560
FXUS66 KPDT 040009
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
509 PM PDT WED JUN 3 2020
..UPDATED AVIATION DISCUSSION
AVIATION...00Z TAFS
LOW AVIATION CONCERNS THE NEXT 24 HOURS
WITH GENERALLY VFR CONDITIONS ANTICIPATED. LATEST SATELLITE
IMAGERY SHOWS CIRRUS MOVING EAST ACROSS NORTHEAST OR AND PARTS OF
CENTRAL OR WITH SOME MID CLOUDS OVER PARTS OF THE KITTAS VALLEY.
OBS SHOW LIGHT BREEZES IN PLACE THAT WILL BY AND LARGE LESSEN
OVERNIGHT WITH THEN INCREASING WEST TO NORTHWEST BREEZES BY
TOMORROW AFTERNOON. THIS WILL COINCIDE WITH PARTLY CLOUDY SKIES
TOMORROW AS WELL. 80
PREV DISCUSSION
/ISSUED 228 PM PDT WED JUN 3 2020/
SHORT TERM...TONIGHT THROUGH THURSDAY...WATER VAPOR AND VISIBLE
SATELLITE SHOW A WEAK SHORTWAVE TRAVERSING THE REGION, WITH
ASSOCIATED HIGH DECK OF CIRRUS COVERING MUCH OF THE FORECAST AREA.
REGION WILL CONTINUE TO BE FAIRLY QUIET THROUGH TOMORROW NIGHT AS
A DRY WESTERLY FLOW PERSISTS ALOFT. BREEZY CONDITIONS WILL
CONTINUE ACROSS THE COLUMBIA GORGE AND KITTITAS VALLEY THROUGH
THIS EVENING UNDER A TIGHTENING OF SURFACE PRESSURE GRADIENTS AND
HIGHER UPPER LEVEL WINDS MIXING DOWN TO SURFACE.
THURSDAY NIGHT THROUGH FRIDAY NIGHT...BY THURSDAY NIGHT, FLOW
ALOFT WILL BEGIN TO SHIFT TO THE SOUTHWEST AS AN UPPER LEVEL
CLOSED LOW STARTS TO DIVE SOUTH OUT OF THE GULF OF ALASKA,
RESULTING IN INCREASED MOISTURE AND CLOUD COVER EAST OF THE
CASCADES. FRIDAY, CLOSED LOW WILL CONTINUE TO SLOWLY MOVE SOUTH
DOWN THE BC COAST WHILE PUSHING A FEW EMBEDDED IMPULSES ACROSS THE
REGION. THESE IMPULSES WILL BRING SHOWER CHANCES TO MOST OF THE
FORECAST AREA. SOME INSTABILITY WILL BE AVAILABLE FOR ISOLATED
THUNDERSTORM DEVELOPMENT OVER THE EASTERN MOUNTAINS WITH A 500MB
JET OF 60-65KTS PROVIDING SHEAR THAT WILL SUPPORT FURTHER
ORGANIZED CONVECTION IN THESE AREAS. THAT SAID, THE INCREASE IN
CLOUD COVER OVERNIGHT AND INTO THE AFTERNOON MAY STIFLE SURFACE
INSTABILITY FROM DAYTIME HEATING, POTENTIALLY LIMITING
THUNDERSTORM ACTIVITY FOR FRIDAY. LAWHORN/82
LONG TERM...SATURDAY THROUGH NEXT WEEK...ON SATURDAY, A CUTOFF
LOW ORIGINALLY IN SOUTHERN CA WILL STILL BE IN THE PROCESS OF
REJOINING THE MAIN TROUGH OFF THE PAC NW COAST, GIVING THE
OVERALL TROUGH ORIENTATION A BIT OF A NEGATIVE TILT AS THE PATTERN
MOVES EAST ACROSS OUR REGION. THIS WILL RESULT IN CONTINUED
SHOWER/LIGHT RAIN CHANCES THROUGH MUCH OF THE EARLY WEEK AS LIFTED
