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FXUS66 KPDT 201201 AAA

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. 


.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 


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 


WA...Flood Watch through Tuesday afternoon for WAZ026-027-521.


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