802
FXUS66 KPDT 072109
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
209 PM PDT Mon Apr 7 2025

.SHORT TERM...Today through Wednesday...

1. Isolated thunderstorms along the Cascade ridges and eastern
   mountains this afternoon and Tuesday afternoon.

2. Isolated showers will continue through Tuesday

3. Drying and warming begins again Wednesday

Current radar imagery is showing some showers moving across the
region from north central OR across the foothills of the Blues as
well as along the eastern slopes of the WA Cascades through Yakima
and Kittitas Valleys. So far little to no indications of
lightning from any of the cells with the exception of 1 strike in
Kittitas Valley. The brief clearing of the sky between these
systems is enough daytime heating to assist with isolated
thunderstorms popping up between now and within the next few
hours.

Looking at the CAMs models coupled with the ensembles, confidence in
isolated thunderstorms has increased to 30-40%. Models show
MUCAPE values to be between 200-300 J/kg, LIs between -1 and -3,
lapse rates of 8.3 C/km and higher with moderate bulk shear of 35
knots. All of these ingredients coupled with the orographic lift
and daytime heating has allowed confidence to increase to the
lower end of moderate probabilities of 30-40%. With the incoming
showers bringing more cloudy skies across the region overnight and
into Tuesday, CAMs models and ensembles are showing a decrease in
all the ingredients needed for thunderstorm initiation. With the
said, only 5-10% of the raw ensemble members show thunderstorms
across the area tomorrow.

As mentioned above, precipitation will continue today through
tomorrow as the upper level system continues pushing onshore. Much
of the moderate/heavy precipitation will stay along the crests of
the Cascades with 70-90% probabilities of 0.50 inches of rain with
light snow above 5000 feet today decreasing slightly overnight then
ramping back up again tomorrow with 80-100% probabilities of near
0.50 inches of additional rain. The Blue mountains of northern OR
will also see 60-80% chances of 0.25 inches of rain Monday and
another round Tuesday. The remainder of the region except central,
north central Yakima and Kittitas Valleys will see 30-50% chances of
between 0.10-0.20 inches of rain decreasing to 10-30% chances of
0.01-0.05 inches Tuesday.

Lastly, models show an upper level ridge beginning to back build
into the region Wednesday. With the incoming ridge, ensembles as
well as deterministic guidance shows the region to be under the
influence of drier and a bit warmer conditions. Bennese/90

.LONG TERM...Thursday through Monday...An upper level ridge will
be over the Pacific Northwest on Thursday and will bring
unseasonably warm temperatures to the area. This ridge will move
eastward into Friday as the next weak trough approaches the coast.
Precipitation will develop later Thursday into Friday, mainly
over the mountains. A second, deeper trough will bring another
shot of precipitation, also mainly for the mountains Friday night
into Saturday. A ridge will then build back in bringing more dry
weather and warming temperatures for Sunday into Monday.

QPF amounts are fairly light, generally 0.25 inches or less over
the Cascades Thursday into Friday and even less Friday into Saturday
only perhaps up to 0.10 inches.

Model guidance is in very good agreement through Monday, then there
are some discrepancies, but these involve a ridge and little
sensible weather.  Snow levels will remain quite high, generally
over 5000 feet.  However, as the second trough moves onshore, they
will drop to between 2000 and 2500 feet in the Washington Cascades
and 3000 4000 feet most elsewhere.  However, due to the high snow
levels, little if any snow accumulations are expected.

There will be some diurnally breezy winds Friday, but especially
Saturday with the trough especially across the Simcoe Highlands,
Kittitas Valley, Columbia Basin and Blue Mountain Foothills.  Winds
could gust in the 25 to 35 mph range.  The NBM probabilities of wind
gusts >= 25 mph are 70 90 percent across much of the area.  However,
the probabilities of wind gusts >= 39 mph  are 50 to 70 percent
across the previously mentioned locations and about 80 percent in
the Kittitas Valley.

Due to the warm temperatures and snow melt, rivers will continue to
run high, especially the John Day and Naches and portions of the
Grande Ronde.

High temperatures will range about 10 degrees above normal on
Thursday.  The ECMWF EFI does key in on these temperatures, with 0.6
to 0.7 anomalies for much of eastern and central Oregon, with an
area of 0.7 to 0.8 anomalies for portions of the Blue Mountain
Foothills and points east.  Highs be closer to normal Friday and
then will be a few degrees below normal on Saturday and Sunday
before rebounding on Monday.


&&

.AVIATION...18Z TAFS...VFR conditions are expected across the
region through the TAF period. However, another round of RA is
expected later this afternoon into early evening for all sites but
BDN/RDM. If the rain is heavy enough, much like this morning
there could be lower conditions for a brief period of time.

Winds are expected to increase at all TAF sites this afternoon and
gust in the 20 to 25 kt range before decreasing during the
evening. All sites should be 10 kts or less on Tuesday, except BDN
and RDM where they will see gust winds to around 25 kts again on
Tuesday.

There is also a chance of TS mainly from ALW and PDT eastward this
afternoon and early evening. However, probabilities are low
enough (<20%) to not include in the individual TAFS. Will amend
as necessary if thunder develops.


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  40  62  41  65 /  50  60  30   0
ALW  42  60  41  62 /  70  70  50  10
PSC  42  65  39  67 /  10  40  10   0
YKM  37  60  34  63 /  10  50   0   0
HRI  39  65  39  67 /  20  50  20   0
ELN  36  57  34  60 /  30  60  10   0
RDM  32  60  33  67 /  10  30  10   0
LGD  37  58  37  61 /  80  60  60  10
GCD  35  57  36  64 /  50  40  20   0
DLS  41  61  41  66 /  40  80  20   0

&&

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

$$

SHORT TERM...90
LONG TERM....77
AVIATION...77