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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS66 KPDT 191636
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
936 AM PDT Mon Apr 19 2021

.MORNING UPDATE...The weak, dry cold front that brought periods of
breezy conditions and patchy blowing dust last night is exiting
the region this morning. Cooler air is filtering into the region
behind the frontal passage and will lower afternoon temperatures
around 15 degrees cooler than yesterday. Tonight, cooler dry air
over the region combined with light winds will allow low
temperatures to dip into the lower 30s across much of the forecast
area. Freeze warnings will be in effect across the Yakima valley,
Columbia Basin, and into north central OR for tonight through
early Tuesday morning. Otherwise, cloud cover will increase later
this afternoon over central OR today as a shortwave moves into
southwest OR. This system will be fairly dry with any
precipitation chances remaining south of the forecast area.
Made minor updates and added Yakima valley to the freeze warning,
with rest of morning forecast package on track. Lawhorn/82

&&

.PREV DISCUSSION... /issued 230 AM PDT Mon Apr 19 2021/

SHORT TERM...TODAY THROUGH WEDNESDAY...A dry cold front from Canada
is working its way southward across the forecast area at this time.
This is ushering in cooler temperatures with todays high
temperatures being around 15 degrees cooler than on Sunday which
puts us back to near normal. Cool dry air over the region tonight
combined with light winds will allow Monday night low temperatures
to dip into the lower 30s. A freeze warning will be in effect
through early Tuesday morning. Those who have begun growing outdoor
vegetation that would be sensitive to freezing temperatures should
take necessary precautions to provide protection.

Meanwhile, a piece of energy over the eastern Pacific will begin to
undercut the ridge of high pressure along the coast and move into
southwest Oregon late today and overnight before moving into the
Great Basin on Tuesday. This system will have little impact to the
forecast area other than some cloudiness over central Oregon. Any
precipitation threat will remain south of the forecast area. The
ridge will then remain off the coast keeping us under a dry
northerly flow through Wednesday. Will see a gradual warming trend
through the first of the week with coolest temperatures being today.

LONG TERM...Thursday through Sunday...Models and ensemble guidance
coming into better agreement for the long term. Thursday will see
northwest flow as model guidance is better in line with keeping
ridge offshore. Another back door cold front will slide down east
side of ridge down the Rockies and will likely clip the region.
Expect a chance of showers over the east, esp over the northern
Blues and Wallowas. Increasing winds through the gorge and Cascade
gaps Thur as thermal and pressure gradients tighten west to east
across the Cascades and with frontal passage. While majority of
model and ensemble guidance have the ridge building over the CWA
with dry conditions For Friday, some solutions are keeping ridge off
shore with northwest flow continuing with a few lingering showers
for northeast mountains. For Friday night into weekend expect ridge
axis to quickly work overhead and push east as the main large scale
upper low approaches the coast. Flow is expected to turn more
southwest with increasing mid to high level moisture and cloudiness
streaming overhead Friday night into early Saturday. As the low
approaches the region, it is expected to pull in a fairly deep plume
of Pacific moisture ahead of it and spread it over the region. Rain
chances look to return by Saturday afternoon and continue through
Sunday as the large upper low approaches northern Cali coast. Mild
Thu/Fri with highs in the upper 60s to 70s. Breezy winds possible
and slightly cooler temps expected for the weekend as cold front
passes through, with highs by Sunday forecasted to be in the upper
50s to 60s.

AVIATION...12Z TAFs...VFR conditions expected through the period.
Skies sct-bkn 8-10kft at taf sites except RDM/BDN this morning will
give way to clear skies this afternoon. Winds 8-14g16-22kts through
early evening will become light overnight.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  62  33  67  35 /   0   0   0   0
ALW  66  37  69  40 /   0   0   0   0
PSC  68  35  72  37 /   0   0   0   0
YKM  67  32  71  35 /   0   0   0   0
HRI  68  32  72  35 /   0   0   0   0
ELN  64  31  68  34 /   0   0   0   0
RDM  65  27  66  28 /   0   0   0   0
LGD  59  31  62  33 /   0   0   0   0
GCD  63  32  64  35 /   0   0   0   0
DLS  70  38  73  40 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Freeze Warning from midnight tonight to 9 AM PDT Tuesday for
     ORZ044-507-508-510.

WA...Freeze Warning from midnight tonight to 9 AM PDT Tuesday for
     WAZ027>029.

&&

$$

MORNING UPDATE...82
SHORT TERM...91
LONG TERM....84
AVIATION...84