Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 211715

Area Forecast Discussion
National Weather Service Pendleton OR
1015 AM PDT Sat Sep 21 2019

Updated Aviation Discussion.

.UPDATE...Areas of fog/low stratus showing up on the satellite
this morning across portions of central/northeast Oregon. Added
fog until 11am for these areas. Otherwise, only minor edits to the
grids. Ridging today with just a few high clouds and warmer temps
expected. A cold front sweeps across the region tomorrow and
tomorrow night, bringing a good chance of rain showers,
especially over the mountains. An very outside chance of a storm
or two over central OR late afternoon/early evening, but
instability is very marginal, so have kept thunder out of
forecast. Northwest flow follow the departing system for early
next week. Drier conditions expected, but expect variable
cloudiness and a slight chance for showers over the mountains,
especially the WA Cascades, as Pacific moisture in the nw flow
tries to clip the region. A dry cold front on Tuesday could bring
breezy to windy conditions as it mixes down stronger winds aloft.
Advisory level winds possible as winds aloft are running +2 to +3
standard deviations. Warm today with highs in the upper 60s to
upper 70s. Slightly cooler tomorrow and early next week with highs
in the lower 60s to mid 70s.

AVIATION...18Z TAFS...VFR conditions continue with light winds
expected for the next 24 hours. A few clouds above 25,000 ft across
the eastern portion of the region will gradually diminish through
the afternoon. As a cold front arrives from the west tomorrow
morning expected showers and light rain to gradually move into the
region. Because of this have added VCSH to KYKM, KDLS, KRDM & KBDN
after 15z Sunday morning. Richards


.PREV DISCUSSION... /issued 205 AM PDT Sat Sep 21 2019/

SHORT TERM...Today through Monday...An upper ridge with warmer and
dry conditions will move across the region and forecast area today.
Winds will be light and temperatures will be pleasant in the mid to
upper 70s in the lower elevations and mostly 60s in the mountains.
Then a change is in store for tonight and Sunday as another upper
trough drops down from the northwest into the region. This will
bring a period of rain by morning and through the morning on Sunday,
followed by instability showers Sunday afternoon and evening as the
upper trough axis passes over the forecast area with colder air
aloft. This instability will be too marginal to mention any
thunderstorms, but would not rule a stray lightning strike somewhere
in the forecast area Sunday afternoon or early evening. Temperatures
on Sunday will only be a degree or two cooler than today due to
mainly the southwest flow ahead of the trough axis. On Monday a
transitory ridge will move across the region with mostly dry
conditions. It will be a several degrees cooler behind Sunday`s
upper trough. There will be some slight increase in wind with the
passing trough on Sunday, and then again on Monday afternoon due to
mixing, but winds will be mostly light through the short term
forecast period. Despite the few degrees differences in temperatures
from day to day, temperatures will be not be too far from normal for
late mid-late September on any of the days in the short term. 88

LONG TERM...Monday night through Saturday...A dry northwest flow
will be over the region Monday night through Wednesday. It will be
warm on Tuesday with highs in the 70s and 60s in the mountains. A
dry cold front will cross the area Tuesday with gusty west winds. By
Wednesday night a few showers will be possible as an upper low
starts to develop over the Northwest. The low will settle over
Oregon by Friday with cold temperatures, continued showers and some
snow showers above 5000 feet especially at night. Snow levels lower
even further on Saturday with the upper low lingering. Snow showers
will be possible down to 3500-4000 feet Saturday morning before snow
levels rise and temperatures warm during the afternoon. Friday and
Saturday`s high temperatures could be 10 to 15 degrees below normal
for this time of year. 78


PDT  74  48  72  48 /   0   0  40  40
ALW  76  52  77  52 /   0   0  40  50
PSC  78  54  75  53 /   0   0  40  20
YKM  76  49  69  45 /   0   0  60  20
HRI  79  51  76  50 /   0   0  40  30
ELN  74  49  67  46 /   0   0  60  30
RDM  73  46  67  40 /   0   0  60  40
LGD  71  47  71  48 /   0   0  40  60
GCD  73  46  73  46 /   0   0  40  60
DLS  78  55  70  52 /   0   0  60  30




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