769
FXUS66 KPDT 122056
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
156 PM PDT Fri Jul 12 2024

.SHORT TERM...Tonight through Sunday...Water vapor satellite this
afternoon shows potent upper level high pressure centered over the
Four Corners region, with a west to southwest flow aloft over the
PacNW.

Model guidance is in good agreement that the west to southwest
flow aloft will persist across the PacNW through the weekend as
high pressure aloft meanders across the Four Corners area.
Ultimately, this pattern will promote warming conditions across
the lower elevations again, with widespread moderate to localized
major HeatRisk developing through the weekend. Saturday looks to
be the hottest day through the weekend, with widespread
probabilities of 60-90% for reaching or exceeding 100 degrees,
with portions of the Basin looking at 35-50% chances of reaching
or exceeding 105 degrees. As for Sunday, breezy winds developing
through Cascade gaps will lower temperatures through areas along
the Cascade east slopes, but portions of the Yakima valley,
Columbia Basin, and John Day Basin will see a 60-90% chance of
reaching or exceeding 100 degrees Sunday afternoon, with mod-high
(70-855) confidence all other areas will be in the mid to upper
90s. Heat advisories will continue to be in effect through Sunday.

Besides heat, there are several fire weather concerns through the
weekend. First off, guidance shows a series of shortwave impulses
attempting to ride up the backside of the upper high and across
southeastern OR Saturday and Sunday. As for moisture support,
forecast soundings from high-res guidance indicate very dry low
to mid levels with the moisture support being at the 500mb level.
While increased cloud cover is expected, there is a low(15-20%)
chance in isolated thunderstorms clipping the southern periphery
of the eastern mountains Saturday and Sunday afternoons. That
said, confidence is still only moderate(60%) in red flag
conditions being met, so will keep the Fire Weather watches going
in the eastern mountains. Second, while locally breezy winds will
develop through the Cascade gaps today and tomorrow, surface
pressure gradients will tighten further on Sunday resulting in
breezy west winds of 15-25mph with gusts up to 35-40mph developing
in the eastern Gorge, Kittitas valley, and portions of the
Columbia Basin(confidence 60-75%). These winds will also coincide
with critically low RHs in the teens Sunday afternoon, resulting
in the potential for critical fire weather behavior. As a result,
have issued Fire Weather Watches for the wind and low RH
combination in the aforementioned areas. Lawhorn/82


.LONG TERM...Monday through Friday...A high pressure system over
The Four Corners remains in place as dry conditions persist, while
an upper level trough over the eastern Pacific with westerly flow
over the region will prevent monsoon moisture from impacting the
forecast area. Models remain in great agreement through the long
term forecast periods.

High temperatures will continue to be above normal through next
week. Locally breezy conditions will occur with occasional wind
gusts between 20-30 mph each afternoon and evening along the
Columbia River Gorge, Kittitas and Yakima valleys, and Simcoe
Highlands (50-70% confidence). This could pose a threat to fire
spread. Overall, a typical summer weather pattern is in favor for
this extended period. Feaster/97


&&

.AVIATION...Previous Discussion...18Z TAFS...VFR conditions are
expected for all sites through the period with clear skies.
However, haze will be produced by smoke from wildfires but will
not reduce surface visibility below VFR at these sites. Feaster/97


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  60  99  62  97 /   0   0   0   0
ALW  64 102  66 100 /   0   0   0   0
PSC  64 103  66 102 /   0   0   0   0
YKM  65 101  64  99 /   0   0   0   0
HRI  63 103  66 102 /   0   0   0   0
ELN  64  98  63  96 /   0   0   0   0
RDM  53  98  55  96 /   0   0   0  10
LGD  56  98  59  95 /   0   0   0   0
GCD  58 102  61  98 /   0   0  20  10
DLS  63  99  65  96 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory until 10 PM PDT Sunday for ORZ041-044-049-503-
     505>508-511.

     Fire Weather Watch from Sunday afternoon through Sunday evening
     for ORZ641.

     Fire Weather Watch from Saturday afternoon through Sunday
     evening for ORZ642-644.

WA...Heat Advisory until 10 PM PDT Sunday for WAZ024-026>029-521.

     Fire Weather Watch from Sunday afternoon through Sunday evening
     for WAZ690-691.

&&

$$

SHORT TERM...82
LONG TERM....97
AVIATION...97