737
FXUS66 KPDT 142125
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
225 PM PDT Sun Jul 14 2024

.SHORT TERM...Today through Tuesday...Little relief in store for the
forecast area as far as fire weather conditions are concerned. Above-
normal heat is expected to continue, keeping the atmosphere very
dry. This, combined with a series of upper-level waves passing
through the region, will make for a myriad of impacts that will only
exacerbate ongoing wildfires in the area, not to mention the risk
for new fire starts.

Today, breezy winds have picked up through the Cascade Gaps and into
the Basin as a result of a mid-level shortwave trekking through the
PacNW, resulting in a Red Flag Warning. This wave has also oriented
the winds aloft more SW, leading to some moisture advection across
southern and eastern Oregon. Cloud cover is evident, however the
bulk of shower and thunderstorm activity has remained to our south.
Current thinking is that cloud cover will put a bit of a cap on
instability across the southernmost portion of the CWA, however this
shortwave will still promote extreme fire behavior via a very dry
air mass combined with instability. Red Flag Warning remains in
effect for OR642 as a result.

Things quiet down a bit heading into Monday on the back end of
today`s shortwave, however heat will persist and breezy winds will
continue through the Cascade Gaps. Next concern comes in the form of
an upper-level low that looks to pass through from the SW overnight
Tuesday into Wednesday. These types of systems this time of year
always raise a concern for thunderstorms and elevated winds. As of
now, confidence is low on the exact extent and magnitude of the
thunderstorm threat, given how dry models depict the mid-levels of
the atmosphere, however the synoptic pattern is still suitable for
at least some isolated storm activity across the region. And given
how dry the boundary layer has been over the last week or so,
thunderstorms are almost certain to be dry. This feature will be the
focal point of our forecast concerns over the next few days.
Evans/74

.LONG TERM...Wednesday through Sunday...

 Bottom Line Up Front

1. Thunderstorms across the crests and east slopes of the WA
   Cascades Wednesday

2. Elevated winds Wednesday especially through the Cascade Gaps

3. Continued very hot temperatures

Models remain in firm agreement with the mundane synoptic set up.
The region will continue to sit wedged between the Four Corners high
with the upper level low off the coast. An upper level shortwave
will wiggle its way around the top of the ridge and will assist with
the chances of thunderstorms as well as a change in winds. This will
keep the region under a dry southwesterly flow through much of the
term. This set up can be privy to orographically lifted
thunderstorms with the highest chances for them are at the very
beginning of the period along the Cascade Crests of WA and through
the Columbia Basin of WA. However, with the lack of mid level
moisture to assist with the accent, thunderstorm probabilities are
low (less than 10%).  Keep in mind with the hot and dry conditions
st the surface, any fire start will exhibit some extreme fire
behaviors.

Although the flow remains southwest through the period, there is a
weak shortwave that makes its way up and over the top of the ridge.
Surface guidance shows a tightening of the pressure gradient at the
surface which will cause and increase in the winds along the
Columbia River Gorge, foothills of the southern Blues and the
Kittitas Valley. The signal is strongest through the Gorge and along
the foothills of the southern Blue Mountains. Over 60% of the raw
ensembles are in agreement the aforementioned with probabilities of
15% through the Kittitas Valley of sustained winds near 20 mph and
gusts to 30 mph. Again, this is nothing new but with the fire on the
landscape and any new fire, the winds coupled with the dry
vegetation, any new fire start will flow with the winds.

Lastly, the EFI continues to have much of region above
climatologically normal temperatures through the long term. NBM
shows central OR, foothills of the Cascades and Blue Mountains as
well as Wallow Valley to be in the mid to upper 90s while the
remainder of the lower elevations will be in the 100s. NBM shows
very little variance with the temperatures through the long term
with maybe only a few degrees less each day. Looking at the raw
ensembles and setting the max temperature to 95 and greater, more
than 90% show the raw ensembles in agreement across the majority of
the area with the exception of the highest terrains. Not looking to
get any reprieve through the long term just yet. Bennese/90

&&

.AVIATION...18z TAFs (Previous Discussion)...VFR conditions will
prevail through the forecast period. CIGs will remain mostly
clear with a few scattered upper level clouds with a bit of smoke
aloft across the eastern TAF sites. Breezy conditions across all
sites at 10 to 15 with gusts near 25 kts before settling down and
returning to diurnally driven and below 10 kts near/after 4Z.
Bennese/90

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  59  95  57  99 /   0   0   0   0
ALW  63  98  62 102 /   0   0   0   0
PSC  66 100  62 102 /   0   0   0   0
YKM  62  98  63 100 /   0   0   0   0
HRI  64  99  61 103 /   0   0   0   0
ELN  61  94  58 100 /   0   0   0   0
RDM  54  94  53  98 /   0   0   0   0
LGD  55  93  52  97 /   0   0   0   0
GCD  57  95  55  98 /  10   0   0   0
DLS  61  97  61 104 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory until 10 PM PDT this evening for ORZ041-044-049-
     503-505>508-511.

     Red Flag Warning until 9 PM PDT this evening for ORZ641.

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

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

     Red Flag Warning until 9 PM PDT this evening for WAZ690-691.

&&

$$

SHORT TERM...74
LONG TERM....90
AVIATION...90