876
FXUS66 KPDT 161136
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
436 AM PDT WED SEP 16 2026
KEY MESSAGES
- VERY LOW (5-15%) CHANCE OF THUNDERSTORMS TODAY FOR CENTRAL
OREGON, MAINLY SOUTH OF THE BEND METRO.
- INCREASING CHANCES OF SHOWERS TONIGHT (THURSDAY NIGHT)
THROUGH FRIDAY FOR CENTRAL/EASTERN OREGON AND SOUTHEAST
WASHINGTON. HIGHEST CHANCES FOR THE BLUE MOUNTAINS.
- SLIGHT CHANCE TO CHANCE (10-30%) OF THUNDERSTORMS OVER THE
BLUE MOUNTAINS AND VICINITY THURSDAY. LOWER CHANCES (10-20%)
FOR THE NORTHEAST BLUE MOUNTAINS REGION FRIDAY.
- TEMPERATURES WILL SLOWLY WARM TO ABOVE NORMAL BY THE END OF
THE WEEK, WITH ABOVE-NORMAL TEMPERATURES AND DRY CONDITIONS
PERSISTING THIS WEEKEND.
DISCUSSION
WATER VAPOR IMAGERY SHOWS A CLOSED UPPER LOW CENTERED OVER
SOUTHWEST OREGON EARLY THIS MORNING. EAST OF THE LOW CENTER,
SHOWERS ARE ONGOING ACROSS SOUTH-CENTRAL OREGON WHERE FORCING
FOR ASCENT IS CO-LOCATED WITH AMPLE MOISTURE, MAINLY SOUTH OF
THE BEND METRO AREA. SHOWERS WILL CONTINUE TO TAPER OFF THROUGH
MORNING AS THE LOW DIVES SOUTH-SOUTHWEST, RETROGRADING SLIGHTLY
AS IT MOVES OVER NORTHWEST CALIFORNIA. LOOKING AHEAD TO THIS
AFTERNOON, THERE IS A VERY LOW TO SLIGHT CHANCE (5-15%) OF
AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS ACROSS CENTRAL
OREGON, BUT MOST ACTIVITY IS EXPECTED TO REMAIN TO OUR SOUTH IN
KLAMATH AND LAKE COUNTIES.
SHOWER ACTIVITY IS FORECAST TO RAMP AGAIN LATER TONIGHT AS
MOISTURE SURGES NORTHWEST, MID-LEVEL LAPSE RATES STEEPEN, AND
SYNOPTIC-SCALE FORCING ASSOCIATED WITH THE LOW MOVES OVERHEAD.
WILL NOTE THERE IS A LOW/SLIGHT (5-15%) CHANCE OF NOCTURNAL
THUNDERSTORMS TONIGHT AND AGAIN THURSDAY NIGHT.
ENSEMBLE NWP GUIDANCE IS IN REASONABLY GOOD AGREEMENT REGARDING
THE TRACK OF THE LOW, BUT SOME UNCERTAINTY EXISTS IN
TIMING/LOCATION AS IT MOVES ACROSS THE REGION THROUGH FRIDAY. IN
GENERAL, ENSEMBLE MEAN 500-HPA HEIGHTS AND VORTICITY SHOW THE
LOW EJECTING NORTHEAST ACROSS THE PACIFIC NORTHWEST THURSDAY
THROUGH FRIDAY, THOUGH CLUSTERS OF ENSEMBLE SOLUTIONS CONTINUE
TO SHOW SOME DIFFERENCES IN TIMING AND MAGNITUDE OF THE LOW
DURING THIS PERIOD. ALL CLUSTERS OF ENSEMBLE SOLUTIONS NOW
ADVERTISE A SCENARIO THAT WOULD INDUCE CONVECTION THURSDAY, WITH
ROUGHLY HALF SHOWING A SOLUTION THAT IS CONDUCIVE TO CONVECTION
PERSISTING FRIDAY FOR THE BLUE MOUNTAINS (MAINLY NORTHEAST BLUE
MOUNTAINS).
