Area Forecast Discussion
Issued by NWS Pendleton, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KPDT 280528
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1030 PM PDT WED MAY 27 2015

.SHORT TERM...UPPER LOW IS LOCATED OVER IDAHO THIS EVENING.
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS MOVED ACROSS THE
AREA DURING THE AFTERNOON AND EARLY EVENING. THESE ARE CURRENTLY
DIMINISHING IN AREAL COVERAGE. FOR THE REMAINDER OF THE EVENING
AND OVERNIGHT EXPECT CLEAR TO PARTLY CLOUDY SKIES. A WEAK RIDGE
WILL BUILD OVER THE REGION THURSDAY. SKIES SHOULD BE MOSTLY SUNNY
WITH THE EXCEPTION OF THE MOUNTAINS WHERE PARTLY CLOUDY SKIES ARE
LIKELY. ISOLATED SHOWERS POSSIBLE OVER THE CASCADES AND BLUES IN
THE AFTERNOON. THE AIRMASS ALOFT WILL BE WARMING AND HIGHS
EXPECTED TO BE 3-7 DEGREES WARMER THAN TODAY. THE FLOW ALOFT
BECOMES MORE SOUTHWESTERLY FRIDAY WITH A LITTLE INSTABILITY OVER
THE MOUNTAINS. ISOLATED SHOWERS OR THUNDERSTORMS POSSIBLE IN THE
AFTERNOON AGAIN. TEMPERATURES WILL CONTINUE TO INCREASE WITH HIGHS
INTO THE 80S AND LOWER 90S. MODELS CONSISTENT IN SHOWING AN UPPER
LEVEL LOW MOVING ACROSS THE REGION LATE SUNDAY INTO MONDAY WITH A
GOOD CHANCE OF SHOWERS AND THUNDERSTORMS. TEMPS REMAINING WELL
ABOVE NORMAL THROUGH THE WEEKEND. 94

.AVIATION...06Z TAFS. MAINLY CLEAR SKIES TONIGHT INTO THURSDAY
MORNING. WEAK INSTABILITY WITH SOME CUMULUS DEVELOPMENT IN THE
AFTERNOON MAINLY OVER THE MOUNTAINS. WINDS 5-15KT.
&&

.PREV DISCUSSION... /ISSUED 408 PM PDT WED MAY 27 2015/

SHORT TERM...TONIGHT THROUGH SATURDAY...UPPER LEVEL CLOSED LOW
PRESSURE SYSTEM OVER WALLOWA COUNTY THIS AFTERNOON WILL CONTINUE ITS
SLOW DRIFT TO THE SOUTHEAST OVERNIGHT AND BE OUT OF THE AREA BY
THURSDAY. AS SUCH CAN EXPECT THE SHOWERS AND FEW THUNDERSTORMS TO
CONTINUE INTO THIS EVENING AND THEN DECREASE AND DIE OUT AFTER
SUNSET. A RIDGE OF HIGH PRESSURE WILL BEGIN TO BUILD OVER THE REGION
ON THURSDAY BUT WITH SOME LINGERING INSTABILITY FROM THE DEPARTING
LOW THERE WILL CONTINUE TO BE SOME SHOWERS AND POSSIBLE
THUNDERSTORMS MAINLY OVER THE MOUNTAINS DURING THE AFTERNOON AND
EARLY EVENING PERIOD. ON FRIDAY THE WEAK RIDGE WILL REMAIN IN PLACE
WITH A ANOTHER CLOSED LOW PRESSURE SYSTEM OVER BRITISH COLUMBIA.
THIS LOW WILL SEND A SMALL SHORTWAVE THROUGH WASHINGTON LATE FRIDAY
WHICH WILL TRIGGER SOME SHOWERS AND POSSIBLE THUNDERSTORMS AGAIN
MAINLY OVER THE MOUNTAINS. SOME OF THIS ACTIVITY COULD CONTINUE
THROUGH FRIDAY NIGHT MAINLY OVER NORTHEAST OREGON AND SOUTHEAST
WASHINGTON. THE UPPER LEVEL RIDGE WILL BEGIN TO INTENSIFY ON
SATURDAY IN RESPONSE TO YET ANOTHER UPPER LEVEL CLOSED LOW ADVANCING
TOWARDS THE WEST COAST FROM THE EASTERN PACIFIC. THIS WILL PRODUCE
SOME INSTABILITY OVER CENTRAL OREGON EXTENDING TO NORTHEAST OREGON
FOR MORE CHANCES OF SHOWERS AND THUNDERSTORMS. HIGH TEMPERATURES
WILL BE GRADUALLY WARMING OVER THE NEXT THREE DAYS WITH LOWERS 90S
IN THE BASIN FRIDAY AND SATURDAY.


LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY NIGHT...THE WEATHER
BEGINS TO TURN MUCH MORE ACTIVE BY SUNDAY AS A CLOSED UPPER LEVEL
LOW PRESSURE SYSTEM BEGINS TO APPROACH THE AREA. BY SUNDAY AFTERNOON
THE REGION WILL BE UNDER A DIFFLUENT UPPER LEVEL PATTERN WITH A
SOUTH TO SOUTHWESTERLY FLOW ADVECTING WARM AIR AND MOISTURE INTO THE
CWA. THE CURRENT THINKING IS THAT THERE WOULD BE ENOUGH MOISTURE AND
INSTABILITY TO IGNITE SCATTERED SHOWERS AND THUNDERSTORMS OVER MOST
OF OUR OREGON ZONES BY THE AFTERNOON AND EVENING HOURS SUNDAY AS THE
SYSTEM CONTINUES TO MOVE NORTHEASTWARD. CAPE VALUES BETWEEN 500-1000
J/KG APPEAR POSSIBLE OVER MUCH OF OUR OREGON ZONES...WITH 0-6KM BULK
SHEAR VALUES OF 30-40KTS. SUNDAY NIGHT SOME NOCTURNAL SHOWERS AND
EMBEDDED THUNDERSTORMS WOULD REMAIN POSSIBLE AS SYNOPTIC SCALE LIFT
MOVES OVER THE REGION...THEREFORE LEFT CHANCES POPS IN THE FORECAST
AND ALSO BEGAN TO SHIFT SOME ACTIVITY NORTH INTO WASHINGTON. IF THE
CURRENT GUIDANCE REMAINS CONSISTENT MONDAY WOULD LIKELY BE THE BEST
DAY FOR MORE WIDESPREAD SHOWER AND THUNDERSTORM DEVELOPMENT. CURRENT
GUIDANCE IS SUGGESTING A STRONG VORTICITY MAXIMUM ALONG WITH A
CLOSED MID TO UPPER LEVEL CIRCULATION MOVING INTO OUR CWA LATER
MONDAY INTO MONDAY NIGHT. THIS COMBINED WITH CAPE VALUE BETWEEN 500-
1000 J/KG AND LI OF -1 TO -5 WILL LEAD TO CHANCE/LOW END LIKELY POPS
FOR SHOWERS AND THUNDERSTORMS OVER MUCH OF THE AREA. 0-6KM BULK
SHEAR VALUES WILL AGAIN BE BETWEEN 30-40KTS...WHICH COULD INITIATE
SOME ISOLATED STRONGER CONVECTION...THIS IS SOMETHING THAT WILL NEED
TO BE WATCHED CLOSELY IN THE COMING DAYS. ON ANOTHER NOTE...AS THE
SYSTEM APPROACHES THE AREA SEVERAL FRONTAL BOUNDARIES WILL MOVE
THROUGH...BEHIND THESE FRONTS EXPECT BREEZY CONDITIONS TO DEVELOP
BOTH MONDAY AND TUESDAY AFTERNOON...EARLY INDICATIONS ARE SUSTAINED
WINDS OF 15-25KTS WITH HIGHER GUSTS POSSIBLE. THE UPPER LOW IS THEN
FORECAST TO MOVE DIRECTLY OVER THE CWA DURING THE DAY ON
TUESDAY...WHICH WILL AGAIN LEAD TO A GOOD CHANCE FOR SHOWERS AND
ISOLATED THUNDERSTORMS. CONDITIONS BEGIN TO DRY OUT BY TUESDAY NIGHT
AS A DRIER NORTHWESTERLY FLOW DEVELOPS. THIS SYSTEM WILL EJECT EAST
INTO THE INTERMOUNTAIN WEST BY WEDNESDAY AND THURSDAY WITH A
BUILDING RIDGE AND DRIER WEATHER CONDITIONS OVER OUR REGION.
TEMPERATURES WILL START OUT ABOVE AVERAGE SUNDAY BEFORE FALLING BACK
TO NEAR OR SLIGHTLY BELOW AVERAGE MONDAY AND TUESDAY WITH THE CLOUDS
AND PRECIPITATION AROUND...BY WEDNESDAY AND THURSDAY EXPECT A
GRADUAL WARMING TREND TO TAKE HOLD. 77

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  52  81  58  86 /  20   0   0  10
ALW  57  83  63  88 /  30  10  10  10
PSC  56  87  59  91 /  20   0   0  10
YKM  55  85  59  87 /  20  10  10  10
HRI  55  85  58  90 /  20   0   0  10
ELN  53  85  58  87 /  20  10  10  10
RDM  44  80  49  82 /  10   0  10  10
LGD  47  77  52  81 /  40  20  10  20
GCD  46  80  50  84 /  30  10  10  20
DLS  57  88  61  90 /  10   0   0  10

&&

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

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

$$

94/


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.