Area Forecast Discussion
Issued by NWS Pendleton, OR

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928
FXUS66 KPDT 211804 AAB
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
1104 AM PDT Sat Apr 21 2018

Updated AVIATION discussion

.SHORT TERM...A surface cold front is moving across eastern OR/WA
this morning, and will exit to the east this afternoon. With
limited mid/upper support and deep layer moisture, other than for
a few showers along the immediate WA Cascade crest, dry conditions
prevail. Clouds will decrease this afternoon as the front and mid
level shortwave exits. Breezy to windy conditions will prevail
into this evening in the wake of the front, but expect wind speeds
to remain under advisory criteria. For tonight, with decreasing
winds and cloud cover under a cooler air mass, low temperatures
tonight will fall to the lower/mid 30s for the lower elevations.
With any freezing temperatures brief in duration, will not issue
a freeze warning.

&&

.AVIATION...18Z TAFs...VFR conditions over next 24 hours. FEW-SCT
060-090 today at air terminals at lower elevations, except KBDN and
KRDM will have SCT-BKN045-060 through this afternoon. Higher clouds
150-250 move east of Cascades to TAF sites tonight. Winds will be
breezy mainly across the lower Columbia Basin and adjacent valleys
this afternoon and then diminish this evening.  Polan

&&

.PREVIOUS DISCUSSION... /issued 219 AM PDT Sat Apr 21 2018/

SHORT TERM...Today through Monday...A shortwave and surface
cold front are moving through WA and OR at this time. Precipitation
is light with this system since deep layer moisture is very limited
and located mainly to the north of the area. Precipitation is mainly
in the Cascades but orographic effects may trigger a few showers in
the NE OR mountains this morning. The main effect of the system will
be breezy to windy conditions this afternoon/evening. Cooler
temperatures will develop behind the cold front. Clearing skies will
allow strong radiational cooling, with lows tonight in the 30s for
the lower elevations. Near freezing temperatures possible for the
higher foothill locations. Dry zonal flow will prevail this evening,
with another weak short wave moving into the Cascades Sunday
afternoon. With very little moisture to work with, dry conditions
are expected.  Highs Sunday will be similar to Saturday. An upper
level ridge will build near the coast Sunday night and Monday with
subsidence from the ridge providing clearing skies Sunday night and
warming trend Monday. Coonfield

LONG TERM...Monday night through Saturday...The long range models
are in good agreement for most of the extended period with an upper
ridge over the forecast area for fair and warm weather. Temperatures
will be above normal with dry conditions. The lower elevations of
the forecast area will see widespread 70s to near 80 degrees for
high temperatures by Tuesday of next week. This scenario will
persist through about Thursday while the flow aloft gradually
becomes more southerly as the upper ridge shift east slowly and an
upper low persists off the coast causes the flow to become
southerly. By the end of the long range moisture will begin to work
its way northward along with instability for possible showers and
afternoon/evening thunderstorms on Friday. This will mark the
beginning of some cooling to take place on Friday and Saturday. The
models begin to diverge a bit by that time, but there is enough
confidence to include thunderstorms over southern and eastern areas
of the CWA on Friday. Then on Saturday there will be a chance of
showers across the entire forecast area with cooler temperatures.
Winds will be light through most of the extended period. 88

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  60  34  60  35 /  10   0   0   0
ALW  63  36  63  38 /  10   0   0   0
PSC  66  35  65  37 /   0   0   0   0
YKM  63  35  63  36 /   0   0   0   0
HRI  64  35  64  35 /   0   0   0   0
ELN  55  33  60  34 /  10   0   0   0
RDM  61  26  60  26 /   0   0   0   0
LGD  58  32  59  34 /  10   0   0   0
GCD  59  33  60  33 /   0   0   0   0
DLS  63  38  67  38 /  10   0   0   0

&&

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

$$

80/99



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