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000 
FXUS66 KPDT 121328 AAB
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
527 AM PST Tue Dec 12 2017

Updated short tern discussion

.SHORT TERM...Today through Thursday...The current weather pattern 
will remain over the area for the next few days with only a few 
subtle changes expected. Low clouds remain over the Columbia Basin 
and adjacent valleys and into North Central Oregon but has not 
returned to Bend and Redmond. A weak low level flow from the 
southwest to southeast appears to have pushed the clouds north. 
Clouds have been moving back into Madras, Prineville and Redmond but 
at around 5000 feet, so it is probably due to a weak wave crossing 
the area rather than the low stratus returning. Have the low clouds 
returning to central Oregon tonight though without a northerly flow 
to push it, confidence is low. The rest of the Columbia Basin and 
most northerly areas will see the low clouds continue through 
Thursday. A freezing fog advisory remains in effect for north 
central Oregon and the southern Blue Mountain Foothills through noon 
today. However, the freezing fog advisory for central Oregon was 
dropped earlier and do not see any sign it is reforming early this 
morning, so I will not issue a new advisory. The low clouds in the 
lower elevations will keep temperatures in the current small range 
from the mid 20s to lower 30s. Elsewhere skies will be partly cloudy 
with highs in the mid 30s to lower 40s and lows mainly in the upper 
single digits and teens. There will be a weak wave moving through 
the flow late tonight and early tomorrow morning so have added very 
light snow flurries to the area under the inversion and low clouds. 
Do not expect any locations will see more than a dusting of snow and 
precipitation will be just a trace.  Perry

.LONG TERM...Thursday night through Monday...A weak disturbance 
looks to begin the process of weakening the upper ridge over the 
Pacific Northwest late Thursday night into Friday. As such will see 
the slow, but gradual elimination of the fog/low clouds across the 
lower levels of the Interior Northwest. Some light precip will be 
possible as this system moves through the region Friday and Friday 
night. Precip Friday morning may be in the form of freezing rain at 
many locations. Friday afternoon into Friday night snow levels will 
lower, but the low levels should warm due to an intrusion of marine 
air. Thus the lower levels would see rain by late Friday while the 
higher elevations would see snow. A more westerly flow pattern looks 
possible Saturday through Monday. Thus would see periods of precip 
with snow in the mountains and rain or snow at the lower elevations 
depending on the time of day. 90 

&&

.AVIATION...12Z TAFS...Low level inversions trapping moisture will 
continue to affect the Interior Northwest through the next 24 hours. 
As such ceilings will generally run between 1000 and 2500 feet AGL 
at KDLS, KYKM, KPSC, KALW and KPDT through the period. Tops of this 
cloud/fog area will generally run between 3500 and 4500 feet MSL. 
Highest surface pressure is over southeast Oregon. This has been 
causing an east to west pressure force into central Oregon that has 
been limiting fog/stratus at KBDN and KRDM. This condition looks to 
last another 24 hours. Yet fog/stratus has made it to KS33 (Madras), 
thus will indicate the potential for brief a appearance at KRDM 
around daybreak into mid morning. Winds will remain light. 90 

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  29  26  29  26 /   0  10  10   0 
ALW  34  29  34  29 /   0  10  10   0 
PSC  34  30  34  30 /   0  10  10   0 
YKM  34  30  33  30 /   0  10  10   0 
HRI  33  29  32  29 /   0  10  10   0 
ELN  31  25  30  25 /   0  10  10   0 
RDM  34  21  31  21 /   0  10  10   0 
LGD  35  22  33  24 /   0   0   0   0 
GCD  44  27  46  27 /   0   0   0   0 
DLS  36  31  36  31 /   0  10  10   0 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Air Stagnation Advisory until 10 AM PST Friday for ORZ041-044-
     050-505-507>511.

     Freezing Fog Advisory until noon PST today for ORZ508-510.

WA...Air Stagnation Advisory until 10 AM PST Friday for WAZ024-
     026>029-520-521.

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