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Area Forecast Discussion (AFD)

Issued by Pendleton, OR (PDT)

FXUS66 KPDT 251510

Area Forecast Discussion
National Weather Service Pendleton OR
810 AM PDT Tue Jun 25 2019

.SHORT TERM...Today and tonight...An upper level low has settled off 
the coast of the Pacific Northwest and has turned the flow over the 
region to southwesterly. This is increasing moisture across the 
region and will further increase instability this afternoon and 
overnight leading to some showers and potential thunderstorms. 
Already seeing a few showers this morning over Wallowa county with 
more expected to develop elsewhere as instability increases. Made 
some minor changes to chance of precipitation, temperatures, sky and 
winds for today and overnight in the morning update.  


.PREV DISCUSSION... /issued 215 AM PDT Tue Jun 25 2019/ 

Today through Thursday...An upper low off the Washington and
Oregon coasts will slowly rotate eastward through Thursday but
remain off the coast. THe low will send several short waves
through the area as the larger flow remains southwesterly. This
will allow for an increase in both moisture and instability. Rain

There will be some shortwave energy and instability this
afternoon, mainly over the mountains, where there could be some
showers or thunderstorms but the best chance looks to be on 
Wednesday when a stronger piece of energy moves through. Lifted
index values are forecast to be -3 to -7 in the eastern third of 
the area and the Storm Prediction Center has placed these 
locations in a Marginal Risk of severe thunderstorms. 

Precip chances remain into Friday, mainly south and east, but the
best instability may be to the south and east of the area as
guidance suggests another piece of energy is further south than
the one on Wednesday. 

Overall, an unsettled period for the next couple of days, due to t
he proximity of the upper low. With a broad trough over the
western CONUS, expect temps to remain below normal for at least
the next few days. 

Thursday night through Tuesday..Unsettled conditions 
will continue through at least Friday evening as an upper level low 
slowly drifts onshore 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 chance likely rain shower pops with a slight 
chance of thunder mostly confined to the Blue Mountains and Cascades 
where there will be more bang for the buck from filtered afternoon 
sunshine. Model consensus indicates continued southwesterly flow 
over the region through at least Sunday with another trough 
developing offshore but keep the best mid-level lapse rates south 
and east of the forecast area. Still, could see a stray shower 
mostly over the Blues Saturday and Sunday afternoon. There is 
significant disagreement (both run to run and model family) amongst 
operational and ensemble guidance by early next week with little 
confidence. As such, have steered the forecast in the general 
direction of the National Blend of Models which suggest a warmer 
drier period. Highs Friday will be around 5 degrees below normal 
with a steady increase to around 5 degrees above normal by the 
middle of next week.

12Z TAFs...Will see an increase in mid-level cloudiness 
this afternoon as synoptic lift associated with approaching jet max 
overspreads the area. Should see some surface-based showers and 
thunderstorms trying to develop in the vicinity of BDN/RDM before 
becoming rooted aloft and quickly tracking to the northwest across 
the Blues, perhaps approaching PDT and ALW by 02-03Z under support 
from the aforementioned jet. Conditions are expected to remain VFR 
outside of any heavier precip cores. Winds mostly 8-13KTs outside of 
gusty and erratic outflow winds near thunderstorms. Peck


PDT  78  53  74  51 /   0  20  30  50 
ALW  81  56  77  52 /   0  20  30  60 
PSC  84  61  79  55 /   0  20  20  50 
YKM  79  55  75  51 /   0  20  40  30 
HRI  82  58  78  53 /   0  20  30  50 
ELN  74  51  71  48 /  10  20  40  40 
RDM  73  46  66  42 /  20  20  50  40 
LGD  73  49  71  46 /  20  40  60  60 
GCD  74  52  72  45 /  30  40  50  40 
DLS  78  56  71  51 /  10  20  30  20