Area Forecast Discussion
Issued by NWS Pendleton, OR

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000
FXUS66 KPDT 241723 AAA
AFDPDT

Area Forecast Discussion...uPDATED
National Weather Service Pendleton OR
1023 AM PDT Sun Sep 24 2017

Updated Aviation Discussion

.SHORT TERM...Satellite showing an area of mid level clouds moving
across southeast Washington and northeast Oregon this morning with
cloudy skies. Otherwise clear for the remainder of the forecast
area. Cirrus will be increasing this afternoon associated with a
weather system offshore. Temps today in the mid 60s to mid 70s
with continued light winds. The upper ridge will remain over the
region the next few days however a weakening system will move
across the Pacific northwest tonight and Monday with mostly cloudy
skies. 94

&&

.AVIATION...18z TAFS...VFR conditions will prevail through the
period. There will be intermittent mid and high level clouds moving
across the region from north to south over the next 24 hours. These
will be mainly above 8K FT AGL. Winds will remain generally under 12
kts through the period. 76

&&

.PREV DISCUSSION... /issued 224 AM PDT Sun Sep 24 2017/

SHORT TERM...Today through Tuesday night...A northerly flow will
dominate the weather today with some moisture moving over the top of
an upper ridge off the coast and then southward over the forecast
area. This moisture will mainly just produce clouds...though cannot
rule out a sprinkle over the mountains, especially over the Cascades
east slopes. Then the upper ridge will amplify and shift eastward
and inland by Tuesday. This will cause a warming trend with light
winds for the rest of the short term forecast period. Temperatures
will start out today in the mid 60s to mid 70s in the lower
elevations and mostly 50s in the mountains. These will warm up to
the mid to upper 70s...with mostly 60s in the mountains by Tuesday.
The warming trend will not be too strong and these temperatures by
Tuesday afternoon will be around normal or slightly above normal,
but slightly cooler than normal today. Skies will be partly to
mostly cloudy due to an upslope flow over the Oregon portion of the
CWA in the northerly flow. In the Washington portion of the CWA
there will be less clouds due to more of downslope flow over the
Lower Columbia Basin and off the Cascade east slopes. Winds will be
light through the short term period with speeds generally 15 kts or
less. 88

LONG TERM...Wednesday through Sunday...A high amplitude upper level
ridge will be over the forecast area for Wednesday through Thursday
night. This will bring mostly clear skies, light winds and above
normal daytime temperatures (75-85 degrees). Temperatures will cool
efficiently at night, with near ideal radiational cooling
conditions. Lows will be in the 40s, except 30s mtns and high
valleys. A weak trough and associated frontal boundary approach the
western portion of the CWA late on Friday. This will bring some
increase in cloud cover and a slight chance for a rain shower along
the East Slopes of the Washington Cascades. Temperatures remain well
above average Friday afternoon...with highs 75-85, except upper 60s
and low 70s mountains. Behind Friday`s system it looks like the
region will be under a shortwave/transient upper level ridge on
Saturday. This should keep conditions dry, under partly cloudy skies
with near average temperatures. Model guidance is in decent
agreement that the overall weather pattern turns more zonal and
westerly by the end of next weekend, with a longwave trough
eventually developing early next week. However, the 00z GFS does
breakdown the ridge faster than the latest ECMWF and CMC
guidance...so the exact details remain uncertain at this time. For
now, just indicated a slight chance of showers in the mountains next
Sunday...especially in the Washington East Slopes. Temperatures are
expected to remain seasonably mild through at least the end of next
weekend. 77

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  70  43  70  49 /   0   0   0  10
ALW  71  47  71  52 /   0   0  10  10
PSC  75  46  74  50 /   0   0   0  10
YKM  74  46  73  47 /   0   0   0  10
HRI  73  45  74  50 /   0   0   0  10
ELN  74  45  71  46 /   0   0  10  10
RDM  67  37  71  40 /   0   0   0  10
LGD  63  37  67  43 /   0   0  10  10
GCD  65  36  68  41 /   0   0  10  10
DLS  77  49  73  52 /   0   0   0  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

94


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