024
FXUS66 KPDT 051026
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
326 AM PDT Sun May 5 2024

.SHORT TERM...Today through Tuesday...The center of the closed
upper level low is moving through NW Nevada this morning and will be
over SW Idaho by this afternoon. Moisture continues to wrap around
the low coming into eastern Oregon from Idaho mainly impacting NE
and north central Oregon and portions of southern Washington. This
will continue through the morning but as the low moves towards SW
Idaho this afternoon this moisture flow gets cut off and leaving
leftover moisture lingering over the forecast area. As the low moves
into Idaho this will allow a northwest flow to push into the Pacific
Northwest and begin to push the lingering moisture eastward
beginning this afternoon and continuing overnight. This flow will
maintain some showers along the Cascade crest and portions of the
east slopes. Meanwhile this flow will place the Blue mountains under
a favorable upslope flow enhancing precipitation over the eastern
mountains that begins to taper off late tonight. This event is still
on track to produce some significant and beneficial precipitation
amounts to the forecast area today and overnight with the main focus
now shifting to the eastern portion of the forecast area, the Blue
Mountain Foothills and eastern mountains. Snow levels over central
Oregon will remain around 3000 to 4500 feet today with some more
accumulation snow accumulations in the mountains for which Winter
Weather Advisories continue. Snow levels over the eastern mountains
will lower tonight to around 3500 feet by Monday morning meaning
there will be some minor accumulation snow as well.

A shortwave in the northwest flow is expected to arrive on Monday
which will once again increase precipitation across the forecast in
the form of showers with a slight chance of thunderstorms over the
eastern mountains. This will be followed by linger mountains showers
on Tuesday that come to an end Tuesday night as a ridge of high
pressure begins to build into the region from the west.

Other concern for today will be the increasing westerly winds
associated with exiting low pressure system and the developing
northwest flow. Expect westerly windy conditions to reach wind
advisory levels of 25 to 35 mph with gusts up to 50 mph across north
central Oregon from the Columbia River Gorge eastward to the
Foothills of the Blue Mountains. Winds will decrease slightly
tonight but still remain breezy to windy through Monday and Tuesday
with further issuances or extension of wind advisories being
possible..

.LONG TERM...Wednesday through Sunday...Significant weather
concerns in the long term will be limited to warming temperatures
and dry conditions as high pressure becomes the primary weather
feature across our region.

In regards to the overall synoptic pattern, aforementioned high
pressure will be the primary feature of our region, though the low
pressure and troughing currently moving across today will have an
influence as well. Ensemble guidance indicates a ridge of high
pressure will begin moving over the PacNW on Wednesday, while low
pressure moves into the middle of the US. As the ridge continues to
stretch into the Northern Rockies and Canada on Thursday and Friday,
part of the low will separate from the primary source and retrograde
into a separate, weaker low over California/Nevada. This will allow
the ridge to continue strengthening over the PacNW and possibly over
the entire West Coast by the weekend. Primary discrepancies in
ensemble guidance revolve around the weak low that moves back over
California, as around 60% of the GFS members have this low stronger
than other ensemble guidance, even bringing a portion of it into
Southern Oregon, which would be a cooler solution compared to other
ensembles, but with the majority of members including the multi-
model ensemble indicating strong ridging for the majority of the
PacNW, this remains an outlier solution.

With this synoptic pattern, expect a quick warming trend and dry
conditions through the long term. Temperatures on Wednesday should
still be on the cooler side, around 2-5 degrees below normal, but
rapidly become 2-5 degrees above normal on Thursday, and by the
weekend could be reaching as high as 10-20 degrees above normal. The
NBM indicates a 30-90% chance of highs greater than or equal to 80
degrees next Saturday for our lower elevation zones, and a 30-50%
chance of highs greater than or equal to 90 degrees for the Columbia
Basin by next Sunday. NWS HeatRisk values still only show around a
category 1, or minor, level of heat for our area, primarily
affecting those extremely sensitive to heat, especially when
outdoors, and heat-related highlights remain very low (less than
5%). Goatley/87


&&

.AVIATION...06z TAFs...Light to moderate rain showers will impact
all sites through the period, leading to MVFR and even IFR
conditions at times as showers lead to reduced cigs and even lowered
vsby`s at times. The bulk of the rain associated with this ongoing
weather system is expected to occur during the overnight hours, with
locally heavy showers possible for PDT and ALW around sunrise
Sunday. Elsewhere, showers will be of a lighter intensity, however
cigs for most of the period are expected to be bkn-ovc between 2 and
7 kft. Rain chances will end earliest across sites near the
Cascades, spreading eastward throughout the period, before rain is
largely expected to end for all sites by nightfall Sunday night.
Winds will remain gusty at times as well, peaking during the day
Sunday as many sites see westerly gusts up to 35 kts, especially DLS
and PDT. Evans/74


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  49  41  57  38 / 100  80  70  30
ALW  52  43  59  41 / 100  90  70  30
PSC  59  46  64  44 / 100  50  30  10
YKM  62  39  62  37 /  80  10  20   0
HRI  56  43  62  42 / 100  40  40  10
ELN  58  41  56  37 /  60  10  20  10
RDM  49  34  52  30 /  70  10  60  30
LGD  46  37  52  36 / 100  90  90  60
GCD  43  34  51  33 / 100  80  90  80
DLS  58  45  57  44 /  90  20  60  20

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 11 PM PDT this evening for ORZ041-044-507-
     508-510.

     Winter Weather Advisory until 11 PM PDT this evening for ORZ506.

     Winter Weather Advisory until 11 AM PDT this morning for ORZ509.

WA...Wind Advisory until 11 PM PDT this evening for WAZ024-521.

&&

$$

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