451
FXUS66 KPDT 131752
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1052 AM PDT THU AUG 13 2026
KEY MESSAGES
- RED FLAG WARNINGS IN EFFECT FOR ABUNDANT LIGHTNING TODAY INTO
FRIDAY MORNING.
- A CONVECTIVE WEATHER PATTERN WILL CONTINUE THROUGH AT LEAST
SATURDAY WITH DAILY SHOWER AND THUNDERSTORM CHANCES. MORE
UNCERTAINTY IN PATTERN DETAILS SUNDAY INTO NEXT WEEK.
- NEAR-SEASONAL TEMPERATURES THROUGH THE WEEK.
DISCUSSION
WATER VAPOR IMAGERY REVEALS A SHORTWAVE TROUGH OVER THE PACIFIC
NORTHWEST, WITH AN EMBEDDED CIRCULATION NOTED OVER NORTHEAST
WASHINGTON. FORCING ASSOCIATED WITH THE AFOREMENTIONED
CIRCULATION HAS LIKELY BEEN THE CATALYST FOR CONVECTION THAT
DEVELOPED YESTERDAY AFTERNOON ACROSS THE WASHINGTON CASCADES AND
REMAINS ONGOING NORTHEAST OF OUR FORECAST AREA. MEANWHILE, THE
BLUE MOUNTAINS REMAIN BENEATH THE ENTRANCE REGION TO A SUBTLE
MID/UPPER JET. COUPLED WITH MODEST VORTICITY ADVECTION AND MID-
LEVEL MOISTURE, SOME WEAK SHOWERS ARE DEVELOPING EARLY THIS
MORNING. NOT ANTICIPATING ANY ROBUST CONVECTION, BUT
OBSERVATIONS ARE CONSISTENT WITH WHAT NWP GUIDANCE HAS BEEN
ADVERTISING: MODEST SYNOPTIC-SCALE FORCING COUPLED WITH
SUFFICIENT MID-LEVEL (700-500 HPA) MOISTURE AND NEGATIVE MID-
LEVEL (700-500 HPA) THETA-E LAPSE RATES TYPICALLY FACILITATE
SOME WEAK NOCTURNAL CONVECTION (PREDOMINANTLY SHOWERS WITH
ISOLATED EMBEDDED THUNDERSTORMS).
THE CIRCULATION MENTIONED ABOVE WILL THEN EXIT TO THE NORTHEAST
INTO THE NORTHERN ROCKIES THROUGH THE DAY, BUT A SECOND
VORTICITY LOBE IS EXPECTED TO DIVE SOUTHEAST INTO THE PACIFIC
NORTHWEST TODAY, REINFORCING THE SHORTWAVE TROUGH. ADDITIONAL
CONVECTION IS EXPECTED (95 PERCENT CONFIDENCE) TO DEVELOP THIS
AFTERNOON ACROSS THE MOUNTAINS, AND THE PREVIOUS DAY SHIFT
ISSUED RED FLAG WARNINGS FOR MULTIPLE FIRE WEATHER ZONES IN
OREGON DUE TO FORECAST SCATTERED THUNDERSTORMS AND ABUNDANT
LIGHTNING. NOTE THAT THE WARNINGS FOR MUCH OF THE BLUE MOUNTAINS
CONTINUE THURSDAY NIGHT FOR NOCTURNAL CONVECTION.
LOOKING AHEAD, ENSEMBLE NWP GUIDANCE SUGGESTS CONTINUED
SOUTHWEST FLOW ALOFT AND ADDITIONAL REINFORCING SHORTWAVES
THROUGH AT LEAST SATURDAY. THIS WILL KEEP A CONVECTIVE PATTERN
IN PLACE RESULTING IN DAILY SHOWER AND THUNDERSTORM CHANCES,
MAINLY OVER THE MOUNTAINS. ADDITIONAL FIRE WEATHER WATCHES OR
RED FLAG WARNINGS MAY BE NEEDED IF CONFIDENCE IN ABUNDANT
LIGHTNING INCREASES FOR FRIDAY AFTERNOON OR OVER THE WEEKEND.
