FXUS66 KPDT 072222
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
225 PM PST MON DEC 7 2009
.SHORT TERM...TONIGHT THROUGH THURSDAY...A HIGHLY AMPLIFIED TROUGH
STRETCHING FROM NORTH CENTRAL CANADA SOUTHWESTWARD INTO CALIFORNIA
HAS FUNNELED BITTERLY COLD ARCTIC AIR INTO THE REGION. EVEN
THROUGH THE TROUGH WILL SHIFT TO THE EAST OVER THE NEXT SEVERAL
DAYS...NORTHERLY FLOW ALOFT WILL ENSURE THAT THIS COLD DRY AIR
REMAINS IN PLACE THROUGH THE MIDDLE OF THE WEEK. TONIGHT WILL LIKELY
BE THE COLDEST NIGHT THIS WEEK WITH LOW TEMPERATURES RANGING FROM
TEN BELOW ZERO IN CENTRAL OREGON TO TEN ABOVE ZERO IN THE LOWER
COLUMBIA BASIN. TUESDAYS HIGH TEMPERATURES WILL BE SIMILAR TO WHAT
THEY WERE TODAY. HOWEVER...FROM TUESDAY NIGHT ONWARD...TEMPERATURES
WILL SLOWLY MODERATE AS THE LARGE SCALE FLOW SHIFTS TO THE NORTHWEST
DUE TO BUILDING HIGH PRESSURE IN THE EASTERN PACIFIC. BY
THURSDAY...DAYTIME TEMPERATURES WILL HAVE WARMED SLIGHTLY...REACHING
INTO THE MID TO UPPER 20S ACROSS EASTERN OREGON AND INTO THE MID 20S
OVER MUCH OF SOUTH CENTRAL WASHINGTON. DESPITE THE EXTREME
COLD...SKIES WILL GENERALLY BE MOSTLY CLEAR AND WINDS WILL BE LIGHT
THROUGHOUT THE PERIOD. 82
.LONG TERM...THURSDAY NIGHT THROUGH MONDAY. COLD AND DRY CONDITIONS
WILL CONTINUE THURSDAY NIGHT AND FRIDAY. THERE ARE SEVERAL
CHALLENGES FOR THE REMAINDER OF THE FORECAST PERIOD. MEDIUM-RANGE
MODELS ALL SHOW A SHORTWAVE TROUGH AND WARM AIR ADVECTION (WAA)
ALOFT BRINGING PRECIPITATION INTO CENTRAL OREGON FRIDAY NIGHT THEN
OVER THE REMAINDER OF THE REGION ON SATURDAY. THE DIFFERENCES LIE
IN THE POSITION AND STRENGTH OF THE SURFACE LOW. THE GFS IS
STRONGER AND FARTHER NORTH WITH THE SURFACE LOW ON SATURDAY COMPARED
TO THE ECMWF...THUS THE WARM FRONT IS STRONGER AND THE QPF IS MORE
IMPRESSIVE. THIS WILL MAKE A BIG DIFFERENCE ON PRECIPITATION TYPE
OVER THE BASIN AND SURROUNDING VALLEYS. AT THIS TIME...LEANING
TOWARDS THE MORE CONSISTENT ECMWF WITH WEAKER WAA. BELIEVE THERE
COULD BE A WINTER MIX OF SNOW...SLEET...AND FREEZING RAIN IN THE LOW
ELEVATIONS ON SATURDAY AND SATURDAY NIGHT SO WILL INCLUDE THIS IN
THE FORECAST AND THE HAZARDOUS WEATHER OUTLOOK. THE SURFACE LOW AND
A WEAK COLD FRONT MOVING ACROSS OR/WA WILL ALLOW PRECIPITATION TO
RETURN TO ALL SNOW BY SUNDAY...BUT THERE WILL ALSO BE SOME DRYING BY
LATE SUNDAY. ANOTHER WARM FRONT IS PROGGED TO BRING PRECIPITATION TO
THE REGION ON MONDAY. DUE TO SLIGHT MODEL INCONSISTENCIES...WILL
HOLD OFF ON MENTIONING FREEZING PRECIP FOR MONDAY AND SEE WHAT
FUTURE MODELS HAVE IN STORE. JOHNSON
&&
.AVIATION...00Z TAFS. VFR CONDITIONS WILL BE PREVALENT FOR THE NEXT
24 HOURS. FEW-SCT MID AND HIGH LEVEL CLOUDS WILL BE PRESENT UNTIL
MIDNIGHT. MID LEVEL CLOUDS ABOVE 15000 WILL INCREASE TUESDAY. WINDS
WILL BE 5-15KT THROUGH THE FORECAST PERIOD. JOHNSON
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 3 18 8 22 / 0 0 0 0
ALW 7 20 12 24 / 0 0 0 0
PSC 6 22 8 24 / 0 0 0 0
YKM -1 20 3 24 / 0 0 0 0
HRI 5 21 6 23 / 0 0 0 0
ELN -2 20 4 24 / 0 0 0 0
RDM -2 18 1 23 / 0 0 0 0
LGD 0 17 5 20 / 0 0 0 0
GCD 2 19 5 21 / 0 0 0 0
DLS 6 22 9 28 / 0 0 0 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
&&
THREAT INDEX
TUESDAY : GREEN
WEDNESDAY : GREEN
THURSDAY : GREEN
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
$$
82/85/85