CHANCES OF THUNDERSTORMS ARE HIGHEST ON THURSDAY (10-30%),
ESPECIALLY FOR THE NORTHEAST BLUE MOUNTAINS, WITH LOWER CHANCES
(5-15%) FOR THE LOWER ELEVATIONS OF CENTRAL OREGON, THE BLUE
MOUNTAIN FOOTHILLS, AND EVEN AS FAR NORTHWEST AS THE LOWER
COLUMBIA BASIN. CHANCES OF THUNDERSTORMS DROP TO 10-15% FOR
FRIDAY, HIGHEST OVER WALLOWA COUNTY, AND WILL BE HEAVILY
DEPENDENT ON HOW QUICKLY THE LOW EXITS TO THE EAST; IF THE LOW
LINGERS (SOLUTION FAVORED MORE BY THE ECMWF ENSEMBLE) CHANCES
OF SHOWERS AND THUNDERSTORMS WILL CONTINUE OVER THE BLUE
MOUNTAINS ON FRIDAY, BUT IF THE LOW EXITS MORE QUICKLY (FAVORED
MORE BY THE GEFS AND CANADIAN ENSEMBLE) WE WILL SEE MORE
SHOWERY WEATHER THAT TAPERS OFF THROUGH THE DAY.
ALL ENSEMBLE MEMBERS INDICATE THE LOW WILL EXIT TO THE EAST BY
SATURDAY, WITH TRANSIENT SHORTWAVE RIDGING REPLACING IT OVER
THE PACIFIC NORTHWEST THROUGH THE WEEKEND. THIS WOULD
FACILITATE ABOVE-NORMAL TEMPERATURES AND DRY CONDITIONS
AREAWIDE.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
VFR CONDITIONS ARE FORECAST THROUGH THE PERIOD FOR ALL SITES
EXCEPT BDN WHERE LOW STRATUS CONTINUES TO PRODUCE MVFR CIGS
EARLY THIS MORNING. -RA IN CENTRAL OREGON IS FORECAST TO TAPER
OFF BY MID-MORNING, AND HAVE INCLUDED A TEMPO FOR BDN FOR
ANTICIPATED INTERMITTENT PRECIPITATION. FARTHER NORTH AT RDM,
CONFIDENCE IN LOW STRATUS PRODUCING SUB-VFR CIGS WAS LOWER
(<30%). LOW STRATUS WILL LIKELY (70-90% CONFIDENCE) LIFT AT
BDN AND RDM BY LATE MORNING TO EARLY AFTERNOON, LEAVING MOSTLY
CLEAR SKIES IN ITS WAKE.
SUSTAINED WINDS OF 12 KTS OR LESS ARE FORECAST, THOUGH PERIODIC
HIGHER GUSTS ARE EXPECTED DURING THE AFTERNOON HOURS. STRONGEST
WINDS ARE FORECAST AT RDM AND BDN LATE MORNING THROUGH EARLY
EVENING, WITH GUSTS OF 15-25 KTS LIKELY (80% CONFIDENCE).
OTHERWISE, THERE IS A VERY LOW (5-15%) CHANCE OF AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS AT BDN/RDM, THOUGH MOST
ACTIVITY IS FORECAST TO REMAIN TO THE SOUTH AND EAST OF THE
METRO AREA.
PRELIMINARY POINT TEMPS/POPS
PDT 74 46 73 51 / 0 0 20 50
ALW 77 51 75 55 / 0 0 20 50
PSC 80 49 79 50 / 0 0 10 20
YKM 75 50 79 51 / 0 0 0 0
HRI 78 48 77 51 / 0 0 20 30
ELN 71 46 77 49 / 0 0 0 0
RDM 70 39 68 40 / 10 0 40 30
LGD 78 46 76 47 / 0 0 50 70
GCD 79 45 73 47 / 0 20 80 70
DLS 80 54 84 57 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...86
AVIATION...86
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