174
FXUS02 KWBC 261825
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
225 PM EDT SAT OCT 26 2024
VALID 12Z TUE OCT 29 2024 - 12Z SAT NOV 02 2024
...HEAVY SNOW AND WIND THREAT FOR THE NORTH-CENTRAL ROCKIES AND
NEARBY HIGH PLAINS TUESDAY-WEDNESDAY...
..HEAVY RAIN THREAT FOR THE PLAINS/MIDWEST MID-LATER NEXT WEEK
..GENERAL OVERVIEW
AN AMPLIFIED UPPER-LEVEL TROUGH ABOUT TO DIG INTO THE PACIFIC
NORTHWEST WILL SPREAD HIGHLY UNSETTLED WEATHER THROUGH MUCH OF THE
WESTERN U.S. EARLY NEXT WEEK TO INCLUDE POTENTIALLY HEAVY HIGH-
ELEVATION SNOW, GUSTY WINDS AND COLDER TEMPERATURES. THIS TROUGH
WILL THEN PUSH EASTWARD AGAINST A WARM AND EXPANDING UPPER RIDGE
OVER THE CENTRAL TO EASTERN U.S., RESULTING IN A WAVY SHARP FRONT
ACROSS THE MID-SECTION OF THE COUNTRY WHERE A MODERATELY HEAVY RAIN
EVENT IS FORECAST FROM THE PLAINS THROUGH THE MISSISSIPPI VALLEY
AND MIDWEST FOR THE LATTER HALF OF NEXT WEEK. THE TRAILING PORTION
OF THE FRONT IS FORECAST TO STALL, FOLLOWED BY A RESURGENCE OF
MODERATE/HEAVY RAIN OVER THE SOUTHERN PLAINS LATE NEXT WEEK AND
INTO THE WEEKEND.
..GUIDANCE/PREDICTABILITY ASSESSMENT
FORECAST SPREAD SEEMS LOWER THAN NORMAL TUE/WED AND A GUIDANCE
BLEND SEEMS TO OFFER A SOLID FORECAST BASE. THE MODEL SPREAD ON THE
TIMING OF A LOW PRESSURE WAVE DEVELOPING ALONG THE FRONT OVER THE
CENTRAL PLAINS ON DAY 4 REMAINS A NOTICEABLE ISSUE BY DAY 5 WHEN
THE WAVE IS FORESCAST TO HEAD TOWARD THE GREAT LAKES. THE GFS
REMAINS THE FASTEST GUIDANCE WHILE THE DETERMINISTIC ECMWF, CMC,
AND UKMET ALL DEPICT A SLOWER AND MORE AMPLIFIED WAVE. ON THE OTHER
HAND, BOTH ECMWF AND CMC HAVE SPED UP THE EASTWARD PROGRESSION OF
THE WAVE FROM PREVIOUS RUNS. MEANWHILE, THE ENSEMBLE MEANS FROM THE
GEFS, EC, AND CMC ALL SHOW VERY GOOD AGREEMENT ON PLACING THE WAVE
NEAR/OVER THE CENTRAL GREAT LAKES BY THURSDAY MORNING, WHICH IS
FASTER THAN THE SLOW GUIDANCE FROM THE EC, CMC AND UKMET. THE WPC
BLEND ADOPTS A SOLUTION THAT IS VERY CLOSE TO THE CONSENSUS OF THE
ENSEMBLE MEANS FOR THIS LOW PRESSURE WAVE.
IN ADDITION, THERE HAS BEEN A GRADUAL TREND FOR THE MODELS TO
PLACE THE PRE-FRONTAL MODERATE TO HEAVY RAINFALL FARTHER SOUTH
TOWARD THE SOUTHERN PLAINS DAYS 4 TO 5. THE WPC BLEND FOR THE
MEDIUM-RANGE FORECAST PERIOD IS BASED ON 40% FROM THE 00Z EC/EC
MEAN, 40% FROM THE 06Z GFS/GEFS, AND 20% FROM THE 00Z CMC/CMC MEAN,
BUT WITH THE 06Z GFS MINIMIZED ON DAY 5.
..WEATHER/HAZARDS HIGHLIGHTS
GUIDANCE CONTINUES TO SHOW EXCELLENT AGREEMENT THAT A COLD FRONT
ASSOCIATED WITH A DIGGING UPPER LEVEL TROUGH FROM THE PACIFIC WILL
BE STEADILY MOVING THROUGH THE WESTERN U.S. EARLY NEXT WEEK.
