Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 281724 AAA
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1025 AM PDT THU MAY 28 2015

UPDATED AVIATION DISCUSSION

.UPDATE...A LOW PRESSURE SYSTEM OVER IDAHO WILL CONTINUE MOVING AWAY
FROM THE AREA AND MOSTLY SUNNY SKIES ARE EXPECTED. MEANWHILE SOME
MOISTURE WILL LINGER OVER THE AREA MOUNTAINS AND COMBINING THIS WITH
DAYTIME HEATING COULD PRODUCE ISOLD TSRA MAINLY OVER THE AREA
MOUNTAINS THAT INCLUDE THE BLUE/WALLOWA AND EAST SLOPES OF THE WA/OR
CASCADES THIS AFTN AND EVENING. SOME MINOR ADJUSTMENTS WERE
COMPLETED ON THE SKY GRIDS THIS MORNING DUE TO THE MOSTLY CLEAR
SKIES. ALSO AFTN TEMPS WERE ADJUSTED SOME MAINLY OVER CENTRAL OREGON
WHERE AN ISOLD TSRA IS POSSIBLE NEAR THE MOUNTAINS. OTHERWISE THE
PRESENT SHORT TERM FORECAST REMAINS ON TRACK FOR NOW.

.AVIATION...18Z TAFS...VFR CONDITIONS ARE EXPECTED WITH JUST A FEW
CU BUILDUPS AT 6-8K FEET MAINLY AROUND MOUNTAINS THROUGH THIS
EVENING. WINDS WILL GENERALLY BE LESS THAN 10 KT.

 &&

.PREV DISCUSSION... /ISSUED 200 AM PDT THU MAY 28 2015/

SHORT TERM...TODAY THROUGH SATURDAY...AN UPPER LOW PRESSURE SYSTEM
OVER IDAHO WILL MOVE TO THE SOUTHEAST TODAY AND AWAY FROM THE
FORECAST AREA. HOWEVER THERE WILL STILL BE SOME LINGERING MOISTURE
ALONG WITH SOME AFTERNOON INSTABILITY TO WARRANT A MENTION OF A
SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS OVER THE NORTHEAST
MOUNTAINS AND THE WASHINGTON CASCADE EAST SLOPES. AN UPPER RIDGE
WILL BUILD OVER THE FORECAST AREA TONIGHT AND FRIDAY. THIS WILL KEEP
A WARMING TREND GOING WITH MAXIMUM TEMPERATURES IN THE MID 80S IN
THE LOWER ELEVATIONS AND MOSTLY 60S AND 70S IN THE MOUNTAINS. THE
UPPER RIDGE WILL NOT BE TOO STRONG AND IT WILL ALLOW MOISTURE AND
INSTABILITY WILL INCREASE AGAIN IN THE AFTERNOON FRIDAY FOR A SLIGHT
CHANCE OF AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS OVER MOST
OF THE FORECAST AREA. THE BEST CHANCE WILL BE OVER THE NORTHEAST
MOUNTAINS AND THE CASCADE EAST SLOPES. THE UPPER RIDGE WILL REMAIN
IN PLACE ON SATURDAY HOWEVER THERE WILL STILL BE SOME MOISTURE AND
INSTABILITY OVER THE EASTERN THIRD OF THE CWA. THIS WILL RESULT IN A
SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS IN THE AFTERNOON OVER THE
SOUTHEAST HALF OF THE FORECAST AREA ON SATURDAY. THE WARMING TREND
WILL CONTINUE ON SATURDAY WITH HIGHS REACHING AROUND 90 IN THE LOWER
ELEVATIONS WITH 70S TO AROUND 80 IN THE MOUNTAINS. WINDS WILL BE
LIGHT THROUGH THE SHORT TERM PERIOD. 88

LONG TERM...FLAT RIDGE OVER THE AREA WILL GIVE WAY TO INCREASING
SLY FLOW ON SUNDAY AS A POTENT SHORTWAVE TROUGH MOVES ACROSS THE
REGION SUNDAY EVENING. THIS WILL BE FOLLOWED BY AN UPPER LEVEL LOW
MONDAY THAT WILL GRADUALLY WEAKEN AS IT MEANDERS ACROSS THE PACIFIC
NW FOR MUCH OF THE WEEK. SETUP APPEARS FAVORABLE FOR A ROUND OF
STRONG STORMS ON SUNDAY EVENING DEPENDING ON THE AMOUNT OF AVAILABLE
INSTABILITY. IT WILL BE PLENTY WARM WITH AFTERNOON HIGHS AROUND 90
LOWER ELEVATIONS BUT WOULD FEEL A LITTLE MORE COMFORTABLE WITH THE
POTENTIAL IF THE SFC DEW POINTS WERE PROGGED TO BE HIGHER. THE GFS
HAS 30S DEW POINTS WORKING INTO THE SRN FORECAST AREA SUNDAY
AFTERNOON CHOKING OFF THE INSTABILITY ACROSS THE SOUTH. HOWEVER
ACROSS THE NORTHERN THIRD OF OREGON INTO FAR SRN WASHINGTON
INSTABILITY WILL BE SUFFICIENT FOR ORGANIZED STORMS GIVEN THE STRONG
VERTICAL WIND SHEAR. BY MONDAY A COLD FRONT WILL SWEEP ACROSS THE
AREA WITH THE POTENTIAL FOR A STRONG STORM OR TWO CONFINED TO THE
FAR NORTHEAST. WINDS MAY ALSO PUSH ADVISORY LEVELS IN THE COLUMBIA
BASIN. FOR THE REST OF THE PERIOD A COOL DOWN IS EXPECTED WITH HIGHS
MOSTLY IN THE 70S LOWER ELEVATIONS AND 50S/60S MOUNTAINS. LOWS WILL
BE IN THE 50S LOWER ELEVATIONS AND 30S/40S IN THE MOUNTAINS. THERE
WILL BE A DECREASING THREAT OF SHOWERS EACH DAY AS THE UPPER LOW
WEAKENS AND GRADUALLY PUSHES TO THE EAST. 78



&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  80  55  86  60 /   0  10  20  20
ALW  83  60  88  64 /  10  10  20  20
PSC  87  56  91  61 /   0   0  20  20
YKM  85  56  87  60 /  10  10  20  20
HRI  85  55  90  62 /   0   0  20  20
ELN  85  55  87  57 /  10  10  20  20
RDM  81  46  82  50 /  10  10  20  20
LGD  77  49  81  55 /  20  10  20  20
GCD  80  47  84  54 /  10  10  20  20
DLS  88  58  90  61 /   0   0  20  20

&&

.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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