SUNDAY INTO NEXT WEEK, UNCERTAINTY IN PATTERN DETAILS BURGEONS
DUE TO MODEL DIFFERENCES IN THE DEVELOPMENT AND EVOLUTION OF A
DEEP CLOSED LOW IN THE PACIFIC. ENSEMBLE CLUSTER ANALYSIS
INDICATES CONCENSUS THAT THE LOW WILL DEVELOP, BUT ROUGHLY EQUAL
CHANCES (40-60 PERCENT) OF EITHER THE DEEP CLOSED LOW REMAINING
WELL OFFSHORE INTO THE MIDDLE OF NEXT WEEK OR A SOMEWHAT MORE
PROGRESSIVE PATTERN WITH A WEAKER OPEN WAVE TROUGH OVER THE
PACIFIC NORTHWEST IN ADDITION TO A WEAKER OFFSHORE LOW. EITHER
SOLUTION PUTS THE FORECAST AREA UNDER A PATTERN THAT IS
FAVORABLE FOR SOME PERIODS OF CONVECTION, BUT CHANCES OF
CONVECTION HAVE TRENDED DOWNWARD SINCE YESTERDAY'S DISCUSSION
FOR SUNDAY INTO EARLY NEXT WEEK. BROADLY, STILL HAVE 10-25%
CHANCES OF PRECIPITATION FOR THE MOUNTAINS WITH LOWER CHANCES
FOR NON-MOUNTAIN AREAS.
LASTLY, AIR QUALITY ALERTS/ADVISORIES ISSUED BY AIR QUALITY
AGENCIES REMAIN IN EFFECT FOR THE MAJORITY OF OUR FORECAST AREA
DUE TO WILDFIRE SMOKE FROM ONGOING REGIONAL WILDFIRES.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
SMOKE WILL BRING DOWN VISIBILITY MARGINALLY TO ABOUT 4 TO 5SM
IN CENTRAL OREGON, WHILE BEING LESS IMPACTING IN MOST OTHER
TERMINAL LOCATIONS. WINDS REMAIN LIGHT ACROSS THE REGION TODAY
AND TONIGHT. MOUNTAIN SHOWERS AND THUNDERSTORM DEVELOPMENT IS
ANTICIPATED TO START BY MID AFTERNOON, AND A TEMPO GROUP WAS
ADDED TO CENTRAL OREGON TERMINALS WHERE THE CAMS DO INDICATE
SCATTERED CONVECTIVE ACTIVITY FROM MID AFTERNOON INTO THE
EVENING.
PRELIMINARY POINT TEMPS/POPS
PDT 85 54 87 55 / 0 0 0 0
ALW 87 59 88 60 / 0 0 0 0
PSC 89 58 90 58 / 0 0 0 0
YKM 88 60 87 59 / 0 10 10 10
HRI 88 58 90 59 / 0 0 0 0
ELN 83 57 82 56 / 10 20 30 10
RDM 84 48 85 50 / 0 10 20 10
LGD 86 55 86 55 / 0 40 20 10
GCD 87 54 85 54 / 10 70 40 10
DLS 90 63 90 63 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...AIR QUALITY ALERT UNTIL 3 PM PDT FRIDAY FOR WAZ026>030-521>523.
RED FLAG WARNING UNTIL 9 PM PDT THIS EVENING FOR WAZ695.
OR...AIR QUALITY ALERT UNTIL 3 PM PDT FRIDAY FOR ORZ041-049-050-502-
503-505-506-509>511.
RED FLAG WARNING UNTIL 5 AM PDT FRIDAY FOR ORZ695>699.
RED FLAG WARNING UNTIL 9 PM PDT THIS EVENING FOR ORZ700-705.
DISCUSSION...86
AVIATION...71
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