Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 240520
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1020 PM PDT Mon Apr 23 2018

Updated aviation discussion

.SHORT TERM...Tonight and Tuesday...Ridge of high pressure will
continue to build over the region providing clear skies and pleasant
Spring weather conditions. Minor changes made to temperatures and
winds for tonight and Tuesday in evening forecast update.

.AVIATION...06Z TAFs...VFR conditions with clear skies for
next 24 hours. Light winds overnight at all TAF sites. Light winds
Tuesday but some SE 10-15kt winds at KBDN and KRDM.
Polan


&&

.PREV DISCUSSION... /issued 427 PM PDT Mon Apr 23 2018/

SHORT TERM...Tonight through Thursday night...A ridge of high
pressure will continue to shift eastward over the inland northwest
tonight with mostly clear skies and light winds expected. A trough
extending from an upper level low over the Hudson bay will graze
eastern Washington during the day Wednesday weakening the ridge
slightly and allowing scattered mid to upper level cloudiness to
make a brief appearance. The ridge will restrengthen as the trough
departs Wednesday afternoon. Under high pressure and mostly clear
skies high temperatures will be on an increasing trend through
Thursday when highs in the lower elevations will reach the upper
70s to lower 80s - 10 to 15F above normal for this time of year.
Focus then turns to the cut-off low off the coast forecast to be
centered near 40N 135W by Thursday morning. 12Z operational GFS is
significantly slower bringing this feature onshore than the ECMWF,
Canadian, and a few GFS ensemble members keeping the region mostly
dry through Friday. Have opted toward a blend favoring the slower
ECMWF/Canadian solution while retaining an existing slight chance
of showers/thunderstorms for central/north central Oregon Thursday
night/Friday morning to give some weight to the faster GFS
solution as considerable uncertainly remains. Peck

LONG TERM...Friday morning through Monday...The big question for
Friday through the weekend is just how quickly the mid-upper level
ridge of high pressure along the Rockies on Friday gives way to a
large mid-level low pressure system, which will be near 41N/129W
Friday morning. Over the past three days the extended models have
predicted that the ridge will eventually break down over the
forecast area during the time frame of Friday and Saturday. Some of
the models favor the aforementioned upper level low undercutting the
ridge by taking a more southerly track across northern California
and the Great Basin, which would allow wrap around moisture to bring
showers to the forecast area. As such the forecast for Friday
through Sunday afternoon is for a chance of showers through the
weekend. The airmass has marginal instability Friday morning into
Friday evening for a slight chance of thunderstorms from daybreak
Friday through Friday evening. Monday looks to be dry due to a drier
airmass moving into the Pacific Northwest on the heels of a
northwest flow aloft.  Polan


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  38  74  44  77 /   0   0   0   0
ALW  39  76  47  79 /   0   0   0   0
PSC  38  77  44  81 /   0   0   0   0
YKM  40  75  45  79 /   0   0   0   0
HRI  37  77  44  81 /   0   0   0   0
ELN  37  71  43  76 /   0   0   0   0
RDM  29  74  37  80 /   0   0   0   0
LGD  35  68  40  74 /   0   0   0   0
GCD  37  70  41  76 /   0   0   0   0
DLS  42  78  47  82 /   0   0   0   0

&&

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

$$

91/91/91



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