783
FXUS66 KPDT 232338
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
438 PM PDT WED SEP 23 2020
SHORT TERM...TODAY THROUGH FRIDAY NIGHT
A SERIES OF SHORTWAVES EMBEDDED IN AN ELONGATED UPPER TROUGH WILL
AFFECT THE REGION THROUGH THE REMAINDER OF THE WEEK. THIS WILL
BRING SEVERAL OPPORTUNITIES FOR RAINFALL, ESPECIALLY OVER THE
MOUNTAINS, AS WELL AS A SPELL OF COOLER TEMPERATURES.
WIDESPREAD LIGHT TO MODERATE RAIN CONTINUES TO SPILL IN ACROSS
NORTHWEST OREGON AND WESTERN WASHINGTON AS PLENTIFUL PACIFIC
MOISTURE IS BROUGHT ONSHORE. MUCH OF THIS IS VANISHING AS IT MOVES
EAST OF THE CASCADE CREST, THOUGH THIS WILL CHANGE AS A FRONT
MOVES ACROSS OREGON AND WASHINGTON THROUGH TONIGHT AND INTO EARLY
THURSDAY, BRINGING MEASURABLE RAINFALL TO MANY AREAS. THE
MOUNTAINS LOOK TO PICK UP THE MOST SUBSTANTIAL RAINS, ESPECIALLY
THE CASCADES AND ADJACENT EAST SLOPES, WHERE 1 TO 2 INCHES WILL BE
POSSIBLE BETWEEN NOW AND THE END OF THE WEEK. LOWER ELEVATIONS
INCLUDING THE COLUMBIA BASIN AND GORGE WILL SEE LESS, GENERALLY
ANYWHERE FROM A TENTH OF AN INCH TO A HALF INCH AT MOST.
REGARDLESS, AFTER THE PREVALENCE OF DRY AND HOT CONDITIONS FOR
MUCH OF SEPTEMBER, ANY RAINS WILL BE WELCOMED AND SHOULD ALSO HELP
TO SCOUR OUT LINGERING SMOKE ACROSS THE REGION.
IN ADDITION TO THE RAIN, GUSTY WINDS WILL PERSIST FOR THE
REMAINDER OF TODAY INTO THIS EVENING. WINDS WILL SPREAD FROM
CENTRAL OREGON, WHERE THEY ARE CURRENTLY LOCATED, NORTH AND EAST
WITH THE PASSAGE OF A FRONT. WINDS MAY LOCALLY GUST TO 30 TO 40
MPH, WITH THE STRONGEST WINDS CONFINED TO PORTIONS OF THE OREGON
CASCADES AND THEIR EAST SLOPES, AND HIGHER ELEVATIONS OF CENTRAL
OREGON. WINDS SHOULD SUBSIDE OVERNIGHT.
ON THURSDAY WITH ABUNDANT CLOUD COVER, AND IN THE WAKE OF A COLD
FRONT, EXPECT NOTICEABLY COOLER CONDITIONS WITH OVERCAST SKIES.
HIGHS IN THE LOWER ELEVATIONS WILL STRUGGLE TO REACH THE LOW 70S
WITH MOUNTAINS IN THE 50S AND 60S. WITH A MORE ZONAL FLOW PATTERN,
MOST SHOWER ACTIVITY WILL BE CONFINED TO THE CASCADES AND
MOUNTAINS OF EASTERN OREGON WITH MAINLY DRY CONDITIONS ELSEWHERE.
ON FRIDAY, MODELS DEPICT A SECOND SHORTWAVE MOVING THROUGH THE
REGION, BRINGING ANOTHER CHANCE AT WIDESPREAD RAINS, EVEN ACROSS
THE COLUMBIA BASIN. MODELS VARY QUITE A BIT WITH RESPECT TO
AMOUNTS, BUT ANOTHER WETTING RAIN APPEARS PROBABLE FOR MANY AREAS
WITH THE MOUNTAINS GETTING THE BULK OF THE MOISTURE. A STOUT
PRESSURE GRADIENT WILL ALSO FOSTER BREEZY WINDS ACROSS MUCH OF THE
COLUMBIA BASIN AND GORGE. WITH EXPANSIVE CLOUDINESS, ANOTHER
RELATIVELY COOL DAY IS ON TAP WITH HIGHS IN THE LOW 70S IN THE LOW
ELEVATIONS AND 50S AND 60S IN THE MOUNTAINS.
