659
FXUS66 KPDT 110844
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
144 AM PDT Thu Jul 11 2024

.SHORT TERM...Today through Saturday...Winds have begun to subside
across the forecast area, save for the Cascade Gaps, as the pressure
gradient across the region weakens in wake of a ridge breakdown.
With high pressure ridging no longer prevailing, temperatures will
cool slightly, and our synoptic pattern will become more that of
weak SW flow, however an upper-level low does look to threaten the
region over the weekend with a slight chance of thunderstorms,
primarily for the mountains of central and eastern Oregon.

Heat headlines have all dropped off, and the last of the Red Flag
Warnings associated with this ridge breakdown will end by sunrise,
save for the Kittitas Valley where breezy conditions are expected to
continue until later tonight. And while temps won`t be quite as
oppressive as they have been recently, a very dry airmass will
remain over the region, allowing for efficient daytime heating that
will lead to afternoon highs climbing well into the 90s for most of
the forecast area, and even over 100 still across the lower Basin.
Until we get a NW low or a more robust SW trough with better
moisture advection, expect these hot conditions to persist for the
near-future.

Fire weather concerns then shift away from that of dry and breezy
conditions to that of dry thunderstorms, as deterministic models are
in good agreement of a SW low arriving in the region by the weekend.
Better chances for orographic storms look to be Sunday rather than
Saturday, yet models still tap into sufficient mid-level moisture
for convection to develop primarily over the John Day/Ochoco
Highlands late Saturday afternoon. Will hold off on issuing any fire
weather products associated with this storm threat this far out, but
should note that the boundary layer is much too dry to support a
wetting rain of any kind. Once confidence further increases on the
thunderstorm forecast, would not be surprised if a Fire Weather
Watch is issued for the central and eastern Oregon mountains,
especially for Sunday. Evans/74

.LONG TERM...Sunday through Thursday...Models remain fairly
consistent in maintaining the Four Corners high pressure in position
through the extended period. This places the Pacific Northwest under
a dry southwest to west flow with the exception of some monsoon
moisture clipping SE Oregon. Main impacts remain basically the same.

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 minor fire weather concern
for spread of fires that develop or are occurring.

Second is the threat of thunderstorms Sunday across SE Oregon. Some
of this will clip the forecast area from Lapine to Joseph. Models
continue to show 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 SE Oregon
Sunday. This makes for a slight chance (15%) of thunderstorms over
portions of central and NE Oregon. The GFS models shows some
lingering instability over NE Oregon on Monday from a weak
shortwave passing to the north but this is not supported by other
models at this time. Otherwise, the dry southwest to west flow will
suppress the monsoon moisture south and east of the forecast area
through the remainder of the long term period.

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.

&&

.AVIATION...12z TAFs...VFR conditions are expected to continue
under clear skies. Winds have decreased to generally under 10kts
except for the DLS site where some 10-20kt winds persist. Winds
will increase again midday becoming 8-15kts through evening with
gusts to around 25 kts before decreasing overnight.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  96  60  97  60 /   0   0   0   0
ALW  99  64 101  66 /   0   0   0   0
PSC 101  64 101  65 /   0   0   0   0
YKM  99  61  99  63 /   0   0   0   0
HRI 100  63 101  65 /   0   0   0   0
ELN  95  62  98  64 /   0   0   0   0
RDM  95  53  96  54 /   0   0   0   0
LGD  95  58  98  60 /   0   0   0   0
GCD  98  59 102  61 /   0   0   0   0
DLS  95  62  98  64 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 5 AM PDT early this morning for ORZ639-
     641.

WA...Red Flag Warning until 5 AM PDT early this morning for WAZ691.

     Red Flag Warning until 8 PM PDT this evening for WAZ690.

&&

$$

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