848
FXUS66 KPDT 170527
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1027 PM PDT THU APR 16 2026
KEY MESSAGES
- FREEZING MORNING LOWS FRIDAY AND NEAR-FREEZING MORNING LOWS
SATURDAY IN THE LOWLANDS
- WARMER, DRIER THIS WEEKEND
- UNCERTAINTY IN PATTERN DETAILS MONDAY AND BEYOND
DISCUSSION
SATELLITE SHOWS SCATTERED TO NUMEROUS CU ACROSS THE FORECAST
AREA BENEATH A COOL, WEAKLY UNSTABLE NORTHWESTERLY FLOW ALOFT.
RADAR SHOWS SNOW SHOWERS HAVE DEVELOPED THIS AFTERNOON, MAINLY
OVER THE BLUE MOUNTAINS WHERE MID-LEVEL LAPSE RATES OF 8-9 C/KM
ARE PRESENT PER SPC'S RAP-BASED MESOSCALE ANALYSIS.
BREEZY TO LOCALLY WINDY WESTERLY WINDS ARE PRESENT IN THE
COLUMBIA BASIN AND VICINITY DUE TO SOMEWHAT TIGHT CROSS-CASCADE
PRESSURE GRADIENTS (7-9 HPA DIFFERENCE BETWEEN PDX AND GEG) AND
A WELL-MIXED BOUNDARY LAYER. SHOWERS AND BREEZY WINDS SHOULD
TAPER OFF THIS EVENING AND OVERNIGHT AS DAYTIME CONVECTION WANES
AND THE DEEP UPPER-LEVEL LOW CONTINUES TO TRACK EAST OF THE
REGION.
AN UPPER-LEVEL RIDGE WILL ALMOST CERTAINLY (99 PERCENT
CONFIDENCE) BUILD INTO THE PACIFIC NORTHWEST FRIDAY INTO THE
WEEKEND, YIELDING LIGHTER WINDS AND MOSTLY DRY CONDITIONS. THE
MAIN HEADLINE-WORTHY CONSIDERATION FOR FRIDAY REMAINS NEAR- TO
SUB-FREEZING TEMPERATURES FOR THE LOWLANDS, AND FREEZE WARNINGS
HAVE BEEN ISSUED. THIS SET-UP LOOKS MORE FAVORABLE FOR MOSTLY
CLEAR TO CLEAR SKIES AND LIGHTER WINDS RELATIVE TO THIS
MORNING, SO RADIATIONAL COOLING SHOULD BE MORE EFFICIENT.
MOREOVER, AFTERNOON SURFACE DEW POINTS ARE IN THE UPPER TEENS
AND TWENTIES ACROSS THE REGION, AND RAOBS SHOW LOW PWATS OF
0.15-0.40 OF AN INCH; BOTH OF THESE ARE GOOD INDICATORS OF
EFFICIENT RADIATIONAL COOLING WHERE WINDS SLACKEN.
UNCERTAINTY IN THE 500-HPA PATTERN GROWS THROUGH THE WEEKEND,
BUT SOME FLAVOR OF A 500-HPA CLOSED LOW IS ADVERTISED BY ALL
ENSEMBLE CLUSTERS TO BE IN THE VICINITY OF THE PACIFIC NORTHWEST
SATURDAY THROUGH THE REMAINDER OF THE PERIOD. MOST MEMBERS KEEP
THE LOW OFFSHORE THROUGH EARLY NEXT WEEK, A SOLUTION WHICH WOULD
RESULT IN ABOVE-NORMAL TEMPERATURES ACROSS THE INLAND NORTHWEST
DOWN INTO CENTRAL OREGON.
PRECIPITATION CHANCES INCREASE SUNDAY FOR THE CASCADES, BUT
EXPAND EASTWARD MONDAY THROUGH WEDNESDAY IN WHAT IS LOOKING
LIKE A POTENTIAL CONVECTIVE SET-UP FOR PORTIONS OF THE FORECAST
AREA. ENSEMBLE CLUSTERS SHOW ~45 PERCENT OF MEMBERS ARE
ADVERTISING THE UPPER LOW JUST OFF THE OR/CA COAST, A LOCATION
THAT IS FAVORABLE FOR CONVECTION. ANOTHER DEFORMATION BAND
SIMILAR TO WHAT WAS OBSERVED EARLIER IN THE WEEK IS ALSO LOOKING
LIKE A POTENTIAL OUTCOME TUESDAY THROUGH WEDNESDAY SHOULD THE
CLOSED LOW TRACK INLAND ALONG A SUPPORTIVE PATH, BUT CONFIDENCE
IN THAT SOLUTION IS CURRENTLY LOW (10-20 PERCENT).
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
VFR CONDITIONS WILL PERSIST THROUGH THE FORECAST PERIOD. WINDS
HAVE BEGUN TO SETTLE ACROSS ALL SITES EXCEPT ALW/PDT WHICH IS
STILL SEEING SUSTAINED WINDS OF UP TO 10-15 KTS RESPECTIVELY.
WINDS WILL CALM AT PDT AFTER 12Z AND ALW AFTER 18Z. WINDS WILL
REMAIN AT OR BELOW 6 KTS ACROSS THE REMAINING SITES. 90
PRELIMINARY POINT TEMPS/POPS
PDT 30 57 35 69 / 0 0 0 0
ALW 34 58 38 68 / 0 0 0 0
PSC 33 63 36 72 / 0 0 0 0
YKM 30 61 37 67 / 0 0 0 0
HRI 32 61 35 71 / 0 0 0 0
ELN 29 56 33 63 / 0 0 0 0
RDM 20 58 28 70 / 0 0 0 0
LGD 27 54 33 61 / 0 0 0 0
GCD 23 55 32 64 / 0 0 0 0
DLS 34 64 40 71 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...FREEZE WARNING UNTIL 9 AM PDT FRIDAY FOR WAZ026>029.
OR...FREEZE WARNING UNTIL 9 AM PDT FRIDAY FOR ORZ044-507.
DISCUSSION...86
AVIATION...90
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