Hermiston, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

962
FXUS66 KPDT 121732
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1032 AM PDT Tue Aug 12 2025

.UPDATED AVIATION.


.AVIATION...18Z TAFs...VFR conditions persist. Clear conditions
are depicted on satellite. Some smoke detected near RDM, but
nothing to suggest to impede visibility`s. Winds currently light
and variable, but will pick up in the DLS at 23Z. Some winds will
gust up to 25-35 knots. PDT will see a wind increase at 16Z at the
tail end of the period. No other notable hazards expected.

&&


PREV DISCUSSION... /issued 255 PM PDT Mon Aug 11 2025/

DISCUSSION...

KEY MESSAGES:

1. Extreme Heat Warning active through Tuesday.

2. Red Flag Warning issued for Oregon Tuesday and Wednesday.

3. Fire Weather Watch issued for Washington Wednesday.

Current radar and visible satellite imagery showing dry conditions
and clear skies as an upper level ridge is present over the area.
This pattern has brought hot and dry conditions across the Pacific
Northwest, with high temperatures breaking into the triple digits
both today and again on Tuesday. These high temperature values
are about 15 degrees above normal, with little overnight relief as
morning lows only dip down into the mid-to upper 60s. Thus, an
Extreme Heat Warning is currently active across the Lower Columbia
Basin, Eastern Gorge, Blue Mountain foothills, Central Oregon,
John Day Basin, and the Yakima/Kittitas valleys through 10 PM
Tuesday. These areas are highlighted in the Major (3 of 4)
HeatRisk category, which is a risk to much of the population
especially anyone without effective cooling or hydration.
Tuesday`s high temperatures will reach between 95-105 for
aforementioned areas, with high confidence (85-95%) in these
values as the NBM advertises an 80-90% chance of 100 degree
temperatures for Yakima, Hermiston, Tri-Cities, and Madras. The
upper level ridge begins to break down into Wednesday to allow
high temperatures to drop 4-8 degrees from Tuesday. Wednesday
morning low temperatures will also stay mild in the upper 60s to
low 70s.

Hot and dry conditions today will persist into Tuesday, but the
upper level ridge will slowly lose its grip over the area as a
shortwave drops from the northwest. This shortwave will tighten
the pressure gradient between these two synoptic features,
elevating winds to critical values in the afternoon and evening -
primarily across Central Oregon and the John Day Basin. As a
result, sustained winds of 10-15 mph with gusts up to 25 mph will
be possible. Confidence in these wind values is high (80-90%) as
the NBM suggests a 70-80% chance of sustained winds of 15 mph and
gusts reaching 25 mph. Poor overnight humidity recoveries are also
anticipated to only improve to 25-35%, with the HREF showing a
70-80% chance of humidities staying below 35%. Thus, a Red Flag
Warning has been issued Tuesday beginning at noon for the John Day
Basin, Southern Blue Mountains, Warm Springs Reservation, and the
Northern/Southern Deschutes National Forest. These conditions will
continue into Wednesday as the warning stays active until 10 PM
Wednesday.

A second, stronger upper level shortwave passes through the area
Wednesday to bring more widespread fire weather concerns across
Washington. This second system has additional support from an
upper level trough located over Central Canada, allowing for more
elevated winds between 10-20 mph with gusts up to 30 mph
possible. Antecedent dry conditions will be slow to improve as
flow aloft turns from the northwest to the west Wednesday into
Thursday. Overnight humidity recoveries will improve slightly
Wednesday morning, but afternoon values will drop to between
15-25%. These concerns include areas of the Simcoe Highlands,
Lower Columbia Basin, Eastern Gorge, Wallowa County, northern Blue
Mountains/Foothills, and the Yakima/Kittitas valleys, which are
all included in the 90th percentile of the Hot-Dry-Windy Index
(HDWI). This has warranted the issuance of a Fire Weather Watch
Wednesday from 11 AM to 11 PM for the aforementioned areas.

Humidities improve as temperatures decrease Wednesday onward,
helping to alleviate fire weather concerns through the remainder
of the week. However, the threat of afternoon thunderstorms
arise Friday through next Monday as a strong upper level system
parks itself offshore of the British Columbia coast, spinning
shortwaves through the Pacific Northwest. The silver lining is
that the precipitable Water (PW) looks to be an inch or greater
beginning Friday, reaching values of 200-250% above normal. Those
amounts suggest a wetting rain (=>0.10") will accompany any
developing thunderstorms. 75

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT 100  68  94  59 /   0   0   0   0
ALW 100  73  95  64 /   0   0   0   0
PSC 102  68  98  60 /   0   0   0   0
YKM 102  67  93  59 /   0   0   0   0
HRI 102  71  95  61 /   0   0   0   0
ELN  99  66  86  57 /   0   0   0   0
RDM  99  56  93  49 /   0   0   0   0
LGD  99  63  93  55 /   0   0   0   0
GCD 100  61  93  54 /   0   0   0   0
DLS 102  71  88  63 /   0   0   0   0

&&

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

     Fire Weather Watch from Wednesday morning through Wednesday
     evening for ORZ693.

     Red Flag Warning until 11 PM PDT Wednesday for ORZ696-698-700-
     703>705.

WA...Extreme Heat Warning until 10 PM PDT this evening for WAZ024-
     026>029-521.

     Fire Weather Watch from Wednesday morning through Wednesday
     evening for WAZ690>695.

&&

$$

SHORT TERM...75
LONG TERM....75
AVIATION...95