Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 300344
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
844 PM PDT Wed Mar 29 2017

.UPDATE...Updates to the forecast through Thursday afternoon were
mainly to lower PoPs in some zones and tone down QPF amounts for
most of the area. The warm front that brought widespread rain
earlier today has moved out of region...and satellite and
surrounding WSR-88D are showing clearing behind the system. A
weak cold front will track across eastern Oregon tonight. Earlier
model runs appear to have been too high on the precipitation...as
WSR-88Ds west of the Cascades are only showing scattered showers
at this time unlike the widespread precipitation the models were
advertising. Light to moderate precipitation early Thursday
morning will mainly be over central and northeast Oregon.
Precipitation amounts through 18Z will range from a trace to a
quarter of an inch. Snow levels will be around 4000 feet...and
some of the higher mountains and valleys will get about 1-2
inches of new snow.

After the passage of the upper level trough on Thursday...high
pressure building at the surface and aloft will result in breezy
to windy conditions. The strongest winds will be in the Eastern
Columbia River Gorge and the Kittitas Valley were sustained winds
will be 25-30 mph...possibly stronger in the afternoon and
evening. Confidence is not high that winds will meet advisory
criteria for more than an hour or two so will hold off on any wind
advisories for now.  Wister

&&

.HYDROLOGY...Rainfall amounts varied significantly across the
region over the past 24 hours...and the northern Blue Mountains
received significantly more than most of the forecast area with
amounts of 0.75 to over one inch in a few locations. The Umatilla
River and Walla Walla Rivers are responding with levels expected
to be near bankfull on Thursday. The Grande Ronde River at Troy
is showing sharp rises and is forecast to rise to flood stage
Thursday morning. A Flood Warning is in effect for the Grande
Ronde River at Troy as well as the John Day River at Service
Creek. The John Day River is not showing sharp rises...and there
is question on whether it will get above flood stage. Will keep
the Flood Warning for now and monitor precipitation amounts
tonight and Thursday. Wister

&&

.PREV DISCUSSION... /issued 248 PM PDT Wed Mar 29 2017/

SHORT TERM... A dry northwest to north flow will develop Thursday
night as an upper level ridge builds over the region. Thus will
see lingering mountain showers end late Thursday night with dry
conditions for Friday. The dry conditions will continue into
Friday night, though the next Pacific system may push some light
precip into the Washington Cascade east slopes late in the period.
90

LONG TERM...Saturday through Wednesday...Forecast area will be
under a westerly flow Saturday with a very weak front passing over
the area and some limited mountain showers possible. Then the flow
begins to buckle as an upper level trough develops and deepens over
the Pacific Northwest which will enhance the shower activity Sunday.
The trough will shift eastward on Monday bringing showers to an end
and allow an upper level ridge of high pressure to build in from the
west. The ridge will persist through Tuesday but then gives way to
another upper level trough system on Wednesday and the increasing
chance of precipitation.

AVIATION...00z TAFS...Mainly VFR conditions expected over the next
24 hours. There will be some showers mainly impacting KRDM, KBDN,
KPDT and KALW at least through the early evening in which brief MVFR
conditions are possible. Winds will be 10-15 kts overnight and then
stronger winds on Thursday at 15-25 kts and higher gusts.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  40  52  33  54 /  40  40  20   0
ALW  43  54  38  54 /  40  30  20   0
PSC  43  60  34  60 /  10  20  10   0
YKM  39  62  32  62 /  10  10   0   0
HRI  41  59  34  59 /  20  20  20   0
ELN  38  56  33  59 /  10  10   0   0
RDM  35  47  20  52 /  40  30  10   0
LGD  39  49  32  51 /  80  60  20  10
GCD  36  48  30  54 /  90  70  20   0
DLS  43  60  37  62 /  20  20   0   0

&&

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

$$

85/85


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