Area Forecast Discussion
Issued by NWS Pendleton, OR

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000
FXUS66 KPDT 231748 AAB
AFDPDT

AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE PENDLETON OR
947 AM PST SUN NOV 23 2014

UPDATED FOR AVIATION DISCUSSION

.UPDATE...THE LATEST RADAR WAS SHOWING A LARGE AREA OF PCPN STRIKING
THE WASHINGTON CASCADES WITH MOSTLY RAIN AROUND CLE ELUM AND EASTON.
THE PCPN WAS ASSOCIATED WITH A DISTURBANCE THAT WILL RACE ACROSS THE
TWO STATE AREA TODAY PRODUCING SHOWERS OVER MOST PORTIONS OF OUR
REGION. AS THE SYSTEM PASSES THROUGH THE REGION PRESSURE GRADIENTS
WILL TIGHTEN TO CREATE BREEZY TO WINDY CONDITIONS. ADJUSTMENTS WERE
MADE TO SKY COVER...PCPN...TEMPS...WINDS AND THE PRESENT SHORT TERM
FORECAST APPEARS ON TRACK FOR NOW.

&&

.AVIATION...18Z TAFS...SHOWERS WILL BE MOVING ACROSS MOST TAF SITES
THIS AFTERNOON.  PEAK ACTIVITY SHOULD BE FROM 21Z-03Z...WITH SOME
LINGERING SHOWERS AT KALW AND KPDT FROM 03Z-09Z. KRDM...KBDN...AND
KYKM MAY ESCAPE THE SHOWERS DUE TO RAINSHADOWING.  WINDS WILL BE A
BIT BREEZY AS WELL WITH WIND SPEEDS 10-15KTS...GUSTING TO 25KTS AT
TIMES.  CIGS TONIGHT ARE IN QUESTION...AS THE POTENTIAL FOR MIST/FOG
INCREASES.  HAVE INTRODUCED LOWERED CIGS/VIS INTO THE MVFR/IFR
CATEGORY AT TAF SITES OF CONCERN.  WEBER



&&

.PREV DISC... /ISSUED 359 AM PST SUN NOV 23 2014/

SHORT TERM...TODAY THROUGH TUESDAY. WESTERLY FLOW ALOFT WILL BRING
A SYSTEM ACROSS THE PACIFIC NORTHWEST TODAY. SATELLITE INDICATES
CLOUDS WILL BE INCREASING THIS MORNING. MODELS CONTINUE TO SHOW THE
MAJORITY OF PRECIPITATION WILL BE OVER THE CASCADES AND NORTHEAST
OREGON MOUNTAINS...WITH LIGHT AMOUNTS ELSEWHERE. THE MOUNTAINS ABOVE
4000` WILL SEE SOME ACCUMULATING SNOW. THE STRONGER WESTERLY FLOW
ALOFT COMBINED WITH SURFACE GRADIENTS WILL PRODUCE BREEZY
SOUTHWESTERLY WINDS TODAY. PRECIPITATION WILL TAPER OFF TONIGHT WITH
MOSTLY CLOUDY SKIES. A BUILDING UPPER RIDGE FOR MONDAY WITH MOSTLY
CLOUDY SKIES. PRECIPITATION SHOULD BE LIMITED TO SCATTERED SHOWERS
OVER THE CASCADES. WINDS WILL BE LIGHTER. THE RIDGE WILL REMAIN OVER
THE AREA INTO TUESDAY. HOWEVER A WARM FRONT MOVING THROUGH ALONG
WITH A GOOD STREAM OF MOISTURE WILL PRODUCE RAIN. FREEZING LEVELS
WILL BE RISING AND SNOW WILL BE CONFINED TO THE HIGHER MOUNTAINS.
THE WASHINGTON CASCADES WILL RECEIVE A FAIR AMOUNT OF RAIN WITH THIS
PATTERN. WINDS WILL BE INCREASING TUESDAY BECOMING BREEZY TO WINDY
IN MANY AREAS. TEMPERATURES WILL BE WELL ABOVE NORMAL THE NEXT
SEVERAL DAYS. 94

LONG TERM...TUESDAY NIGHT THROUGH SATURDAY...MODELS START THE
EXTENDED PERIOD IN GOOD AGREEMENT WITH AN UPPER LEVEL RIDGE ALONG
THE CALIFORNIA COAST AND THE NORTHWEST COAST WHILE A FLAT MID/UPPER
LEVEL TROUGH IS IN CENTRAL BRITISH COLUMBIA TUESDAY NIGHT WITH A
FRONTAL BOUNDARY DRAPED ALONG THE SOUTHERN FLANK OF THE TROUGH
RUNNING THROUGH SOUTHERN BRITISH COLUMBIA AND NORTHERN WASHINGTON.
TH ORIENTATION OF THE FRONT AND THE FACT THAT THE TROUGH MAKES ONLY
VERY SLOW MOVEMENT SOUTHWARD TOWARD FORECAST AREA THROUGH WEDNESDAY
AFTERNOON TRANSLATES TO A MAINLY DRY FORECAST THROUGH WEDNESDAY
AFTERNOON. WEDNESDAY NIGHT ONWARD CONFIDENCE DECREASES AS THE 00Z
GFS AND ECMWF RUNS SHOW DIFFERENCES IN HOW THE3Y HANDLE THE RIDGE
ALONG THE COAST. THE GFS INCREASES THE AMPLITUDE OF THE RIDGE, WHICH
PREVENTS SOUTHWARD ADVANCE OF THE FRONTAL BOUNDARY AND ATTENDANT
PRECIPITATION AND KEEPS SNOW LEVELS RELATIVELY HIGH, WHILE THE ECMWF
WEAKENS THE RIDGE, WHICH ALLOWS THE FRONTAL BOUNDARY TO SAG SOUTH
INTO FORECAST AREA FOR INCREASING POPS AND LOWER SNOW LEVELS. SPLIT
THE DIFFERENCE TO MAKE ALLOWANCE FOR POSSIBLE SLOP OVER OF
PRECIPITATION ACROSS THE EAST SLOPES OF THE CASCADES INTO THE
KITTITAS AND YAKIMA VALLEYS BY THURSDAY NIGHT. FRIDAY AND SATURDAY A
MID/UPPER LEVEL TROUGH APPROACHES THE COAST AND SPREADS MOISTURE AND
INCREASING POPS EAST OF CASCADES FRIDAY NIGHT AND SATURDAY. POLAN

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  50  35  48  40 /  30  10  10  40
ALW  51  35  48  42 /  30  10  10  40
PSC  53  34  48  40 /  20  10  10  40
YKM  52  30  46  33 /  30  10  10  30
HRI  53  34  49  40 /  30  10  10  40
ELN  52  27  45  33 /  40  10  10  40
RDM  45  27  45  34 /  20  10  10  20
LGD  44  32  41  34 /  60  30  10  50
GCD  43  25  41  31 /  30  30  10  30
DLS  52  35  49  40 /  40  20  10  30

&&

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

FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON

$$

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