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Area forecast discussion 
National Weather Service Pendleton or
830 am PDT Monday Jul 28 2014

Short through Tuesday...the four corner high pressure
ridge continues to dominate the weather pattern. The flow around
this high places US under a southwest flow with some monsoonal
moisture clipping the forecast area. This will lead to the slight
chance of thunderstorms from central Oregon over to the Wallowa
mountain region today and Tuesday. If storms do develop they will be
high based and produce very little rainfall. High temperatures will
continue to run above normal but below the widespread 103 degrees
needed for heat advisories.


Previous disc... /issued 140 am PDT Monday Jul 28 2014/

Short through upper ridge over the
inland west and a trough in the Gulf of Alaska will continue to keep a
southwest flow over the region and County Warning Area. This pattern will cause hot
and dry conditions to persist through the short term period going
into the long term. Some limited middle level monsoonal moisture will
continue to be pulled northward into the County Warning Area...especially southern
areas. The atmosphere will become unstable due to heating each
afternoon. This combined with the middle level moisture and cape will
result in isolated afternoon and evening thunderstorms each day over
portions of central and northeast Oregon. Today any thunderstorms
that form will be confined to central Oregon and the John Day
Highlands. Elsewhere the atmosphere will be too dry. Thunderstorm
potential coverage will increase each day spreading slowly northward
and eastward as the area of instability increases. The best chances
for any thunderstorms will be over central Oregon and the Oregon
Cascade east slopes. The lower levels will be quite dry so any
thunderstorms will be high based with little rainfall reaching the
ground. Thus there could be a fire weather concern due to lightning
igniting new wildfires. Temperatures will be hot...but not quite as
hot as previously expected. Maximum temperatures will warm to around
100-103 in the lower elevations with 80s and 90s elsewhere. Tuesday
will be the hottest day and then there will be slight cooling as middle
and high clouds increase due to convection. Night time temperatures
will remain warm due to the middle and high clouds preventing strong
radiational cooling. However...temperatures are no longer expected
to reach heat advisory criteria anymore. This weather pattern will
persist into the extended forecast period. 88

Long term...Wednesday night through Sunday...eastern Oregon and
Washington will be on the western side of an upper level ridge
through the long term period. Subsidence from the ridge will bring
south to southwest flow and hot temperatures to the region. This
southerly flow will also bring monsoon moisture into the area at
times. There will be a threat for thunderstorms each day as unstable
southerly flow combines with daytime heating. This threat will
increase later in the week as monsoon moisture increases. Cloud
debris from thunderstorms keep will keep overnight lows elevated
with 60s to lower 70s expected at lower elevations.

Models have been consistent with the overall pattern and increasing
instability with time...but individual weak waves that would enhance
instability...convective activity...and monsoonal moisture advection
vary with each model run. Thunderstorms activity will be enhanced by
heating during the afternoon and evening...but weak waves may
trigger nighttime convection as well. Coonfield

Aviation...12z tafs...VFR conditions are expected for the next 24
hours with scattered middle and scattered-broken high clouds. Will also see the
development of high based cumulus clouds at kbdn and krdm late
Monday afternoon. These clouds will spread north and northeast into
the evening. Stray thunderstorms may develop over central Oregon
after 21z and could impact kbdn and krdm until 05z. At this time
confidence of occurrence of a storm at these two sites is too low to
include in taf. Light terrain driven winds will become northerly at
10 knots or less during the afternoon. 76


Preliminary point temps/pops...
PDT 99 66 98 68 / 0 0 10 10
alw 101 71 101 74 / 0 0 0 0
psc 101 67 102 70 / 0 0 0 0
ykm 98 62 100 68 / 0 0 0 0
hri 101 66 101 68 / 0 0 0 0
eln 97 60 96 65 / 0 0 0 0
rdm 96 46 94 58 / 10 10 20 20
lgd 96 63 94 61 / 10 10 10 20
gcd 96 66 94 66 / 10 20 20 20
dls 98 65 96 68 / 0 0 0 0


PDT watches/warnings/advisories...

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