498
FXUS66 KPDT 091527
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
827 AM PDT Thu May 9 2024

.UPDATE...
High pressure ridge building into the region with few clouds and
warming temperatures. There was little to update this morning, but
made some minor changes where needed.




&&

.PREV DISCUSSION... /issued 426 AM PDT Thu May 9 2024/

SHORT TERM...Today through Saturday...Benign weather will
accompany the upper level ridge overhead accompanied but a
noticeable uptick in temperatures. Temperatures will peak on
Saturday as the upper level ridge continues to amplify.

As stated above, an upper level ridge has made its way towards
the forecast area and models show it tilted towards the east with
the leading edge directed from southwest to northeast. An upper
level low that has formed over the Four Corners will assist in a
synoptic set up that will aid in the strengthening of the upper
level ridge. This set up will bring northeasterly winds across
the region through today as the upper level ridge continues to
strengthen and move fully over the area. Dry conditions will
persist with the EFI signaling an increase above the
climatological normal across the Cascades today. Raw ensembles
show well over 80% probabilities that the Columbia Basin, Gorge
and foothills of the Blues will see temperatures above 80 degrees
today, mid elevations will see low to mid 70s and the higher
elevations will see the low to mid 60s.

Friday through Saturday the models remain in firm agreement with the
amplification of the upper level high pressure persisting over the
region. Dry conditions will continue to dominate with the EFI
signaling the eastern portion of the Cascades will begin seeing
temperatures above climatological normal. Raw ensembles show that 70-
80% of the Columbia Basin, Gorge and the foothills of the Blues will
see temperatures above 80 degrees, the mid elevations will see the
upper 70s to low 80s and the higher terrains in the low to mid 70s.
Saturday raw ensembles show yet another increase in temperatures
with 70-90% of the ensembles showing the Basin, Gorge and foothills
of the Blues seeing temperatures above 85 with a few isolated
locations in the Basin seeing low 90s. The mid elevations will see
low to mid 80s and the higher elevations will see upper 60s. With
the rise in temperatures, guidance has begun to pick up on a slight
heat risk for Saturday through portions of the Columbia Basin. If
you are outside on Saturday enjoying the warmth, please be mindful
and wear sunscreen, drink plenty of fluids and remember that the
rivers will be fast flowing and still dangerous cold. Bennese/90

LONG TERM...Sunday through Thursday...Ensemble models are showing
good agreement with the weakening and flattening of the western USA
ridge Sunday and Monday by a shortwave trough passage. After that
the ECMWF ensemble maintains a more flat ridge pattern with the
storm track north of the region on subsequent shortwave impulses.
Meanwhile, the GFS ensemble allows these subsequent shortwaves to
push the storm track further south and more likely to directly
impact the forecast area. Current deterministic models are even
further apart with ECMWF re-building the ridge over the Pacific
Northwest Midweek while the GFS has a closed low moving through
western Canada and clipping the Pacific Northwest. Overall the WPC
cluster analysis shows higher support of the ECMWF ensemble solution
through the extended forecast period.

So Sunday will see the onset of the weak trough passage. This will
provide some weak cold air advection to increase westerly winds in
the afternoon and lower high temperatures slightly from Saturday
peak highs. Continued breezy cold air advection into Monday with the
trough passage occurring will see high temperatures drop further
into the 70s to low 80s while mountains see 60s. Overall this will
be a dry trough passage other than a few possible showers along the
central and northern Washington Cascade crest.

Going with the ECMWF ensemble solution will continue to see a flat
ridge across the Pacific Northwest Tuesday through Thursday
maintaining a slightly above normal temperature pattern with breezy
conditions. Any precipitation is likely to be confined to a few
showers along the Cascade crest.

AVIATION...12Z TAFs...VFR conditions to prevail through the period
with FEW-SCT AOA 25kft. Winds will be light less than 12kts through
the period, with wind direction diurnally driven becoming N-NE
midday through evening.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  72  46  79  51 /   0   0   0   0
ALW  77  50  82  54 /   0   0   0   0
PSC  81  52  86  55 /   0   0   0   0
YKM  79  48  86  52 /   0   0   0   0
HRI  79  49  85  52 /   0   0   0   0
ELN  79  50  83  52 /   0   0   0   0
RDM  71  40  78  46 /   0   0   0   0
LGD  70  44  76  48 /   0   0   0   0
GCD  71  42  78  47 /   0   0   0   0
DLS  80  54  86  57 /   0   0   0   0

&&

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

$$

SHORT TERM...77
LONG TERM....91
AVIATION...91