602 
FXUS66 KPDT 242328
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
428 PM PDT Wed May 24 2023

Updated Aviation Discussion

.AVIATION...00z TAFs...VFR conditions expected through the period.
Expecting primarily NW/N winds during the day with a few clouds
5-10 kft, clearing at night as winds become more terrain-driven.
Winds expected to become northerly once again during the day
Thursday. Evans/74

&&

.PREV DISCUSSION... /issued 234 PM PDT Wed May 24 2023/ 

SHORT TERM...Tonight through Friday Night...An upper trough
remains over the Pacific Northwest this afternoon and is expected
to remain through Friday night. This will keep weather unsettled
through the next few days. Currently the trough has an upper low 
in northeast Washington radar shows weak thunderstorms rotating 
around the low. Have added a slight chance of thunderstorms for 
the rest of the afternoon north of the Tri- Cities just in case of
some of the cells drift south of their current location. Other 
cells are drifting south towards the Washington Cascades, so also 
have a slight chance of thunderstorms there. Instability is weak 
and moisture is not too impressive, so just expect brief storms 
that develop then quickly die off. Rain amounts will be minimal. 
Storms should end shortly after sundown. Lows tonight will be a 
few degrees warmer than the last couple of nights with mid 40s to 
mid 50s and upper 30s to mid 40s in the mountains. 

Tomorrow, the upper low will have moved into southern British
Columbia and this will increase moisture somewhat and instability,
while mild, will be a bit stronger than today. Would characterize
the coverage from the SREF paintball plot as widely isolated 
thunderstorms. Have a slight chance of showers and thunderstorms 
over the Cascades as well as the Elkhorn and Wallowa Mountains. 
Would not shocked to see a cell or two elsewhere in the eastern 
mountains, but the probability was too low to include it. 
Any thunderstorms should be fairly weak due to the weak 
instability parameters and shear to low to let storms become 
organized. Once again, showers and thunderstorms will die off in 
the evening. Rain amounts should be fairly light though a tenth of
an inch will be possible with thunderstorms. Temperatures will be
up a few degrees tomorrow with highs in the mid 70s to mid 80s 
and in the mid 60s to lower 70s in the mountains. 

Friday becomes a little more interesting as instability increases
along with precipitable water and shear strengthens a bit. SPC 
has general thunderstorm coverage over the entire area but have 
limited it to a chance of showers and a slight chance of 
thunderstorms in the mountains in the afternoon. Also have a 
slight chance of showers in the Blue Mountain Foothills. SREF 
guidance indicates a 5-10 percent chance of strong thunderstorms 
in Wallowa County and have a chance of thunderstorms there. Rain 
amounts will mainly be just a few hundredths of an inch with up to
a tenth of an inch with thunderstorms. Once again showers and 
thunderstorms will end in the evening. The warming trend will 
continue as temperatures warm a couple more degrees to the upper 
70s to mid 80s with upper 60s to mid 70s in the mountains. 
Perry/83

LONG TERM...Saturday through Wednesday...A trough will be over 
the western CONUS at the start of the period. By Monday into 
Tuesday, the models remain in very good agreement that an upper 
low will move south over California and a more zonal flow will 
move into the Pacific northwest. There is considerable uncertainty
by Tuesday into Wednesday, with the GFS developing a ridge and 
the ECMWF still having a trough. The ensemble clusters also show 
the agreement, but begin to diverge by Tuesday and Wednesday. On 
Tuesday, only about 12% of the clusters, show anything but a 
trough over California. However, by Wednesday, only about 25% show
a deep trough, while another about 55% show a weaker trough and 
another 20% show a ridge. Also across the Pacific Northwest, there
are difference with regard to the troughing (or lack thereof), 
with a fairly even split 56% to 44% supporting the trough moving 
further south and east. Obviously this does not lend very high 
confidence in the forecast toward the end of the period. 

There will be at least some rain/thunderstorm chances over far 
eastern Oregon/Wallowa County on Saturday.  There could be very 
small chances on Sunday, and then the remainder of the extended 
period looks dry.  

High temperatures look to be above normal, but not too hot heading 
into the holiday weekend.  Highs Saturday and Sunday will range from 
the mid 70s across central Oregon, to the upper 80s in the Columbia 
Basin. Highs on Monday and Tuesday will be a few degrees warmer, 
ranging from near 80 degrees in central Oregon to near 90 degrees in 
the Basin.  Wednesday could be even a degree or two warmer, with 
highs in the lower 80s in central Oregon to around 90 or perhaps 
lower 90s in the Columbia Basin.  Overnight lows will be in the 40s 
and 50s.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  47  77  50  80 /   0   0   0  10 
ALW  50  81  53  84 /   0   0   0  20 
PSC  54  83  56  87 /   0   0   0   0 
YKM  51  80  55  82 /  10  10  10  10 
HRI  50  82  54  85 /   0   0   0  10 
ELN  48  77  51  78 /  10  10  10  10 
RDM  42  74  45  76 /   0   0  10  10 
LGD  43  73  47  76 /  10  10  10  20 
GCD  42  73  45  75 /  10  10  10  30 
DLS  53  84  56  87 /   0  10  10  10 

&&

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

$$

SHORT TERM...83
LONG TERM....77
AVIATION...74