Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 121155 AAA
AFDPDT

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

Updated Aviation 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. 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. This will keep temperatures in the
current low range of 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. The
evening shift dropped the freezing fog advisories and do not see any
sign it is reforming tonight, so I will not issue a new advisory.
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.

&&

$$

83/90/90



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