Area Forecast Discussion
Issued by NWS Pendleton, OR

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264
FXUS66 KPDT 152322
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
422 PM PDT Sat May 15 2021

Updated aviation discussion

.SHORT TERM...this afternoon through Monday night...just some cu
buildups over/near mountains today. Some breezy northerly winds
over central OR with low off to our south. Otherwise, ridging
continues to overtop the cutoff low and build into the PacNW. This
will bring very warm conditions tomorrow with widespread highs in
the 80s to low 90s, 10-18 degrees above normal. Some breezy winds
possible through the Gorge and Cascade Gaps with thermal low over
the Basin. Ridging begins to weaken slightly and shift east on
Monday as an upper level low drops southeast along the BC coast
and towards the PacNW. Will be slightly cooler as heights lower a
bit but still warm with flow turning more southwest. Highs in the
upper 70s to 80s. Will begin to see a bit of marine push with the
cross Cascade temp/pressure gradient tightening. This will lead to
breezy to windy conditions Monday afternoon/evening. Could
approach advisory criteria in eastern Gorge and Kittitas valley.
Cascade showers possible Monday night as the upper low and cold
front begin to push onshore.

.LONG TERM...TUESDAY THROUGH SATURDAY...The extended period begins
as an approaching upper level trough drops down the BC coast and
into the PacNW. Initially, it will be characterized by increasing
winds on Tuesday as the system nears and isobars tighten. Sustained
west-southwest winds of 13 to 18 mph possible with gusts of 20 to 25
mph. Precipitation should stay confined along the Cascade crest and
west Tuesday before increasing chances for the Blues and Wallowas
late Tuesday into Wednesday. Showers will then become more
widespread through the day Wednesday into Thursday as the low nears
and stalls. Thunderstorms will also be possible Wednesday afternoon
and early evening, with the most instability present just ahead of
the cold front. Breezy conditions set to continue into Wednesday as
the main frontal system and associated closed low pressure moves
near Portland and continues southeast into central OR overnight into
Thursday. A strong upper level ridge develops over the southeast
CONUS, which will keep the closed low just to our south as we
proceed into the weekend. Long-term models are also hinting at the
potential for a reinforcing system to move into the PacNW early in
the work week, so stay tuned.

A cooling trend will initiate through the week as highs will plummet
about 15 degrees from Tuesday to Thursday and subfreezing
temperatures expected in the mountains. Highs for lower elevations
will bottom out in the mid 60s Thursday and mid 50s for the
mountains with lows in the low 40s for lower elevations and upper
20s to low 30s in the mountains. Snow levels are set to drop to 3000
to 3500 feet Thursday before slowly rebounding into the 5000 feet
range Friday afternoon.

Observing the ensembles, the largest discrepancy is associated with
the timing and location of the incoming trough and associated closed
low. The ECMWF is slightly faster than the GFS, and the low is much
closer in proximity - stalling more in south central OR than in
northern NV as is with the GFS. The cluster phase space Wednesday
and Thursday shows much closer means between the ensembles and
deterministic outcomes, as well as less overall spread with the
ECMWF. The ECMWF ensembles do begin to have a little more
variability Friday and Saturday, but still incur slightly more
confidence than the GFS, which still has quite a wide spread across
all ensemble clusters. 75

&&

.AVIATION...00Z TAFs...VFR conditions expected through the period.
Winds 5-15g20-25kts through this evening at KRDM and KBDN otherwise
less than 10kts overnight. Winds increase to 10-15kts with higher
gusts tomorrow afternoon at KDLS, while remaining less than 10kts
elsewhere

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  49  86  51  82 /   0   0   0   0
ALW  52  89  56  85 /   0   0   0   0
PSC  54  92  57  88 /   0   0   0   0
YKM  51  91  53  85 /   0   0   0   0
HRI  50  91  55  86 /   0   0   0   0
ELN  49  85  53  76 /   0   0   0   0
RDM  42  84  43  80 /   0   0   0   0
LGD  47  82  48  80 /   0   0   0   0
GCD  46  83  47  83 /   0   0   0   0
DLS  55  88  54  79 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.

&&

$$

SHORT TERM...84
LONG TERM....75
AVIATION.....84



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