Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 290538
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1030 PM PDT Tue Mar 28 2017

.SHORT TERM...Light rain showers have been moving across the
region over the past few hours with weak warm advection pattern.
Expect this will increase overnight. Satellite shows larger area
of enhanced clouds approaching the coast associated with a surface
low and warm front. Models have been indicating rain will increase
this evening and overnight as this feature moves through. A strong
upper level trough will then push the cold front through on Wednesday
with additional rain. The Cascades and northeast Oregon mountains
will receive a fairly significant rainfall over the next 36 hours
which will likely cause most rivers and streams to increase.
Steady precipitation will turn to showers Thursday as the upper
trough moves overhead. Could have some gusty winds associated
with the cold front Wed night into Thursday. 94

.AVIATION...06z tafs. Rain will be increasing in coverage overnight
and continue into Wednesday. Ceilings lowering to 030-060 with
visibility lowering to 4-6sm -ra br at times. Winds 5-15kt overnight
and 10-20kt Wed.

&&

.PREV DISCUSSION... /issued 432 PM PDT Tue Mar 28 2017/

SHORT TERM...Tonight through Thursday night...A warm front with
attendant moisture and lift will move into the forecast area tonight.
Rain expected beginning this evening along the east slopes of the
Washington Cascades and rain arriving at the crests of the Oregon
Cascades late in the evening. Rain will spread east across the
region overnight with valley rain likely in the Lower Columbia Basin
and the northern Foothills of the Blue Mountains as well as rain and
snow likely in the Blue Mountains where snow levels will be 5000-
6000 feet overnight. Rain shadowing expected in central Oregon
overnight so went with just a slight chance of rain through tonight
for Bend and Redmond. Mesoscale models are showing rain shadowing
immediately east of the Cascades at lower elevations during the day
on Wednesday so significant measurable rain is not expected at the
usual rain shadowed locations from daybreak through Wednesday
afternoon. Snow Levels rise through the day on Wednesday to 6500-
7500 feet in the afternoon along the east slopes of the Washington
Cascades and rise to 7500-8500 feet in the afternoon in the central
and eastern mountains in Oregon.

The rain and high snow levels will produce runoff due to the rain
and snowmelt, thus yielding rising creeks streams and rivers through
the day on Wednesday and water levels continuing to rise Wednesday
night into Thursday morning. Crests at main stem river forecast
points are expected late Wednesday into Thursday morning.

Wednesday night a cold front enters the interior Pacific Northwest
and moves slowly east through overnight for the best chance of
significant rainfall. Thursday morning the cold front exits into
Idaho while the mid/upper trough that pushed the cold front through
the region closes off and moves southeast across central and
northeast Oregon during the the day on Thursday, which results in
wrap around moisture giving a chance of snow showers in the Blue
Mountains and the Wallowa Mountains through Thursday afternoon into
Thursday evening. Snow levels lower to around 3500 feet by Thursday
morning in the northeast Oregon mountains. Snow showers in the
eastern mountains taper off and end Thursday evening with overnight
prior to daybreak on Friday morning dry areawide.  Polan

LONG TERM...Friday through Tuesday...The region looks to be under a
weak upper ridge, and between systems, Friday and Friday night. Thus
expect mainly dry conditions during these two periods. A moist and
unsettled west to northwest flow looks to develop Saturday. This
pattern then looks to persist into Monday. For now, precip chances
on Saturday look to be limited to the mountains. Precip chances then
are expected to increase Saturday night through Monday with the best
chances over the higher terrain. Confidence is still low enough
during this period to only indicate precip chances of 20 to 40
percent. Weak ridging may move over the area Tuesday for a decrease
in precip chances. Temps look to be near or slightly below seasonal
through this period. 90

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  43  59  42  54 /  70  70  80  40
ALW  47  60  45  56 /  70  90  80  50
PSC  46  61  45  59 /  70  60  50  20
YKM  44  59  41  60 /  70  50  30  20
HRI  43  60  43  59 /  70  60  60  30
ELN  39  53  39  52 /  80  60  30  20
RDM  42  57  36  49 /  30  60  70  30
LGD  41  54  40  50 /  60  90 100  60
GCD  40  57  41  47 /  40  80  90  80
DLS  46  57  44  58 /  60  60  60  20

&&

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

$$

94


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