Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 271236 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
435 AM PST FRI FEB 27 2015

UPDATED AVIATION DISCUSSION

.SHORT TERM...TODAY THROUGH SUNDAY...A LOW PRESSURE SYSTEM AT THE
SURFACE AND ALOFT WILL MOVE SOUTHWARD ACROSS WESTERN OREGON. THIS
WILL CAUSE PRECIPITATION TO SPREAD INTO MOSTLY WESTERN AREAS OF THE
CWA TODAY...AFFECTING CENTRAL OREGON...THE OREGON CASCADE EAST
SLOPES...THE JOHN DAY HIGHLANDS/BASIN AND THE SOUTHERN BLUE
MOUNTAINS WITH RAIN AND HIGHER ELEVATION SNOW. WINTER WEATHER
ADVISORIES ARE IN PLACE FOR THESE AREAS EXCEPT FOR THE JOHN DAY
HIGHLANDS WHICH HAS A WINTER STORM WARNING FOR HEAVY SNOW. SNOW
LEVELS ARE EXPECTED TO FALL DURING THE NEXT FEW DAYS TO AROUND 1000
TO 1500 FEET BY SATURDAY AFTERNOON...SO PRECIPITATION IN THE
MOUNTAINS WILL BE PRIMARILY SNOW. PRECIPITATION HAS BEEN SPOTTY
ACROSS THE CWA SO FAR. HOWEVER...A MORE STEADY AREA OF RAIN IS
DEVELOPING OVER NORTHWEST WASHINGTON WHICH WILL SPREAD
SOUTH-SOUTHEAST INTO OREGON BY THIS AFTERNOON AND TONIGHT WITH
COLDER AIR. THE WINTER WEATHER ADVISORIES AND WINTER STORM WARNING
BEGAN AT 06Z LAST EVENING FOR THE SOUTHERN BLUE MOUNTAINS...JOHN DAY
HIGHLANDS AND THE OREGON CASCADE EAST SLOPES. CENTRAL OREGON
INCLUDING REDMOND AND BEND WILL HAVE A WINTER WEATHER ADVISORY
BEGINNING AT 00Z THIS AFTERNOON. SNOW AND LOW ELEVATION RAIN IS
EXPECTED TO PERSIST THROUGH AT LEAST 15Z SATURDAY MORNING. ONCE THIS
SYSTEM MOVES OUT OF THE REGION BY SATURDAY NIGHT IT WILL BE REPLACED
BY A COLD BUT DRY NORTHERLY FLOW ALOFT ON SUNDAY...WHICH WILL BE A
MOSTLY CLEAR DAY WITH INCREASING NORTHEAST WINDS. 88

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...THE 00Z GFS AND ECMWF
RUNS INDICATE A STRONG MID/UPPER LEVEL RIDGE OF HIGH PRESSURE NEAR
130W WITH NORTHERLY FLOW ALOFT ON THE EASTERN FLANK OF THE RIDGE
ACROSS THE PACIFIC NORTHWEST. THE GFS RUN SHOWS A WEAK TROUGH MOVING
SOUTH IN THIS NORTHERLY FLOW INTO WASHINGTON OVERNIGHT AS DOES THE
ECMWF, BUT THE ECMWF SHOWS THE TROUGH WITH CONSIDERABLY MORE
AMPLITUDE AND THUS MORE PRECIP SPREADING SOUTH ALONG THE CASCADES
OVERNIGHT. AS SUCH I SPLIT THE DIFFERENCE AND WENT WITH A SLIGHT
CHANCE OF PRECIP ALONG THE EAST SLOPES OF THE WASHINGTON CASCADES
FOR SUNDAY NIGHT. ON MONDAY THE ECMWF SHOWS THE TROUGH REMAINING
OVER THE REGION SO I KEPT CHANCE POPS FOR THE MOUNTAINS FOR MONDAY
THROUGH MONDAY NIGHT. TUESDAY THE NORTHERLY FLOW ALOFT CONTINUES AND
THUS KEEPS A LOW CHANCE OF SHOWERS IN THE BLUE MOUNTAINS. TUESDAY
NIGHT ONWARD A DRIER NORTHERLY FLOW USHERS IN A DRYING TREND WHICH
PERSIST THROUGH THURSDAY.  POLAN

&&

.AVIATION...12Z TAFS...RAIN HAS OVERSPREAD KYKM KDLS KRDM KBDN
OVERNIGHT WITH CEILINGS LOWERING TO 030-060. THE RAIN MAY SPREAD FAR
ENOUGH EAST LATER THIS MORNING TO REACH KPDT KPSC ALW. LOWERING SNOW
LEVELS WILL BRING A PERIOD OF SNOW TO RDM BDN FRIDAY EVENING WITH
RAIN CHANGING TO SNOW BY AROUND 04Z/28TH. WINDS LESS THAN 10KT THIS
MORNING THEN INCREASING FROM THE NORTH AT 10-20 KTS LATER TODAY.
POLAN

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  48  27  39  21 /  30  30  10   0
ALW  51  30  42  24 /  20  30  10   0
PSC  54  31  47  23 /  30  20  10   0
YKM  51  29  44  23 /  70  30  10   0
HRI  51  29  45  22 /  40  30  10   0
ELN  51  28  44  22 /  70  30  10   0
RDM  44  22  33  12 /  70  60  30   0
LGD  45  26  38  18 /  30  50  20   0
GCD  42  26  34   9 /  90  80  40   0
DLS  50  32  47  27 /  60  40  20   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WINTER STORM WARNING UNTIL 7 AM PST SATURDAY ORZ506.

     WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 4 AM PST
     SATURDAY ORZ511.

     WINTER WEATHER ADVISORY UNTIL 7 AM PST SATURDAY ORZ505.

     WINTER WEATHER ADVISORY UNTIL 4 AM PST SATURDAY ORZ503.

     WINTER WEATHER ADVISORY UNTIL 4 AM PST SATURDAY ORZ509.

WA...NONE.
&&

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

$$

88/99/99





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