771
FXUS66 KPDT 191018
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
318 AM PDT Fri Jul 19 2024

.SHORT TERM...Today through Sunday...The strong upper level ridge
over the western USA will continue its grip over the region through
Sunday for continued very hot conditions across the forecast area.
The good news is the ridge weakens allowing an upper level trough to
impact the Pacific Northwest first of next week ending the heat
wave.

For today, a weak short wave off the coast will lift northeast into
Canada while clipping the Pacific Northwest. The main impact will be
slightly suppressing the upper level ridge over the region with high
temperatures only reaching around 100 in the Lower Columbia Basin.
However, the upper level ridge will push northward back into the
region on Saturday with lower elevations highs of 100-105 degrees.
On Sunday high temperatures will peak at 100-110 degrees across the
lower elevations and mountain valleys with probability of exceeding
110 degrees in the Lower Columbia Basin at 40-60%. Both days could
see some record high temperatures in many location of the forecast
area. Various Heat Advisories and Excessive Heat Warnings are in
effect over the weekend.

There is an upper level trough in the Gulf of Alaska that is slowly
moving towards western Canada over the weekend. Models are showing
that it lifts a shortwave near the northern California coast up the
Pacific Northwest coast on Sunday. This could provide enough
instability to trigger some convection (10-20% chance) across
central Oregon Sunday afternoon and then spread north into the
Washington Cascades in the evening.

Winds will generally be light over the next couple of days. However,
on Sunday the approaching upper level trough begins to increase the
pressure gradient along the Cascades as cooler marine air floods
into western Oregon and Washington. This will lead to a push of this
cooler air through the Columbia River Gorge and lower gaps of the
Cascades resulting in some increasing breezy conditions (10-20mph)
in the late afternoon and evening.


.LONG TERM...Monday through Friday...

Key Messages:

1. Potential thunderstorms on Monday.

2. Locally breezy conditions through next week.


The strong high pressure ridge over our region begins breaking down
Monday as a low off British Columbia coast moves inland, bringing SW
wind aloft. Potential thunderstorms are possible for late Monday
through early night, mainly across the John Day Basin and eastern
mountains (50% confidence). Most unstable CAPE values are 500 J/Kg
or less with lapse rates above 7 C/Km, showing marginal instability.
Mountain showers are also possible as the trough really starts to
move in, but confidence is very low (<15%) due to limited moisture
advection from persistent hot, dry conditions.

Potential fire weather conditions remains to be advised with this
ridge breakdown and incoming breezy winds. Given these conditions,
this will facilitate gusty conditions with RHs remaining in the
teens to lower 20s. Moderate HeatRisk will be across some portions
of the lower elevations. With Major HeatRisk at Wallowa county
including Yakima Valley, heat advisories and warnings have been
issued for those areas through Monday.

Locally breezy conditions (15-25 mph) will occur across the Columbia
River Gorge, Simcoe Highlands, Yakima and Kittitas valleys through
next week. Probability for wind gusts exceeding to 40 mph Monday is
at 30-50%. High confidence for increased wind gusts in these areas
as well as the ridge breakdown continues with a low pushing through.
As the trough passes, breezy conditions will continue across the
forecast area with wind gusts at around 20-30 mph.

High temperatures will be in the 90s and 100s Monday with the ridge
over the region. Driven by a low, the trough will bring cool
temperatures into the 80s and 90s across the forecast area Tuesday
through next week. Feaster/97


&&

.AVIATION...06Z TAFs...VFR conditions will persist through
the forecast period, however, there will be some lingering high
level haze. DLS remaining breezy at 15 kts while the remaining sites
are below 9 kts. Bennese/90


&&

.FIRE WEATHER...Hot, dry and unstable conditions increase and peak
over the weekend. With significant fires occurring in Oregon zones
642 and 644 there is a Fire Weather Watch in effect for Saturday
through Sunday. There are concerns for elevated fire threat due to
increasing winds late Sunday as the cooler air associated with 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. This will be monitored for highlight needs at a later time.



&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  97  60 102  64 /   0   0   0   0
ALW 100  64 106  67 /   0   0   0   0
PSC 101  65 105  67 /   0   0   0   0
YKM  99  63 102  68 /   0   0   0   0
HRI 101  63 106  66 /   0   0   0   0
ELN  95  61 102  66 /   0   0   0   0
RDM  93  54 101  63 /   0   0   0   0
LGD  95  58 102  62 /   0   0   0   0
GCD  98  59 105  65 /   0   0   0   0
DLS  97  64 106  70 /   0   0   0   0

&&

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

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

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

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

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

&&

$$

SHORT TERM...91
LONG TERM....97
AVIATION...97