570
FXUS02 KWBC 021900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT THU NOV 02 2023
VALID 12Z SUN NOV 05 2023 - 12Z THU NOV 09 2023
..SYNOPTIC OVERVIEW
A GENERAL QUASI-ZONAL FLOW ACROSS THE CONTINENTAL U.S. IS EXPECTED
GOING INTO THE WEEKEND, WITH BROAD CYCLONIC FLOW ALOFT OVER
SOUTHERN CANADA AND A SHORTWAVE TROUGH QUICKLY TRAVERSING THE
SOUTHEASTERN U.S. ON SUNDAY. A SHORTWAVE TROUGH THAT DEVELOPS
ACROSS THE PLAINS BY MONDAY WILL SPUR SURFACE CYCLOGENESIS ACROSS
THE UPPER MIDWEST AND GREAT LAKES REGION, AND THEN THE LOW REACHES
NEW ENGLAND ON TUESDAY. UNSETTLED CONDITIONS ARE EXPECTED TO
CONTINUE ACROSS THE PACIFIC NORTHWEST WITH ADDITIONAL ROUNDS OF
RAINFALL AND MOUNTAIN SNOW FOR THE NORTHERN ROCKIES. A CANADIAN
SURFACE HIGH WILL CONTINUE TO GOVERN THE OVERALL WEATHER PATTERN
ACROSS THE NORTHERN PLAINS WITH COLD WEATHER CONTINUING.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE EARLY MEDIUM RANGE PERIOD FEATURES A PROGRESSIVE, MOSTLY ZONAL
FLOW REGIME WITH A SERIES OF SHORTWAVES TRAVERSING THE CONUS, THE
TIMING OF WHICH IMPACTS EXPECTED FRONTAL SYSTEM MOVEMENT AND
SENSIBLE WEATHER DURING THE TIMEFRAME. AN INITIAL SHORTWAVE OVER
THE MISSISSIPPI VALLEY SUNDAY SHOULD QUICKLY DROP SOUTHEAST OVER
THE ATLANTIC AS HIGH PRESSURE REMAINS IN PLACE AT THE SURFACE,
WITH THE MOST RECENT RUNS OF THE GFS (00Z/06Z) MOVING TOWARDS THE
ECMWF WITH THIS TIMING/PLACEMENT/MOVEMENT. THE NEXT UPSTREAM WAVE
DEVELOPS OFF THE LEE OF THE ROCKIES AND PASSES OVER THE PLAINS,
WITH CYCLOGENESIS HELPING TO DEEPEN SURFACE LOW PRESSURE AND
BETTER ORGANIZE A QUASI-STATIONARY FRONTAL SYSTEM OVER THE
MIDWEST. SIMILAR TO THE PRIOR WAVE THE ECMWF HAS BEEN MORE
CONSISTENT RUN-TO-RUN WITH THE TIMING AND STRENGTH OF THIS WAVE,
AND THE MOST RECENT 00Z/06Z GFS RUNS ONCE AGAIN BETTER MATCH THE
00Z ECMWF AFTER VARIABLE SOLUTIONS FROM THE PREVIOUS DAYS
GUIDANCE, PARTICULARLY THE 18Z GFS WHICH HAD DEPICTED ADDITIONAL
ENERGY DROPPING SOUTHWARD FROM CENTRAL CANADA THAT WOULD DISRUPT
THE EXPECTED PATTERN OVER THE CONUS. THE UKMET IS ALSO IN
RELATIVELY GOOD AGREEMENT, WHILE THE CMC REMAINS A WEAKER OUTLIER.
PREDICTABILITY DECREASES BETWEEN THE GFS/ECMWF BY THE MIDDLE OF
THE PERIOD TURNING BACK UPSTREAM OVER THE PLAINS, AS RECENT
SOLUTIONS HAVE BEEN VARYING PHASING BETWEEN WEAK MEAN RIDGING AND
YET ANOTHER SHORTWAVE. ANOTHER PIECE OF UPPER-LEVEL ENERGY ALSO
DROPS SOUTHWARD FROM A DEEPER UPPER-LEVEL TROUGH LINGERING OVER
THE NORTHEASTERN PACIFIC TOWARDS THE WEST COAST DURING THIS
TIMEFRAME AND FEATURES A SIMILAR LACK OF RUN-TO-RUN CONSISTENCY,
PARTICULARLY WITHIN THE GFS BUT ALSO WITH THE ECMWF. EARLIER RUNS
OF THE GFS ARE FASTER THAN THE ECMWF AS THIS ENERGY TRANSLATES
INLAND OVER THE WEST AND TOWARDS THE PLAINS AT THE END OF THE
PERIOD. FORTUNATELY THE MOST RECENT 00Z ECMWF AND 00Z/06Z RUNS AS
WELL AS THE ECENS AND GEFS MEANS ARE MORE IN PHASE WITH THE WAVE
PROGRESSION AND OFFER A REASONABLE COMPOSITE SOLUTION THAT AVOIDS
AVERAGING OUT TOO MANY DETAILS.
