525
FXUS66 KPDT 231739
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1039 AM PDT Mon Sep 23 2024

.AVIATION...18Z TAFs...VFR conditions are forecast for all sites
through the TAF period, with low chances (<30%) of smoke/haze
reducing CIGs/VSBYs to sub-VFR again overnight into Tuesday
morning at BDN/RDM. Otherwise, predominantly FEW-BKN high-level
clouds through the day, becoming SKC to FEW250 overnight through
Tuesday at TAF sites. Sustained winds of 10 kts or less,
diurnally driven for all sites. Plunkett/86

&&

.PREV DISCUSSION... /issued 836 AM PDT Mon Sep 23 2024/

MORNING UPDATE...Slight update to the forecast this morning with
regards to the smoke and haze lingering over Bend and Redmond.
Smoke through Bend has brought visibility to 300 ft above ground
while not necessarily impacting the ground. Smoke and haze will
linger through the day with northwest winds continually wafting
smoke over the area. Bennese/90

PREV DISCUSSION... /issued 219 AM PDT Mon Sep 23 2024/

SHORT TERM...Today through Wednesday...The short term will see a
couple of overall calm and warm days as we heat to well above
normal temperatures with an incoming deep trough then beginning a
cooling trend that will extend into the long term, along with
gusty winds that will flirt with both advisory level criteria and
critical fire behavior conditions, along with a chance at most of
the region to see a small amount of rain.

A ridge of high pressure will be traversing across the Western US,
ending up centered across the Four Corners region by Wednesday
morning. This ridge will bring increasing warmth, which will be
the main weather feature of note today and tomorrow. High
temperatures today will range in the upper 70`s to mid 80`s for
our population centers, with highs tomorrow around 5 to 10 degrees
warmer. Ensembles continue to come into better and better
agreement on tomorrow`s unseasonable warmth, with much of CWA now
in the mid 80`s to low 90`s for highs. Currently, central and
north-central Oregon, the John Day valley, and the foothills of
the Blue Mountains look to be the warmest locations, with the NBM
producing a 50-90% probability of highs 90+.

Into Wednesday, a deep upper level low in the Gulf of Alaska will
swing a long wave trough into the Pacific Northwest alongside a
cold front, ending the warming trend and producing areas of
showers and gusty winds. For temperatures and precipitation - the
front will swing across through the course of the day, but
afternoon warming should still allow for highs in the 80`s for
most of our population centers, warmest in the Columbia Basin as
the front doesn`t move across until the mid to later part of the
afternoon for the eastern part of our CWA. The NBM is gaining
confidence in precipitation as well, with all but the southern
portions of Grant and Crook county expecting at least a 20-30%
chance of precipitation. Outside of the Cascades, this translates
to a 10-40% probability of 0.1 inch or more of QPF - nothing
exciting but noteworthy enough for how dry we`ve been of late.

As for winds, a 700 mb jet streak of 50-60 knots will move across
with the system. These winds should have a good chance of mixing
down with the front, and the NBM indicates 24-hour max wind gusts
of 45+ mph have a 30-80% probability for the Columbia Gorge, lower
Columbia Basin of Oregon, Simcoe Highlands, and Kittitas Valley.
The previous forecast was used as a base and blended in the NBM
90th percentile, giving widespread gusts of 30-40 knots - just
barely outside of wind advisory levels, but barely. For our fire
weather partners, this does bring near critical fire weather
conditions to portions of Crook, Grant, and Harney counties. This
shouldn`t be a long duration period of low RH`s lining up with
breezy winds, but any ongoing fires in this area will be subject
to some critical fire behavior. Currently don`t have enough
confidence to issue a fire weather watch and conditions aren`t
sustained for long enough to warrant it, but will continue to
message the heightened risk alongside working with our partners to
ensure we remain prepared for (hopefully) one of the last
enhanced fire weather concerns of the year. Goatley/87

LONG TERM...Thursday through Monday...

Models in good agreement with the PacNW entering a zonal pattern
through Saturday. And with the arrival of the cold front, chances
of showers occurring at the WA Cascades could increase for
Thursday through Friday evening due to orographic lifting.
However, confidence is on the low end (<30%). Breezy winds will
develop up to 20 mph with increased westerly flow until decreasing
to light Saturday (30-50% probability).

A transient trough will then pass through the forecast area Sunday
before an upper ridge takes over starting Monday. Winds will
remain fairly light until breezy conditions return Sunday
afternoon into Monday evening around 20 mph or less (40-60%
probability). Though, models start to deviate a bit for Sunday.
The GFS and ECMWF model both favor a shortwave trough passing
through the forecast area, but with the GFS showing it slightly
more deeper and the Canadian model remaining zonal. High
temperatures will be mainly in the 70s through the long term
period. Feaster/97

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  79  53  89  57 /   0   0   0   0
ALW  82  56  90  61 /   0   0   0   0
PSC  84  57  88  60 /   0   0   0   0
YKM  84  53  88  55 /  10   0   0   0
HRI  84  56  90  58 /   0   0   0   0
ELN  83  55  87  56 /  10   0   0   0
RDM  81  48  91  52 /   0   0   0   0
LGD  78  50  86  57 /   0   0   0   0
GCD  78  50  87  53 /   0   0   0   0
DLS  86  58  94  60 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

MORNING UPDATE...90
SHORT TERM...87
LONG TERM....97
AVIATION...86