399
FXUS02 KWBC 230700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT WED OCT 23 2024
VALID 12Z SAT OCT 26 2024 - 12Z WED OCT 30 2024
..GENERAL OVERVIEW
PREDOMINANTLY ZONAL FLOW ACROSS THE CONUS AT THE BEGINNING OF THE
PERIOD (THIS WEEKEND) WILL GIVE WAY TO A MORE AMPLIFIED PATTERN
TOWARD THE END. A CLOSED UPPER LOW OVER THE GULF OF ALASKA WILL
FILL AND DIG INTO THE WEST COAST OF THE CONUS THIS WEEKEND. THIS
SYSTEM WILL BRING COOL TEMPERATURES, RAIN AND SNOW TO THE
NORTHWEST U.S. THROUGH EARLY NEXT WEEK BEFORE SHIFTING THE FOCUS
FOR HEAVY RAINFALL AND THUNDERSTORMS TO THE CENTRAL U.S. MID-WEEK.
A PRONOUNCED RIDGE DOWNSTREAM OF THE WESTERN SYSTEM WILL GENERATE
ABOVE AVERAGE TEMPERATURES ACROSS THE PLAINS AND MISSISSIPPI VALLEY
BEGINNING NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS ARE IN REASONABLE AGREEMENT REGARDING THE OVERALL SYNOPTIC
PATTERN ACROSS THE CONUS DURING THE MEDIUM RANGE PERIOD. THE
DETERMINISTIC EURO AND GFS GUIDANCE HAVE TRENDED SLOWER WITH THE
DIGGING EAST PACIFIC TROUGH NEXT WEEK, WHILE THE ENSEMBLE MEANS
STILL HAVE SOME TIMING SPREAD. THERE'S PRETTY GOOD CLUSTERING OF
THE ENSEMBLES ON THE DEPTH OF THE TROUGH.
ON DAYS 3 AND 4 A GENERAL MODEL BLEND CONSISTING OF EQUAL PARTS 12Z
ECMWF/CMC/UKMET AND 18Z GFS WERE UTILIZED DUE TO THE PREDOMINANTALY
ZONAL FLOW ACROSS THE LOWER 48 AND LARGE RIDGE OVER THE SOUTHERN
TIER STATES/NORTHERN MEXICO. THE 12Z ECE/CMCE AND 18Z GEFS WERE
INTRODUCED TO THE BLEND ON DAY 5 AND CONTINUED THROUGH THE END OF
THE PERIOD TO MITIGATE SOME DETERMINISTIC SOLUTIONS THAT SIGNAL THE
FORMATION OF A CLOSED MID-LEVEL LOW OVER THE FOUR CORNERS REGION BY
MID-WEEK. THERE'S SOME SIGNAL FOR ANOTHER SPLIT FLOW PATTERN ACROSS
OVER THE CENTRAL U.S. ON DAY 7.
..WEATHER/HAZARDS HIGHLIGHTS
A COLD FRONT, ASSOCIATED WITH A CLOSED MID-LEVEL LOW OVER THE GULF
OF ALASKA, WILL FOCUS RAIN AND HIGH ELEVATION MOUNTAIN SNOW
SHOWERS OVER MUCH OF THE PACIFIC NORTHWEST AND NORTHERN ROCKIES
THIS WEEKEND. SNOW SHOWERS WILL REMAIN CONFINED TO THE NORTHERN
CASCADES AND OLYMPIC MOUNTAINS BEFORE EXPANDING INTO THE SOUTHERN
CASCADES AND NORTHERN ROCKIES ON SUNDAY, THE NORTHERN SIERRA AND
YELLOWSTONE/ABSAROKAS ON MONDAY AND COLORADO ROCKIES BY TUESDAY.
CYCLOGENESIS IS LIKELY TO OCCUR ON THE LEE SIDE OF THE ROCKIES AND
INTERACT WITH MOISTURE FROM THE GULF OF MEXICO OVER THE
LOWER MISSOURI VALEY AND UPPER MIDWEST BEGINNING ON TUESDAY.
SHOWERS AND THUNDERSTORMS MAY PROLIFERATE ACROSS THOSE REGIONS AS
A RESULT BUT THERE'S STILL PLENTY OF SPREAD IN THE GUIDANCE.
KEBEDE
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC MEDIUM
RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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