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FXUS66 KPDT 052129
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
229 PM PDT Fri Jun 5 2020

...ISOLATED STRONG STORMS LIKELY FROM BLUE MTNS EASTWARD...

.SHORT TERM...Tonight through Sunday night...The pieces to our
storm setup today are in place with sharp trough to our west,
coupled jet streaks providing synoptic lift, and good clearing
through morning on a line from eastern Crook Cnty toward the ID
panhandle encouraging instability. A cumulus field is evident
with some radar returns and lightning flashes beginning to
appear. Storms are expected to increase over the next few hours
and will ultimately become isolated in coverage over the Blue
Mountains and in much of Grant, Union, and Wallowa Counties. A
well mixed surface has kept convective bases in the 8-9kft range
per KGCD ASOS confirming the high based nature of convection and
shear in 50kt range will support organization, with some weak
supercell structures possible. Primary threat continues to be
damaging wind gusts and the potential for hail up to quarter size
from the Blue Mountain crest eastward. The severe weather threat
moves east tonight but deep layer winds shifting southward may
allow for a decaying storm to escape into the near Blue Mtn
foothills overnight. A bit of a drying period is expected tomorrow
before increased upstream moisture is lifted over the region in
the afternoon. This combined with some clearing in morning is
expected to lead to enough instability for chance to isolated
showers and storms over elevated areas of Oregon, though these
storms are likely to lack the storm structure of Friday's storms.
Snow levels will also decrease rapidly Saturday night with
elevations in the 4500-5000ft range possibly seeing flakes fly
early Sunday. Accumulations are likely to be limited, but those
participating in recreational activities in elevated areas this
weekend should check their plans and communities in the Ochocos
and the highest portions of US-97 near La Pine to Chemult should
stay alert to slick road conditions and cold. This same moisture
will promote showers elsewhere, though just how moist the Basin's
airmass gets Sunday and if it will be enough for light rain here
remains a forecast challenge. As we finally clear the axis of the
upper level trough and see a stronger front move over the Cascades
Sunday afternoon, winds will become breezy to gusty. Though some
model output indicates this to be in the 12-18kt range, most
model guidance indicates winds to be a bit higher in the 20-30kt
range during peak mixing on Sunday. Renewed rain and showers over
the Grande Ronde and Wallowa region may lead to swollen rivers and
streams though QPF guidance at this time indicates flooding to be
a low chance event. 76

.LONG TERM...Monday through Friday. Showery conditions and becoming
warmer through the week. On Monday, northwest flow is expected with
most showers confined to the eastern mountains. On Tuesday, moisture
increases from west to east with a weak shortwave moving through for
more showers. There is some instability for a chance of thunder over
the Ochocos and southern Blue Mountains. Dry and warmer Wednesday
with a ridge moving through. There will be a return to mountain
showers and a few thunderstorms by Thursday afternoon as southwest
flow brings moisture and instability back to northeast Oregon and
these can be expected to increase on Friday as another upper level
low moves towards southwest Oregon. Temperatures will be slightly
below normal with highs in the upper 60s to lower 70s Monday and
Tuesday,50s in the mountains and then near normal with 70s to lower
80s, 60s mountains through the rest of the week. Another chilly
night for central Oregon and the Blue Mountains Monday night with
some readings near freezing with 40s elsewhere, then mainly 40s and
50s through the rest of the week. 93

&&

.AVIATION...00z Tafs. Mainly VFR conditions. A cold front will
continue to move east across far eastern Washington and Oregon this
evening with showers mainly along and ahead of front. Thunderstorms
with strong winds and hail over the eastern mountains. These may
come close to PDT and ALW until 03z with some MVFR possible with
heavier showers. The upper low will swing across Oregon on Saturday
with showers from central Oregon northeast through the Blue and
Wallowa Mountains. Winds will be shifting west/northwest 10-20kt and
gust thru the evening, decreasing overnight and then increasing back
to 10 to 20 kts Saturday. 93

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT 49 66 46 63 / 60 20 20 30
ALW 51 69 47 65 / 70 20 20 30
PSC 54 73 51 71 / 30 10 10 10
YKM 47 69 45 68 / 20 20 20 10
HRI 52 71 50 68 / 40 10 10 10
ELN 46 65 45 63 / 30 20 20 10
RDM 40 59 36 57 / 30 30 40 40
LGD 48 61 42 55 / 50 40 50 70
GCD 48 62 40 54 / 40 40 70 60
DLS 50 66 49 64 / 20 20 30 20

&&

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

$$

76/93/93
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