Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 300541 AAA
AFDPDT

Area Forecast Discussion...Update
National Weather Service Pendleton OR
1040 PM PDT THU SEP 29 2016

Updated Aviation Discussion

.UPDATE...Heights are lowering across the area in response to an
offshore upper level low approaching. A weak shortwave is seen on the
IR Sat this evening pushing into Central/North-Central Oregon at this
time. A gradually moistening southwest flow is out ahead of, and in
conjunction with this shortwave disturbance. Showers and even a few
thunderstorms have developed over parts of the area
this evening...mainly across the Southern Blue Mtns, Northern Blue
Mtns, Grande Ronde Valley and Wallowa County zones. However, recently
there was even an isolated thunderstorm or two evident in parts of
Central Oregon (near Redmond and Prineville). The short term forecast
was updated to include the chance of showers and isolated
thunderstorms in these areas through the evening and even into the
overnight hours. Conditions look to remain dry during the day on
Friday, but sky cover was increased, as much of the forecast area
will be partly to mostly cloudy through the day. Westerly winds will
also become breezy Friday afternoon, between 10 to 25 MPH as
the pressure gradient tightens over the region. 77

&&

.AVIATION...06Z TAFS...VFR conditions expected to prevail across the
area for the next 24 hours. There will be ample mid and high level
clouds as an upper level trough begins to push into the area. SCT to
BKN clouds between about 7K to 25K FT AGL are expected much of the
time. There will also be a few shra around and even an isolated -
ts...however at this time, it seems much of this activity will miss
the TAF sites. For now, included VCSH for KBDN and KRDM through
30/09z before the activity pushed further east and away. Winds will
become breezy out of the west mainly between 10 to 20 KTS after
30/18z...winds could gust up to 25 KTS at KDLS in the afternoon. 77

&&

.PREV DISCUSSION... /issued 315 PM PDT THU SEP 29 2016/

SHORT TERM...Tonight through Sunday...A transition of the
weather pattern is occurring as the ridge of high pressure over the
region shifts eastward and a closed low pressure system off the
Canadian coast drops southward and stalls off the Pacific Northwest
coast. The impact of this will be some increasing clouds and cooler
temperatures Friday and through the weekend. Precipitation
associated with the low will be light and spotty Saturday. Best
chance of precipitation will come on Sunday when the low begins to
move inland through northern California. Southern and central Oregon
will see some precipitation from this while the rest of the forecast
area should remain dry.

LONG TERM...Sunday Night Through Thursday...General
Overview...While high temperatures should slowly climb each day they
will still be below normal for the extended, with highs in the 60s.
Some areas will be near 70 by Wednesday, with most areas in the
upper 60s to lower 70s by Thursday.

The focus of shower activity for the extended will be mainly along
the east slopes of the Cascades and the mountains of northeast
Oregon. Overall, the chances of showers look pretty weak, and any
showers that occur will likely be light in precipitation. Monday
afternoon and evening looks to have breezy winds as the area will be
under a westerly flow.  Winds should be fairly light for the rest of
the extended barring no major pattern shifts.

Technical Synopsis...Models are in good agreement with the low
pressure system that impacted the area over the weekend to depart to
the southeast.  This will leave a residual chance of showers to the
Cascade east slopes and the central Oregon area on Sunday night.
West flow will set in Monday with breezy winds associated.
Expect pretty dry conditions on Monday before another surge of
moisture moves in Monday night. This moisture is fairly limited and
will likely be rainshadowed over the lower elevations, since we will
be under westerly flow.  This would favor upslope showers across the
mountains of northeast Oregon.  As this push of moisture exits
Tuesday night a building ridge of high pressure will attempt to warm
us up a bit and keep the area dry, at least for Wednesday. Models do
have some discrepancy as to whether or not the dry air will be in
place or if a system from the north will suppress the dry air and
keep a cooler moist westerly flow in place. Have hedged the forecast
towards the drier trend Wednesday.  Wednesday night moisture ahead
of another system may impact the area.  Have gone with increased
pops for the northern portion of the forecast area, and covering all
areas by Thursday.  This may be a bit fast as other models don`t
quite have the system inland by Thursday.  Will continue to monitor
and make changes as necessary. Weber

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  51  73  47  65 /  10  10  10  10
ALW  55  74  52  66 /  10  10  10  10
PSC  53  77  50  69 /  10  10  10  10
YKM  46  77  41  68 /  10  10  10  10
HRI  51  75  47  69 /  10  10  10  10
ELN  46  74  42  66 /  10  10  10  10
RDM  39  72  32  62 /  20  10  10  10
LGD  47  77  46  64 /  20  10  20  20
GCD  46  75  39  61 /  10  10  10  10
DLS  52  74  48  70 /  10  10  10  20

&&

.PDT Watches/Warnings/Advisories...
OR...None.
WA...None.
&&

$$

77/89/77


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