FXUS66 KPDT 110444
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
844 PM PST THU DEC 10 2009
.UPDATE...RELATIVELY WARMER AIR HAS BEGIN INTRUDING IN TO THE
PACIFIC NORTHWEST FROM THE SOUTHERN BRANCH OF THE STORM TRACKS.
MEDFORD AND SALEM SOUNDINGS MIRROR OBSERVATIONS ALONG THE CASCADE
EAST SLOPES SHOWING SEVERAL DEGREES OF WARMING THROUGH THE 2500
TO 5500 FOOT LAYER THIS AFTERNOON. MANY OREGON CASCADE EAST SLOPE
OBSERVATIONS SHOWED MAX TEMPERATURES TODAY IN THE MID TO UPPER
30S WHILE COLD AIR REMAINED TRAPPED AT THE LOWER ELEVATIONS
THROUGHOUT THE REMAINDER OF THE REGION. TEMPERATURES AT THIS HOUR
ARE RUNNING FROM 5 TO 15 DEGREES HIGHER THAN YESTERDAY WITH THE
GREATEST WARMING OCCURRING WELL ABOVE PASS ELEVATIONS. HAVE
INCREASED FORECASTED TEMPERATURES ACROSS NORTHEAST AND CENTRAL
OREGON BY SIMILAR AMOUNTS TO ACCOUNT FOR THE 24 HOUR TRENDS.
TEMPERATURE CHANGES WILL BE PUBLISHED SHORTLY WITH TEST PRODUCTS
TO FOLLOW THEREAFTER.
WINDS IN THE SOUTHERN GRANDE RONDE VALLEY CONTINUE TO KNOCK ON THE
ADVISORY LEVEL DOOR. 00Z NAM12 HAS THE STRONGEST KBKE-KMEH
GRADIENTS OCCURRING BETWEEN 4 AM AND 1 PM BUT ACTUALLY HAS THE
PRESSURE DIFFERENCES UNDERDONE VERSUS CURRENT REALITY SO WILL
LEAVE THE WIND ADVISORY IN PLACE. FOLLOWING SHIFTS WILL NEED TO
CONSIDER EXTENDING IT AS ANOTHER SLIGHTLY WEAKER INCREASE IS
SHOWN BY THE NAM12 TO OCCUR AGAIN TOMORROW NIGHT.
EARLY LOOK AT THE 00Z MODEL TEMPERATURE PROFILES SHOW LITTLE
CHANGE FROM WHAT DAY SHIFT OBSERVED. MIXED PRECIP TYPES REMAIN
PROBABLE SO WILL CONTINUE THE WINTER STORM WATCH AS WELL. /JBONK
&&
.PREV DISCUSSION... /ISSUED 220 PM PST THU DEC 10 2009/
SHORT TERM...TONIGHT THROUGH SUNDAY...CONTINUED CLEAR AND COLD
THROUGH TONIGHT. CHANGES START TO TAKE PLACE ON FRIDAY. A WEATHER
SYSTEM WILL APPROACH THE WEST COAST TAKING AIM ON NORTHERN
CALIFORNIA AND SOUTHERN OREGON OVER THE WEEKEND. AS THIS SYSTEM
PASSES TO THE SOUTH IT WILL SPREAD PRECIPITATION INTO THE FORECAST
AREA STARTING LATE FRIDAY AFTERNOON. THE PRECIPITATION WILL SPREAD
NORTH INTO NORTHERN OREGON FRIDAY NIGHT AND SATURDAY. SOUTHERN
WASHINGTON WILL SEE A LITTLE LIGHT PRECIPITATION BEGINNING ON
SATURDAY. PRECIPITATION TYPE WILL BEGIN AS SNOW BUT THERE WILL BE
SOME FREEZING RAIN AND SLEET DEVELOPING FRIDAY NIGHT AND SATURDAY
ACROSS NORTH CENTRAL OREGON. HAVE ISSUED A WINTER STORM WATCH FOR
THE POTENTIAL OF A WINTERY MIX PRECIPITATION EVENT FRIDAY NIGHT
THROUGH SATURDAY IMPACTING CENTRAL AND NORTH CENTRAL OREGON. SEE
LATEST PDXWSWPDT PRODUCT FOR DETAILS. PRECIPITATION WILL CARRY OVER
INTO SUNDAY WITH A MIX OF RAIN AND SNOW IN THE LOWER ELEVATIONS AND
SNOW IN THE MOUNTAINS. OTHER CONCERN WILL BE THE SOUTHERLY WINDS IN
THE SOUTHERN GRANDE RONDE VALLEY. WILL ISSUE A WIND ADVISORY
TONIGHT THROUGH FRIDAY TO COVER THIS.
LONG TERM...SUNDAY NIGHT THROUGH THURSDAY. MOISTURE ALONG WITH AN
UPSLOPE FLOW WILL KEEP SHOWERS IN THE FORECAST ESPECIALLY IN THE
MOUNTAINS THROUGH MONDAY. ANOTHER STORM SYSTEM IS FORECAST TO TAKE
AIM ON THE PACNW MONDAY NIGHT INCREASING THE CHANCES FOR PCPN INTO
TUESDAY. A THIRD STORM SYSTEM PASSES ACROSS THE REGION WEDNESDAY AND
WED NITE. SOME DRIER AIR ON A WESTERLY FLOW MAY DECREASE PCPN
CHANCES THURSDAY. SOMEWHAT WARMER AIR INVADES THE REGION SUNDAY
NIGHT BUT TEMPS WILL STILL REMAIN BELOW NORMAL THROUGH THE EXTENDED.
AVIATION...VFR CONDITIONS WILL PERSIST FOR THE NEXT 24 HOURS ACROSS
ALL TAF SITES. SOME MID AND HIGH LEVEL CLOUDS MAY MOVE INTO KRDM
AFTER 18Z TOMORROW BUT THOSE CONDITIONS SHOULD REMAIN VFR.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 7 27 16 30 / 0 0 20 50
ALW 10 29 18 29 / 0 0 10 40
PSC 7 28 15 29 / 0 0 10 30
YKM 5 27 13 30 / 0 0 10 20
HRI 3 27 14 31 / 0 0 20 40
ELN 7 29 12 27 / 0 0 10 20
RDM 6 35 23 35 / 0 10 50 50
LGD 9 27 16 31 / 0 0 30 50
GCD 11 33 20 33 / 0 0 50 50
DLS 12 30 18 32 / 0 0 20 40
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WINTER STORM WATCH FROM FRIDAY AFTERNOON THROUGH LATE SATURDAY
NIGHT FOR ORZ042-043-504>506.
WIND ADVISORY UNTIL 8 PM PST FRIDAY FOR ORZ049.
WA...NONE.
&&
THREAT INDEX
FRIDAY : GREEN
SATURDAY : YELLOW
SUNDAY : YELLOW
GREEN: NONE OR LIMITED NEED FOR WATCHES, WARNINGS, OR ADVISORIES.
YELLOW: A FEW WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.
RED: NUMEROUS WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.
FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON
$$
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