712
FXUS66 KPDT 201006
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
306 AM PDT Sat Jul 20 2024

.SHORT TERM...Today through Monday...Following the passage a weak
system over the top of the western USA ridge yesterday the ridge
will undergo an amplification northward into western Canada. This
amplification will result in warming temperatures across the
forecast area today through Sunday before cooling on Monday. High
temperatures today and Sunday could set record highs across portions
of the forecast area. Heat Advisories and Excessive Heat Warnings
continue over most of the forecast area which run through Monday.

A weak system off the California coast will move up the coast late
Saturday night and Sunday. This will provide enough atmospheric
forcing combined with the limited moisture to trigger some isolated
thunderstorms over central Oregon Sunday afternoon then spread them
northward along the east slopes of the Cascades through the evening
before ending.

Meanwhile, an upper level low pressure system in the Gulf of Alaska
will begin moving towards western Canada over the weekend. The
associated upper level trough will begin to push the upper level
ridge eastward Sunday before slowly moving inland through the first
of the week. The eastward progression will shift the thunderstorm
potential to over the eastern mountains Monday afternoon and
evening. Again, coverage of storms looks to be isolated as moisture
is limited. Temperatures will run around 10 degrees cooler on Monday
as this will be the end of the heat wave as temperatures return back
to near normal by midweek.

.LONG TERM...Tuesday through Saturday...

The extended period will be characterized by an upper-level trough
moving over the region with cool near normal temperatures and breezy
winds, driven by a low over British Columbia area. Dry conditions
will persist with low relative humidity in the teens to lower 20s.
Temperatures will lower to the 80s and 90s across the forecast area
through next week as the trough passes.

Locally breezy conditions (15-25 mph) will arrive with occasional
wind gusts between 20-30 mph each day through evening along the
Cascade Gaps and east slopes of the Cascades. This could pose a
threat to any ongoing fires as well. Probability for wind gusts
exceeding to 45 mph for Kittitas valley is at 30-60%. Feaster/97


&&

.AVIATION...06z TAFs...VFR under dry conditions with smoke/haze
present at times. Visibility obscuration due to smoke are not
currently anticipated, though will remain monitored. Wind will
generally remain light at 12 kts or less through the TAF period.
Rising temperatures over the weekend could result in High Density
Altitude at terminals. Branham/76


&&

.FIRE WEATHER...Hot, dry and unstable conditions increase over the
weekend. With significant fires occurring in Oregon zones 642 and
644 there is a Red Flag Warning in effect through Sunday. Also
expecting some isolated thunderstorms in central Oregon Sunday then
moving northward along the east slopes of the Cascades towards
Washington. There are concerns for elevated fire threat due to
increasing winds late Sunday as the cooler air associated with an
the approaching trough beginning to push into the region.  This will
produce winds of 10-20 mph with RH values in the teens to lower 20s.
Winds continue on Monday but RH values will be higher generally in
the upper teens and 20s.


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT 102  63 103  65 /   0   0   0  10
ALW 105  67 109  67 /   0   0   0   0
PSC 104  66 107  68 /   0   0   0  10
YKM 102  67 105  68 /   0   0   0  10
HRI 105  66 107  69 /   0   0   0  10
ELN 101  65 104  69 /   0   0   0  10
RDM 100  61  98  58 /   0  10  20  20
LGD 101  61 105  64 /   0   0   0   0
GCD 104  65 106  65 /   0   0  10  20
DLS 106  69  97  70 /   0   0  10  20

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning from 11 AM this morning to 10 PM PDT
     Monday for ORZ041-044-049-050-502-503-505-507-508.

     Red Flag Warning from 11 AM this morning to 11 PM PDT Sunday for
     ORZ642-644.

     Heat Advisory from 11 AM this morning to 8 PM PDT Monday for
     ORZ506-510-511.

WA...Excessive Heat Warning from 11 AM this morning to 10 PM PDT
     Monday for WAZ024-026>030-521.

     Heat Advisory from 11 AM this morning to 8 PM PDT Monday for
     WAZ523.

&&

$$

SHORT TERM...91
LONG TERM....92
AVIATION...92