584
FXUS66 KPDT 140533
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1033 PM PDT SUN SEP 13 2026
.UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- ADDITIONAL MOUNTAIN RAINFALL WITH AMOUNTS IN OF 1 TO 1.5
INCHES OVER THE NEXT 18-HRS PROMOTING A FLASH FLOOD AND DEBRIS
FLOW RISK FOR BURN SCARS IN THE NORTHERN BLUE MOUNTAINS.
- GENERAL DRYING AND MODEST WARMING TREND THIS UPCOMING WORK
WEEK.
- NEXT CHANCES FOR RAIN CONFINED MAINLY TO THE MOUNTAINS MID-
WEEK, LATE TUESDAY/TUESDAY NIGHT AND LATE THURSDAY/THURSDAY
NIGHT.
DISCUSSION
LATEST WATER VAPOR IMAGERY SHOWS THE UPPER-LEVEL
LOW OVER EASTERN WA AND COMPLEX TROUGHING OVER THE WEST COAST.
MEANTIME, AMPLE MOISTURE IS SEEN ON THE WESTERN SIDE OF THIS
LOW THAT IS STEADILY PROGRESSING EASTWARD INTO THE INTERIOR WITH
THE MAIN SHORTWAVE TROUGH ROTATING EAST INTO SOUTHEAST OR.
LATEST RADAR DISPLAY SHOWS A SWATH OF LIGHT RAIN STARTING TO
CROSS THE WESTERN WA LOWER BASIN TOWARDS THE EASTERN MOUNTAINS.
1-HR RAINFALL TOTALS HAVE BEEN LIGHT, A FEW HUNDREDTHS TO A
TENTH OF AN INCH AT LOWER ELEVATIONS, WHILE 6-HR TOTALS HAVE
BEEN REACHING 0.1-0.2 INCHES. ELSEWHERE, A QUARTER INCH TO A
HALF INCH HAS BEEN SEEN ALONG THE EASTERN SLOPES OF THE WA
CASCADES AS OF 1 PM PDT.
THE AFOREMENTIONED AREA OF LIGHT PRECIP WILL CONTINUE EASTWARD
THIS AFTERNOON ACROSS THE REST OF THE LOWER BASIN WITH
OROGRAPHIC ENHANCEMENT ANTICIPATED ACROSS THE NORTHERN BLUE
MOUNTAINS. APPRECIABLE MOISTURE IS BEING TAPPED INTO THIS SYSTEM
FOR THIS TIME OF YEAR WITH IVT FORECASTS SHOWING 200-300 KG/MS
PENETRATING INTO THE BASIN AND THE EASTERN MOUNTAINS; EPS MEAN
PRECIPITABLE WATER FORECASTS APPROACHING/REACHING 150% OF
NORMAL ACROSS THE AREA. THIS INCREASES CONFIDENCE IN THE NEXT
ROUND OF MODERATE TO LOCALLY HEAVY RAIN IN THE NORTHERN BLUES
AND WALLOWAS. LATEST 24-HR LPMM BY HREF SHOW A REASONABLE 1-1.5
INCHES ENDING 12 Z TOMORROW MORNING/MONDAY, ELSEWHERE A TENTH
TO A QUARTER INCH IN THE LOWER BASIN AND FOOTHILLS WITH LESS
THAN A TENTH ACROSS NORTH CENTRAL AND CENTRAL OR. CONFIDENCE IS
BOLSTERED IN THIS OUTCOME WITH NBM PROBS SHOWING 50-70% CHANCE
FOR OVER 1 INCH ACROSS THE NORTHERN BLUES. OTHERWISE, THE
COMBINATION OF RESIDUAL MOISTURE AND RECENT RAINFALL COULD
PROMOTE A MINOR RISK FOR PATCH FOG, MAINLY ALONG VALLEYS AND
DRAINAGES OF THE LOWER BASIN AND IN AREAS OF THE EASTERN
MOUNTAINS. CONFIDENCE IN THE FOG THREAT ISNT HIGH (30-50%) AT
THIS TIME WHEN IT COMES TO OCCURRENCE.
AFTER THIS UPPER-LEVEL SYSTEM DEPARTS EAST ACROSS THE NORTHERN
PLAINS AND CANADIAN PRAIRIES, LARGE SCALE GUIDANCE IS CONSISTENT
IN THE DEVELOPMENT OF ANOTHER UPPER-LEVEL TROUGH MIDWEEK
OVERHEAD WITH ADDITIONAL AMPLIFICATION SEEN UPSTREAM OF THE
UPPER-LEVEL RIDGE ACROSS THE GULF OF ALASKA INTO AK. WHILE
ENSEMBLE GUIDANCE SHOWS SOME SPREAD, THE UPPER TROUGH AND ITS
CLOSED LOW DIGS FARTHER SOUTH INTO CA BY MID-WEEK WITH
CLUSTERING GUIDANCE TILTING MODERATELY TOWARDS THIS OUTCOME BY
THURSDAY (~60%) WITH THEN INCREASING ODDS IN GENERAL MEAN
TROUGHING PERSISTING TO FRIDAY (~50%). OVER THIS TIME PERIOD, A
SHORT DRYING TREND WILL BE SEEN AFTER THIS CURRENT SYSTEM EXITS
THE AREA BEFORE PRECIP CHANCES INCREASE LATE TUESDAY-TUESDAY
NIGHT (20-50%, HIGHEST IN THE MOUNTAINS) FOLLOWED BY AN UPTICK
AGAIN IN PRECIPITATION CHANCES OVER THE EASTERN MOUNTAINS
THURSDAY/THURSDAY NIGHT. MEANWHILE, A WARMING TREND IS EXPECTED
WITH HIGHS NEAR AVERAGE BY THURSDAY WITH READINGS SLIGHTLY ABOVE
AVERAGE FRIDAY.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
VFR CONDITIONS CURRENTLY ACROSS MOST SITES, WITH THE EXCEPTION
OF IFR CEILINGS OF 700 FEET AT KYKM. THESE CEILINGS ARE EXPECTED
TO IMPROVE SHORTLY AS THE SYSTEM CONTINUES TO PUSH EAST.
CEILINGS ARE ALSO EXPECTED TO DEGRADE TO 3KFT AT KALW OVERNIGHT,
LEADING TO MVFR CONDITIONS THAT WILL IMPROVE BY MID-MORNING.
ELSEWHERE, SHOWERS WILL DEPART TO THE EAST AS CEILINGS LIFT TO
25KFT FOR ALL SITES BY LATE MORNING. BREEZY AFTERNOON WINDS ARE
ANTICIPATED FOR KPDT/KALW WITH GUSTS OF 15-20KTS LIKELY. 75
PRELIMINARY POINT TEMPS/POPS
PDT 45 70 44 67 / 80 0 0 0
ALW 50 70 49 69 / 90 0 0 0
PSC 46 74 45 70 / 50 0 0 0
YKM 44 69 47 66 / 20 0 0 10
HRI 46 73 44 70 / 60 0 0 0
ELN 41 65 43 61 / 30 0 0 30
RDM 33 71 36 70 / 10 0 0 0
LGD 43 69 41 72 / 100 0 0 0
GCD 41 70 42 75 / 50 0 0 0
DLS 51 74 50 73 / 10 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...80
AVIATION...75
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page