Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 242335 AAA
AFDPDT

Area Forecast Discussion...Update
National Weather Service Pendleton OR
435 PM PDT Wed May 24 2017

Updated Aviation Discussion

.SHORT TERM...Tonight through Saturday...Breezy to windy conditions
will continue through this evening and then winds will decrease
overnight. The upper level low over western Canada has shifted into
central Canada but is leaving an deepening upper level trough in its
wake. This will place the forecast area under a cool northerly flow
over the next 24 to 48 hours. A weak shortwave dropping south in the
flow will bring some increasing instability to the forecast area
Thursday leading to an increasing chance of showers and possible
thunderstorms through the evening for portions of the forecast area.
There will be some lingering showers and possible thunderstorms
Friday afternoon near the Idaho border otherwise a ridge of high
pressure off the coast will begin to move inland Friday bringing
temepratures back to near normal. The ridge will shift over the
forecast area on Saturday for a return of above normal temperatures
through the holiday weekend.

.LONG TERM...Late Saturday evening through Wednesday...The Pacific
Northwest looks to be under an upper level ridge at least through
Tuesday. Thus should see mostly dry conditions with high temps 15 to
20 degrees above seasonal. Also low temps would run around 5 to 10
degrees above seasonal. Subsidence should be fairly strong,
especially over our eastern zones Sunday and Monday. Thus convective
activity should be very limited despite increased heating driven
instability. Will continue to indicate patchy areas of slight chance
thunder along the Cascades Sunday and Monday afternoons/evenings.
Any stray storms would be quite high based. There is some indication
that a Pacific disturbance may begin to approach the region Tuesday,
shifting the ridge axis east towards western Idaho. Thus the limited
chances of thunderstorms could shift east to the eastern mountains,
and have continued to show this trend. For Wednesday, mid range
models diverge some on the timing and strength of a possible break
down of the upper ridge due to the aforementioned Pacific system.
For now will follow the slower ECMWF, keeping temps well above
seasonal on Wednesday. Will also keep thunderstorm chances limited
to the mountains as well. 90

&&

.AVIATION...00Z TAFs...An upper low will continue to move east
across the Canadian Prairie provinces through the next 24 hours.
Meanwhile the upper level flow over the Pacific Northwest will be
northerly. This will allow a disturbance to swing across the region
tonight and Thursday. A low chance of showers will be possible
Thursday afternoon at KYKM, KPSC, KALW and KPDT. Cigs/vis will
mainly be VFR through the period, though may see some clouds between
2000 and 3000 ft AGL at KRDM and KBDN Thursday morning. Will keep
these lower clouds SCT at these two sites for now. Otherwise will
see increasing clouds at most sites with lowest bases around 6-8000
ft AGL. Winds will continue to be breezy with sustained speeds
running between 14 and 24 kts into this evening. Winds will decrease
mid to late evening, becoming light and drainage. Winds Thursday are
expected to be 10 kts or less. 90

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  46  67  46  75 /   0  20  20   0
ALW  50  70  50  78 /   0  20  20   0
PSC  49  74  49  82 /   0  10  10   0
YKM  48  76  48  82 /   0  20  20   0
HRI  48  72  47  80 /   0  10  10   0
ELN  46  72  46  80 /   0  20  20   0
RDM  34  71  38  76 /   0  10  10   0
LGD  42  63  41  69 /  10  30  20  10
GCD  41  67  40  73 /   0  20  30  10
DLS  49  76  51  85 /   0  10  10   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Wind Advisory until 10 PM PDT this evening for WAZ026.

&&

$$

91/90/90



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