008
FXUS02 KWBC 241859
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 PM EDT THU OCT 24 2024
VALID 12Z SUN OCT 27 2024 - 12Z THU OCT 31 2024
..GENERAL OVERVIEW
AN UPPER-LEVEL TROUGH DIGGING INTO THE PACIFIC NORTHWEST THIS
WEEKEND WILL SPREAD UNSETTLED WEATHER ACROSS MUCH OF THE WESTERN
U.S. EARLY NEXT WEEK WITH HIGH-ELEVATION SNOW, GUSTY WINDS AND
COLDER TEMPERATURES. THIS TROUGH WILL THEN PUSH EASTWARD AGAINST AN
EXPANSIVE WARM HIGH PRESSURE SYSTEM ANCHORED OVER THE EASTERN
U.S., RESULTING IN A WAVY SHARP FRONT ACROSS THE MID-SECTION OF
THE COUNTRY WHERE A MODERATE TO HEAVY RAIN EVENT APPEARS TO EMERGE
ACROSS THE MID-MISSISSIPPI VALLEY TO THE MIDWEST BY MIDWEEK NEXT
WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE MAINTAINS FAIRLY GOOD AGREEMENT WITH THE OVERALL
SYNOPTIC EVOLUTION ACROSS THE MAINLAND U.S. THROUGH THE MEDIUM-
RANGE PERIOD. THE DIGGING TROUGH OVER THE WESTERN U.S. EARLY NEXT
WEEK IS FORECAST TO ATTAIN MAXIMUM AMPLITUDE BY ABOUT TUESDAY WHILE
ON THE VERGE OF SPLITTING INTO A SOUTHERN STREAM UPPER LOW. THE
CANADIAN MODEL IS MOST PRONOUNCED WITH THIS SCENARIO WHILE ALL
OTHER MODELS SHOW A DECENT AMOUNT OF TROUGH SPLITTING, BEFORE THE
ENTIRE TROUGH LIFTS AND HEADS EASTWARD INTO THE MID-SECTION OF THE
COUNTRY BY MIDWEEK. THERE IS MORE NOTICEABLE MODEL SPREAD ON HOW
FAST THE TROUGH WILL LIFT NORTHEAST TOWARD THE UPPER MIDWEST OR
GREAT LAKES BY NEXT THURSDAY.
OTHERWISE, MODELS TODAY GENERALLY SHOW BETTER AGREEMENT ON THE
TIMING OF THE PRECIPITATION MOVING THROUGH THE WESTERN U.S. THROUGH
EARLY NEXT WEEK.
THEREFORE, THE WPC MEDIUM-RANGE FORECASTS WERE BASED ON A GENERAL
MODEL COMPROMISE OF 40% FROM THE 06Z GFS/GEFS, 40% FROM THE 00Z
ECMWF/EC MEAN, AND 20% FROM THE CMC/CMC MEAN. HIGHER WEIGHTINGS
WERE GIVEN TO THE ENSEMBLE MEANS FOR DAY 6 AND 7. THIS BLEND
YIELDED A SOLUTION COMPATIBLE WITH THE PREVIOUS WPC FORECASTS.
..WEATHER/HAZARDS HIGHLIGHTS
THE COLD FRONT ASSOCIATED WITH A DIGGING UPPER-LEVEL TROUGH FROM
THE PACIFIC NORTHWEST WILL CONTINUE TO PENETRATE FURTHER INLAND AS
THE MEDIUM-RANGE PERIOD BEGINS ON SUNDAY. PERIODS OF RAIN, HIGH-
ELEVATION SNOW, WINDY AND COLDER CONDITIONS ARE EXPECTED TO
OVERSPREAD MUCH OF THE REST OF THE WESTERN U.S. THROUGH EARLY NEXT
WEEK BEHIND THE FRONT. HIGH WINDS COULD LOCALLY IMPACT THE LEE OF
THE NORTHERN ROCKIES THIS WEEKEND, AND THEN DOWN INTO THE SOUTHERN
ROCKIES AND SOUTHERN HIGH PLAINS BY ABOUT TUESDAY.
MODEST CYCLOGENESIS ACROSS THE CANADIAN PRAIRIES WILL ADVANCE A
FRONT ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST THROUGH EARLY
NEXT WEEK. THIS FRONT IS FORECAST TO SHARPEN WITH TIME AS IT
CONTINUES TO PUSH AGAINST AN EXPANSIVE HIGH PRESSURE SYSTEM
ANCHORING ACROSS THE EASTERN AND SOUTHERN U.S. SNOW WILL APPEAR TO
LINGER OVER THE NORTHERN TO CENTRAL ROCKIES AND INTO THE NORTHERN
HIGH PLAINS BEHIND A LOW PRESSURE WAVE WHERE ACCUMULATING SNOWFALL
APPEARS LIKELY. AHEAD OF THE SHARPENING FRONT, A LONG FETCH OF
RETURN FLOW FROM THE GULF OF MEXICO COULD LEAD TO A MODERATE TO
HEAVY RAIN EVENT TO EMERGE ACROSS THE MID- MISSISSIPPI VALLEY TO
THE MIDWEST WITH EMBEDDED THUNDERSTORMS BY MIDWEEK NEXT WEEK
ESPECIALLY IF A LOW PRESSURE WAVY IS ABLE TO CONSOLIDATE ALONG THE
FRONT. IN THE MEANTIME, PRECIPITATION ASSOCIATED WITH THE NEXT
PACIFIC SYSTEM IS FORECAST TO MOVE INTO THE PACIFIC NORTHWEST
DURING MIDWEEK NEXT WEEK.
THE DIGGING TROUGH IN THE WEST WILL BE MIRRORED BY A STAUNCH
DOWNSTREAM RIDGE OVER THE SOUTHERN AND CENTRAL U.S. NEXT WEEK. THIS
RIDGE WILL SUPPORT TEMPERATURES BETWEEN 20-30 DEGREES ABOVE AVERAGE
ACROSS THE PLAINS ON MONDAY BEFORE SPREADING INTO THE MISSISSIPPI
VALLEY AND EAST ON TUESDAY, WEDNESDAY AND THURSDAY. THERE'S ALSO A
POTENTIAL FOR WIDESPREAD HIGH TEMPERATURE RECORDS TO BE TIED OR
BROKEN ACROSS FROM ARIZONA TO TEXAS ON SUNDAY FOLLOWED BY
AN EXPANSION INTO THE PLAINS AND UPPER MIDWEST ON MONDAY.
KONG/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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