106 
FXUS66 KPDT 170926
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
230 AM PDT Tue Sep 17 2019

.SHORT TERM...Today through Thursday...Fall has arrived early, as 
yesterday's cold front brought temperatures in the 50s to mid 60s 
(65-70 in the Lower Columbia Basin) and numerous showers.  Rainfall 
amounts generally ranged from a few hundredths across south central 
WA and north central OR to 0.1-0.25 inch for areas east-southeast of 
the Blue Mountains and 0.25-0.6 inch along the Blue Mountains down 
to central OR.  The parent upper low is over central ID with wrap 
around precipitation continuing in far eastern Wallowa County.  The 
rest of the area will have a brief break in precipitation before the 
next system arrives today.  A warm front will spread precipitation 
to the WA and northern OR Cascades by sunrise this morning, then 
over the remainder of the OR Cascades and as far east as Prosser-
Arlington-Condon-Prineville by noon.  By 5 PM, the warm front will 
bring widespread rain (snow levels 7000-9000 feet) to all areas. 
Temperatures this afternoon will only rise into the mid-50s to mid-
60s.  These are temperatures that are seasonal average for mid 
October--not mid September.  Winds aloft are increasing and there 
will be breezy winds in some areas with high gusts along exposed 
ridges.

The closed low associated with today's warm front will weaken into 
an open trough as it travels across WA/OR Wednesday.  Numerous 
showers will develop during the day, and just about anywhere in the 
forecast area may observe a few lightning strikes and small hail due 
to the cold air advection aloft and steep lapse rates. Rainfall 
amounts over the next 36 hours will range from 0.2-0.6 inch with 
higher amounts along the Cascades.  Some of the higher peaks of the 
Cascades, Strawberry Mountains, and the Wallowas above 7000 feet 
will have at least several inches of snow.  

By 12Z Thursday, the trough will be over the eastern third of WA/OR 
and will continue to bring scattered showers Wednesday night over 
central and northeast OR. A drier northerly flow aloft will follow, 
and precipitation will end over south central WA and north central 
OR.  The trough will show little movement on Thursday, therefore 
showers are likely and possibly a few thunderstorms will develop 
from the Blue Mountains eastward while the western half of the 
forecast area will have partly to mostly cloudy skies and a few 
mountain showers. Temperatures will be about the same or a little 
warmer on Thursday. Wister


.LONG TERM...Thursday night through Tuesday...An upper trough will 
exit the region Thursday night and be replaced by a northerly flow 
on Friday and Friday night ahead of an upper ridge building in from 
the west to arrive on Saturday. There will still be some lingering 
showers over the mountains in an upslope northerly flow behind the 
trough on Friday, but then it will be dry in all areas on Saturday 
and a few degrees warmer with temperatures rebounding back into the 
lower to mid 70s in the lower elevations on Saturday. The upper 
ridge will persist Saturday night, but then a cold front and another 
upper trough will drop down from the northwest on Sunday bringing 
another chance for rain, especially in northern areas. After that 
the long range model diverge from each other significantly for 
Monday and Tuesday. The Canadian has a broad upper ridge over the 
region while the ECMWF and GFS both have a deep upper trough exiting 
the area with a northerly flow aloft over the forecast area. Due to 
the uncertainty and inconsistency in the models, have opted to not 
make too many changes and go with the National Blend of the Models 
(NBM) almost entirely. This has a few showers over the forecast area 
on Monday, with mostly dry conditions on Tuesday. Temperatures are 
to be near normal by Tuesday. It will be breezy at times, especially 
on the ridge tops while weather systems move through the area, but 
otherwise winds will not be too strong, and generally 5 to 15 mph. 88

&&

.AVIATION...12Z TAFs...A wet weather system will move into the 
region and bring lowering CIGs and visibilities with increasing rain 
from the west. This may cause periods of MVFR conditions by this 
afternoon and tonight. The lower elevation TAF sites will be mostly 
VFR. It will also become locally breezy to windy this afternoon and 
evening as this weather system moves into the region with wind 
speeds of 15 to 25 kts at flight levels between 5K-15K feet MSL, and 
5 to 15 kts at the surface. 88


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  63  51  64  50 /  70  80  50  40 
ALW  66  54  67  50 /  50  70  50  40 
PSC  67  54  69  51 /  60  50  30  40 
YKM  59  46  65  47 /  80  50  50  30 
HRI  66  53  69  52 /  70  60  40  40 
ELN  60  46  64  45 /  80  60  60  30 
RDM  58  43  59  42 /  80  90  80  50 
LGD  62  47  59  45 /  60  90  80  60 
GCD  58  47  58  45 /  80 100  80  60 
DLS  63  52  65  52 /  90  70  70  30 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

85/88/88