672
FXUS66 KPDT 031707
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1007 AM PDT Sun Aug 3 2025

Updated Aviation Discussion

.AVIATION...00Z TAFs...Mostly VFR conditions to prevail through
the period. Exceptions will be sites RDM/BDN, where scattered
thunderstorms are expected to impact these sites between 21Z-02Z
today. These storms may produce MVFR or less conditions under
heavy rainfall (50-60% confidence). Winds will be mostly light,
12kts or less, at sites PDT/RDM/BDN/YKM/ALW/PSC through the
period. However, sites RDM/BDN could also see gusty erratic winds
from thunderstorm outflows between 21Z-02Z. Winds at site DLS will
be 12-20kts with gusts up to 30kts through the period. Lawhorn/82


&&

PREV DISCUSSION... /issued 128 PM PDT Sat Aug 2 2025/

.DISCUSSION...An active weather pattern accompanied by showers
and thunderstorms as well as locally breezy winds is forecast
this weekend into Monday as an offshore upper-level trough swings
onshore Sunday through Monday. There is significantly more
uncertainty in the 500-hPa pattern, and forecast details, by the
middle to end of next week in the wake of this first trough.
However, ensemble NWP is trending towards a broad troughing
pattern with some potential (10-40%) for precipitation for the
entire forecast area; highest chances will be over the Washington
Cascades, followed by the Oregon Cascades and northern Blue
Mountains.

Today, isolated thunderstorms have developed across the Blue
Mountains. A mix of wet and dry storms is forecast, with no fire
weather products in effect due to insufficient confidence in
abundant lightning.

Elsewhere, there is medium (40%) confidence in small pockets of
wind/rh overlap meeting Red Flag conditions in the eastern
Columbia River Gorge and western reaches of the lower Columbia
Basin this afternoon and Sunday afternoon.

Looking ahead to tonight, NWP guidance shows a weak shortwave
tracking over eastern Oregon and south-central Washington,
embedded within a broader region of synoptic-scale forcing
associated with the aforementioned upper-level trough. Coupled
with pockets of negative mid-level (700-500mb) theta-e lapse rates
and ample mid-level moisture (RH of 70-100%), this may induce
isolated nocturnal shower/thunderstorms tonight/Sunday morning
over central Oregon, eastern mountains, Blue Mountain foothills
into the lower Columbia Basin. Confidence in occurrence is
currently medium (40-60%), highest across the Ochocos, southern
Blue Mountains, and adjacent foothills.

Sunday, there is high confidence (80%) in scattered showers and
thunderstorms across central Oregon and the Blue Mountains.
Activity will be more isolated across the foothills and Columbia
Basin. Isolated dry thunderstorms are forecast with most storms
remaining wet (0.10" of precipitation or greater), thus no fire
weather products have been issued despite anticipated lightning.
Forecast CAPE of 500-1000 J/kg, effective shear of 25-35 kts, and
inverted-v soundings should facilitate a marginal threat of severe
(50 kts or greater) outflow winds and small to marginally severe
(1-inch diameter) hail across portions of central and eastern
Oregon.

A brief lull in active weather is anticipated Tuesday, followed by
a return to active weather Wednesday through Friday. While the
most likely outcome keeps the bulk of the precipitation from the
Washington Cascades north through southern Canada, a more
interesting alternate scenario is present in ensemble solutions.
More specifically, there is a low potential (10% or less) for an
early-season, inland-penetrating atmospheric river coupled with
sufficient synoptic forcing to facilitate a noteworthy
precipitation event for inland areas. While ensemble-mean PWATs
of 120-180% of normal are advertised area-wide across eastern
Oregon and eastern Washington, significant ensemble spread is
present with regard to timing of said moisture transport into the
region. Will note the 00Z Aug 7 to 00Z Aug 8 ECMWF EFI shift of
tails is positive for the lower Columbia Basin, Blue Mountain
foothills, and northern Blue Mountains. That said, it is small
(0-1), indicating the tail of the QPF distribution is forecasting
an anomalous event relative to model re-forecasts.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  88  59  84  55 /  20  40  30  10
ALW  89  63  83  60 /  20  30  30  10
PSC  91  59  87  57 /  20  20  20   0
YKM  91  59  87  58 /   0  10  10   0
HRI  91  61  86  57 /  20  20  20   0
ELN  86  58  82  56 /   0   0  10   0
RDM  83  48  81  46 /  20  30  10   0
LGD  83  55  79  51 /  30  50  50  10
GCD  85  53  81  51 /  60  60  30  10
DLS  83  60  81  60 /   0  10   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 2 PM this afternoon to 8 PM PDT this
     evening for ORZ698.

WA...None.
&&

$$

SHORT TERM...86
LONG TERM....86
AVIATION...82