Area Forecast Discussion
Issued by NWS Pendleton, OR

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886
FXUS66 KPDT 131018
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
218 AM PST SAT FEB 13 2016

.SHORT TERM...TODAY THROUGH MONDAY...THERE ARE STILL A FEW SHOWERS
OVER THE EASTERN MOUNTAINS AND OVER THE CASCADE EAST SLOPES FROM A
WEATHER SYSTEM THAT MOVED ACROSS THE FORECAST AREA LAST EVENING.
EXPECT THESE TO DECREASE THROUGH THIS MORNING. THE NEXT WEATHER
SYSTEM WILL MOVE INTO THE REGION TODAY WITH MOISTURE AND
PRECIPITATION EXPECTED TO SPREAD EAST OF THE CASCADES TODAY...MAINLY
IN THE AFTERNOON. THIS SYSTEM WILL BE STRONGER AND WETTER WITH
ABUNDANT RAINFALL...EXCEPT SNOW IN THE MOUNTAINS. SNOW LEVELS WILL
LOWER TO AROUND 3000-4000 FEET TONIGHT. THERE WILL BE SOME
ACCUMULATING SNOW IN THE HIGHER MOUNTAINS AS A RESULT. MAY POSSIBLY
NEED WINTER WEATHER HIGHLIGHTS TONIGHT FOR SOME OF THE HIGHER PASSES
SUCH AS TOLLGATE...MEACHAM AND THE CASCADE PASSES. WILL KEEP A CLOSE
EYE ON THIS SITUATION. HOWEVER...THE MAIN THREAT FROM THIS SYSTEM
WILL BE MELTING SNOW IN THE LOWER MOUNTAINS WITH ABUNDANT RAINFALL
WHICH WILL CAUSE RAPID RISES ON RIVERS AND STREAMS. THERE MAY BE
HYDROLOGY IMPACTS (FLOODING OR HIGH RIVER LEVELS) AS A RESULT SUNDAY
CONTINUING INTO MONDAY. SNOW LEVELS WILL RISE AGAIN TO AROUND 6000-
7000 FEET BY SUNDAY AFTERNOON CAUSING PRECIPITATION TO BE MAINLY
RAIN...SO THE GREATEST FLOODING THREAT WILL BE FROM LATER SUNDAY
THROUGH MONDAY. AN UPPER RIDGE WILL BE TRYING TO BUILD BACK OVER THE
REGION FROM THE WEST ON MONDAY WITH DRYING TAKING PLACE OVER THE
SOUTHWEST CWA...WITH DRIER CONDITIONS GOING INTO THE EXTENDED
PERIOD. TEMPERATURES WILL BE QUITE ABOVE NORMAL WITH READINGS IN THE
50S TODAY RISING TO THE LOWER TO MID 60S SUNDAY AND MONDAY OVER THE
LOWER ELEVATIONS. NIGHT TIME LOWS WILL BE ABOVE FREEZING IN MOST
AREAS EXCEPT FOR THE HIGHER MOUNTAINS. IT WILL ALSO BECOME BREEZY TO
WINDY IN AREAS...ESPECIALLY IN THE OPEN EXPOSED TERRAIN OF THE LOWER
COLUMBIA BASIN AND ADJACENT VALLEYS. AN AIR STAGNATION ADVISORY WILL
CONTINUE THIS MORNING UNTIL AT LEAST 18Z ACROSS MUCH OF THE CWA DUE
TO LACK OF MIXING. HOWEVER MIXING WILL INCREASE THIS AFTERNOON AS AN
UPPER TROUGH MOVES ACROSS THE REGION. 88

