764
FXUS66 KPDT 061749
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1049 AM PDT Sat Jul 6 2024

.AVIATION...18Z TAFs...VFR conditions are expected (99-100%
chance) for all sites through the period. Aside from a few passing
high clouds, skies will be clear. Diurnally driven winds will
increase through the morning and afternoon, with gusts of 15-25
kts forecast at KDLS/KBDN/KRDM. Elsewhere, confidence in
prevailing gusty conditions is too low (<50% chance) to warrant
mention in the TAFs, but anticipating periodic gusts of up to 15
kts by afternoon as the boundary layer deepens and higher momentum
air mixes down to the surface. Plunkett/86

&&

.PREV DISCUSSION... /issued 323 AM PDT Sat Jul 6 2024/

SHORT TERM...Today through Monday...An upper level ridge of high
pressure will continue to dominate the synoptic pattern into next
week. The upper ridge will continue to produce hot and dry
conditions throughout the region, with critical fire weather
concerns developing this afternoon. Confidence remains very high
(90-100%) that most of the lower elevation zones across the
forecast area will reach or exceed the 100 degree mark by Sunday.
Temperatures through early next week will continue a warming trend
of 1 to 4 degrees in both high and low temperatures, with lows in
the 60s to low 70s by Monday night. The weak to modest overnight
relief combined with hot afternoon temperatures will result in
HeatRisk values increasing into the high moderate to locally
extreme values, with even moderate to major HeatRisk developing in
most mountain zones. Excessive heat warnings and heat advisories
across most of the forecast area will continue into portions of
next week.

Besides heat, another shortwave trough sliding down the ridge into
the northern Rockies today will tighten pressure gradients in the
area, resulting in breezy conditions across central OR into the
Malheur National Forest further east. The winds combined with
relative humidities in the single digits to lower teens will
result in critical fire weather conditions this afternoon.
Lawhorn/82

LONG TERM...Tuesday through Saturday...

Bottom Line Up Front

1. HEAT.

2. Breezy conditions return Wednesday.

3. Fire weather concerns Wednesday.

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. 89% of
the raw ensembles shows the Pendleton area to be between 100 to
110 degrees with the NBM putting Pendleton at 108 Tuesday, 110
through the Basin, 105 in central Wa and 110 through the Gorge.
These temperatures are expected to continue through the work week
with confidence in temperatures staying above or near 100 degrees
being high (80-90%). 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 60s
to low 70s, there is no real cool off period. Please see
weather.gov/safety/heat for tips to remain safe during remainder
of this heat event.

Temperatures may `cool` ever so slightly Thursday with the models
in firm agreement with a shortwave rippling across the region.
70% of the raw ensembles have the Pendleton area between 90 to 100
with the NBM showing Pendleton`s high Wednesday to be 98, the
Basin at 102/103, Yakima and Kittitas Valleys at 95 as well as the
Gorge, and central OR between 95 and 97 degrees. Along with
`cooling` temperatures, this shortwave will bring with it a
tightening of the pressure gradients at the surface along the
Cascades. The pressure gradient tool is already showing a 9 to 10
mb change and deterministic guidance shows a tightening along the
Cascades. This will increase the winds through the Cascade Gaps
and east slopes of the OR Cascades. Raw ensembles show a 80%
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 and central OR.

Lastly, fire weather concerns will pick up Wednesday as the winds
increase through the aforementioned areas as the shortwave moves
across. 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. With the increase in the winds and the critically low
daytime RH values, there are some fire weather concerns across
those areas at this time with confidence at this time being 60%.
Bennese/90

FIRE WEATHER...Red Flag Warnings remain in effect from 2PM to 9PM
today for wind and low relative humidity for fire weather zones
OR610, 611, 640, and 642. Relative humidities in the single digits
to lower teens will combine with breezy winds of 10-20 mph this
afternoon, resulting in critical fire weather conditions conducive
to rapid fire spread and extreme fire behavior. Winds are
expected to be lighter Sunday into early next week, precluding the
need of any additional fire weather highlights at this time.
Lawhorn/82

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  97  62 100  64 /   0   0   0   0
ALW  99  64 102  66 /   0   0   0   0
PSC 101  65 105  66 /   0   0   0   0
YKM 101  63 102  65 /   0   0   0   0
HRI 102  64 105  66 /   0   0   0   0
ELN  99  62 101  66 /   0   0   0   0
RDM 102  56 100  58 /   0   0   0   0
LGD  92  57  96  60 /   0   0   0   0
GCD  97  58  98  60 /   0   0   0   0
DLS 107  68 105  69 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning until 10 PM PDT Thursday for ORZ041-044-
     505-507-508-510-511.

     Heat Advisory from noon Monday to 10 PM PDT Thursday for ORZ049-
     050-502-503.

     Red Flag Warning from 2 PM this afternoon to 9 PM PDT this
     evening for ORZ610-611-640-642.

     Heat Advisory from noon Monday to 10 PM PDT Tuesday for ORZ509.

WA...Excessive Heat Warning until 10 PM PDT Thursday for WAZ024-
     026>029-521-523.

     Heat Advisory from noon Monday to 10 PM PDT Thursday for WAZ030.

     Heat Advisory from noon Monday to 10 PM PDT Tuesday for WAZ522.

&&

$$

SHORT TERM...82
LONG TERM....90
AVIATION...86