Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 280249
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
749 PM PDT TUE SEP 27 2016

.SHORT TERM...Dry southwest flow aloft across the region tonight
into Wed with mainly clear skies. Temperatures will be cooler
than last night with lows in the 40s to lower 50s. Mostly sunny
Wed with highs in the 80s. An upper low will be approaching the
Pacific northwest Thu and Fri. This should bring an increase in
cloudiness with a slight chance of showers. The low moves slowly
inland Sat and Sun with a better chance of rain and much cooler
temps. 94

&&

.PREV DISCUSSION... /issued 230 PM PDT TUE SEP 27 2016/

SHORT TERM...Tonight through Friday afternoon...Water vapor
satellite loop shows a mid/upper level trough in the Gulf of Alaska
that will migrate to the SE over the next several days. The trough
will reach the offshore waters between 130-140W by Thursday
afternoon and will back the SW flow aloft on Wednesday to the
south on Thursday. Dry and warm conditions will continue through
Wednesday night. By daybreak Thursday, there will be a slight chance
of showers in the northern Blue Mountains and Wallowa County.
Thursday afternoon increasing moisture and elevated instability
moves into central and NE Oregon. As such I have introduced a slight
chance of afternoon showers and thunderstorms in the forecast area,
mainly in central and NE Oregon. Thursday evening, models are
showing convection and elevated instability moving into north
central Oregon and SE Washington with a chance of showers in the
mountains of NE Oregon through Thursday night. I kept a slight
chance of thunderstorms for Thursday evening in central and north
central Oregon, the Blue Mountains and Wallowa County and introduced
a slight chance of showers and thunderstorm in the Lower Columbia
Basin as well for Thursday evening. Friday the flow aloft remains
out of the south for a slight chance of showers throughout the day.
Polan

LONG TERM...Friday night through Tuesday.  A large upper
level trough will be moving into the area starting Friday night and
will move across the area through the weekend and into early next
week. This will bring cooler temperatures and a chance of showers
across most of the area with the best chance of showers on Sunday.
The airmass will be somewhat unstable on Saturday afternoon as a
piece of energy drops in to the trough along the cooler 500 mb
temperatures.  I have not included thunderstorms over the Blue
Mountains at this time as the forcing is weak, but will need to
watch this area as we get closer. Current model runs have additional
moisture and energy moving through the trough into Tuesday. Snow
levels through the weekend will decrease to between 5000 and 6000
feet. Temperatures will be below normal with the coolest day looking
to be Monday. Highs will be in the 60s/50s mountains, with the upper
50s/upper 40s mountains expected for Monday. 93

AVIATION...00Z TAFs...VFR conditions will prevail over the next
24 hours.  A weak frontal boundary is falling apart as it moves
southeast through the area tonight and will expect only SCT 15000-
20000 ft AGL overnight.  Winds will be decreasing to 5-10 kts
overnight.  Some mid and high level moisture will remain over the
area on Wednesday in the southwest flow with winds 5-10kts. 93

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  51  82  53  81 /   0   0   0  20
ALW  54  83  52  82 /   0   0   0  20
PSC  52  84  52  83 /   0   0   0  10
YKM  49  83  49  82 /   0   0   0   0
HRI  51  84  52  82 /   0   0   0  10
ELN  47  81  49  79 /   0   0   0   0
RDM  44  83  43  79 /   0   0   0  20
LGD  48  84  50  83 /   0   0   0  10
GCD  47  86  47  83 /   0   0   0  10
DLS  54  85  54  79 /   0   0   0  10

&&

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

&&

$$

94



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