MOISTURE LINGERS. STORMS MAY RE-FIRE FOR MUCH OF THE OR CASCADES
AND EASTERN MOUNTAINS SATURDAY AFTERNOON AND EVENING BUT CONTINUED
CONVECTION AND CLOUD COVER MAY STILL INHIBIT THE FULL POTENTIAL
OF THE NEGATIVE TILT TROUGH. SNOW LEVELS WILL ALSO LOWER TOWARD
5-6KFT. WHILE THESE LOWER SNOW LEVELS ARENT UNCOMMON, IT IS
UNUSUAL FOR MODELS TO INDICATE ENOUGH MOISTURE TO LINGER IN SUCH
A COOL ENVIRONMENT. WITH THE SPRING RECREATION SEASON COMMENCING,
SOME EARLY HIKERS ON THE SLOPES OF THE CASCADE VOLCANOS OR IN THE
EAGLE CAPS/WALLOWAS MAY SEE SOME FLAKES FLY SUNDAY INTO MONDAY. A
FINAL CONCERN IS EXPRESSED FOR THE SLIGHT POTENTIAL FOR EXCESSIVE
RAINFALL. MOST DETERMINISTIC GLOBAL MODELS HAVE A RELATIVELY SLOW
SWATH OF RAIN TRAVERSING FROM NEAR THE KLAMATH REGION TOWARD
THE ID PANHANDLE SUNDAY. IT'S A BIT EARLY TO IDENTIFY WHAT BASINS
MAY BE AFFECTED, IF ANY, BUT THE PATTERN OF A CUTOFF LOW
REJOINING A PROGRESSIVE TROUGH IN A NEGATIVE TILT DOES SIGNAL THIS
RAINFALL POTENTIAL. MONDAY INTO TUESDAY MAY FEATURE WEAK RIDGING,
ENOUGH TO PREVENT AT LEAST THE BASIN/VALLEYS FROM SEEING
CONTINUED RAIN. ANOTHER WEAK PLUME OF MOISTURE APPROACHES THE
REGION TUE, BRINGING AN UPTICK IN SHOWERS/LIGHT RAIN BY
AFTERNOON. ANOTHER QUICK RIDGE/POSSIBLE DRYING IS EXPECTED FOR
MID TO LATE WEEK, BUT MODEL PREDICTABILITY BEGINS TO FALTER HERE
THOUGH THE OVERALL PATTERN SEEMS QUITE COOL AND WET FOR MID-JUNE.
WE SEEM TO END THE WEEK WITH STRENGTHENING DEEP SOUTHERLY FLOW
ALOFT AND INCREASING MOISTURE. CLARK/76
PREV DISCUSSION... /ISSUED 1053 AM PDT WED JUN 3 2020/
UPDATED AVIATION DISCUSSION
AVIATION...18Z TAFS...VFR CONDITIONS TO PREVAIL. WINDS MAY BE
BREEZY THIS AFTERNOON, PARTICULARLY IN THE KITTITAS VLLY AND
COLUMBIA GORGE, GUSTING TO ABOUT 20KTS. OTHERWISE, GOOD CEILINGS
AND SURFACE VISIBILITY EXPECTED. SOME PASSING CLOUDS EVIDENT WITH
A BKN MID LEVEL DECK OVER NE OREGON AND A HIGH LEVEL CIRRUS
SHIELD MOVING OVER THE OR CASCADES. WINDS WILL EASE OVERNIGHT. 76
PRELIMINARY POINT TEMPS/POPS
PDT 50 76 52 76 / 0 0 0 10
ALW 51 78 53 78 / 0 0 0 20
PSC 54 80 55 80 / 0 0 0 10
YKM 50 77 52 75 / 0 0 0 10
HRI 53 79 54 78 / 0 0 0 10
ELN 48 73 49 72 / 0 0 0 10
RDM 44 77 47 74 / 0 0 0 10
LGD 46 72 50 77 / 0 0 0 30
GCD 47 76 52 81 / 0 0 0 30
DLS 52 77 53 74 / 0 0 0 10
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
76/82/80
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