222
FXUS66 KPDT 281059
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
359 AM PDT Tue Apr 28 2026

.KEY MESSAGES...
- Temperatures warming to above normal into early next week

- Uncertainty over the weekend and early next week in potential
  for mountain shower activity

&&

.DISCUSSION...Today through Friday: Satellite imagery tonight
shows a deck of mid to high level cloud cover drifting into and
over portions of the Blue mountains, while a stratus deck is
butting up against the west side of the Cascade crest. Breezy
Cascade gap winds have weakened tonight as well, while the
remainder of the forecast area is under quiet conditions.

Today, 500mb heights will begin to rise ahead of an approaching
upper level ridge in the northeast Pacific, while a shortwave
clips Wallowa County in the afternoon. The approaching ridge
will keep much of the forecast area dry today, though isolated
showers will develop along the ridges of the Wallowa mountains
throughout the afternoon. While conditions remain dry, the
cross-Cascade pressure gradient will tighten into the afternoon,
producing breezy winds (15-25mph with gusts up to 40mph)
through the Cascade gaps and into the Lower Columbia Basin.

Wednesday, upper level ridging will build over the region and
persist overhead through early Friday (confidence 75-85%). The
building high pressure aloft will result in drying and warming
conditions across much of the forecast area. High temperatures
will warm well above normal, with mid to upper 70s in the mid
elevations (central OR) and upper 70s to lower 80s in the lower
elevations by Friday.

Ensemble guidance is in agreement that the upper ridge will
flatten and push east as an upper trough approaches the PacNW
the second half of Friday. However, conditions will remain dry
and warm throughout the forecast area (confidence 65-75%).

Saturday through Monday: Ensemble cluster guidance begins in
good agreement of the aforementioned upper trough digging south
and transitioning into a closed low off the northern CA coast
late Saturday. During this time, the trough/low will place a
southerly flow over OR and into southeast WA, with weak
instability developing over the eastern mountains and OR
Cascades. This will lead to chances (20-35%) of isolated to
scattered showers developing with a slight chance (~15-20%) of
isolated thunderstorms as well.

Sunday through Monday, ensemble members of the ECMWF, GFS, and
Canadian are split 50/50 on the evolution of the closed low near
CA. The prevailing solutions are either: the closed low
retrogrades slightly offshore Sunday with little shower activity
over the eastern mountains and OR Cascades, then approaches
Monday with shower activity limited to the southern half of OR;
or the closed low stays along the CA coast with
shower/weak convective activity across the eastern mountains
Sunday, then the low gradually moves inland Monday, resulting in
another round of shower/weak convective activity across the
eastern mountains. There`s not a clear winner in either of these
scenarios at the moment, so confidence is low (20-25%) in
precipitation scenarios Sunday into Monday. That said, either of
these solutions do result in a Rex Block pattern along the
coast, which will result in continued above normal temperatures
for the inland PacNW. And to give an idea of how warm it may
get, portions of the WA Columbia Basin and Yakima valley will
see a 30-50% chance of afternoon temperatures exceeding 90
degrees, while the remainder of the lower to mid elevations will
see a 60-90% chance of exceeding 80 degrees Monday afternoon.
Lawhorn/82

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...VFR conditions to
prevail through the period. Winds will increase to 12-17kts with
gusts to around 25kts at site DLS this afternoon. Sites
PDT/RDM/ALW will see winds around 12kts with gusts up to 21kts
this afternoon. Otherwise, winds will be light through the
period. Lawhorn/82

&&

.Preliminary Point Temps/PoPs...
PDT  65  40  69  43 /   0   0   0   0
ALW  66  44  71  47 /   0   0   0   0
PSC  70  43  74  44 /   0   0   0   0
YKM  69  41  74  45 /   0   0   0   0
HRI  68  41  73  42 /   0   0   0   0
ELN  62  38  69  42 /   0   0   0   0
RDM  64  30  67  34 /   0   0   0   0
LGD  63  39  67  39 /  10   0  10   0
GCD  63  38  67  38 /   0   0  10   0
DLS  66  42  74  47 /   0   0   0   0

&&

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

&&

$$

DISCUSSION...82
AVIATION...82