142
FXUS66 KPDT 160508
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1008 PM PDT MON SEP 15 2025
UPDATED AVIATION DISCUSSION
AVIATION...06Z TAFS
VFR CONDITIONS EXPECTED, WITH SKC
PREVAILING AND WINDS TERRAIN-DRIVEN OVERNIGHT, PULLING MORE E/NE
DURING THE DAY LESS THAN 10 KTS. EVANS/74
PREV DISCUSSION... /ISSUED 207 PM PDT MON SEP 15 2025/
DISCUSSION...
KEY MESSAGES:
1. WARM AND DRY TREND THROUGH MIDWEEK.
2. WARM TEMPERATURES PERSIST THROUGH SATURDAY.
3. NEXT CHANCE OF SHOWERS OVER THE WEEKEND.
CURRENT RADAR AND VISIBLE SATELLITE IMAGERY SHOWS DRY CONDITIONS,
WITH A FEW HIGH LEVEL CLOUDS MOVING SOUTH ALONG THE NORTHERN BLUE
MOUNTAINS. THIS IS A RESULT OF AN UPPER LEVEL RIDGE BUILDING
ALONG THE WASHINGTON/OREGON COASTS COUPLED WITH A THERMAL TROUGH
DEVELOPING OVER THE UMPQUA AND WILLAMETTE VALLEYS WEST OF THE
CASCADES. THE BUILDING THERMAL TROUGH AND UPPER LEVEL RIDGE HAVE
ALLOWED FOR EAST WINDS TO DEVELOP ACROSS THE AREA, WHICH WILL
ENHANCE THIS EVENING THROUGH TUESDAY. THE BREEZIEST CONDITIONS
WILL OCCUR THROUGH THE EASTERN GORGE AND THE KITTITAS VALLEY WITH
SUSTAINED WINDS OF 10-15 MPH WITH GUSTS OF BETWEEN 20-25 MPH
TUESDAY AFTERNOON. CONFIDENCE IN THESE WIND VALUES IS MODERATE
(50-70%) VIA THE NBM. HOWEVER, HUMIDITIES IN THESE AREAS HOVER
BETWEEN 40-50%, WELL ABOVE CRITICAL FIRE WEATHER VALUES. A DRIER
AND WARMER AIRMASS WILL MOVE OVER THE AREA TO BUMP HIGH
TEMPERATURES FROM THE LOW TO MID-70S TODAY INTO THE LOW TO MID-80S
ON TUESDAY. HUMIDITIES WILL ALSO TREND DOWNWARD INTO THE MID-TO
UPPER TEENS ACROSS CENTRAL OREGON AND AROUND 30% ACROSS SOUTH-
CENTRAL WASHINGTON BY TUESDAY. OVERNIGHT HUMIDITIES WILL CONTINUE
TO TREND DRIER AND BECOME MODERATE TO POOR (35-50%) WEDNESDAY
THROUGH FRIDAY ACROSS HIGHER TERRAIN OF THE EAST SLOPES OF THE
CASCADES, EASTERN MOUNTAINS, AND THE JOHN DAY HIGHLANDS.
THE UPPER LEVEL RIDGE STRENGTHENS TUESDAY BEFORE SHIFTING TO OUR
EAST ON WEDNESDAY AS AN UPPER LEVEL TROUGH APPROACHES THE COAST.
THIS TROUGH WILL SLOW AND SHEAR NORTH, KEEPING CONDITIONS DRY BUT
BREEZY AS A PRESSURE GRADIENT DEVELOPS BETWEEN THE APPROACHING
TROUGH AND ANTECEDENT RIDGE. THE APPROACHING TROUGH WILL ALSO
PROMOTE SOUTHWEST FLOW ALOFT TO KEEP TEMPERATURES ABOUT 10 DEGREES
ABOVE NORMAL AS HIGH TEMPERATURES STAY IN THE MID-TO UPPER 80S
ACROSS THE BASIN, BLUE MOUNTAIN FOOTHILLS, AND THE YAKIMA VALLEY
WEDNESDAY THROUGH FRIDAY. THE NBM SUGGESTS A HIGH CONFIDENCE
(85-95% CHANCE) OF HIGH TEMPERATURES REACHING 85 OR GREATER OVER
THE AFOREMENTIONED AREAS.
ENSEMBLE MEMBERS ARE IN GOOD AGREEMENT WITH AN UPPER LEVEL LOW
PRESSURE DEVELOPING OFF THE CALIFORNIA COAST ON FRIDAY, WITH 68%
OF ENSEMBLES SUGGESTING THE LOW MERGE WITH A PASSING UPPER LEVEL
TROUGH TO PROVIDE LIGHT SHOWERS SATURDAY EVENING THROUGH SUNDAY.
BOTH FEATURES LOOK RATHER WEAK AS FLOW IS MORE ZONAL ACROSS THE
PACIFIC NORTHWEST. THESE SYSTEMS ARE ALSO FOLLOWING A DRY AND HOT
AIRMASS ASSOCIATED WITH THE DEPARTING RIDGE, SO ONLY A COUPLE
HUNDREDTHS OF A INCH OF RAINFALL IS ANTICIPATED ACROSS THE EAST
SLOPES OF THE CASCADES AND THE BLUE MOUNTAINS, WITH ALL OTHER
AREAS LOOKING TO STAY DRY AT THIS TIME. 75
PRELIMINARY POINT TEMPS/POPS
PDT 49 83 52 85 / 0 0 0 0
ALW 53 84 58 86 / 0 0 0 0
PSC 49 83 51 86 / 0 0 0 0
YKM 50 81 54 87 / 0 0 0 0
HRI 50 83 51 86 / 0 0 0 0
ELN 46 81 49 85 / 0 0 0 0
RDM 38 83 43 85 / 0 0 0 0
LGD 43 81 47 85 / 0 0 0 0
GCD 44 81 47 87 / 0 0 0 0
DLS 53 86 57 89 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...75
LONG TERM....75
AVIATION...74
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