Area Forecast Discussion
Issued by NWS Pendleton, OR

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000
FXUS66 KPDT 240524
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
924 PM PST SUN NOV 23 2014

.SHORT TERM...EVENING UPDATE...THE REGION WILL REMAIN UNDER A
NORTHWEST UPPER LEVEL FLOW TONIGHT THROUGH MONDAY. THE WAVE THAT
BROUGHT SHOWERS TO PORTIONS OF THE AREA TODAY HAS MOVED EAST. AS A
RESULT SHOWER ACTIVITY HAS BEEN DIMINISHING ACROSS THE AREA. A FEW
BANDS OF LIGHT SHOWERS CONTINUE TO CROSS THE CASCADE CREST AND
AFFECT PARTS OF THE CASCADE EAST SLOPES. THIS PROCESS WILL CONTINUE
THROUGH THE NIGHT, BUT WILL GRADUALLY DECREASE AND END TOWARDS
DAYBREAK. ALSO A FEW BANDS CONTINUE OVER THE INTERIOR MOUNTAINS OF
NORTHEAST OREGON. THESE TOO WILL GRADUALLY DECREASE AND COME TO AN
END OVERNIGHT. STILL EXPECT A MOSTLY DRY DAY MONDAY, THOUGH THE NEXT
SYSTEM IMBEDDED WITHIN THE NORTHWEST UPPER FLOW WILL BEGIN TO SPREAD
PRECIP INTO THE CASCADE EAST SLOPE ZONES DURING THE AFTERNOON. SNOW
LEVELS WILL FALL TO BETWEEN 2000 AND 3500 FEET TONIGHT, THEN RISE
AGAIN MONDAY, RANGING FROM 3500 FEET IN CENTRAL WASHINGTON AND 5000
FEET IN CENTRAL OREGON BY LATE AFTERNOON. LOCALLY BREEZY WINDS WILL
DECREASE OVERNIGHT. CURRENT FORECAST PACKAGE GENERALLY IN GOOD SHAPE
AND ONLY MADE ADJUSTMENTS BASED ON LATEST TRENDS. 90

.LONG TERM...PREVIOUS DISCUSSION...A VERY BUSY EXTENDED AS ACTIVE
WEATHER THREATENS THE HOLIDAY WEEKEND. A RIDGE OF HIGH PRESSURE WILL
CONTINUE TO BUILD OVER THE AREA BY MID WEEK. MOISTURE IS EXPECTED TO
OVERRUN JUST TO THE NORTH OF THE CWA...MAINLY AFFECTING THE SPOKANE
CWA. SLIGHT CHANCE TO CHANCE PRECIPITATION WILL REMAIN OVER THE EAST
SLOPES OF THE WASHINGTON CASCADES AND THE MOUNTAINS OF NORTHEAST
OREGON THROUGH WEDNESDAY NIGHT. A STRONG COLD FRONT MOVING SOUTH
FROM CANADA WILL FLATTEN OUT THE RIDGE OF HIGH PRESSURE THURSDAY...
PROVIDING A MOIST WESTERLY FLOW TO THE AREA FOR THANKSGIVING. RIGHT
NOW HAVE NOT GONE TOO AGGRESSIVE WITH POPS ON THURSDAY...AS IT IS
EXPECTED TO BE ALL RAIN...AND THERE MAY BE A DECENT RAINSHADOW
AFFECT FOR THE BASIN. SO 20-30 PERCENT POPS IN THE FORECAST FOR THE
LOWER ELEVATIONS WITH 30-50 PERCENT FOR THE MOUNTAINS.

WARM SOUTHERLY FLOW FROM THE SOUTH LOOKS TO SLOW THE ARRIVAL OF THE
CANADIAN COLD FRONT UNTIL LATE FRIDAY NIGHT INTO SATURDAY. SATURDAY
ONWARD IS WHERE IT GETS INTERESTING. THESE TWO AIR MASSES CONTINUE
TO BATTLE THROUGH THE HOLIDAY WEEKEND...AND THERE IS STILL SOME
MODEL DISCREPANCY AS TO HOW MUCH PRECIPITATION WILL FALL ACROSS THE
AREA...AND THE TIME IT WILL FALL. THE CURRENT OVERALL CONSENSUS
INDICATES THAT THE COLD AIR WILL REACH ABOUT 50 MILES SOUTH OF THE
I-84 CORRIDOR...AND ALL AREAS TO THE NORTH WILL SEE SNOW AS THE
GENERAL FORM OF PRECIPITATION. CENTRAL OREGON AND THE JOHN DAY
HIGHLANDS IS WHERE IT GETS CHALLENGING. THESE AREAS COULD SEE A RAIN
SNOW MIX...OR POSSIBLY FREEZING RAIN. HAVE NOT INTRODUCED THE
FREEZING RAIN TO THE FORECAST DUE TO TIMING AND UNCERTAINTY. BY
SUNDAY MORNING PARTS OF NORTH CENTRAL OREGON AND SOUTHERN WASHINGTON
ARE EXPECTED TO BE BELOW FREEZING AND MAY HAVE SOME SNOW
ACCUMULATIONS. WILL CONTINUE TO MONITOR THE FORECAST AND MAKE
UPDATED AS CHANGES OCCUR.

&&

.AVIATION...PREVIOUS DISCUSSION...00Z TAFS...SHOWERS CONTINUE TO
MOVE ACROSS MOST TAF SITES THIS EVENING. PEAK ACTIVITY SHOULD BE
THROUGH 06Z...WITH SOME LINGERING SHOWERS AT KALW AND KPDT THROUGH
09Z. KRDM...KBDN...AND KYKM MAY ESCAPE THE SHOWERS DUE TO
RAINSHADOWING. WINDS WILL BE A BIT BREEZY AS WELL WITH WIND SPEEDS
10-15KTS...GUSTING TO 25KTS AT TIMES. CIGS TONIGHT ARE IN
QUESTION...AS THE POTENTIAL FOR MIST/FOG INCREASES. HAVE INTRODUCED
LOWERED CIGS/VIS INTO THE MVFR/IFR CATEGORY AT TAF SITES OF CONCERN.
CIGS SHOULD START TO IMPROVE AFTER 18Z AND BECOME SCT-BKN 7-10KFT.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  36  48  40  58 /  20  10  40  30
ALW  37  48  42  60 /  20  10  40  40
PSC  35  48  40  58 /  10  10  40  30
YKM  29  42  33  53 /  10  10  30  30
HRI  36  49  40  58 /  10  10  40  30
ELN  30  42  33  52 /  20  10  40  30
RDM  25  47  34  61 /  10  10  30  20
LGD  32  45  34  53 /  60  10  50  60
GCD  30  41  31  55 /  30  10  40  30
DLS  38  51  40  54 /  20  10  40  40

&&

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

FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON

$$

90/89/77






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