Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Pendleton or
720 PM PDT Wednesday Apr 23 2014

Update...showers continue to increase over the County Warning Area from west to
east as the next weather system moves into the region. A warm front
will move up across the County Warning Area this evening and overnight bringing rain
to the forecast area. Snow levels will be high...above 5000 feet so
snow will only be expected on the highest peaks. The cold front with
this system will move across the County Warning Area on Thursday. The cold front
should be east of the Cascades by 18z and to the Idaho border by
00z. The atmosphere will become more unstable on Thursday with the
colder moving in aloft. As such there will also be a slight chance
of thunderstorms over the eastern and northeast mountains in the
afternoon. These thunderstorms are not expected to become severe
though some could produce small hail and gusty winds. The active
weather pattern will persist with another system moving into the County Warning Area
on Friday and again Saturday night into Sunday with more rain or
rain showers. Current forecast looks to be on track. 88

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Aviation...there may be brief periods of MVFR and possibly even IFR
conditions tonight due to lowered ceilings and showers reducing
visibility. However most of the time VFR conditions will prevail.
Winds will range from 5 to 15 kts overnight and then will increase
to 10 to 20 kts with locally 15 to 25 kts on Thursday as a cold
front moves across the County Warning Area and mixes down stronger winds from aloft
with convective rain showers and possibly even thunderstorms. The
thunderstorm threat will primarily be at kpdt and kalw. 88

&&

Previous disc... /issued 225 PM PDT Wednesday Apr 23 2014/

Short term...tonight through Friday night. The challenge with this
package is the rain chances across the area. A storm system will
spread additional clouds and showers to the region tonight and
Thursday as a low pressure system approaches the pacnw coast toward
the end of the work week. The atmosphere also becomes increasingly
unstable Thursday afternoon and an isolated thunderstorms and rain is possible over the
eastern zones. The system moves into Washington/or Friday and the unsettled
weather will persist into Friday night. The best chances for precipitation
should occur later tonight and Thursday before lessening into
Thursday night. However the chances for showers will persist
especially in the area mountains. Snow levels should remain above 4k
feet despite cooler temperatures expected by Friday.

Long term...Saturday through Wednesday night...upper level trough
over the area will push off to the east Saturday...with progressive
westerly flow to follow. A break in the moisture Saturday into
Sunday...but still a chance for showers over the mountains and a
slight chance across the valleys. Overall...snow levels will be
3500-4500 feet Saturday into Sunday...with snow levels rising Monday
Onward. By Monday night...a drier southwest flow will set in and
snow levels are expected to rise between 6500-7500 feet. An upper
level ridge will build over the area for the extended. Temperatures
will start off in the middle 60s across the lower elevations over the
weekend...and should be in the middle 70s by Tuesday and Wednesday.
There is some discrepancies with model consistency and continuity
after Tuesday. GFS model has a strong cold front to push through
the area...with increased chances of precipitation. Thunderstorms
can't be ruled out with this scenario as well. However...European model (ecmwf)
continues to hold onto the upper level ridge with continued warm and
dry temperatures. Leaning toward the European model (ecmwf) for the
extended...therefore the current forecast reflects drier and
slightly warmer Wednesday afternoon and evening. No thunder has
been added to the extended...as confidence is not high enough to
mention. Weber

&&

Preliminary point temps/pops...
PDT 44 58 39 57 / 60 70 60 50
alw 47 58 42 58 / 60 80 60 50
psc 48 64 43 63 / 60 60 20 20
ykm 41 59 35 60 / 50 50 20 10
hri 46 62 42 61 / 60 60 40 30
eln 40 57 36 59 / 50 60 20 10
rdm 39 55 30 49 / 60 50 60 60
lgd 43 53 36 52 / 70 80 70 70
gcd 38 54 34 46 / 60 80 70 80
dls 46 60 40 60 / 70 60 40 40

&&

PDT watches/warnings/advisories...
or...none.
Washington...none.
&&

Threat index
Thursday : green
Friday : green
Saturday : 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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