa county back to Klamath county late 
Friday through Saturday evening. The potential is there for some 
hefty precipitation occurring over Grant and Wallowa counties from 
late Friday through Saturday evening with an inch of rain or more 
possible. The front finally moves off to the southeast Saturday 
night and another ridge of high pressure rebuilds over the region on 

LONG TERM...Sunday night through Thursday. Models are in fairly 
good agreement in the long term. Mainly dry weather expected through 
Tuesday. Ridging builds in Sunday into Monday. Ridge axis shifts 
east and ridge flattens a bit Monday night into Tuesday, allowing 
for a more west to southwesterly flow aloft. This will lead to 
increased mid to high level moisture and can't rule out a few 
showers for the WA Cascades and possibly for the OR Cascades and 
Blues. A cold front is then expected to sweep through Tuesday night 
into Wednesday and bring a chance of showers across the region. 
Enough instability expected to suggest at least a chance of storms 
from central OR up through the Blues and Wallowas on Wednesday 
afternoon. Breezy to windy conditions also possible ahead and behind 
the frontal passage Wednesday. Some discrepancy between models 
beyond Wednesday but some output has frontal boundary stalling and 
allowing for a slight chance of showers across central OR up through 
the Blues and Wallowas on Thursday. Warm temps expected with highs 
in the upper 60s to 70s; slightly cooler Thursday behind the front.

AVIATION...00Z TAFs...Mostly clear to partly cloudy skies today. 
Mid to high clouds increasing overnight and could see a few showers 
over the mountains, but dry at the terminals through tomorrow 
morning. A cold front swinging through will bring a chance of 
showers near all sites tomorrow afternoon. Thunderstorms possible 
from central OR up through the Blues/Wallowas, so an outside shot of 
thunder near BDN, RDM, PDT and ALW after 18Z. Light winds through 
tomorrow morning, picking up 12-17g20-25kts tomorrow afternoon.

HYDROLOGY...Many rivers will be on the rise over the next couple of 
days due to the warmer weather creating snowmelt combined with the 
expected precipitation through Saturday. The John Day and Grande 
Ronde rivers are likely to see a return of some flooding due to 
these conditions and flood warnings have been issued. 


PDT  52  68  44  63 /   0  60  50  10 
ALW  54  71  46  64 /   0  60  50  10 
PSC  55  71  47  69 /   0  20  20  10 
YKM  52  68  42  67 /  10  20  10   0 
HRI  53  71  47  67 /   0  20  20  10 
ELN  49  60  37  63 /  10  20   0   0 
RDM  46  67  41  57 /   0  30  40  30 
LGD  46  68  41  56 /   0  80  80  30 
GCD  47  71  43  55 /   0  80  70  60 
DLS  52  65  45  68 /  10  20  10   0