550
FXUS66 KPDT 101743
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1043 AM PDT Wed Jul 10 2024

.UPDATED AVIATION...VFR conditions will prevail through the
period. Winds will be the primary concern across all TAF sites
except ALW/PSC. Sustained winds will be between 15 to 20 kts,
slightly higher at DLS with gust nearing 30 kt possible. Winds
will settle in the evening and overnight period as they will be
mostly diurnally driven. CIGs will remain SKC. Bennese/90


&&

.PREV DISCUSSION... /issued 146 AM PDT Wed Jul 10 2024/

SHORT TERM...Today through Friday...Today will mark the last
substantially hot day of this ongoing heat wave before the high
pressure ridge driving this event shifts to our east and is replaced
by WSW flow aloft. That being said, temperatures will remain
unseasonably hot through the near-future, as the airmass in place is
still very dry and prone to efficient daytime heating. The lack of
high pressure will only work to slightly cap high temperatures after
Wednesday, with highs still well into the 90s and even lower 100s
for most of the populated areas of our CWA. Messaging-wise, however,
ongoing heat warnings and advisories are expected to be allowed to
expire later tonight, as the bulk of the heat wave impacts are
expected to end after today.

The more zonal flow in place of high pressure will also
unfortunately exacerbate ongoing fire weather concerns, as the
accompanying marine push will help drive breezy winds through the
Cascade Gaps and into the Basin through Thursday. Decreasing high
pressure also means increasing instability, which can promote
extreme wildfire behavior. Numerous Red Flag Warnings are in effect
as a result, with the breeziest winds expected today and waning a
bit Thursday, but still remaining stout through the Cascade Gaps,
primarily the Kittitas Valley where the RFW is in effect through
Thursday, rather than the end of the day today for most other zones.

Only other concern will be area smoke and haze, which is increasing
as wildfire activity flares up across the region. Unfortunately,
given the conditions expected over the coming days, the possibility
exists that degraded air quality and haze extent will increase
across the Interior Northwest, as no real relief looks to be in
store for these hot and dry conditions any time soon. Already seeing
wildfire activity flare up in the area, namely in Wasco County with
the Larch Creek Fire, so members of the public are strongly
encouraged to act responsibly and avoid activities that may spark a
wildfire. Under these conditions, even small embers can quickly grow
out of control. Evans/74

LONG TERM...Saturday through Wednesday...Two main concerns
through the extended period. First, with the flattening of the upper
level ridge over the region this will produce some locally breezy
conditions along the east slopes of the Cascades each afternoon and
evening that spills out into the Columbia Basin. This will be a fire
weather concern for spread of fires that develop or are occurring.

Second is the threat of thunderstorms Saturday and Sunday. Models
are beginning to increase this threat as the Four Corners centered
ridge of high pressure combines with a small closed upper level low
off the California coast to direct some monsoon moisture into
southern and central Oregon late Saturday. This then proceeds to be
directed across NE Oregon on Sunday as a weak upper level trough
approaches the Pacific Northwest. Precipitable water values begin to
increase across the region Saturday then peak on Sunday. This makes
thunderstorms more likely over a larger portion of the forecast area
(central to NE Oregon) but probability is still only around 15-25%
at this point.

The weak trough pushes into the region Monday which pushes the
moisture to the east and ushers in some drier air ending the
thunderstorm threat for most of the forecast area. A low probability
of around 10% remains over Wallowa county for some thunderstorms.

A dry westerly flow looks to remain in place Tuesday and Wednesday
but there is some model differences regarding the position of the
Four Corners High and the next approaching upper level trough.

Overall high temperatures will remain slightly above normal through
the extended period with some highs around 100 in the Lower Columbia
Basin but mainly in the mid to upper 90s. In other words, not as hot
as the current heat wave.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT 103  62  97  60 /   0   0   0   0
ALW 107  67 100  65 /   0   0   0   0
PSC 109  66 101  64 /   0   0   0   0
YKM 106  62  99  61 /   0   0   0   0
HRI 108  65 101  63 /   0   0   0   0
ELN 101  64  95  62 /   0   0   0   0
RDM  98  54  95  55 /   0   0   0   0
LGD 101  60  95  59 /   0   0   0   0
GCD 101  59  99  60 /   0   0   0   0
DLS 100  64  96  63 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning until 10 PM PDT this evening for ORZ041-
     044-505-507-508-510-511.

     Red Flag Warning from 2 PM this afternoon to 11 PM PDT this
     evening for ORZ639>641.

     Heat Advisory until 10 PM PDT this evening for ORZ049-050-502-
     503.

     Red Flag Warning until 11 PM PDT this evening for ORZ642>645.

WA...Excessive Heat Warning until 10 PM PDT this evening for WAZ024-
     026>029-521-523.

     Red Flag Warning from 2 PM this afternoon to 11 PM PDT this
     evening for WAZ691.

     Heat Advisory until 10 PM PDT this evening for WAZ030.

     Red Flag Warning until 11 PM PDT this evening for WAZ692-693.

     Red Flag Warning from 2 PM this afternoon to 8 PM PDT Thursday
     for WAZ690.

&&

$$

SHORT TERM...74
LONG TERM....91
AVIATION...91