177
FXUS66 KPDT 160208
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
708 PM PDT Sat Jun 15 2024

.EVENING UPDATE...A Freeze Warning is in affect through Wallowa
Valley with temperatures expected to be widespread below freezing
(70-90% probabilities). Main update to the forecast is to better
reflect the region where the isolated showers are still affecting,
otherwise no large changes to the forecast.

Current radar is showing some lingering showers over the Cascades
as well as along the Blues and into Wallow County. Westerly winds
are still elevated with localized areas seeing gusts above 40
mph. Winds are expected to decrease overnight to 10-15 mph (80%
probabilities) with the exception of the ridgetops. Showers will
also begin to dissipate and remain along the far northern portion
of the WA Cascades. Bennese/90

&&

.PREV DISCUSSION... /issued 436 PM PDT Sat Jun 15 2024/

AVIATION...00z TAFs...VFR conditions expected. Breezy winds will
continue through the evening, before letting off after sunset,
leaving primarily terrain-driven winds less than 10 kts. Winds
will pick back up again across many sites by late tomorrow
morning, especially at DLS, PDT, and the central Oregon sites
RDM/BDN. A few light showers have developed this afternoon as
well, however most showers are light enough such that rain is
having trouble reaching the ground, so expecting a primarily dry
forecast period. All showers are expected to dissipate by sunset
along with the winds, before another round of weak showers develops
tomorrow as well. Evans/74

PREV DISCUSSION... /issued 219 PM PDT Sat Jun 15 2024/

SHORT TERM...Tonight through Monday...

Key Messages:

1) Thunderstorms possible through this evening, primarily across
WA Columbia Basin and WA/OR Blue Mountains.

2) Cool temperatures keep us well below normal, including
temperatures tonight producing near to locally freezing lows.

3) Another slug of moisture brings a second round of shower
chances and high elevation snow Sunday into Monday.

A deep upper level low moving inland along the borders of the US
and Canada will continue eastwards, with part of the troughing
splitting off from the main low and remaining over the PacNW. This
secondary system will close off into it`s own low, bringing a
second round of moisture across the forecast area Sunday into
Monday before fully departing into Tuesday.

This progressive pattern will continue to bring a cool and wet
weather through the duration of the short term period. For this
evening, some scattered showers are seen on radar, with a few
thunderstorms noted across portions of Franklin County as well as
the Blue Mountains. Mesoanalysis indicates a bullseye of 500 J/kg
of CAPE in this region, which combined with orographic enhancement
into the Blues should continue to promote a few lightning strikes
through this evening. These storms should be weak, with lightning
and perhaps locally gusty winds the only expected hazards.
Temperatures should then drop overnight, with widespread low 40`s
and 30`s for our population centers. Central Oregon even has a
risk of nearing freezing, but currently not seeing enough
indication in models that we`ll see a widespread freeze justifying
a freeze warning. Also of note, models have run cold compared to
actual overnight lows by around 2-5 degrees over the past couple
of days, leading to low confidence in hitting 32, let alone
getting below it. Expectation is that this area will near but not
quite reach freezing, but if any location were to reach this
threshold, it would be Redmond with a 60% chance according the to
NBM.

Temperatures will continue to run seasonably below normal by 5 to
10 degrees, with highs Sunday and Monday into the 60`s to mid
70`s. Meanwhile, the aforementioned secondary system will bring
another round of precipitation, primarily affecting the Cascades
and adjacent valleys, and from Central Oregon up through the Blues
and Wallowas. QPF amounts remain unimpressive outside of the
mountains, with the NBM showing only around a 15% chance of
amounts greater than or equal to a tenth of an inch for locations
including Pendleton, Walla Walla, and La Grande. The best moisture
as usual should be in the mountains, but less than half an inch is
forecast at best for this portion of the short term. This may
translate into several inches of snow about 4500 feet, including
1-5 inches for the Wallowas. By late Monday into early Tuesday
morning precipitation should be exiting as we begin to see
warmth return in the coming week. Goatley/87

LONG TERM...Tuesday through Saturday...Models are in good agreement
through the extended period. The departing trough system will leave
the region under a northwest flow with some lingering moisture over
far NE Oregon and SE Washington that will produce a few showers over
the mountains. After that the region will be under a dry westerly
flow Wednesday through Friday providing temperatures getting back to
5-10 degrees above normal. Then an upper level low pressure in the
Gulf of Alaska will move towards Canada on Sunday which will begin
to amplify a ridge over the inland Pacific Northwest and northern
Rockies. This will place the forecast area under a SW flow with high
temperatures around 10 degrees above normal. This pattern could lead
to some convection by late Saturday and into Sunday but for now
chances are less than 10%. There will be some lingering locally
breezy conditions Tuesday through Friday mainly along the east
slopes of the Cascades but overall winds are not much of a
concern.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  40  65  43  67 /  10  10  30  20
ALW  43  69  45  71 /  10   0  30  30
PSC  45  71  48  75 /  20   0  20  10
YKM  38  69  42  72 /  10  20  10   0
HRI  44  71  47  74 /  10  10  20  10
ELN  40  66  44  67 /  10  20  10   0
RDM  33  61  35  63 /  10  10  10   0
LGD  37  62  40  61 /  20  10  40  40
GCD  36  63  38  61 /  10  10  40  30
DLS  46  69  49  69 /  10  10   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Freeze Warning from 11 PM this evening to 9 AM PDT Sunday for
     ORZ050.

WA...None.
&&

$$

SHORT TERM...87
LONG TERM....91
AVIATION...74