Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pendleton or
835 am PDT Tuesday may 5 2015
Short term...today through Wednesday...a cold front swept across
the forecast area overnight. Cooler air is filtering into the region
associated with the breezy westerly winds. This means todays high
temperatures will be 10 to 20 degrees cooler and tonight lows will
be 5 to 10 degrees cooler. The upper level trough behind the front
will be settling into western Washington today which will lead to
some instability showers during the afternoon and evening period.
Most of this will occur near the Cascade mountains and mainly in
Washington. The threat of thunderstorms today look minimal and
mainly confined to the east slopes of the Washington Cascades. The
upper level low will spread over the entire Pacific northwest on
Wednesday so the instability will be more widespread and a slight
chance of thunderstorms will be possible across the entire forecast
Aviation...18 tafs...VFR conditions will prevail through the
forecast period. Expect scattered cumulus/stratocumulus at 5-6 thousand
feet above ground level this afternoon with a few buildups possible around kykm.
This cloud layer will persist into the evening. Some middle level
cloudiness will also develop/move in from the west overnight tonight
and affect mainly the western taf sites. Winds will be mainly
westerly at 15-25 knots and gusty this afternoon and evening...slowly
diminishing after 06z tonight. 78
Previous discussion... /issued 432 am PDT Tuesday may 5 2015/
Short term...today through Wednesday night. Upper low currently
over Vancouver Island will move into the Pacific northwest today.
Expect to see a gradual increase in clouds during the day. Best
chance for any showers will be over central and northern
Washington. Temperatures today much cooler than yesterday. Highs
mainly in the 60s with breezy westerly winds. The low moves slowly
southward tonight and will be centered over Oregon on Wednesday.
There will be more instability this day and we will likely see
better coverage of showers and thunderstorms. 500mb temperatures at -28.
The stronger showers could have some graupel or small hail.
Precipitation will continue into the evening hours then diminish
overnight. Temperatures on Wednesday will be a few degrees cooler
with upper 50s and 60s. Gradients still favor some breezy
northwesterly winds in the afternoon. 94
Long term...Thursday through Monday...upper level low will continue
to spin south of the forecast area...leaving central and northeast
Oregon under the deformation zone through Thursday evening. Slight
chance showers will continue for these areas...but thunder has been
removed due to low confidence and a building narrow...yet amplified
ridge over the inland northwest for the weekend. Will keep very
borderline slight chance probability of precipitation along the northeast mountains through
Friday evening...in case the low stalls out allowing for lingering
showers. Conditions will remain dry through Sunday morning...as the
ridge remains overhead. By middle day Sunday European model (ecmwf) has a shortwave
pushing through the area. Moisture seems limited...so have
increased probability of precipitation along the mountains...but no valley precipitation
expected. GFS solutions continues very warm and dry for the period.
It's not until Monday night that the GFS brings in a stronger more
unstable system to impact the area by middle next week. Will continue
to monitor the forecast for updates...but it looks to be a fairly
warm and mostly dry weekend. Weber
Aviation...12z tafs...VFR conditions expected over the next 24
hours. Breezy conditions out of the northwest this morning and
afternoon...with winds 5-15 kts...gusting up to 25 kts at times.
Winds should diminish 10kts or less at all taf sites after 06z
tonight. Scattered 7-10 kft clouds this afternoon with a scattered-broken 25kft
cloud deck as well. Slight chance thunderstorms on approach west of
kykm...kdls...kbdn...and krdm. Thunderstorms may make it within the
vicinity of kykm and kdls...but confidence is not high enough to
mention in the current taf package. Weber
Preliminary point temps/pops...
PDT 63 39 61 39 / 10 10 20 20
alw 66 42 64 41 / 10 10 20 20
psc 70 43 67 42 / 10 10 20 20
ykm 65 38 64 40 / 20 20 30 20
hri 68 41 66 40 / 10 10 20 20
eln 62 37 62 38 / 20 20 30 30
rdm 60 30 56 32 / 10 10 20 30
lgd 61 36 58 37 / 10 0 20 20
gcd 63 34 58 34 / 10 0 20 30
dls 65 42 66 42 / 20 20 20 20
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