518
FXUS66 KPDT 061724
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1024 AM PDT MON JUL 6 2026
KEY MESSAGES
- WARMING TREND CONTINUES, PEAKING TUESDAY.
- ISOLATED THUNDERSTORMS POSSIBLE THROUGH TUESDAY.
- DRY AND WINDY CONDITIONS TUESDAY.
*FIRE WEATHER WATCH ISSUED*
DISCUSSION
CURRENT RADAR AND INFRARED SATELLITE IMAGERY SHOWS LIGHT RETURNS
EXTENDING ACROSS DESCHUTES, GRANT, CROOK, AND WHEELER COUNTIES
UNDER PARTLY CLOUDY SKIES. THIS IS IN RESPONSE TO AN UPPER LEVEL
SHORTWAVE TROUGH MOVING INTO SOUTH-CENTRAL OREGON AND
CONTINUING INTO EASTERN OREGON THROUGH THE DAY, AS A LARGE UPPER
LEVEL TROUGH STRENGTHENS ALONG THE BRITISH
COLUMBIA/WASHINGTON/OREGON COASTS TO ENHANCE SOUTHWEST FLOW
ALOFT. THE WARMING TREND THAT WAS BRIEFLY PAUSED ON SUNDAY WILL
COMMENCE THROUGH TUESDAY AS HIGH TEMPERATURES REACH INTO THE LOW
TO MID-90S TODAY AND UPPER 90S TO LOW 100S ON TUESDAY FOR AREAS
OF THE LOWER COLUMBIA BASIN, BLUE MOUNTAIN FOOTHILLS, CENTRAL
OREGON, AND THE YAKIMA VALLEY. THE NBM ADVERTISES A 30-50%
CHANCE FOR WALLA WALLA, MILTON-FREEWATER, TRI-CITIES, AND YAKIMA
REACHING HIGH TEMPERATURES OF 100 DEGREES OR GREATER ON
TUESDAY. LITTLE OVERNIGHT RELIEF IS ALSO EXPECTED WITH MORNING
LOWS OF AROUND 60 DEGREES. THESE HIGH AND LOW TEMPERATURES
ALLOW FOR HEAT CONCERNS TO ARISE, AS MODERATE (2 OUR OF 4)
HEATRISK IS PRESENT ACROSS THE DALLES, YAKIMA, AND ELLENSBURG ON
MONDAY, EXTENDING ACROSS THE LOWER COLUMBIA BASIN, BLUE
MOUNTAIN FOOTHILLS, JOHN DAY BASIN, AND THE YAKIMA/KITTITAS
VALLEYS ON TUESDAY. THE MODERATE HEATRISK CATEGORY PRIMARILY
RELATES TO CONCERN FOR MEMBERS OF HEAT-SENSITIVE GROUPS, BUT IT
ALSO EXTENDS TO THE GENERAL PUBLIC WHO ARE EXPOSED TO THE SUN
FOR LONGER PERIODS OF TIME. MAKE SURE TO STAY HYDRATED AND
REDUCE TIME OR MOVE EVENTS DURING PEAK AFTERNOON HOURS.
THE EARLIER MENTIONED PASSING SHORTWAVE ACROSS CENTRAL AND
EASTERN OREGON TODAY, WILL BE CLOSELY FOLLOWED BY A DEVELOPING
TRANSIENT RIDGE AND ENHANCED BY AN APPROACHING UPPER LEVEL
SHORTWAVE FROM THE NORTHWEST. THESE SYNOPTIC FEATURES WILL
PROMOTE INSTABILITY ACROSS THE REGION, ESPECIALLY THROUGH
CENTRAL AND EASTERN OREGON DURING THE AFTERNOON AND EARLY
EVENING. HREF MEMBERS SUGGEST CAPE VALUES OF 500-600 J/KG WITH
LAPSE RATES OF 7-7.2C/KM, WHICH DOES SUGGEST THUNDERSTORM
POTENTIAL ACROSS DESCHUTES, CROOK, GRANT, AND WHEELER COUNTIES -
WITH HIGHEST POTENTIAL CENTERED OVER DESCHUTES COUNTY. THE
PRIMARY LIMITING FACTOR RELATED TO THESE STORMS STAYING SUB-
SEVERE IS THE LACK OF LOW LEVEL WIND SHEAR, WHICH IS ONLY 10-18
KTS. AS A RESULT, STORM MOTION SHOULD BE RATHER SLOW AND
UPDRAFTS SHOULD BE LIMITED IN DEVELOPMENT. THIS DOES STILL
RELATE TO STORM THREATS THAT INCLUDE BREEZY OUTFLOW WINDS,
FREQUENT LIGHTNING, AND SMALL HAIL. THE PASSING UPPER LEVEL
TROUGH TO OUR NORTH ON TUESDAY WILL AGAIN ALLOW FOR ISOLATED
THUNDERSTORM CHANCES TO EXTEND ACROSS THE BLUE MOUNTAINS AND
CENTRAL/EASTERN OREGON THROUGH THE AFTERNOON AND EARLY EVENING.
