Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 051726 AAA

Area Forecast Discussion
National Weather Service Pendleton OR
1030 AM PDT Fri Jun 5 2020

Updated Aviation Discussion

.UPDATE...Morning satellite shows a broken deck of mid level
altostratus beginning to take on more cumuliform appearance as
lift increases associated with our cutoff low merging with more
progressive trough over the OR/WA Coast. Today, high temperatures
are expected to be in the upper 70s in Basin and valleys and upper
60s for the mountains with some form of cloud cover remaining
likely for much of the area. Breaks in the clouds are evident over
portions of E/SE Oregon where sunlight may aid destabilization
this afternoon. Expecting a good impulse evident in both model
data and a kink in water vapor imagery to move across region
around 21-00Z to be responsible for convective initiation on a
SW-NE trending line from near Paulina to the Lewiston region.
Plenty of bulk and rotational shear will likely allow some
organization with the cells leading to possible gusty winds and
small hail, though storm motion may be quick. The region most
likely to see storms continues to be Grant (Oregon), Union, and
Wallowa Counties. Storms may last into the early overnight hours
and it`s not out of the question they may reach the crest of the
Blue Mtns, though conditions are expected to be quite unfavorable
for any storms that venture into the Basin. More shower-like
light rain will overspread higher elevations overnight, possibly
creeping into Blue Mtn foothills and portions of the Basin late. 76

AVIATION...18Z TAFs...VFR conditions with increasing mid to high
level cloudiness through this afternoon. A cold front swinging
across the region will help fire off showers after 21Z, mainly over
the higher terrain. A few storms with strong winds and hail are
possible over eastern OR/WA, possibly impacting PDT and ALW from
around 23Z to 03Z. Could see MVFR CIGs/VIS under heavier showers.
Precip dies off after sundown. Winds generally around 10kts or less
through the period , except DLS, BDN and RDM which will increase to
13-18g20-25kts this afternoon/early evening.  Winds will die down
slightly overnight but then increase to 10-20kt and gusty at all
locations after 15z Saturday with scattered showers developing. DS/ML


.PREV DISCUSSION... /issued 253 AM PDT Fri Jun 5 2020/

SHORT TERM...Today through Sunday night. Upper low approaching
the region today. Satellite shows flow aloft has become
southwesterly and clouds are increasing. Expect a mostly cloudy
day with highs in the 70s. Models remain consistent on instability
and shear over northeast Oregon with a chance of thunderstorms
late this afternoon into the evening. Cold front will move through
the forecast area overnight with a chance of showers. Orientation
of the jet should create some heavier precipitation over northeast
Oregon. The upper low will be centered just offshore on Saturday.
Colder air aloft will produce scattered showers mainly over the
mountains. A short wave moving through the low will enhance the
rainfall Sat night into Sunday morning. Models have been
indicating this feature will generate heavier rain over Oregon.
During the day Sunday the low moves into Idaho with the flow
becoming northwesterly. Showers will be decreasing later in the
day and become more upslope over the Cascades and Blues. Cooler
temperatures over the weekend with highs in the 50s and 60s.
Breezy westerly winds Saturday becoming windy on Sunday. 94

LONG TERM...Monday through Friday...The big upper low/trough
continues to push east into the northern plains on Monday with a few
lingering showers in the northwest flow.  Transient ridging will
move overhead Monday night into early Tuesday and bring dry
conditions. This will be short-lived as the next upper-level feature
will bring unsettled weather Tuesday afternoon onward. Warm front
lifts north across the with a swath of Pacific moisture behind it
overrunning the region. Expect a chance of showers Tue/Wed, esp on
Tue, with a outside shot at a storm or two. Remaining cool through
Tue with highs in the mid 50s to near 70, warming behind the front
Wed (70s to low 80s). For late week, the upper-level flow becomes
more amplified with as the low drops south off the PacNW coast. Flow
over the region responds and turns more south/southwest. Initially
will see warmer and drier conditions through Thursday afternoon, but
as the low approaches the region, increasing moisture and
instability will bring the potential for showers and storms starting
Thursday late afternoon/evening. Potential increases for Friday as
the low/trough move onshore. Warm again Thursday with highs in the
mid 70s to mid 80s, slightly cooler Friday (70s to low 80s). Breezy
to windy conditions at times through the period with the progressive
weather pattern in place, especially behind the upper low/trough on


PDT  74  49  67  46 /  10  50  20  30
ALW  76  51  68  48 /  10  50  20  30
PSC  78  54  73  51 /  10  30  10  10
YKM  75  47  70  46 /  10  20  20  20
HRI  77  52  71  49 /  10  30  10  20
ELN  72  46  65  45 /  10  30  20  20
RDM  73  40  59  38 /  10  40  30  50
LGD  76  48  59  42 /  30  60  40  60
GCD  78  48  59  42 /  30  40  40  80
DLS  73  50  65  48 /  10  20  20  30




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