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Area Forecast Discussion (AFD)

Issued by Pendleton, OR (PDT)

FXUS66 KPDT 240912

Area Forecast Discussion
National Weather Service Pendleton OR
212 AM PDT Mon Jun 24 2019

.SHORT TERM...Today through Wednesday night. Dry westerly flow
aloft today. Satellite showing mainly clear skies early this
morning except for some marine clouds banked up to the Cascades.
Today will be mostly sunny with highs in the 70s to lower 80s.
Lighter winds as surface gradients have diminished. An upper low
currently off the central BC coast will approach the Pacific
northwest on Tuesday. The flow will become southwesterly with
increasing mid and high level clouds. Showers and thunderstorms
may develop later in the day in response to the low and increasing
instability. The low will be centered just offshore on Wednesday.
Moisture and instability will continue to increase and expect more
widespread showers and thunderstorms. 94

.LONG TERM...Thursday through Monday...Unsettled conditions will 
continue through at least Friday morning as an upper level low 
lingers just off the Oregon coast with continued advection of 
favorable mid-level lapse rates atop afternoon surface temperatures 
in the upper 60s to lower 70s and surface dewpoints near 40. 
Instability is rather marginal and shallow for thunderstorms, but 
weakening mid-level winds should limit potential of updrafts 
shearing out. Will continue with chance to likely rain shower pops 
with a slight chance of thunder mostly confined to the Blue 
Mountains west to the Oregon Cascades. The upper low will slowly 
drift ashore Friday with a round of afternoon instability showers 
possible region-wide. Forecast ELs are looking a little too low for 
thunder over much of the area, but may see a little activity over 
far eastern Wallowa County. Model consensus tries to develop another 
offshore trough Saturday through Monday which may keep us under 
southwesterly flow, although the most substantial mid-level lapse 
rates will be to our south and east which will limit any 
precipitation chances to our southern tier of counties. High 
temperatures start out about 5 degrees below normals for this time 
of year Thursday rising to near to normal Monday as cloud coverage 
begins to lessen. Peck


.AVIATION...12Z TAFs...Winds through and downwind of gaps through 
the Cascades should be a good deal lighter today with weakening of 
onshore flow, mostly 10-14KTs during the afternoon thermal gradient 
equalization across the mountains. As moist surface flow begins to 
weaken, should see the persistent upslope cigs near the northern 
Blues dissipating by late morning. Cirrus will build into the region 
late this afternoon/evening as southwesterly flow begins to increase 
ahead of a more unsettled period beginning Tuesday. Peck


PDT  78  50  80  52 /   0   0  10  30 
ALW  78  53  82  55 /   0   0  10  30 
PSC  81  52  84  56 /   0   0   0  20 
YKM  78  50  80  52 /   0   0  10  20 
HRI  80  52  83  55 /   0   0  10  20 
ELN  74  47  76  50 /   0   0  10  20 
RDM  75  43  74  45 /   0   0  30  30 
LGD  74  46  76  48 /   0   0  20  40 
GCD  74  44  75  47 /   0   0  30  30 
DLS  78  52  79  55 /   0   0  10  20