HAMweather.com Area Forecast Discussion for County Warning Area PDT

Thu, 16 Feb 2012 12:04:49 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
335 AM PST THU FEB 16 2012

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT...MID AND HIGH CLOUDS ARE 
CONTINUING TO WORK THEIR WAY INTO WESTERN WASHINGTON AND NORTHWEST 
OREGON AT THIS TIME WITH A WARM FRONT. THIS IS SLIGHTLY FASTER THAN 
THE NAM12 MODEL AND A LITTLE BETTER AGREEMENT WITH THE GFS MODEL. IN 
EITHER CASE PRECIPITATION WILL BEGIN TO ALSO MOVE TO THE CASCADES 
AND BEGIN TO SPILL OVER TO THE EAST SIDE BY AROUND 18Z OR 10 AM 
LOCAL TIME. SOME VERY LIGHT AMOUNTS OF PRECIPITATION IS EXPECTED TO 
REACH THE EASTERN BORDER OF THE FORECAST AREA. HOWEVER THIS SYSTEM 
IS FORECAST TO SIGNIFICANTLY WEAKEN AS IT ENCOUNTERS A FAIRLY STRONG 
HIGH PRESSURE RIDGE ALREADY OVER THE REGION. THE MAIN EFFECT FROM 
THIS SYSTEM WILL BE TO WEAKEN THE RIDGE AND CAUSE SOME MOUNTAIN 
SHOWERS. THE LOWER ELEVATIONS SHOULD STAY MOSTLY DRY...BUT THERE 
COULD BE A FEW ISOLATED SHOWERS THERE AS WELL...ESPECIALLY OVER THE 
BLUE MOUNTAIN FOOTHILLS AND THE EAST SLOPES OF THE CASCADES AND 
THEIR ADJACENT VALLEYS. THE UPPER RIDGE WILL THEN REBUILD OVER THE 
REGION LATE TONIGHT BEFORE THE WARM FRONT WITH THE NEXT SYSTEM MOVES 
INTO THE AREA BY FRIDAY AFTERNOON. THIS NEXT SYSTEM WILL BE MUCH 
STRONGER THAN THE ONE MOVING IN AT THE CURRENT TIME. PRECIPITATION 
WITH THE WARM FRONT WILL MOVE EAST OF THE CASCADES BY LATE FRIDAY 
AFTERNOON AND THEN WILL SPREAD OVER THE REMAINDER OF THE FORECAST 
AREA OVERNIGHT FRIDAY NIGHT WITH ABUNDANT MOISTURE. WILL GO WITH 
HIGH POPS OF AT LEAST IN THE LIKELY CATEGORY FRIDAY NIGHT WITH THIS 
SYSTEM. THE COLD FRONT IS EXPECTED TO MOVE ACROSS THE REGION DURING 
THE EARLY EXTENDED PERIOD WITH AN UNSTABLE COLD POOL ALOFT. 
TEMPERATURES BETWEEN NOW AND THEN WILL RUN NEAR TO SLIGHTLY BELOW 
NORMAL TODAY...BUT THEN THEY WILL BECOME ABOVE NORMAL ON FRIDAY AS 
WARMER AIR FROM THE SOUTH IS PUMPED NORTHWARD AHEAD OF THE FRIDAY 
NIGHT SYSTEM. HOWEVER...SNOW LEVELS WILL STILL BE LOW ENOUGH FOR AT 
LEAST A FEW POSSIBLE INCHES OF SNOW AT PASS LEVELS...BUT SNOW 
AMOUNTS ARE EXPECTED TO STAY BELOW ADVISORY CRITERIA AT THIS TIME. 88

.LONG TERM...SATURDAY THROUGH WEDNESDAY. A COLD UPPER LEVEL LOW WILL 
BE MOVING OVER THE AREA SATURDAY. EXPECT NUMEROUS RAIN AND SNOW 
SHOWERS THROUGH THE DAY. GIVEN THE STEEP LAPSE RATES AND INSTABILITY 
MIGHT HAVE SOME ICE PELLET SHOWERS OR ISOLATED LIGHTNING STRIKES. 
SEVERAL INCHES OF SNOW ACCUMULATION IS LIKELY IN THE MOUNTAINS. A 
SURFACE LOW ALONG WITH WINDS ALOFT AND UNSTABLE CONDITIONS WILL 
PRODUCE BREEZY SOUTHWESTERLY WINDS. THE LOW WILL MOVE OFF TO THE 
EAST BY SUNDAY HOWEVER A COOL NORTHWEST FLOW ALOFT WILL CONTINUE TO 
BRING SCATTERED RAIN AND SNOW SHOWERS. A WARM FRONT WILL MOVE 
THROUGH THE PACIFIC NORTHWEST LATER MONDAY INTO TUESDAY WITH A 
CHANCE OF PRECIPITATION. THE AIRMASS WILL BE WARMING SO EXPECT 
MOSTLY RAIN WITH MOUNTAIN SNOW. TEMPERATURES WILL BE BELOW NORMAL 
OVER THE WEEKEND THEN RISE TO NEAR OR ABOVE NORMAL EARLY NEXT WEEK. 
94

.AVIATION...12Z TAFS. INCREASING CLOUDS TODAY WITH LOWERING CEILINGS 
AS A FRONT MOVES ACROSS THE AREA. CEILINGS AT 200 WILL LOWER TO 
050-100 LATER IN THE DAY. COULD SEE A FEW SHOWERS THIS AFTERNOON. 
SURFACE WINDS 5-10KT. CEILINGS WILL BE IN THE 040-080 RANGE TONIGHT. 
94

.PRELIMINARY POINT TEMPS/POPS...
PDT  40  31  49  33 /  10  20  10  70 
ALW  39  33  48  36 /  10  20  10  70 
PSC  42  31  50  35 /  10  10  10  70 
YKM  40  27  47  31 /  20  20  10  70 
HRI  41  31  50  34 /  10  10  10  70 
ELN  38  27  43  29 /  20  20  20  70 
RDM  41  28  50  29 /  10  20  10  80 
LGD  38  29  47  32 /  10  20  10  60 
GCD  39  30  48  30 /  10  20  10  60 
DLS  42  33  50  36 /  20  20  20  80 

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.

THREAT INDEX
TODAY : GREEN
FRIDAY : GREEN
SATURDAY : 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