304
FXUS66 KPDT 051739
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1039 AM PDT Fri Jul 5 2024

.AVIATION....18Z TAFS...VFR. High pressure across the region will
continue to produce VFR conditions at area terminals. In addition to
dry conditions, terminals will see wind less than 12 kts through
the forecast period. Branham/76

&&

.PREV DISCUSSION... /issued 310 AM PDT Fri Jul 5 2024/

SHORT TERM...Today through Sunday...Water vapor imagery tonight
shows an upper level ridge strengthening offshore western CONUS.
Meanwhile, nighttime microphysics periodically has shown
"hotspots" from vegetation fires starting up across the landscape
from the days festivities, though most of these fires seem to have
been by local authorities.

Through the weekend, the upper ridge offshore will continue to
build as it meanders east. Already under the influence of the
ridge, temperatures increased into the 90s, with another 5 to 10
degrees of warming expected this afternoon. In fact, today will be
the first real chance for areas of central OR, eastern Gorge, and
the Columbia Basin to reach the century mark, with chances of 100
degrees between 55-70% in these areas. Chances will expand and
increase across the lower elevations through the weekend, with
chances in the aforementioned areas increasing to 85-95%, and
60-80% elsewhere in the lower elevations. With modest nighttime
cooling expected over the coming days, HeatRisk will be
increasing from moderate to major by Sunday. With such high
HeatRisk, heat highlights have been issued and are in effect
through next week for a prolonged heat wave.

Besides heat, winds will generally be light and diurnally driven
through the next several days as the ridge builds and shifts
overhead. That said, confidence is high(80-85%) that breezy winds
will develop through the Kittitas valley this afternoon, and will
combine with relative humidities in the teens, resulting in the
issuance of a Red Flag Warning this afternoon. A shortwave trough
sliding down the northern Rockies will also help to increase winds
Saturday through central OR and the OR Cascade east slopes, where
Fire Weather Watches have been issued for wind and low RH. That
said, confidence is only moderate(55-70%) in criteria being met
Saturday, though best synoptic setup is advertised east of US97.
Lawhorn/82

LONG TERM...Monday through Friday...

Bottom Line Up Front

1. HEAT.

2. Breezy conditions return Wednesday and Thursday.

3. Fire weather concerns.

Models are in firm agreement with an upper level ridge continuing to
dominate the region through the midweek. Dry and hot conditions will
persist through much of the long term. High temperatures will
steadily increase through the period with the `hottest` day being
Tuesday followed closely by Wednesday. 70% of the raw ensembles
shows the Pendleton area to be over 100 degrees with the NBM putting
Pendleton at 107 Tuesday, 110 through the Basin, 105 in central Wa
and 109 through the Gorge. These temperatures are expected to
continue through the work week with confidence temperatures staying
above 100 degrees being high. EFI shows temperatures remaining well
above seasonal normal of nearly 10 to 20 degrees.  Looking at the
HeatRisk tool, Tuesday is the day with the highest concern with
HeatRisk levels reaching level 4 or extreme. You can find the
definitions of the categories on the HeatRisk page
wpc.ncep.noaa.gov/heatrisk/. With temperatures remaining above 100
for multiple days and overnight lows remaining in the upper 50s
to low 60s, there is no real cool off period. Please see
weather.gov/safety/heat for tips to remain safe during this heat
event.

Temperatures may `cool` ever so slightly Thursday with the models in
firm agreement with a shortwave rippling across the region. This
shortwave will bring with it a tightening of the pressure
gradients at the surface along the Cascades. This will increase
the winds through the Cascade Gaps and east slopes of the OR
Cascades. Raw ensembles show a 60% probability of seeing winds of
15 mph or greater through the Kittitas Valley, the Columbia River
Gorge as well as the foothills of the Southern Blues.

While the winds are not entirely `elevated` this still brings us to
the final point. Winds of 15 mph and relative humidities expected to
be in the single digits to below 15% (80-100% of the raw ensembles
show this) across the majority of the region. Due to the winds in
the aforementioned regions as well as the critically low daytime RH
values, there are some fire weather concerns across those areas at
this time. This will continue to be monitored through period.
Bennese/90

AVIATION...12Z TAFs...VFR conditions will persist through the period
with mostly terrain driven winds. CIGs will be non-existent with
SKC. Bennese/90

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  95  61  96  61 /   0   0   0   0
ALW  97  63  98  64 /   0   0   0   0
PSC  99  65 101  64 /   0   0   0   0
YKM 100  62 100  63 /   0   0   0   0
HRI 100  62 102  63 /   0   0   0   0
ELN  96  63  99  61 /   0   0   0   0
RDM  97  56 100  56 /   0   0   0   0
LGD  91  58  92  57 /   0   0   0   0
GCD  94  58  98  57 /   0   0   0   0
DLS 104  66 104  66 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning until 10 PM PDT Thursday for ORZ041-044-
     507-508-510.

     Heat Advisory from noon Monday to 10 PM PDT Thursday for ORZ050.

     Heat Advisory until 10 PM PDT Thursday for ORZ505-511.

     Fire Weather Watch from Saturday afternoon through Saturday
     evening for ORZ610-611-640.

WA...Excessive Heat Warning until 10 PM PDT Thursday for WAZ024-
     026>029-521.

     Heat Advisory until 10 PM PDT Thursday for WAZ523.

     Red Flag Warning from 2 PM this afternoon to 9 PM PDT this
     evening for WAZ690.

&&

$$

SHORT TERM...82
LONG TERM....90
AVIATION...76