Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 190515

Area Forecast Discussion
National Weather Service Pendleton OR
1015 PM PDT Thu Apr 18 2019

Not much change with the forecast rationale regarding TAFs through
early Friday with high pressure in control. Clouds will lower and
thicken into the afternoon as a cold front approaches and by late
afternoon/early evening there could be SHRA, but at this time it
looks to be light enough to maintain the VFR conditions. Expect
some wind gusts to around 20 kt from the W to NW in the late
morning early aftn.


.PREV DISCUSSION... /issued 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




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