806
FXUS66 KPDT 220927
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
227 AM PDT Sun Sep 22 2024

.SHORT TERM...Today through Tuesday...The short term should be an
overall benign period in terms of significant weather concerns,
with a trough bringing the smallest of chances for some Central
Washington Cascade rain and breezy winds through the gaps, with
high pressure then overtaking and causing a warming trend lasting
through the end of the forecast period.

As mentioned for today, an upper level shortwave passes across the
region, but the majority of the energy from this system remains
over Canada. Because of this, we`ll see little in the way of
significant effects from it. Perhaps an isolated shower makes its
way into the Central WA Cascades, but the NBM only paints <25%
chance at a hundredth of an inch for Snoqualmie Pass, barely worth
mentioning. The pressure gradients will briefly tighten though,
and we should get some breezy winds through the Cascade Gaps. The
NBM shows a 30-60% probability of maximum wind gusts 30+ mph today
in the Columbia Gorge and Kittitas Valley, but this seems a bit
low. Winds at 850 mb are are around 35-40 knots during the peak
windy period, and models indicate a 5-7 mb difference in the
pressure gradient from Seattle to Vantage. Because of this and the
fact that Ellensburg tends to run a little higher than the NBM
performs in terms of gusts, have upped the max gusts this
afternoon to show around 35 mph as the peak in the Kittitas
Valley. Minimum RH values will be lowest further south in Central
and eastern Oregon, which should help to preclude any sort of
fire weather headlines for the day (it also helps that the
Autumnal Equinox is today and generating extreme fire behavior
will get more and more difficult each day!).

After today an upper level high will take over and shift across
our region through Tuesday, centering over the Four Corners area
by early Wednesday. This will allow for a steady warming trend,
bringing our highs notably above normal. Temperatures today start
in the upper 70`s to mid 80`s across our population centers, with
a slight increase on Monday, and by Tuesday will be around 5 to 10
degrees warmer, in the upper 80`s to low 90`s - around 10-18
degrees above normal for this time of year. Central Oregon will
be the warmest region with highs in the lower 90`s at a 30-70%
probability of occurring. Daily record highs are around the mid
90`s, so hopefully we shouldn`t see any broken, but we could come
close. If you like warmer temperatures, enjoy this brief little
return to summer before we cool back off in the long term.
Goatley/87


.LONG TERM...Wednesday through Sunday...Ensemble runs continue to
support a pattern change beginning Wednesday with a couple of
shortwave troughs impacting the forecast area through the extended
period and returning us to cooler Autumn conditions.

The upper level ridge of high pressure over the western USA through
the first of the week will be pushed into the central USA midweek as
an upper level trough in the Gulf of Alaska moves towards the
Pacific Northwest. The trough will move inland on Wednesday pushing
a cold front across the forecast area ushering in breezy to windy
conditions and providing a chance of precipitation mainly over the
mountainous areas. This system quickly moves east and exits the
region overnight before another system sweeps across the forecast
area Thursday night and Friday. This system will also produce a
chance of precipitation and provide breezy conditions as a cold
front moves through the forecast area. Ensemble runs are showing
this trough exiting and being followed by a westerly flow with
relative dry conditions for next weekend. However, there are some
variations in the deterministic models that range from another
trough passage in the ECMWF to a southwest flow under a ridge
pattern in the GFS. For now the forecast leans towards the dry
westerly flow scenario on the ensemble but with moderate to low
confidence.


&&

.AVIATION...12z TAFs...VFR conditions to prevail through the
period with increasing high level clouds sct-bkn200-250 late today
and overnight. Winds will be light through the morning then will
see westerly 5-15 kts and in the afternoon through evening. DLs
will see the strongest winds at around 15kts with gusts to 25kts.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  78  51  79  51 /   0   0   0   0
ALW  81  54  81  54 /   0   0   0   0
PSC  82  56  83  56 /   0   0   0   0
YKM  81  52  83  53 /  10  10   0   0
HRI  82  54  83  54 /   0   0   0   0
ELN  80  56  82  54 /  10  10   0   0
RDM  80  46  80  48 /   0   0   0   0
LGD  78  47  78  48 /   0   0   0   0
GCD  78  46  79  49 /   0   0   0   0
DLS  84  57  86  58 /  10  10   0   0

&&

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

$$

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