439
FXUS02 KWBC 311850
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
250 PM EDT THU OCT 31 2024
VALID 12Z SUN NOV 3 2024 - 12Z THU NOV 7 2024
***HEAVY RAIN AND SEVERE WEATHER EXPECTED ACROSS PORTIONS OF THE
SOUTHERN AND CENTRAL PLAINS GOING INTO EARLY NEXT WEEK***
..GENERAL OVERVIEW
THE FIRST HALF OF THE EXTENDED FORECAST PERIOD IS FORECAST TO BE
QUITE ACTIVE ACROSS THE SOUTH-CENTRAL U.S., WITH STRONG RETURN GULF
OF MEXICO INFLOW INTO A DEEPENING MOISTURE CHANNEL BETWEEN A
SOUTHEAST U.S. UPPER RIDGE AND THE SLOW APPROACH OF AN AMPLIFIED
UPPER TROUGH AND FRONT FROM THE WEST. THE UPPER TROUGH ENERGY IS
EXPECTED TO DIG SHARPLY ACROSS THE WESTERN U.S. THIS WEEKEND,
YIELDING HEAVY RAINFALL AND POTENTIAL SEVERE WEATHER ACROSS THE
PLAINS, AND HIGH ELEVATION SNOWS FROM THE NORTHWEST U.S. TO THE
CENTRAL/NORTHERN ROCKIES. WARM WEATHER WILL CONTINUE TO MAKE
HEADLINES FOR THE EASTERN U.S. WITH ADDITIONAL RECORD HIGHS
POSSIBLE.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 12Z MODEL GUIDANCE SUITE FEATURES GOOD OVERALL AGREEMENT
ACROSS THE CONTINENTAL U.S. GOING INTO SUNDAY AND EARLY NEXT WEEK,
GIVEN A MORE AMPLIFIED UPPER FLOW PATTERN EVOLVING WITH A DEEP
WESTERN U.S. TROUGH AND A BUILDING RIDGE AXIS EAST OF THE
MISSISSIPPI RIVER. THIS WILL RESULT IN A PRONOUNCED TEMPERATURE
DICHOTOMY ACROSS THE COUNTRY, WITH HIGHS RUNNING UP TO 20 DEGREES
ABOVE EARLY NOVEMBER AVERAGES ACROSS THE OHIO VALLEY EARLY NEXT
WEEK, AND 15 DEGREES BELOW AVERAGE FOR PORTIONS OF THE
INTERMOUNTAIN WEST. GOING INTO THE MIDDLE OF THE WEEK, THE MODELS
HAVE CONVERGED ON A MORE AGREEABLE SOLUTION WITH A LARGE POSITIVELY
TILTED TROUGH FROM THE ROCKIES TO THE NORTH-CENTRAL U.S., WITH SOME
DIFFERENCES ACROSS SOUTHERN CANADA AND THE GREAT LAKES REGION. THE
GUIDANCE STILL AGREES QUITE WELL ON THE ANOMALOUS UPPER RIDGE JUST
OFF THE SOUTHEAST U.S. COAST. THE ENSEMBLE MEANS WERE GRADUALLY
INCREASED TO ABOUT 40% BY NEXT WEDNESDAY/THURSDAY.
..WEATHER/HAZARDS HIGHLIGHTS
WITH A NEARLY CONTINUOUS PLUME OF DEEP-LAYERED RETURN FLOW FROM
THE GULF BETWEEN THE AMPLIFYING WESTERN TROUGH AND THE RIDGE
ANCHORED OVER THE SOUTHEAST U.S., A MULTI-DAY HEAVY RAIN EVENT
IS EXPECTED FROM THE SOUTHERN PLAINS TO THE SOUTHERN GREAT LAKES.
THIS ACTIVITY IS EXPECTED TO EXPAND AND FOCUS ALONG A SOUTHWEST TO
NORTHEAST ORIENTED AXIS AHEAD OF ADDITIONAL FRONTAL BOUNDARIES
THIS WEEKEND AND INTO EARLY NEXT WEEK AS ROBUST UPPER TROUGH/CLOSED
LOW ENERGY DIGS UPSTREAM ACROSS THE WESTERN U.S. TO RE-AMPLIFY THE
FLOW OVER THE LOWER 48 AND VICINITY. MULTIPLE DAYS OF DEEP SOUTHERLY,
MOIST GULF INFLOW LOOK TO INCREASE THE CHANCES OF MORE WIDESPREAD
AND HEAVY RAINFALL WITH INCREASING FLOODING CONCERNS DESPITE THE
RECENT DROUGHT CONDITIONS. THIS INCLUDES THE RISK OF REPEAT AND
TRAINING CONVECTION WITH LOCALLY HIGH RAINFALL RATES IN EXCESS OF
AN INCH PER HOUR, ALONG WITH FAVORABLE INSTABILITY AND SHEAR
PARAMETERS IN PLACE. STRONG TO SEVERE THUNDERSTORMS ARE ALSO LIKELY
ACROSS SOME OF THESE SAME AREAS FOR SUNDAY AND INTO MONDAY.
AFTER CONSULTATION WITH THE AFFECTED WEATHER FORECAST OFFICES, AND
TAKING INTO ACCOUNT THE HEAVY RAINFALL OVER THE SAME GENERAL AREAS
IN THE SHORT RANGE FORECAST PERIOD, A MODERATE RISK IS NOW PLANNED
ACROSS PORTIONS OF NORTHEAST OKLAHOMA AND INTO SOUTHEAST KANSAS
FOR THE DAY 4 EXCESSIVE RAINFALL OUTLOOK (12Z SUNDAY-12Z MONDAY),
AND THE SURROUNDING SLIGHT RISK AREA WILL BE A LITTLE LARGER
COMPARED TO THE PREVIOUS ISSUANCE. FOR THE DAY 5 PERIOD PERIOD, THE
SLIGHT RISK AREA FROM OVERNIGHT HAS BEEN ADJUSTED SLIGHTLY TO THE
EAST TO ACCOUNT FOR A LITTLE FASTER TREND IN THE LATEST GUIDANCE
DURING THIS TIME.
FOR THE PACIFIC NORTHWEST, TERRAIN ENHANCED PRECIPITATION CAN BE
EXPECTED, ALONG WITH HIGHER ELEVATION SNOW REACHING THE
INTERMOUNTAIN WEST/ROCKIES. COOLER TEMPERATURES WILL FILTER IN
ACROSS THE WEST THAT WILL HELP SPREAD RAIN INTO THE SOUTHWEST AND
INTO THE SOUTH-CENTRAL GREAT BASIN AND ROCKIES INTO EARLY NEXT
WEEK. MEANWHILE, ADDITIONAL PACIFIC SYSTEM ENERGY UPSTREAM MAY ALSO
BRING ANOTHER ROUND OF MODERATE PRECIPITATION BACK INTO THE
NORTHWEST.
CAMPBELL/HAMRICK
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.PHPSCHICHTEL/HAMRICK
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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