FXUS66 KPDT 221026
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
230 AM PST TUE DEC 22 2009
.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT. A CLOSED UPPER LOW IS
CENTERED OVER THE FORECAST AREA. THE EASTERN SIDE OF THE FORECAST
AREA IS UNDER A SOUTHERLY FLOW ALOFT WHILE THE WESTERN SIDE ALONG
THE CASCADE RANGE IN UNDER A NORTHERLY FLOW ALOFT. AT THIS
TIME...DOPPLER RADAR SHOWS A BAND OF PRECIPITATION FROM THE BLUE
MTNS EASTWARD. SNOW ACCUMULATIONS THIS MORNING IN THE WALLOWA
VALLEY COULD REACH AROUND 2 INCHES...JUST SHY OF ADVISORY CRITERIA.
PRECIPITATION WILL TAPER OFF THIS MORNING IN OUR EASTERN MOUNTAINS.
HOWEVER...THERE APPEARS TO BE A WAVE ON THE WEST SIDE OF THE LOW
THAT COULD BRING SCATTERED SNOW SHOWERS OVER CENTRAL OREGON THIS
AFTERNOON. WILL INCREASE POPS INTO THE CHANCE CATEGORY FOR CENTRAL
OREGON. ACCUMULATIONS SHOULD BE LIGHT BUT WOULD NOT BE SURPRISED IF
LOCAL ACCUMULATIONS AROUND AN INCH ARE REPORTED. ELSEWHERE...SKIES
WILL BE PARTY CLOUDY WITH A FEW FLURRIES POSSIBLE.
SKIES WILL BE CLEARING TONIGHT AS THE SYSTEM MOVES SOUTH AND OUT OF
THE REGION WITH COLD OVERNIGHT LOW TEMPERATURES--TEENS TO LOWER 20S
WITH A FEW AREAS IN THE SINGLE DIGITS IN THE MOUNTAINS. AS AN UPPER
RIDGE OFFSHORE SHIFTS EASTWARD...EASTERN WA/OR WILL BE ON THE EAST
SIDE OF THE RIDGE AND UNDER A NORTHERLY FLOW ALOFT ON WEDNESDAY.
COLD DRY AIR WILL SPREAD ACROSS THE REGION BY WEDNESDAY NIGHT. THIS
WILL INHIBIT FOG DEVELOPMENT...YET MODELS ARE HINTING AT SOME LOW
LEVEL MOISTURE IN CENTRAL OREGON LATE WEDNESDAY NIGHT. PATCHY
FREEZING FOG OR STRATUS IS POSSIBLE IN THE LOWER DESCHUTES PLATEAU
AS A N-NE GRADIENT PROVIDES SOME WEAK LOW LEVEL UPSLOPE. JOHNSON
.LONG TERM...THURSDAY THROUGH NEXT TUESDAY...HIGH PRESSURE ALOFT
WILL GRADUALLY BUILD INTO THE REGION ON THURSDAY FROM THE WEST. A
NORTHERLY FLOW ALOFT AHEAD OF THE RIDGE WILL KEEP TEMPERATURES ON
THE COOL SIDE...WHICH WILL PERSIST THROUGH AT LEAST CHRISTMAS DAY.
BY SATURDAY THE RIDGE AXIS WILL SHIFT EASTWARD AND INLAND INTO THE
PACIFIC NORTHWEST. THIS WILL ALLOW SOME MODERATION IN TEMPERATURES
BUT ONLY A LITTLE. A WEAK WEATHER DISTURBANCE WILL TRY TO MOVE INTO
AND THROUGH THE UPPER RIDGE BUT WILL WEAKEN SIGNIFICANTLY AS IT
ENCOUNTERS IT. IN ADDITION IT WILL LIKELY NOT BE STRONG ENOUGH TO
MIX OUT ANY AREAS OF FOG COMPLETELY IN THE LOWER COLUMBIA BASIN AND
ADJACENT LOW LANDS. THE MAIN EFFECT WILL BE JUST SOME INCREASING MID
AND HIGH CLOUDS WITH POSSIBLE LIGHT RAIN OR SNOW SHOWERS NEAR THE
CREST AND UPPER EAST SLOPES OF THE CASCADES AND OTHER MOUNTAINS
ACROSS EASTERN OREGON MONDAY AND TUESDAY. THE UPPER RIDGE WILL TRY
TO REESTABLISH ITSELF AGAIN BY THE MIDDLE OF NEXT WEEK...BUT AT THIS
TIME THERE IS UNCERTAINTY OF HOW STRONG IT WILL BECOME AND IF IT
WILL BE ENOUGH TO END ANY RAIN OR SNOW SHOWERS ACROSS THE FORECAST
AREA. 88
&&
.AVIATION...12Z TAFS...MAINLY VFR CONDITIONS WILL PREVAIL FOR THE
NEXT 24 HOURS. HOWEVER A WEATHER DISTURBANCE WILL BRING CLOUDS AND A
CHANCE OF SHOWERS TO CENTRAL OREGON...AFFECTING KRDM WHERE THERE MAY
BE RESULTANT MVFR OR IFR CONDITIONS FOR BRIEF TIMES TODAY. WINDS OF
10 TO 20 KTS WITH HIGHER GUSTS MAY ACCOMPANY ANY SHOWERS. THESE
CONDITIONS WILL IMPROVE TONIGHT WITH ALL AREAS BECOMING VFR WITH
LIGHT WINDS UNDER 15 KTS BY MIDNIGHT. 88
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 38 23 35 20 / 10 10 10 0
ALW 39 25 35 22 / 10 10 10 0
PSC 43 23 34 20 / 10 10 0 0
YKM 38 16 33 17 / 10 0 0 0
HRI 42 23 35 20 / 10 10 0 0
ELN 37 18 31 18 / 10 0 0 0
RDM 38 14 37 13 / 30 20 0 0
LGD 35 20 33 18 / 40 10 10 0
GCD 34 18 33 19 / 30 20 10 0
DLS 44 27 39 24 / 20 10 0 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
&&
THREAT INDEX
TODAY : 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
$$
85/88/88
