669
FXUS66 KPDT 090516
AFDPDT
Area Forecast Discussion
National Weather Service Pendleton OR
1016 PM PDT Sun Jun 8 2025
.EVENING UPDATE...Red Flag Warnings have been issued for the lower
Kittitas Valley and the Lower Columbia Basin for winds and RHs
beginning 2 PM Monday and lasting through until Tuesday at 8 PM.
Winds will to increase through the Kittitas Valley, Columbia
River Gorge,and into the Columbia Basin starting Monday
afternoon. Probabilities of these areas seeing 25 mph gusts is
90-100% and 39 mph gusts is 49%, 10-40%, 20-30% respectively.
This, combined with very low RHs due to the ongoing heat wave,
will make for increased risks for wildfire spread, especially
during the afternoon and early evening hours on both Monday and
Tuesday. Bennese/90
.UPDATED AVIATION...06Z TAFs...VFR conditions will persist
through the forecast period with warm and dry conditions. CIGs
will be SKC through the period with diurnally driven winds
overnight and through the day until 19-22Z beginning with DLS then
RDM and followed by BDN. These TAF sites will see winds increase
nearing 15-20 kts sustained and gusts nearing 20-30 kts gusts.
Otherwise, the remaining sites will remain below 10 kts.
Bennese/90
&&
PREV DISCUSSION... /issued 1250 PM PDT Sun Jun 8 2025/
SHORT TERM...Today through Tuesday...Temperatures are quickly
warming up today as a strong high pressure ridge moves into the
PacNW. Monday still looks to be the hottest day of the period, when
the ridge axis is expected to be over the forecast area. Not much
change in the temperature forecast, with mid to upper 90s expected
today and Tuesday across most of the lowlands of the forecast area,
while highs reach as high as 105 in the Columbia Basin on Monday.
Ridging starts to move out by late Monday evening heading into
Tuesday, but SW flow will keep the heat in place, allowing the lower
Basin to potentially see another day of triple digit temperatures
(20-30% chance according to NBM probabilistic).
Heat Advisories remain in effect until Tuesday evening across the
Basin, Yakima/Kittitas Valleys, foothills of the Blues, and Columbia
River Gorge. As mentioned yesterday, HeatRisk guidance technically
called for Extreme Heat Warnings for some areas (namely the Gorge
and Yakima/Kittitas Valleys) on Monday, but in order to simplify
messaging, and with criteria only really being met on one day, opted
to go with straight Heat Advisories instead. This also keeps the
heat headlines geographically consistent.
Once SW flow kicks in on Tuesday, focus will shift toward that of
winds and mountain thunderstorms. These type of ridge breakdown
scenarios after a period of hot and dry conditions are often
conducive for dry thunderstorms over the mountains of central and
eastern Oregon. Even the NBM, which notoriously downplays dry
thunderstorm risks, is picking up on the potential Tuesday
afternoon. This, combined with the relatively progressive pattern
expected once this ridge moves out of the region, may create a
prolonged period of heightened wildfire risk through the week, as
winds will pick up through the Cascade Gaps and into the Basin
through the midweek. Concerns would primarily be centered around the
Basin and adjacent valleys, as not only are fuels in the mountains
generally not at critical levels, but as SW flow persists through
the midweek, PWATs kick up enough to increasingly dilute the
wildfire risk from dry thunderstorms. Evans/74
LONG TERM...Wednesday through Sunday...A parent low off the Gulf of
Alaska will drive a progressive pattern through next weekend, as
this low circulates persistent SW flow, as well as some shortwaves,
through the PacNW. Ensembles more or less have us locked in under
this SW flow pattern through the period as a result, with the only
variations being in how strong SW flow will be, based on the arrival
of attendant shortwaves (seen more clearly through the deterministic
GFS) and overall upper-level wind speeds.
While the Tuesday-Wednesday period looks to be dicey for the Basin,
as well as the Yakima/Kittitas Valleys as far as fire weather danger
is concerned, the longer we remain locked in this pattern, the more
RHs will trend upward over the course of the week. Guidance overall
holds steady on breezy winds through the Cascade Gaps, spilling into
the Basin as well, but as this aforementioned low gradually eases
its way on shore, so does its cooler air, resulting in high
temperatures trending more toward the low 80s for the Basin and 70s
elsewhere. The increase in moisture will also make for more of a
shower rather than thunderstorm threat as cloud cover pours in and
instability is hindered, although to be fair the dry thunderstorm
risk for wildfire starts across the mountains was admittedly
downplayed given how early in the warm season we are for fuels to be
at critical levels. Still, it`ll be good to see at least some
semblance of relief over time given the potentially critical
conditions that look to shape up Tuesday into Wednesday, assuming
that said period doesn`t end up being too active in terms of new
fire starts. Evans/74
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 62 100 64 97 / 0 0 0 0
ALW 67 99 69 96 / 0 0 0 0
PSC 62 103 64 100 / 0 0 0 0
YKM 67 102 65 99 / 0 0 0 0
HRI 62 104 65 99 / 0 0 0 0
ELN 64 100 64 95 / 0 0 0 0
RDM 55 97 55 94 / 0 0 0 0
LGD 58 94 61 92 / 0 0 0 10
GCD 56 96 59 94 / 0 0 10 10
DLS 69 101 65 94 / 0 0 0 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory until 9 PM PDT Tuesday for ORZ041-044-507.
WA...Heat Advisory until 9 PM PDT Tuesday for WAZ024-026>029.
Red Flag Warning from 2 PM Monday to 8 PM PDT Tuesday for WAZ690-
691.
&&
$$
SHORT TERM...74
LONG TERM....74
AVIATION...90