PERIODS OF RAIN, HIGH-ELEVATION SNOW, WINDY AND COLDER CONDITIONS
ARE EXPECTED TO OVERSPREAD MUCH OF THE REGION WITH FRONTAL PASSAGE.
LOCALLY HIGH WINDS COULD IMPACT PORTIONS OF THE SOUTHERN ROCKIES
AND SOUTHERN HIGH PLAINS AS THE COLDER AIRMASS DIGS INTO THE
REGION. THIS MAY ALSO LEAD TO THE ONSET OF FROST/FREEZE FOR SOME OF
THESE AREAS FOR THE FIRST TIME THIS SEASON.
MODEST CYCLOGENESIS 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 ACROSS THE EASTERN AND SOUTHERN
U.S. SNOW WILL LINGER OVER THE NORTHERN TO CENTRAL ROCKIES AND
INTO THE NORTHERN HIGH PLAINS BEHIND A LOW PRESSURE WAVE. THE SNOW
COULD BE HEAVY FOR THE HIGHER ELEVATIONS OF WYOMING TUESDAY INTO
WEDNESDAY GIVEN UPPER DIVERGENCE AND LOWER LEVEL UPSLOPE FLOW.
ACCUMULATING SNOW COULD SPILL INTO THE NEARBY HIGH PLAINS AND BLACK
HILLS AS WELL. AHEAD OF THE SHARPENING FRONT, A LONG FETCH OF
RETURN FLOW FROM THE GULF OF MEXICO APPEARS TO INITIATE AND SUPPORT
A THREAT OF HEAVY RAIN FROM THE CENTRAL/SOUTHERN PLAINS THROUGH
THE MISSISSIPPI VALLEY AND INTO THE MIDWEST WITH EMBEDDED
THUNDERSTORMS MIDWEEK. THE TRAILING PORTION OF THE FRONT IS
FORECAST TO STALL OVER THE SOUTHERN PLAINS WHERE MODERATE TO HEAVY
RAINFALL COULD LINGER AND THEN EXPAND NORTHEASTWARD BY NEXT WEEKEND.
THE WPC DAY5/WED-THU EXCESSIVE RAINFALL OUTLOOK INTRODUCED A
MARGINAL RISK AREA GIVEN POTENTIAL FOR TRAINING AND FAVORABLE UPPER
TROUGH AND RIGHT ENTRANCE REGION JET DYNAMICS. IN THE MEANTIME,
PRECIPITATION ASSOCIATED WITH THE NEXT PACIFIC SYSTEM AND LONG-
FETCH MOISTURE IS FORECAST TO RE-FOCUS MODERATE PRECIPITATION INTO
THE PACIFIC NORTHWEST THROUGH LATTER NEXT WEEK, WITH HIGH-
ELEVATION SNOW REACHING INTO THE NORTHERN ROCKIES.
THE DIGGING TROUGH IN THE WEST WILL USHER IN AND SUSTAIN COLDER
THAN NORMAL TEMPERATURES FOR PRETTY MUCH THE ENTIRE WESTERN U.S.
THROUGH LATE NEXT WEEK. IN CONTRAST, HIGH TEMPERATURES REACHING
INTO THE UPPER 80S TO LOWER 90S WILL CHALLENGE SOME DAILY RECORDS
ACROSS THE SOUTHERN PLAINS TO THE MID-SOUTH EARLY NEXT WEEK. THE
EXPANDING UPPER RIDGE TOGETHER WITH A LONG FETCH OF STRONG AND
GUSTY SOUTHERLY WINDS AT THE SURFACE WILL SEND THE WARMTH WELL TO
THE NORTH AND EAST, REACHING INTO THE GREAT LAKES AND EVENTUALLY
NEW ENGLAND THROUGH THE MIDDLE AND LATE NEXT WEEK. HIGH
TEMPERATURES REACHING WELL UP INTO THE 70S TO NEAR 80 DEGREES
WILL BE ENOUGH TO SET SOME NEW DAILY RECORD HIGH TEMPERATURES FROM
THE GREAT LAKES TO NEW ENGLAND WEDNESDAY AND THURSDAY. TEMPERATURES
ACROSS THE COUNTRY APPEAR TO MODERATE BY NEXT WEEKEND AS THE UPPER
TROUGHING WEAKENS IN THE WEST WHILE A LARGE HIGH PRESSURE SYSTEM
BUILDS IN THE EASTERN U.S. WITH GULF MOISTURE RETURNING ACROSS THE
SOUTHERN PLAINS.
KONG/SCHICHTEL
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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