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Area forecast discussion...updated 
National Weather Service Pendleton or
1011 am PDT Tuesday Jul 29 2014

Updated aviation discussion

Short through Wednesday...high pressure will continue
to dominate the weather pattern with hot daytime temperatures and
mild overnight lows. Some moisture moving around the high will
continue to bring the threat of thunderstorms across central to
northeast Oregon mainly during the late afternoon and evening hours.


Aviation...18z tafs...VFR conditions are expected for the next 24
hours with few-scattered middle-high clouds developing this afternoon. Will
also see the development of scattered-broken high based cumulus clouds in
central Oregon including kbdn and krdm in the 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. Confidence is a little higher today
so have included thunderstorms in the vicinity at kbdn and krdm but it is still marginal that
ts will occur near those sites. Residual cloudiness will continue
through the night with gradual dissipation. Surface winds will
generally remain below 15 kts for the next 24 hours though kdls may
have some gusts to 20 kts this afternoon and early evening. Perry


Previous disc... /issued 244 am PDT Tuesday Jul 29 2014/

Short through Thursday. Southerly flow aloft will
continue for the next several days. Middle and high level moisture
will be transported northward across the forecast area. Instability
will also be present each day as surface temperatures are in the 90s to
lower 100s and model cross sections continue to show middle level
instability. Waiting on stronger short waves to provide lift to get
more widespread thunderstorms coverage. No significant impulses seen
on satellite for the short term...a couple weak ones vicinity of
northern California. Models are showing these weak short waves
moving through at times over the next 3 days with convection
concentrated mostly over central and northeast Oregon. As for
temperatures...they will remain hot. Highs today will be similar to
yesterday. Have issued a heat advisory for a portion of the
Washington Columbia Basin where highs will be 100-105. Some middle and
high level cloud cover will keep overnight lows fairly warm as
well. 94

Long term...Thursday night through Monday...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. Thunderstorms activity will be enhanced by heating during the
afternoon and evening...but weak waves may trigger nighttime
convection as well. However, models diverge on details of the day to
day situation so confidence on any particular day is low.

Southwest flow will be over the area Thursday night and early
Friday. The GFS brings a wave into the area Friday afternoon while
the European model (ecmwf) develops a closed low near the eastern Washington/Oregon
border. Have kept a chance of thunderstorms over the entire area on
Friday since either scenario has moist unstable air with a trigger
for convection. The wave/upper low moves into Montana (gfs) or north
into Canada (ecmwf) on Saturday. Both models indicate a weak wave
forming offshore and moving into Oregon Saturday night and Sunday.
This will reinforce the southerly flow and keep a chance of
thunderstorms over eastern Oregon. Monday the GFS keeps a southerly
flow and brings another weak wave to enhance thunderstorm activity.
The European model (ecmwf) develops a westerly flow with the best convective
potential in Idaho and Montana. The GFS ensembles show both
scenarios. Kept a persistence forecast with low confidence in
details. Coonfield


Preliminary point temps/pops...
PDT 100 68 99 67 / 10 10 10 10
alw 101 71 99 69 / 0 0 10 10
psc 103 68 102 68 / 0 0 0 0
ykm 100 65 100 65 / 0 0 0 0
hri 103 68 101 67 / 0 0 10 10
eln 99 59 99 60 / 0 0 0 0
rdm 95 57 94 58 / 20 20 20 20
lgd 97 61 94 61 / 10 20 20 20
gcd 95 66 93 61 / 20 20 20 20
dls 98 67 97 66 / 0 0 10 10


PDT watches/warnings/advisories...
Washington...heat advisory from 1 PM this afternoon to 9 PM PDT Wednesday


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