Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 201201 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
401 AM PST Mon Feb 20 2017

Updated aviation discussion

.SHORT TERM...Today through Wednesday...An active weather pattern
will persist through at least mid week with one Pacific storm after
another. One moving through now is bring moderate rain to the Blue
Mountains and Foothills with rain also covering most other areas of
the CWA. Snow levels are fairly high so snow does not look to be a
problem. Once this system moves off to the east later this morning
expect showers this afternoon. There may even be a stray lightning
strike over the extreme northeast corner of the CWA but not enough
to include in the forecast. Winds will also increase this afternoon
and it will become breezy to windy...mostly on the ridge tops that
are exposed to the free air winds. Another weather system will then
move into the region on Tuesday...with a brief break and then a
third system on Wednesday. Tuesday will be stronger and wetter
though. Snow levels will lower by Wednesday but the amount of
precipitation will not be that much on Wednesday and so snow amounts
in the mountain will be too light for any winter weather highlights.
There are some hydrology concerns with the rain and melting snow
over the next couple of days...mainly in the Yakima and Kittitas
Valleys and the Simcoe Highlands due to rain and snow melt. There is
a flood watch in effect for these areas which is discussed in more
detail below. Temperatures will be slightly above normal today and
then will lower to near or slightly below normal by Wednesday. It
will become breezy again on Tuesday. 88

.LONG TERM...Wednesday Night through Monday...Unsettled weather is
expected through the long term period as a trough will be over the
western CONUS and Canada. Wednesday night and Thursday a wave will
be moving south through the trough. This will give the mountains a
chance of mainly snow as snow levels will start out at 1500 feet and
drop to the surface by Thursday afternoon. Snow levels will remain
below 1500 feet through Monday. The lower elevations won`t see much
precipitation though there should be a slight chance of rain and
snow showers on Thursday. Precipitation amounts will be light and
even in the mountains snow amounts will be an inch or less. After a
lull Thursday night, another wave will graze the coast Friday and
Friday night. This will give the mountains another chance of snow
while in the lower elevations there will be a slight chance of snow
mixed with rain during the daytime. The Columbia Basin will
generally remain dry. The wave will slide south into California on
Saturday while another wave starts to move south out of the Gulf of
Alaska. Some weak ridging will keep much of the area dry Saturday
and Saturday night though the northerly flow will generate a slight
chance of light snow showers in the mountains. That next wave will
arrive either Sunday or Sunday night (models have timing
differences) and affect the region through Monday. Due to the
uncertainty, have a chance of snow showers in the mountains and a
slight chance of snow showers mixed with daytime rain showers in the
lower elevations. Temperatures will be in the 30s to around 40
during the day and generally in the mid teens to mid 20s at night.
Perry

&&

.AVIATION...12Z TAFS...A Pacific disturbance will move through the
area today with rain showers at times at all TAF sites through this
afternoon. This morning will see a mix of MVFR/VFR conditions at
KDLS improving to VFR by late morning while other TAF sites will be
at VFR through this evening. Another system will begin moving into
the area after 09Z tonight with a snow/rain mix at KRDM and KBDN and
rain elsewhere. MVFR ceilings will be possible with these showers.
Later this morning and this afternoon, southerly winds at KRDM and
KBDN will increase to 15 to 25 kts with gusts to 30 kts. KPDT, KALW
and KPSC will have south to southwest winds of 10 to 20 kts with
gusts to 25 kts. Winds will diminish after 03Z. Winds at KYKM and
KDLS will remain below 15 kts for the next 24 hours. Perry

&&

.HYDROLOGY...Previous Discussion...Significant rain will fall Monday
and Tuesday with these warm fronts. Rising snow levels from the warm
air aloft will add snowmelt to the runoff. Rainfall up to three
quarters of an inch in the Simcoe Highlands and up to one half an
inch in the Yakima and Kittitas Valleys may create localized
flooding. A flood watch has been issued for these areas Monday
through Tuesday afternoon. Lesser amounts of rain will fall in the
Lower Columbia Basin and Foothills of the Blue Mountains. A
Hydrological Outlook - product PDXESFPDT - has been issued for these
areas. 76

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  52  34  42  31 / 100  60  50  20
ALW  53  36  42  32 / 100  50  70  30
PSC  50  33  42  30 / 100  40  70  10
YKM  44  28  38  26 / 100  40  60  10
HRI  52  32  42  29 / 100  50  50  10
ELN  39  27  35  25 / 100  30  60  10
RDM  49  29  40  26 / 100  50  30  20
LGD  48  36  40  29 / 100  60  50  30
GCD  52  34  42  29 / 100  50  50  40
DLS  44  31  38  32 / 100  50  40  20

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Flood Watch through Tuesday afternoon for WAZ026-027-521.

&&

$$

88/83/83/76


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