553
FXUS66 KPDT 071538
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
840 AM PDT TUE OCT 7 2008
SHORT TERM
COLD FRONT IS MOVING ACROSS THE REGION THIS MORNING.
WINDS ARE INCREASING AND SHOULD BECOME STRONG FROM THE KITTITAS AND
YAKIMA VALLEYS INTO THE COLUMBIA BASIN DURING THE AFTERNOON. WINDS
WILL DIMINISH LATER THIS EVENING AS HIGH PRESSURE BUILDS INTO THE
PACIFIC NORTHWEST. SOME LIGHT RAIN WILL CONTINUE ALONG THE FRONT
THIS MORNING AS IT EXITS THE FORECAST AREA...OTHERWISE PRECIPITATION
FOR THE REMAINDER OF THE DAY WILL BE MAINLY SHOWERS OVER THE
MOUNTAINS. CLEARING SKIES AND DECREASING WINDS WILL PRODUCE A COOL
NIGHT WITH LOWS IN THE 20S AND 30S. DRY WESTERLY FLOW ON WEDNESDAY
FOR A BREAK IN THE WEATHER WITH PARTLY CLOUDY SKIES. NEXT SYSTEM
MOVES IN ON THURSDAY WITH RAIN AND MOUNTAIN SNOW. 94
PREV DISCUSSION
/ISSUED 450 AM PDT TUE OCT 7 2008/
SHORT TERM...TODAY THROUGH WEDNESDAY...A STRONG...FAST MOVING
FRONTAL SYSTEM IS CURRENTLY PASSING OVER THE LOCAL AREA. VERY LIGHT
RAIN SHOWERS HAVE BEEN OBSERVED ALONG THE EAST SLOPES OF THE
CASCADES AND IN PARTS OF THE LOWER COLUMBIA BASIN. YET DESPITE THE
STRENGTH OF THIS SYSTEM...PRECIPITATION AMOUNTS WILL BE LIGHT DUE TO
A LACK OF AVAILABLE MOISTURE AND THE SHEER SPEED OF THE FRONT.
HOWEVER...A VERY STRONG UPPER LEVEL JET WILL CAUSE WINDY CONDITIONS
ACROSS MOST OF EASTERN WASHINGTON AND IN THE LOWER COLUMBIA BASIN OF
OREGON. THEREFORE...WIND ADVISORIES WILL REMAIN IN EFFECT UNTIL 8 PM
THIS EVENING FOR THOSE AFFECTED AREAS. THESE STRONG WINDS ARE
EXPECTED TO DIMINISH OVERNIGHT AND HIGHER PRESSURE WILL MOVE INTO
THE REGION. AS SKIES CLEAR AND NORTHWESTERLY FLOW ALOFT USHERS IN A
COLDER AIR MASS...OVERNIGHT TEMPERATURES WILL FALL...WITH SOME
LOCATIONS DIPPING BELOW FREEZING. AS A RESULT...FREEZE WARNINGS WILL
BE ISSUED FOR NORTHERN WHEELER AND SOUTHERN GILLIAM COUNTIES AND THE
GRANDE RONDE VALLEY. MILDER WEATHER WILL RETURN ON WEDNESDAY...WITH
MOSTLY CLEAR SKIES...LIGHT WINDS AND ONLY A SLIGHT CHANCE OF
PRECIPITATION ALONG THE EAST SLOPES OF THE WASHINGTON CASCADES.
CALDER
LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY. MODELS ARE FINALLY IN
BETTER AGREEMENT...AND THE ECMWF HAS BEEN THE MOST CONSISTENT MODEL
ADVERTISING A CLOSED LOW OVER THE SW U.S. LATE IN THE WEEK. THE GFS
IS NOW FOLLOWING THIS TREND. PROBLEMS DO ARISE IN THE MODELS OVER
THE WEEKEND...BUT THOSE PROBLEMS ARE FARTHER DOWNSTREAM. A
SHORTWAVE TROUGH MOVING ACROSS WA/OR WEDNESDAY NIGHT WILL DEEPEN
INTO A CLOSED LOW SYSTEM WITH THE CENTER OF THE LOW OVER SE OREGON
THURS NIGHT THEN OVER NEVADA FRI AND FRI NIGHT. SCATTERED SHOWERS
ARE EXPECTED THURS AND THURS NIGHT...MAINLY ALONG THE CASCADES AND
OVER THE EASTERN MOUNTAINS. AS THE TROUGH DIGS SOUTH...COLD AIR
WILL SPILL ACROSS THE REGION WITH SNOW LEVELS DOWN TO 3500-4000 FEET
LATE THURSDAY. THIS DOESN'T LOOK LIKE A BIG SNOW PRODUCER BUT IT
COULD BE THE FIRST SNOW OF THE SEASON IN SOME OF THE VALLEY
LOCATIONS. THE ECMWF MAY BE TOO FAST AT SHIFTING THE LOW E-NE OVER
THE WEEKEND AND PREFER THE SLOWER GFS. EITHER WAY...MODELS SHOW A
RIDGE BUILDING BEHIND THE SYSTEM WITH DRIER AND WARMER CONDITIONS BY
SUNDAY AND COLUMBUS DAY. JOHNSON
AVIATION...12Z TAFS. MAIN AVIATION CONCERN TODAY WILL BE WINDS.
WINDS WILL INCREASE AS THE DAY PROGRESSES AND THERE IS A POTENTIAL
FOR GUSTS AS STRONG AS 40-45 KNOTS. WINDS OF THESE MAGNITUDES MAY
CAUSE PATCHY BLOWING DUST. RECENT RAINFALL WILL PREVENT SIGNIFICANT
BLOWING DUST TODAY...SO WILL NOT INCLUDE THESE IN THE TAFS.
HOWEVER...AMENDMENTS TO THE VISIBILITY MAY BE NEEDED IF BLOWING DUST
IS OBSERVED. CIGS WILL REMAIN VFR. SKIES WILL CLEAR OVERNIGHT...AND
WINDS WILL DIMINISH BETWEEN 02Z-12Z. JOHNSON
PRELIMINARY POINT TEMPS/POPS
PDT 62 37 61 36 / 20 10 0 0
ALW 65 39 62 39 / 20 10 0 0
PSC 67 37 64 36 / 10 0 0 10
YKM 62 30 61 30 / 10 0 0 10
HRI 66 34 64 33 / 10 0 0 0
ELN 61 33 60 33 / 20 0 0 10
RDM 62 25 59 26 / 10 0 0 0
LGD 61 32 56 32 / 20 10 0 0
GCD 61 32 57 33 / 20 10 0 0
DLS 64 38 66 40 / 20 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...FREEZE WARNING FROM 2 AM TO 9 AM PDT WEDNESDAY FOR ORZ049-504.
WIND ADVISORY UNTIL 8 PM PDT THIS EVENING FOR ORZ041-044-501.
WA...WIND ADVISORY UNTIL 8 PM PDT THIS EVENING FOR WAZ024-026>029.
TI:GGG
FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON
94/
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page