536
FXUS66 KPDT 131150
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
450 AM PDT Thu Aug 13 2026

.KEY MESSAGES...

- Red Flag Warnings in effect for abundant lightning today into
  Friday morning.

- A convective weather pattern will continue through at least
  Saturday with daily shower and thunderstorm chances. More
  uncertainty in pattern details Sunday into next week.

- Near-seasonal temperatures through the week.

&&

.DISCUSSION...
Water vapor imagery reveals a shortwave trough over the Pacific
Northwest, with an embedded circulation noted over northeast
Washington. Forcing associated with the aforementioned
circulation has likely been the catalyst for convection that
developed yesterday afternoon across the Washington Cascades and
remains ongoing northeast of our forecast area. Meanwhile, the
Blue Mountains remain beneath the entrance region to a subtle
mid/upper jet. Coupled with modest vorticity advection and mid-
level moisture, some weak showers are developing early this
morning. Not anticipating any robust convection, but
observations are consistent with what NWP guidance has been
advertising: modest synoptic-scale forcing coupled with
sufficient mid-level (700-500 hPa) moisture and negative mid-
level (700-500 hPa) theta-e lapse rates typically facilitate
some weak nocturnal convection (predominantly showers with
isolated embedded thunderstorms).

The circulation mentioned above will then exit to the northeast
into the northern Rockies through the day, but a second
vorticity lobe is expected to dive southeast into the Pacific
Northwest today, reinforcing the shortwave trough. Additional
convection is expected (95 percent confidence) to develop this
afternoon across the mountains, and the previous day shift
issued Red Flag Warnings for multiple fire weather zones in
Oregon due to forecast scattered thunderstorms and abundant
lightning. Note that the warnings for much of the Blue Mountains
continue Thursday night for nocturnal convection.

Looking ahead, ensemble NWP guidance suggests continued
southwest flow aloft and additional reinforcing shortwaves
through at least Saturday. This will keep a convective pattern
in place resulting in daily shower and thunderstorm chances,
mainly over the mountains. Additional Fire Weather Watches or
Red Flag Warnings may be needed if confidence in abundant
lightning increases for Friday afternoon or over the weekend.

Sunday into next week, uncertainty in pattern details burgeons
due to model differences in the development and evolution of a
deep closed low in the Pacific. Ensemble cluster analysis
indicates concensus that the low will develop, but roughly equal
chances (40-60 percent) of either the deep closed low remaining
well offshore into the middle of next week or a somewhat more
progressive pattern with a weaker open wave trough over the
Pacific Northwest in addition to a weaker offshore low. Either
solution puts the forecast area under a pattern that is
favorable for some periods of convection, but chances of
convection have trended downward since yesterday`s discussion
for Sunday into early next week. Broadly, still have 10-25%
chances of precipitation for the mountains with lower chances
for non-mountain areas.

Lastly, Air Quality Alerts/Advisories issued by air quality
agencies remain in effect for the majority of our forecast area
due to wildfire smoke from ongoing regional wildfires.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
VFR conditions are forecast at all sites through the period.
However, smoke from regional wildfires is anticipated to be
present and will pose some risk of sub-VFR CIGs/VSBYs.
Confidence was too low to forecast anything below 6SM based on
current observations and model guidance.

Showers and thunderstorms are forecast this afternoon in central
Oregon, mainly south and east of BDN/RDM, but did have
confidence to put a PROB30 group in at BDN for showers.
Elsewhere, there are lower chances (20% or less) at RDM/YKM.

Winds of 10 kts or less are forecast at all sites, albeit with
periodic higher gusts. Additionally, any showers and
thunderstorms that develop will be capable of producing gusty
outflow winds.

&&

.Preliminary Point Temps/PoPs...
PDT  85  54  87  57 /   0   0   0   0
ALW  87  59  88  62 /   0   0   0   0
PSC  89  58  90  58 /   0   0   0   0
YKM  88  61  88  59 /   0  10  10   0
HRI  88  59  90  60 /   0   0   0   0
ELN  83  57  82  56 /  10  20  30   0
RDM  84  49  85  49 /   0  10  10  10
LGD  86  55  86  55 /   0  30  30  10
GCD  87  54  86  54 /  10  60  40  20
DLS  90  63  91  63 /   0   0  10   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Air Quality Alert until 3 PM PDT Friday for WAZ026>030-521>523.
OR...Air Quality Alert until 3 PM PDT Friday for ORZ041-049-050-502-
     503-505-506-509>511.
     Red Flag Warning from 1 PM this afternoon to 5 AM PDT Friday
     for ORZ696>699.
     Red Flag Warning from 1 PM this afternoon to 9 PM PDT this
     evening for ORZ700-705.

&&

$$

DISCUSSION...86
AVIATION...86