.LONG TERM...MONDAY NIGHT THROUGH FRIDAY. A RIDGE OF HIGH PRESSURE
REBUILDS OVER THE REGION MONDAY NIGHT AND TUESDAY PUSHING MOST OF
THE MOISTURE NORTH OF THE AREA, BUT IT MAY STILL MAY CLIP NORTHWEST
KITTITAS COUNTY.  THE MODELS BRING IN ANOTHER SYSTEM WITH MAINLY
RAIN BY WEDNESDAY AFTERNOON WITH THE GFS MODEL MUCH FASTER THAN THE
ECMWF. THE SNOW LEVEL IS EXPECTED TO DECREASE TO NEAR 5000 FEET IN
THE EAST SLOPES OF THE WASHINGTON CASCADES...TO NEAR 6000 FEET OVER
CENTRAL AND EASTERN OREGON WEDNESDAY NIGHT. THE TROUGH OF LOW
PRESSURE MOVES THROUGH THURSDAY WITH RAIN AND MOUNTAIN SNOW. IT
APPEARS THAT A RIDGE MOVES QUICKLY ACROSS THE REGION THURSDAY NIGHT.
THE MODELS ARE IN DISAGREEMENT FROM FRIDAY ONWARD AS THE ECMWF WANTS
TO BRING ANOTHER SYSTEM THROUGH THE AREA, WHILE THE GFS KEEPS THE
MAIN FRONT WELL OFFSHORE UNTIL THE WEEKEND. TEMPERATURES WILL REMAIN
QUITE MILD THROUGH THE PERIOD. 93.

&&

.AVIATION...06Z TAFS...MAINLY VFR CONDITIONS ARE EXPECTED FOR THE
NEXT 24 HOURS, EXCEPT AT KYKM WHERE FOG AND LOW CIGS DUE TO STRATUS
CLOUD DECK ARE EXPECTED TO YIELD LIFR/IFR CONDITIONS THROUGH TONIGHT
AND PROBABLY FOR A FEW HOURS AFTER DAYBREAK BEFORE THE FOG AND LOW
CEILING DISSIPATES AT KYKM.

SKIES WILL PARTIALLY CLEAR OVERNIGHT AND WITH RECENT RAIN, FOG MAY
DEVELOP OVERNIGHT AT COLUMBIA BASIN TAF SITES. DID NOT ADD TO TAFS
BEYOND A MENTION OF 6SM WITH BR AS AN INCREASE IN WINDS TO AROUND 5-
10 KTS AT MOST TAF SITES IS EXPECTED TO KEEP FOG AT A MINIMUM. CLOUD
COVER WILL BEGIN TO INCREASE AGAIN AFTER 18Z TOMORROW WITH MID LEVEL
CLOUD BASES LOWERING THROUGH THE AFTERNOON AS ANOTHER DISTURBANCE
APPROACHES THE AREA. SHOWERS WILL GENERALLY HOLD OFF UNTIL AFTER
14TH/00Z. HOWEVER, SHOWERS ARE POSSIBLE AT KDLS AFTER 22Z. WINDS
WILL GENERALLY BE UNDER 5-10 KTS THROUGH 13TH/ 20Z AND THEN INCREASE
TO 10-15 KTS SATURDAY AFTERNOON.  POLAN

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  51  42  58  48 /  10  80  60  50
ALW  52  45  59  51 /  20  80  60  60
PSC  55  41  58  49 /  10  60  30  30
YKM  49  34  54  43 /  30  60  30  30
HRI  55  40  58  49 /  10  60  40  30
ELN  45  36  49  42 /  30  60  30  30
RDM  50  38  55  40 /  10  40  40  30
LGD  50  38  51  47 /  20  80  70  60
GCD  49  36  53  43 /  10  70  60  40
DLS  52  40  54  48 /  30  60  50  30

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...AIR STAGNATION ADVISORY UNTIL 10 AM PST THIS MORNING FOR ORZ041-
     044-050-505-507-508-510.

WA...AIR STAGNATION ADVISORY UNTIL 10 AM PST THIS MORNING FOR WAZ024-
     026>029-520-521.

&&

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

$$

88/93/93



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