THE HREF SUGGESTS SLIGHTLY BETTER CONVECTIVE PARAMETERS ON
TUESDAY, WITH CAPE VALUES OF 600-800 J/KG, LAPSE RATES OF
7.1-7.4C/KM, AND LOW LEVEL SHEAR OF 20-30KTS. THERE IS SOME
UNCERTAINTY IN HOW STRONG THE TRANSIENT RIDGE IS ABLE TO BUILD
BETWEEN TODAY'S SHORTWAVE AND TUESDAY'S TROUGH PASSAGE, AND HOW
EFFICIENT THE TROUGH WILL BE IN EXTENDING SOUTH FROM ITS PARENT
LOW LOCATED IN NORTHERN/CENTRAL BRITISH COLUMBIA. THESE
INCONSISTENCIES ARE PREVALENT WITH OBSERVING THE DIFFERENCES IN
TROUGH/LOW STRENGTH BETWEEN THE ECMWF AI ENSEMBLES AND THE GFS
AI ENSEMBLES. THIS WILL NEED TO BE FURTHER ANALYZED AS THE EVENT
NEARS, BUT AT THIS TIME SEVERE STORMS ARE NOT ANTICIPATED (70%
CONFIDENCE).
THE PASSING TROUGH ON TUESDAY, COUPLED WITH THE TRANSIENT
RIDGE, WILL ALLOW A PRESSURE GRADIENT TO DEVELOP ACROSS THE
LOWER COLUMBIA BASIN, KITTITAS VALLEY, AND THE WARM SPRINGS AREA
PROMOTING FIRE WEATHER CONCERNS RELATED TO STRONG WINDS AND LOW
RELATIVE HUMIDITIES. THUS, A FIRE WEATHER WATCH HAS BEEN ISSUED
BETWEEN 11 AM AND 10 PM ON TUESDAY ACROSS THESE AREAS.
ZONAL, WEST FLOW ALOFT EXPECTED WEDNESDAY AND THURSDAY, RETURNS
HIGH TEMPERATURES TO NEAR NORMAL VALUES. ANOTHER UPPER LEVEL
TROUGH WILL DEEPEN OFFSHORE LATE IN THE WEEK TO SHIFT WEST FLOW
TO MORE FROM THE SOUTHWEST. THIS WILL RELATE TO A SLIGHT
INCREASE IN HIGH TEMPERATURES, BUT MORE IMPORTANTLY WILL BRING
BREEZY WINDS ACROSS THE LOWER COLUMBIA BASIN. WIND HIGHLIGHTS
ARE NOT CURRENTLY EXPECTED, BUT FIRE WEATHER CONCERNS MAY ARISE
FRIDAY ONWARD AS DRY CONDITIONS SINCE TUESDAY WILL KEEP
AFTERNOON HUMIDITIES BELOW 25%. 75
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
VFR CONDITIONS CURRENTLY PREVAIL THROUGH THE ENTIRE FORECASTING
PERIOD. THERE IS SMALL CHANCES (5-15%) THAT TEMPORARY SUB-VFR
CONDITIONS WITH ERRATIC WIND GUSTS DEVELOP WITH THUNDERSTORMS IN
BDN AND RDM AT 20-24Z. OTHERWISE, LIGHT WINDS THROUGHOUT WITH
HIGH CEILINGS EXPECTED FOR ALL TAF SITES.
