125
FXUS66 KPDT 072336
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
436 PM PDT Tue May 7 2024

Updated Aviation Discussion...

.SHORT TERM...Tonight through Thursday Night...The main weather
concerns will occur during the next 24 hours as a longwave trough
over much of the CONUS shifts east as an upper ridge strengthens out
in the eastern Pacific. Currently we have a northwest flow over the
area and that is promoting an upslope flow into the Cascade crest
and the eastern Oregon mountains where some lingering showers
continue. Temperatures have warmed, so snow has turned over to rain
and have let the Winter Weather Advisory for the East Slopes of the
Oregon Cascades and Northern Blue Mountains expire a few hours ago.
The northwest flow will continue this evening with just light
precipitation amounts and as the flow turns more northerly and drier
overnight, precipitation will end. Pressure gradients remain tight
though the Kittitas Valley and models show the pressure differences
between Seattle and the Tri-Cities beginning to relax in the
evening. The current Wind Advisory in the Kittitas Valley will
remain in effect through 11 PM this evening and winds there will
continue at around 20 mph overnight while the rest of the Columbia
Basin will see breezy winds through this evening dropping off to 5
to 10 mph overnight. Another concern is that skies will clear over
much of the area overnight. radiative cooling will allow
temperatures to cool several degrees from last night with lows in
the mid 30s to around 40 in the Columbia Basin and in the mid 20s to
lower 30s elsewhere. Have some concerns about temperatures dropping
to around freezing in pockets in the Columbia Basin, Yakima Valley
and Blue Mountain Foothills. The forecast low temperatures at
Yakima, Pendleton and Connell are around 34-35 degrees, but
probabilistic guidance shows a less than a 10 percent chance of
freezing temperatures in Yakima and Pendleton and only about a 25-35
percent chance around Connell and in isolated rural areas around
Pendleton and Yakima. Other locations in the Columbia Basin and
Gorge are warmer, so will not issue a freeze warning for zones
eligible for one.

Tomorrow will see the offshore ridge strengthen and move closer to
the coast and the flow will turn to the northeast in the afternoon.
The northeast flow will allow for a slight chance of light rain and
snow showers in far eastern Wallowa county but further west impacts
will be just partly to mostly cloudy skies. With the ridge having
more influence, temperatures will warm 6 to 10 degrees from today
with highs in the 60s and lower 70s in the lower elevations and in
the 50s in the mountains.

As we get into Wednesday night through Thursday night, the trough to
our east will split with a lobe of low pressure retrograding
westward into southern California and Nevada while the main energy
of the trough will move eastward into the Midwest. This will tilt
the ridge along our coast, but will not have a significant impact on
our weather. A period of dry and sunny weather is expected with
temperatures warming another 10 degrees or so on Thursday. Highs
will be in the 70s and lower 80s and in the 60s in the mountains,
roughly 10 degrees above normal. The pressure differences between
the ridge and the low to the south will generate some breezy 10 to
20 mph northeast winds Thursday afternoon but do not expect any wind
highlights will be needed. Perry/83

.LONG TERM...Friday through Tuesday...High pressure remains the
prevailing weather feature during on the onset of the forecast
period. Dry and warming conditions will be present through at least
Sunday under the influence of this pattern. The warmest locations
anticipated to be across the Columbia Basin and into the Kittitas
Valley on Friday, where guidance indicates an 80 to 100% chance for
temperatures to reach or exceed 80 degrees. The warm air will spread
to include more of the lower elevation locations on Saturday with
numerous locations indicating a high chance (80-100%) for
temperatures of 80 degrees. Additionally, on Saturday, portions of
south-central Washington, including the Tri-Cities area will see a
70-80% chance for high temperatures of 90 degrees. Saturday will be
the warmest day of the forecast period as the area of high pressure
flattens and progresses eastward on Sunday. During the warmest
periods, temperatures will be between 15 and 20 degrees above normal.

As the ridge flattens on Sunday, temperatures will be able to cool
slightly, though a wide swath of south-central Washington remains in
a high chance (80-95%) of seeing daytime temperatures of 80 degrees.
Lower elevations in northern and central Oregon will see values
between 70 degrees and 80 degrees, though guidance indicates a
moderate (40-60%) chance for temperatures to reach 80 degrees. Dry
conditions will still prevail through the remainder of the weekend.

Conditions will continue to cool for the beginning part of next
week. By Monday morning, guidance indicates a low chance (10-20%)
for showers to develop over the Washington Cascades, with the
remainder of the area remaining dry. QPF related clusters indicate
additional disagreement on the development of showers, helping to
keep those probabilities low. Even with the cooling, temperatures at
the warmest locations will still be around 5 degrees above normal.

Through the forecast period, the pattern related Cluster Analysis
indicates decent agreement. There is some variation on intensity of
the high pressure, which will impact the level of warmth across the
area, but placement is generally similar. Branham/76

.AVIATION...00z TAFs...VFR conditions to prevail through the
period. Light showers will continue across the mountains this
evening, especially east of sites PDT/ALW, but are expected to end
tonight. Breezy west/northwest winds at sites DLS/RDM/BDN/YKM and
west/southwest winds at sites PDT/ALW/PSC will continue through
this evening, with 12-20kts and gusts up to around 30kts, then
becoming 12kts or less overnight and through tomorrow...except at
site DLS where northwest winds will be 12-15kts with gusts
20-25kts after 17Z tomorrow.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  35  62  40  73 /   0   0   0   0
ALW  38  64  42  77 /   0   0   0   0
PSC  40  71  45  81 /   0   0   0   0
YKM  35  73  42  81 /   0   0   0   0
HRI  37  69  42  79 /   0   0   0   0
ELN  37  69  42  80 /   0   0   0   0
RDM  27  60  34  71 /   0   0   0   0
LGD  32  57  37  71 /   0  10   0   0
GCD  31  57  32  72 /  10   0   0   0
DLS  40  71  46  80 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Wind Advisory until 11 PM PDT this evening for WAZ026.

&&

$$

SHORT TERM...83
LONG TERM....76
AVIATION...82