LONG TERM...SATURDAY THROUGH WEDNESDAY
RAIN CHANCES WILL LINGER THROUGH THE WEEKEND AS THE BROAD TROUGH
PROGRESSES EASTWARD, ALTHOUGH RAIN CHANCES WILL GENERALLY BE
LIMITED TO THE MOUNTAINS, AS ANY ROBUST UPPER-LEVEL FORCING
DRIVING THE SHOWERS FROM EARLIER THIS WEEK WANES AS THE TROUGH
ENTERS THE GREAT PLAINS. SATURDAY NIGHT THROUGH SUNDAY LOOKS TO BE
MOSTLY DRY OTHERWISE, WITH HIGHS RAPIDLY CLIMBING FROM THE UPPER
60'S/LOW 70'S SATURDAY TO UPPER 70'S ON SUNDAY.
HEADING INTO NEXT WEEK, THE BROAD TROUGH IMPACTING OUR AREA THIS
WEEK WILL DIG INTO THE EASTERN CONUS, ALLOWING A RIDGE AND STRONG
HIGH PRESSURE TO BUILD OVER THE WEST COAST. MODELS IN PRETTY GOOD
AGREEMENT THIS FAR OUT FOR CONDITIONS TO WARM DRAMATICALLY THROUGH
AT LEAST WEDNESDAY, POSSIBLY LONGER, AS BOTH THE GFS AND ECMWF
DEPICT A HIGH-AMPLITUDE, POSITIVELY TILED RIDGE SETTLING IN OVER
OUR AREA STARTING MONDAY NIGHT. HIGHS LOOK TO CLIMB INTO THE MID
80'S BY WEDNESDAY THROUGHOUT THE BASIN, WHICH WOULD BE AROUND
10-15 DEGREES HIGHER THAN WHAT WE'D EXPECT FOR THE LAST WEEK OF
SEPTEMBER IN SOME AREAS. QUESTION REMAINS HOW MUCH DOES NIGHTTIME
RADIATIONAL COOLING OFFSET RAPID DAYTIME HEATING, AS WE APPROACH
DAYS WITH LONGER NIGHTS HEADING INTO OCTOBER. WILL STICK WITH NBM
GUIDANCE FOR NOW, BUT WOULD NOT BE SURPRISED IF TEMPS START TO
TREND HIGHER, GIVEN THE CONSENSUS GLOBAL MODELS HAVE ON OVERALL
PATTERN THIS FAR OUT IN ADVANCE.
AVIATION
00Z TAFS. LIGHT RAIN WILL OVERSPREAD THE TAF SITES
THIS EVENING AS A FRONT SLOWLY MOVES SOUTH ACROSS THE REGION. YKM
DLS WILL BE THE FIRST SITES STARTING 00-03Z. THE REMAINING SITES
WILL LIKELY HAVE RAIN BEGIN 04-08Z. BREEZY SOUTHWESTERLY WINDS
10-20KT. CEILINGS LOWERING TO BKN-OVC 030-060.
PRELIMINARY POINT TEMPS/POPS
PDT 54 70 49 69 / 80 10 20 50
ALW 57 72 51 70 / 80 20 20 60
PSC 58 74 55 71 / 70 0 20 50
YKM 49 72 49 69 / 90 20 50 70
HRI 57 74 53 72 / 70 0 20 40
ELN 48 68 46 64 / 90 20 60 70
RDM 47 69 41 66 / 80 10 10 40
LGD 54 69 44 66 / 70 50 20 50
GCD 55 71 44 71 / 60 50 10 20
DLS 57 73 56 70 / 90 30 50 70
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
UPDATE...94
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