FIRE WEATHER
PRIMARY FIRE WEATHER CONCERNS ON TUESDAY ACROSS THE LOWER
COLUMBIA BASIN, KITTITAS VALLEY, AND THE WARM SPRINGS AREA AS A
PASSING UPPER LEVEL SHORTWAVE WILL DEVELOP A PRESSURE GRADIENT
ACROSS THE REGION. HIGH TEMPERATURES WILL ALSO COINCIDE WITH
THIS PRESSURE GRADIENT AS AFTERNOON VALUES WILL APPROACH TRIPLE
DIGITS AND HUMIDITIES IN THE MID-TEENS. TUESDAY MORNING
OVERNIGHT HUMIDITY RECOVERIES WILL ALSO BE MODERATE (30-55%) AS
WEST WINDS OF UP TO 20 MPH AND GUSTS UP TO 30 MPH ARE EXPECTED.
THE NBM HIGHLIGHTS A 50-75% OF RED FLAG CONDITIONS BEING MET
ACROSS THE AFOREMENTIONED AREAS TUESDAY AFTERNOON AND EVENING.
THUS, A FIRE WEATHER WATCH HAS BEEN ISSUED FOR FIRE WEATHER
ZONES: WA690, WA691, OR691, AND OR703 FOR STRONG WINDS AND
RELATIVE HUMIDITIES AS LOW AS 13%.
IN ADDITION TO THE FIRE WEATHER CONCERN TUESDAY, THERE IS ALSO
CONCERN LATER TODAY RELATED TO DRY THUNDERSTORM POTENTIAL ACROSS
OR 705 AND SOUTHERN OR 700. THE EARLIER MENTIONED SHORTWAVE
PASSING THROUGH CENTRAL AND EASTERN OREGON, COUPLED WITH POOR TO
MODERATE (25-40%) OVERNIGHT HUMIDITY RECOVERIES THIS MORNING,
MAY PROVIDE CONCERN FOR NEW FIRE STARTS DUE TO THE DRY NATURE OF
ANY DEVELOPING THUNDERSTORMS. THE HRRR SUGGESTS THIS AFTERNOON'S
DEWPOINT DEPRESSION AND VERTICAL TEMPERATURE CHANGES AT 850 MB
ARE ABOVE CRITICAL DRY THUNDERSTORM CRITERIA, HOWEVER THE NAM
SUGGESTS MORE MUTED CONCERNS - ESPECIALLY RELATED TO DEWPOINT
DEPRESSIONS IN THE 850MB LEVEL. THIS PARAMETER HIGHLIGHTS HOW
DRY LOWER LEVELS OF THE ATMOSPHERE ARE, WITH A NORMAL THRESHOLD
OF 11C OR ABOVE. A LARGE SPREAD OF BETWEEN 7C AND 21C IS
SUGGESTED BY THE NAM AND HRRR RESPECTIVELY, WITH THE ECWMF AND
GFS ADVERTISING 11C AND 6C. GUIDANCE DOES SUGGEST PRECIPITABLE
WATER AMOUNTS OF 0.80-0.90" OR 140-160% ABOVE NORMAL. THESE
CONDITIONS, ALONG WITH THE SLOW MOVING NATURE OF ANY DEVELOPING
STORM CELLS DUE TO WIND SHEAR OF 10-18 KTS, MAY ALLOWS THESE
AREAS TO ACCUMULATE A WETTING RAIN DUE TO THEIR LONGER RESIDENCE
TIME. THIS WILL BE FURTHER ANALYZED AS GUIDANCE IS UPDATED
LATER THIS MORNING, AS A RED FLAG WARNING MAY BE NECESSARY OVER
OR705 THIS AFTERNOON/EVENING. 75
PRELIMINARY POINT TEMPS/POPS
PDT 89 57 95 58 / 0 0 0 10
ALW 91 62 97 64 / 0 0 0 10
PSC 93 58 99 61 / 0 0 0 10
YKM 95 61 98 59 / 0 0 0 0
HRI 92 59 98 62 / 0 0 0 20
ELN 92 59 92 56 / 0 0 0 0
RDM 89 53 91 50 / 10 10 10 10
LGD 87 56 94 58 / 10 0 20 10
GCD 87 53 94 54 / 60 10 10 10
DLS 96 64 93 61 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...FIRE WEATHER WATCH FROM TUESDAY MORNING THROUGH TUESDAY
EVENING FOR WAZ690-691.
OR...FIRE WEATHER WATCH FROM TUESDAY MORNING THROUGH TUESDAY
EVENING FOR ORZ691-703.
DISCUSSION...75
AVIATION...95
FIRE WEATHER...75
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