000
FXUS66 KPDT 271743
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1043 AM PDT Mon Jun 27 2022

.Updated Aviation Discussion

MORNING UPDATE... Hot conditions are slated for this afternoon as
a robust ridge of high pressure moves over-top the Pacific
Northwest. This morning temperatures are running roughly 4-8
degrees warmer compared to this time yesterday, so widespread
highs in the triple-digits across the lower Columbia Basin appears
very likely. The axis of the ridge begins accelerating east this
evening in response to an approaching upper-level closed low off
the coast. Within the resulting SW flow a slight chance for
T-storms looks possible into the overnight hours for parts of the
region although there still remains significant uncertainty
between the various models as to placement and coverage of the
convection. Based off the latest HREF and how T-storm development
played out yesterday in central Oregon, a slight chance for
T-storms was expanded into the east slopes of the Oregon Cascades
and portions of the central Blues/Wallowas; the best chance
remains in the WA Cascades and northern Blue mtns. Otherwise, the
forecast remains on track with slightly cooler albeit breezy to
windy conditions returning Tuesday. 99

AVIATION...18Z TAFs...VFR conditions are expected through the
period with just FEW to SCT mid/high cloud. Could see an isolated
high-based shower, and perhaps an isolated lightning strike,
around KYKM late this afternoon into tonight, but chances are low
so have omitted from the 18Z issuance. Otherwise, diurnally
driven winds this afternoon of 5 to 15 kts with higher gusts.
Plunkett/86

PREV DISCUSSION... /issued 345 AM PDT Mon Jun 27 2022/

SHORT TERM...Today through Wednesday night...Strong high
pressure over the region will once again lead to very hot
temperatures today, with today being the hottest day of the year.
Temperatures across the area will generally be in the upper 90s
with 100+ in the lower elevations including the Yakima Valley and
Columbia Basin. The heat advisories will remain in effect
unchanged.

An area of low pressure off the coast will move northeastward into
British Columbia tonight into Tuesday. This low will push the
ridge eastward and bring a more westerly flow cooler temperatures
to the area beginning on Tuesday and continuing into Wednesday.
High temperatures on Tuesday will be, on average, 10 to 15
degrees cooler than today, and a couple degrees cooler on
Wednesday, especially across the Basin and Foothills.

Highs Tuesday will mainly be in the low to mid 80s with upper 80s
to around 90 possible in the Basin. Wednesday will see highs
generally in the low to mid 80s. Overnight lows will be in the 50s
and 60s tonight, though across the Columbia Basin, temperatures
may be hard pressed to drop below 70 degrees. Temperatures will
cool Tuesday night and Wednesday night, with lows in the 40s and
50s, though some spots in the Basin will not drop below 60 degrees
Tuesday night.

The ECMWF EFI has the whole areas covered in the 60-70% range for
high temperature today and potions of the Basin and Gorge are in
the 70 to 80% range. For low temperature tonight, the coverage is
similar, though not as widespread, with much of the area in the
60 to 70% range and a portion of the Gorge in the 70 to 80% range
and and area near the Dalles in the 80-90% range.

While much of the forecast period is dry, there is at least a
small chance of some showers or thunderstorms later this
afternoon into this evening. The HREF keys in on two areas...the
Washington Cascades and eastern portions of the region, Wallowa
County and the eastern mountains. The guidance is very mixed on
this, with the HRRR and RAP having virtually nothing. The NAM has
some indications of slight development over the eastern areas,
which is a reversal from previous runs when it had some coverage
over the Washington Cascades, and the GFS does indicate some
coverage over the Cascades.

While moisture is limited, it does increase this afternoon/evening
and there is some decent instability over Wallowa County/eastern
areas, with less forecast over the Cascades. Nevertheless, the
strong daytime heating coupled with whatever moisture there is and
the instability could potentially trigger a few showers or
storms. The HREF also indicated that there could be a chance over
the Cascades, then the eastern areas, then possibly back over the
Cascades.

Otherwise, the only other precip chances are low chances over the
Cascade crests on Wednesday.

As the low move into British Columbia, the flow will become more
westerly and winds are expected to increase and become breezy
Tuesday afternoon into Tuesday evening.Wind gusts of 25 to 35 mph
are possibly with locally higher values in the Gorge, Basin,
Kittitas Valley and Cascade Gaps. While wind advisory criteria are
not expected at this time, we will have to see how additional
guidance handles the wind.

The ECMWF EFI indicate 80 to 90% for both wind speed and wind
gusts on Tuesday across the Washington portion of the Columbia
Basin, so this is definitely an area that bears watching to see
what later guidance will indicate.

LONG TERM...Thursday through Monday...The long term forecast
begins with zonal flow to weak ridging building in on Thursday,
with temperatures expected to be seasonal to slightly above
average and conditions fairly quiet. Southwesterly flow then sets
in on Friday into Saturday as the ridge builds in to our east
while an upper level low starts to deepen off the PacNW. This will
keep the warming trend going, with widespread 80`s to mid 90`s
across the lower elevations by Saturday. With this offshore low,
an influx of moisture should start to present more chances of
precipitation across the CWA starting on Saturday, and peaking
Sunday as the low moves inland across the coastline and up into
Canada, though QPF amounts should remain on the light side. This
will drop temperatures by several degrees into early next week as
well.

Ensemble guidance shows fairly good agreement on the above
forecast, with troughing presenting itself late in the week and
persisting over the weekend across the region. The real trouble in
the forecast lies in the expected path of the upper low. As the
system traverses the shoreline and into Canada, it will merge
with another deep low dropping down from the Gulf of Alaska, but
deterministic guidance disagrees in the speed of this second low.
This will determine our chances of precipitation, as the GFS`s
faster speeds will bring a better shot of showers and possibly
some storms late in the weekend into early next week, whereas the
slower ECMWF would keep most of the activity on the other side of
the Cascades. For now, the NBM seems to be keeping a happy medium
to show some chances of precipitation over the weekend, which is
acceptable for this far out as guidance continues to come together
in the coming days. Goatley/87

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  98  64  84  55 /   0   0   0   0
ALW 101  67  87  58 /   0  10   0   0
PSC 104  70  90  60 /   0   0   0   0
YKM 100  64  86  53 /   0  20   0   0
HRI 102  67  88  57 /   0   0   0   0
ELN  98  64  82  55 /   0  20   0  10
RDM  98  54  81  49 /   0  10   0   0
LGD  96  59  81  52 /   0  10   0   0
GCD  99  58  86  50 /   0   0   0   0
DLS 101  62  84  59 /   0  10   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory until 11 PM PDT this evening for ORZ041.

     Heat Advisory until 11 PM PDT this evening for ORZ044.

WA...Heat Advisory until 11 PM PDT this evening for WAZ024.

     Heat Advisory until 11 PM PDT this evening for WAZ027>029.

&&

$$

MORNING UPDATE...99
SHORT TERM...77
LONG TERM....87
AVIATION...86

NWS PDT Office Area Forecast Discussion