High Wind in Oregon, April 7, 2017

Area Forecast Discussion
National Weather Service Pendleton OR
435 AM PDT Fri Apr 7 2017

Updated Wind Headlines at the Bottom of the Discussion

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.PREV DISCUSSION... /issued 300 AM PDT Fri Apr 7 2017/

SHORT TERM...Today through Sunday...A large and powerful storm
system is spinning just off the Oregon coast early this morning(sub
980mb). A warm frontal boundary brought a period of rain to parts of
the area overnight and is now lifting into far Northeast Oregon and
Washington. The latest IR/WV Sat shows the cold pool aloft along
with a bit of a dry slot working toward the forecast area. Sct
thunderstorms are already occurring in SW Oregon early this morning
in association with the system's strong dynamics. As this system
rides along the OR/WA coast today there will be several sensible
weather concerns for our area. First and foremost will be the
potential for strong...possibly damaging winds for parts of the
area. May need to expand the current wind advisory area some and/or
upgrade a few zones to high wind warnings....the highest winds are
expected to be across Central OR and the southern Blue Mountain
foothills starting mid morning and lasting into the afternoon hours.
The latest MAV/LAV/HRRR and 4km UW GFS all agree on the potential
for 45-55kt wind gusts in these zones. Will make a decision on these
wind highlights very shortly. Not much in the way of precipitation
is expected this morning. However, the atmosphere will become
increasing unstable this afternoon, with LI values reaching -1 to -5
and SB CAPE values between 400-900 J/Kg...this is modestly
unstable...but should be enough for isolated to scattered
thunderstorms between about 12-8PM today. 0-6km shear values will be
between 30-50kts and locally up to 60 kts over NE OR and SE WA...and
this could be enough for some isolated strong thunderstorms to
develop. These storms may contain frequent lightning, gusty winds
and some hail...for this reason the Storms Prediction Center (SPC)
has areas east of Pendleton and La Grande under a marginal risk for
severe thunderstorms. After a brief break in most of the activity
later this evening, yet another mid-level low pressure system is
forecast to affect the area starting during the predawn hours
Saturday morning and continuing into Saturday evening. The area with
the highest PoPs and QPF amounts appears to be over the eastern
third to half of the forecast area...along and east of a line from
approximately Paulina---Mitchell---Fossil---Heppner---Pilot Rock and
Walla Walla. Colder air aloft and at the surface will move into the
area tonight and Saturday....this will lower snow levels to between
3000-4000 feet. Snow levels could be locally lower under the mid-
level dynamics of the closed low Saturday morning in Grant, Union
and Wallowa Counties. By the time the precip winds down Saturday
evening look for snow totals of 3 to 6+ inches in the Eastern
mountains above 4500 feet...with 1 to 4 inches between about 3200
feet to 4500 feet again over the eastern portion of the area (John
Day, Meacham, Enterprise, Joseph etc). Some of these zones may come
close to the late season advisory criteria...however there does
remain some uncertainty in the exact low track and temps/snow
levels. The weather finally becomes quieter by Sunday, as the area
is forecast to be under a transient, shortwave ridge. There will
only be a slight chance for mountain showers on Sunday. Otherwise
much of the CWA will be partly to mostly cloudy, with highs in the
50s. 77

LONG TERM...Sunday night through Saturday...The extended period
will be unsettled as a series of weather systems moves across the
region bringing periods of rain or rain showers (and higher mountain
snow) about every 12 to 24 hours. The medium to long range models
such as the ECMWF and GFS are in good agreement and then by day 5
they begin to diverge from each other. However, they both still
indicate trough after trough through next week keeping the forecast
area cool and showery. There will be a system moving in late Sunday
night and Monday with a south to southwest flow and a cold front.
This will bring rain and mountain snow. Then there will be a brief
break on Monday night and Tuesday before the next weather system
moves in on Tuesday night and Wednesday. This next system will be a
very moist system and a slow moving system. This will keep rain
showers in the forecast each day and night through Thursday. Then
there will be another brief break on Thursday night which will be
followed yet another weather system on Friday into next weekend. Due
to cloud cover and the upper troughs keeping lower heights and cool
850 mb temperatures over the region temperatures will be below
normal through the extended period. It will also be locally breezy
to windy at times...especially near showers. 88

AVIATION...12Z TAFs...Conditions will be mostly VFR with cigs
greater than 035...but there will be brief periods of MVFR and
possibly even IFR in rain showers and possible thunderstorms
today...especially over south and eastern areas (TAF sites affected
the most being KPDT...KALW...KRDM...KBDN). It will also be windy
today with wind speeds of at least 15 to 25 mph with higher wind
speeds likely on the ridge tops. Wind advisories are currently in
effect for central and northeast Oregon and southeast Washington
today through early this evening. 88

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  61  38  49  34 /  50  30  50  30
ALW  64  42  51  38 /  60  30  60  40
PSC  67  42  56  37 /  40  10  20  10
YKM  64  35  56  33 /  30  10  20  10
HRI  66  39  55  36 /  20  20  30  20
ELN  58  35  51  32 /  40  20  20  10
RDM  57  28  47  21 /  30  40  20  20
LGD  60  33  42  31 /  60  40  80  40
GCD  57  33  42  22 /  60  70  90  40
DLS  62  42  55  39 /  60  20  20  20

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning until 8 PM PDT this evening for ORZ508>511.

     Wind Advisory from 10 AM this morning to 8 PM PDT this evening
     for ORZ044-505-507.

WA...Wind Advisory from 10 AM this morning to 8 PM PDT this evening
     for WAZ028-029.

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77/88/88