THE UPDATED WPC FORECAST BLEND BEGINS WITH A COMBINATION OF THE
00Z ECMWF, 06Z GFS, AND 00Z UKMET, WITH NO CONTRIBUTION FROM THE
CMC GIVEN THE OUTLIER NATURE OF ITS HANDLING OF THE INITIAL SERIES
OF SHORTWAVES. A PORTION OF THE PRIOR WPC FORECAST IS ALSO KEPT TO
AVOID ANY MORE DRASTIC FORECAST CHANGES GIVEN THE HIGHER
VARIABILITY WITH SHORTWAVES IN THE PATTERN. A CONTRIBUTION FROM
THE MEANS IS INCREASED TO ABOUT HALF THE BLEND BY THE END OF THE
PERIOD TO OFFER A CENTERED COMPROMISE ON INCREASING DIFFERENCES IN
THE DETERMINISTIC SOLUTIONS. THE UPDATED FORECAST RESULTS IN A BIT
MORE NORTHWARD TRACK OF THE FRONTAL SYSTEM DEVELOPING IN THE
MIDWEST AS IT SHIFTS TOWARDS THE INTERIOR NORTHEAST/NEW ENGLAND,
WITH THE FRONTAL BOUNDARY ALSO LINGERING FURTHER NORTH AS IT
STRETCHES BACK TO THE SOUTHWEST THROUGH THE OHIO VALLEY AND
EVENTUALLY TEXAS.
..WEATHER/HAZARDS HIGHLIGHTS
MOST OF THE CONTINENTAL U.S. SHOULD NOT SEE ANY SIGNIFICANT
RAINFALL HAZARDS THROUGH THIS COMING WEEKEND. SIMILAR TO THE PAST
FEW DAYS, THE ONLY REGION WHERE THERE WILL BE A RISK OF EXCESSIVE
RAINFALL LEADING TO POTENTIAL FLOODING CONCERNS WILL BE IN THE
COASTAL RANGES OF THE PACIFIC NORTHWEST WITH THE ENHANCED ONSHORE
FLOW THAT WILL CONTINUE INTO THE WEEKEND. A MARGINAL RISK OF
EXCESSIVE RAINFALL HAS BEEN MAINTAINED ON DAY 4 (SUNDAY) FROM
NORTHWESTERN CALIFORNIA TO THE OREGON CASCADES AND COASTAL RANGES
AS FORECAST QPF PEAKS DURING THIS TIMEFRAME. LOCALLY HEAVIER
RAINFALL ON THE WEST FACING SLOPES MAY JUST BE ENOUGH TO CAUSE
SOME MINOR FLOODING CONCERNS, PARTICULARLY FOR URBAN AREAS AND
BURN SCARS, AND ESPECIALLY AS RAINFALL FROM THE PRIOR DAYS BRINGS
WETTER ANTECEDENT CONDITIONS. LOOKING AHEAD TO DAY 5 (MONDAY) AN
ABATEMENT OF THE ONSHORE FLOW AND ASSOCIATED RAINFALL IS EXPECTED,
AND THEREFORE NO RISK AREAS ARE PLANNED. SOME AREAS OF HEAVIER
SNOW LOOK POSSIBLE FOR HIGHER ELEVATIONS OF THE CASCADES
SUNDAY-MONDAY, AND FOR THE NORTHERN ROCKIES BY MONDAY AS WELL AS
PRECIPITATION CHANCES SPREAD FURTHER INLAND. EXPECT PRECIPITATION
FROM THE PACIFIC NORTHWEST INTO THE ROCKIES TO GENERALLY TREND
LIGHTER BY THE MIDDLE OF NEXT WEEK AS UPPER LEVEL RIDGING BRIEFLY
BUILDS BACK IN.
ACROSS THE EASTERN HALF OF THE COUNTRY, A SHORTWAVE/ASSOCIATED
SURFACE FRONTAL SYSTEM IS EXPECTED TO BRING PRECIPITATION CHANCES
FROM THE GREAT LAKES TO THE NORTHEAST STATES THROUGH TUESDAY.
THERE HAS BEEN A NORTHWARD TREND IN THE GUIDANCE WITH RESPECT TO
THE TRACK OF THE SYSTEM KEEPING THE MORE MODERATE AMOUNTS ALONG
THE UPPER GREAT LAKES AND INTERIOR NORTHEAST/NORTHERN NEW ENGLAND.
LOCATIONS NEAR THE CANADIAN BORDER MAY SEE SOME SNOW OR MIXED
PRECIPITATION DURING THE PERIOD WHILE RAIN WILL BE THE PREVAILING
PRECIPITATION TYPE ELSEWHERE. CONFIDENCE REMAINS LOW IN ADDITIONAL
RAIN CHANCES LINGERING BEYOND TUESDAY FROM THE OHIO VALLEY INTO
THE MID-ATLANTIC AND NORTHEAST DUE TO INCREASING GUIDANCE
DIFFERENCES.
TEMPERATURES ARE EXPECTED TO BE PLEASANTLY MILD FOR THIS TIME OF
YEAR ACROSS MUCH OF THE CENTRAL U.S. ON SUNDAY WITH HIGHS
GENERALLY RUNNING 10 TO 15 DEGREES ABOVE EARLY NOVEMBER AVERAGES.
THIS WILL LIKELY REMAIN THE CASE GOING INTO EARLY NEXT WEEK AS
WELL, SHIFTING FROM THE CENTRAL PLAINS INTO THE SOUTHERN PLAINS
AND EVENTUALLY THE SOUTHEAST. AREAS IN THE WEST AND NORTHEAST WILL
LIKELY HAVE A COOLING TREND GOING INTO THE MIDDLE TO END OF NEXT
WEEK, WITH HIGHS RUNNING 5 TO 10 DEGREES BELOW AVERAGE.
PUTNAM/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.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES ARE AT:
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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