Area Forecast Discussion
Issued by NWS Pendleton, OR

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115
FXUS66 KPDT 271841 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
1140 AM PDT Thu Apr 27 2017

Updated SHORT TERM Discussion and PDT WATCHES/WARNINGS/ADVISORIES to
remove mention of Wind Advisory for the Simcoe Highlands (WAZ521) due
to the Wind Advisory being cancelled.

.SHORT TERM...UPDATE...Northwest flow aloft will yield light snow
showers or show flurries in the northern Blue Mountains this morning.
As such I increased PoPs in Forecast Zone 502 to likely category (60
percent) for the remainder of this morning. Also lowered PoPs to
less than 15 percent to indicate that dry conditions are to be
expected for the remainder of this morning for lower terrain
elevations in central and east central Oregon. Animated loop of
visible satellite imagery shows considerable mid level standing wave
clouds indicative of a stable airmass across central and east
central Oregon this morning. Expect scattered snow showers to
develop this afternoon in aforementioned areas over higher terrain
as surface heating increases vertical temperature lapse rate thus
making airmass less stable allowing orographic lift to trigger
shallow convection. Issued updated PDXZFPPDT product to
reflect these adjustments for today.

The Wind Advisory for the Simcoe Highlands (WAZ521) has been
cancelled. A Wind Advisory remains in effect for the Kittitas Valley
until 9 PM PDT this evening.  Polan

&&

.AVIATION...18Z TAFS...VFR conditions are expected through the
forecast period. SCT-BKN clouds at 5-8 kft feet AGL will persist
through the day and decrease somewhat tonight. Winds will be west at
15-30 kt with some higher gusts today slowly decreasing to 5-15 kt
after sunset this evening. 78

&&

.PREVIOUS DISCUSSION... /issued 349 AM PDT Thu Apr 27 2017/

SHORT TERM...Today through Saturday...Northwest upper level flow
will persist through the period as a ridge builds offshore. A wave
in the northwest flow will increase showery precipitation over the
mountains and Oregon this afternoon. Upslope regions of the eastern
mountains will get the most rain/snow. Snow levels are around 2500-
3000 ft this morning. The showery precipitation may produce a few
inches of snow in the mountains. Gusty W-NW winds will persist until
early evening. Wind Advisories continue for the Kittitas Valley and
Simcoe Highlands for gusty W-NW winds. Friday a drier northerly flow
will develop with decreasing chances for mountain showers. The ridge
will eventually move over the Pacific Northwest on Saturday for a
warmer dry day.  Coonfield

LONG TERM...Saturday night through Wednesday...Models in good
agreement in moving a system across the area Saturday night and
Sunday.  Showers will begin Saturday night over our western CWA and
spread eastward through the day on Sunday. By Monday an upper level
ridge is expected to begin nosing into southwest Oregon.  The upper
ridge is expected to strengthen slowly through Wednesday resulting
in warmer temperatures and a drying trend.  Both GFS and ECMWF do
hint at bringing showers over the area Tuesday, but find this hard
to believe given strengthening ridge so have left the forecast dry.
Earle

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  56  36  58  37 /  10  10  10   0
ALW  59  41  60  41 /  20  20  10   0
PSC  63  40  65  37 /  10  10  10   0
YKM  61  36  64  35 /  10  10  10   0
HRI  61  40  63  36 /  10  10  10   0
ELN  55  37  59  35 /  10  10  10   0
RDM  52  25  54  23 /  20  20  10   0
LGD  49  35  53  33 /  40  20  20  10
GCD  47  28  51  23 /  50  50  10   0
DLS  59  42  62  40 /  10  10  10   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Wind Advisory in effect until 9 PM PDT this evening for WAZ026.

&&

$$

99/78/76/81



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