Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 290550 AAB
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1045 PM PDT THU APR 28 2016

UPDATED THE AVIATION DISCUSSION

.UPDATE...A LOW PRESSURE SYSTEM OVER IDAHO WAS RAPPING MOISTURE
AROUND THE LOW AND INTO OUR AREA FROM THE NORTH. A FEW SHOWERS WERE
DEVELOPING MAINLY OVER THE NORTHERN PORTIONS OF OUR REGION INCLUDING
LOCATIONS TO OUR EAST. THE GRIDS WERE UPDATED TO EXPAND THE SHOWER
COVERAGE TO INCLUDE THESE AREAS OVERNIGHT. OTHERWISE MINOR CHANGES
WERE ALSO COMPLETED TO THE SKY AND PCPN AMOUNTS AND NOW THE PRESENT
SHORT TERM FORECAST APPEARS ON TRACK.

.AVIATION...SHOWERS WERE APPROACHING TAF SITES KALW AND LCL MVFR
CONDITIONS ARE POSSIBLE UNTIL 08Z. OTHERWISE A WEATHER SYSTEM IS
FORECAST TO MOVE INTO THE REGION TOWARD MORNING WITH CLOUDS AND
SHOWERS. MAINLY VFR CONDITIONS WILL TURN TO SOME LCL MVFR CONDITIONS
AFTER 12Z AT KDLS...KRDM...KBDN AND THEN THE REMAINDER OF THE TAF
SITES COULD EXPERIENCE LCL MVFR CONDITIONS AFTER 15Z IN CLOUDS AND
SHOWERS. IN ADDITION WIND GUSTS TO 25 KTS IS POSSIBLE AFTER 15Z.

&&

.PREV DISCUSSION... /ISSUED 445 PM PDT THU APR 28 2016/

SHORT TERM...TONIGHT THROUGH SUNDAY...FORECAST AREA CONTINUES TO BE
UNDER THE INFLUENCE OF A LARGE SCALE UPPER LEVEL TROUGH OVER THE
WESTERN U.S.. INSTABILITY SHOWERS ARE STARTING TO DEVELOP ACROSS
PORTIONS OF THE FORECAST AREA THIS AFTERNOON. THESE SHOWERS WILL
CONTINUE INTO THE EVENING AND THEN DECREASE AFTER SUNSET. A
SHORTWAVE DROPPING INTO THE TROUGH FROM THE GULF OF ALASKA WILL PASS
OVER THE REGION ON FRIDAY THEN DROP INTO THE GREAT BASIN OVERNIGHT
AND SATURDAY. WILL SEE AN INCREASE IN SHOWERS AND BREEZY WESTERLY
WINDS ON FRIDAY AS THIS SYSTEM DESTABILIZES THE ATMOSPHERE. HIGH
PRESSURE WILL BEGIN BUILDING INTO THE REGION FROM THE WEST SATURDAY
AND SUNDAY. THIS WILL LEAD TO A WARMING TREND AND DRY CONDITIONS
THROUGH THE WEEKEND.

LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...SUNDAY NIGHT I CHOSE TO
KEEP DRY CONDITIONS IN FORECAST AREA DESPITE SOME SUGGESTION IN THE
CANADIAN AND THE ECMWF 12Z MODEL RUNS THAT A SMALL SCALE SHORT WAVE
MOVES WEST ACROSS LOWER COLUMBIA BASIN AROUND THE BOTTOM OF A
MID/UPPER LEVEL RIDGE OF HIGH PRESSURE PARKED OVER BRITISH COLUMBIA
AND PACIFIC NORTHWEST. GFS 12Z RUN DOES NOT SHOW THE AFOREMENTIONED
SHORT WAVE. MONDAY DRY CONDITIONS CONTINUE DUE TO THE RIDGE STAYING
OVER PACIFIC NORTHWEST. MONDAY NIGHT DRY CONDITIONS PERSIST BY
VIRTUE OF THE RIDGE HOLDING FAST OVER THE ROCKIES AND THE FORECAST
AREA. TUESDAY A LONG WAVE MID/UPPER LEVEL TROUGH APPROACHES THE
COAST WHILE THE RIDGE AXIS NUDGES EAST A TAD, THUS ALLOWING THE
BROAD SOUTHERLY FLOW ALOFT ON THE EASTERN FLANK OF THE TROUGH TO
BEGIN TRANSPORTING MOISTURE INTO REGION THUS YIELDING INCREASING
POPS OVER THE CASCADES FOR A CHANCE OF SHOWERS IN HIGHER TERRAIN OF
EAST SLOPES OF THE CASCADES DURING THE DAY ON TUESDAY WITH A SLIGHT
CHANCE OF THUNDERSTORMS ALONG THE EAST SLOPES OF THE OREGON CASCADES
TUESDAY EVENING. WITH INCREASING MID LEVEL MOISTURE TUESDAY NIGHT,
THE REGION BECOMES UNSTABLE FOR AN INCREASING CHANCE OF SHOWERS
WEDNESDAY AND THURSDAY ALONG WITH A SLIGHT CHANCE OF THUNDERSTORMS
BOTH DAYS. SOME STRAY NIGHT-TIME THUNDERSTORMS WILL ALSO BE POSSIBLE
WEDNESDAY NIGHT AND THURSDAY EVENING OVER THE ENTIRE FORECAST AREA.
POLAN

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  46  61  44  68 /  10  30  30  10
ALW  48  63  46  69 /  20  30  30  10
PSC  47  67  45  75 /  10  20  20  10
YKM  43  65  43  75 /  20  20  20   0
HRI  48  65  45  73 /  10  20  20   0
ELN  44  60  44  72 /  30  20  20   0
RDM  34  57  34  65 /  10  30  20   0
LGD  41  55  39  62 /  20  40  40  10
GCD  39  55  39  62 /  10  50  40  10
DLS  48  62  45  74 /  10  20  20   0

&&

.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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