Area forecast discussion
National Weather Service Pendleton or
840 am PDT Wednesday Jun 19 2013
Update...low pressure over the pacnw will continue to pump moisture
into our area today. The latest radar was showing a plume of
rain/isolated thunderstorms and rain from around Ontario and this extends northwest toward
PDT/alw. Also there seems to be a convergence zone over the Blue
Mountains of Oregon with heavy rain occurring and have increased
probability of precipitation and quantitative precipitation forecast here. Otherwise the visible satellite was showing some
subtle breaks in the clouds over central Oregon which could enhance
daytime heating and produce a better chance for an isolated thunderstorms and rain this
afternoon.
Otherwise afternoon temperatures should remain below normal as they
climb only into the 60s across the basin and the remainder of the
forecast appears on track for now.
&&
Previous discussion... /issued 444 am PDT Wednesday Jun 19 2013/
Short term...today through Thursday night...a large upper low
pressure system will continue to slowly move inland today and
tonight. The NAM is a little faster in its eastward progression but
all of the models are indicating an increase in moisture and
instability as the low moves across the forecast area today. Showers
will definitely occur in the northern Blue Mountains eastward across
Wallowa County and the Grande Ronde Valley. Showers will be likely
over the southern Blue Mountains and the ochoco-John Day Highlands
while showers will be scattered elsewhere. With colder air aloft to
destabilize the atmosphere and breaks in the overcast to heat the
surface there will also be isolated thunderstorms with the showers.
Thunderstorms will be concentrated mostly over the central and
northeast mountains and Highlands. Severe storms are not expected
due to the lack of heating as there will be a lot of cloud cover.
Thunderstorms will linger into the evening and then dissipate
overnight. The upper low will continue to progress eastward on
Thursday but its main effects will be felt further eastward with a
northwest flow on the back side of it. The NAM model wants to take
it eastward the fastest with the GFS being the slowest model.
Nevertheless there will still be a chance of showers. A thunderstorm
is possible over the northern Blue Mountains eastward on Thursday
afternoon and evening. Again thunderstorms are not expected to
become severe on Thursday either and they will dissipate by late
evening. Showers will also gradually decrease from southwest to
northeast Thursday night as the low pulls away slowly to the east to
northeast. 88
Long term...Friday through Wednesday...on Friday an upper low will
be located over eastern Washington and move into central Idaho
Wednesday night. Our area will start out with a chance of showers
north of Madras and John Day in the morning then gradually dry out
during the day with only a slight chance of showers in the eastern
mountains by the overnight hours. There does appear to be enough
instability for a slight chance of thunderstorms over the higher
terrain of the eastern mountains and Wallowa County in the afternoon
and evening. On Saturday a weak ridge will begin developing over the
area as the low departs to the east. Have kept a slight chance of
some upslope showers in the eastern mountains in the afternoon and
evening as the low departs. On Sunday or Sunday night another low
begins to impact the area. Models disagree as to the timing and
strength of this system. Rather than pick one model timing over
another have kept the existing forecast of a chance of rain in the
mountains through Monday with a slight chance in the lower
elevations Sunday increasing to a chance of rain Sunday night and
Monday before tapering off Monday night. Have also kept a slight
chance of thunderstorms in the Blue Mountain foothills and the
eastern mountains Monday afternoon and evening. Models show an
active weather pattern with weak disturbances Monday and Tuesday and
with significant differences between the models. Have a slight
chance to a chance of rain in the mountains with the lower
elevations mostly dry Tuesday through Wednesday for now. Temperature
will start out well below normal Friday with highs in the middle 60s to
lower 70s with middle 50s to middle 60s in the mountains. With a ridge
over the area highs will rise 8 to 10 degrees Saturday and a few
more on Sunday to the upper 70s to middle 80s with 70s in the mountains
where it will remain through Wednesday..perhaps a degree or two
cooler Tuesday and Wednesday. Perry
Aviation...12z tafs...an upper level low will remain over the
region for the next 24 hours providing broken middle level clouds and
scattered showers. Expect mainly VFR conditions but will see MVFR or
lower conditions at times in the vicinity of showers and
thunderstorms. Isolated thunderstorms will be possible over central
Oregon and the eastern Oregon mountains from 20z to 05z. West winds
will increase this morning with all sites becoming 10 to 20 kts with
gusts to 30 kts...except 15 to 25 kts with gusts to 35 kts at kdls
and kpdt. Winds will remain at 10 to 20 kts with a few gusts to 25
kts after 06z with the exception of kykm, krdm and kbdn which will
drop below 10 kts. Perry
&&
Preliminary point temps/pops...
PDT 65 47 69 47 / 70 40 40 30
alw 63 51 69 51 / 70 50 40 30
psc 70 52 72 52 / 50 40 40 30
ykm 70 50 68 50 / 40 40 40 30
hri 69 51 72 51 / 50 40 40 30
eln 68 50 66 50 / 40 40 40 30
rdm 61 36 69 36 / 50 30 20 20
lgd 57 43 63 43 / 90 60 40 30
gcd 56 39 64 39 / 70 50 30 20
dls 69 51 72 51 / 40 40 30 30
&&
PDT watches/warnings/advisories...
or...none.
Washington...none.
&&
Threat index
today : green
Thursday : green
Friday : green
Green: none or limited need for watches, warnings, or advisories.
Yellow: a few watches, warnings, or advisories possible or in effect.
Red: numerous watches, warnings, or advisories possible or in effect.
For additional weather information, check our web site at...
www.Weather.Gov/Pendleton
$$
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