133
FXUS02 KWBC 040700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT SAT NOV 04 2023
VALID 12Z TUE NOV 07 2023 - 12Z SAT NOV 11 2023
..OVERVIEW
THE UPPER FLOW PATTERN ACROSS THE CONTIGUOUS U.S. LOOKS TO BE
QUASI-ZONAL AND PROGRESSIVE AS THE MEDIUM RANGE PERIOD BEGINS
TUESDAY. BUT A COUPLE OF SHORTWAVES EMBEDDED WITHIN THE FLOW WILL
BE IMPACTFUL IN SPINNING UP LOW PRESSURE/FRONTAL SYSTEMS,
INCLUDING ONE MOVING THROUGH SOUTHEASTERN CANADA TUESDAY AND
ANOTHER TRACKING FROM THE CENTRAL TO NORTHEASTERN U.S.
WEDNESDAY-THURSDAY, WITH SOME ASSOCIATED PRECIPITATION. A COLD
FRONT WITH THE SECOND LOW PRESSURE SYSTEM SHOULD TRACK
SOUTHEASTWARD ACROSS MUCH OF THE COUNTRY AS THE WEEK PROGRESSES
AND GRADUALLY SUPPRESS WHAT STARTS AS A WIDESPREAD AREA OF ABOVE
AVERAGE TEMPERATURES. MEANWHILE IN THE WEST, PRECIPITATION IS
FORECAST TO LINGER INTO TUESDAY BEFORE A LIKELY BREAK AROUND
MIDWEEK, BUT RAIN/SNOW CHANCES COULD RETURN LATE NEXT WEEK AS THE
OVERALL UPPER PATTERN STARTS TO AMPLIFY, INCLUDING EASTERN PACIFIC
TROUGHING.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE SHORTWAVE MOVING THROUGH THE GREAT LAKES REGION INTO THE
NORTHEASTERN U.S./SOUTHEASTERN CANADA AND THE ASSOCIATED SURFACE
LOW EARLY IN THE PERIOD ARE GENERALLY AGREEABLE IN THE MODEL
GUIDANCE. THE NEXT FEATURE SHOWS MORE DETAIL DIFFERENCES AS IT
TRACKS EASTWARD, WITH UNCERTAIN ENERGIES COMING FROM SOUTHERN AND
NORTHERN STREAM SOURCES AND INTERACTING/COMBINING. THIS DOES HAVE
EFFECTS ON THE SENSIBLE WEATHER INCLUDING HOW FAR SOUTH THE
PRECIPITATION REACHES AND THE TEMPERATURES/PRECIPITATION TYPE IN
THE NORTH-CENTRAL TO NORTHEASTERN CONUS. AT THIS POINT THE ONLY
REAL OUTLIER SEEMED TO BE THE 12Z UKMET, BUT THE OTHER GUIDANCE
SHOWED VARIATIONS BUT GENERALLY REASONABLE SOLUTIONS, SO A BLEND
OF THE DETERMINISTIC AND ENSEMBLE GUIDANCE SEEMED BEST TO HANDLE
THE DIFFERENCES. IT APPEARS THAT REINFORCING ENERGY WILL MAINTAIN
TROUGHING ACROSS THE GREAT LAKES INTO LATE WEEK.
FARTHER WEST, ENERGY AND TROUGHING LOOK TO SPILL SOUTHEAST ACROSS
THE NORTHEASTERN PACIFIC FOR THE LATTER HALF OF THE WEEK, LIKELY
MOVING INTO THE WEST COAST IN SOME FORM LATE WEEK. MODELS DO VARY
FROM RUN TO RUN AND CYCLE TO CYCLE WITH THE CHARACTER OF THE
TROUGHING. EVEN THE GFS RUNS THEMSELVES HAVE VARIED CONSIDERABLY,
FROM A MORE PHASED TROUGH IN THE 12/18Z RUNS TO A CLOSED UPPER LOW
DIVING SOUTH ATOP CALIFORNIA IN THE 00Z RUN, AND OTHER MODELS AND
ENSEMBLE MEMBERS HAVE VARIED SIMILARLY. BUT AT LEAST THE GENERAL
IDEA FOR SOMEWHAT MORE AMPLIFIED FLOW IS THERE BY THE LATE PERIOD.
THE WPC FORECAST WAS BASED ON A DETERMINISTIC MODEL BLEND EARLY IN
THE FORECAST, FAVORING THE 12Z ECMWF, 18Z GFS, AND 12Z CMC WITH A
SMALL PORTION OF THE 12Z UKMET INITIALLY. INTRODUCED AND INCREASED
THE PROPORTION OF THE GEFS AND EC ENSEMBLE MEANS WITH TIME TO
AROUND HALF BY LATE PERIOD TO YIELD COMPROMISE SOLUTIONS FOR THE
DETAILS OF THE PATTERN.
..WEATHER/HAZARDS HIGHLIGHTS
THE WESTERN U.S. CAN EXPECT PRECIPITATION TO CONTINUE INTO
TUESDAY, BUT WITH LESSENING AMOUNTS COMPARED TO THE SHORT RANGE
PERIOD. HIGHER ELEVATIONS LIKE THE CASCADES AND NORTHERN ROCKIES
ARE LIKELY TO SEE SNOW. PRECIPITATION SHOULD TREND MUCH LIGHTER
FOR THE WEST ON WEDNESDAY AS UPPER-LEVEL RIDGING BRIEFLY BUILDS
BACK IN, THOUGH THE CENTRAL ROCKIES COULD HAVE A PERIOD OF SNOW.
CHANCES FOR AT LEAST LIGHT PRECIPITATION MAY INCREASE AGAIN LATE
WEEK FOR THE PACIFIC NORTHWEST, BUT WITH UNCERTAINTY IN TIMING.
FARTHER EAST, THE MIDWEST/GREAT LAKES REGION TO NORTHEAST SHOULD
SEE ROUNDS OF PRECIPITATION NEXT WEEK AS LOW PRESSURE AND FRONTAL
SYSTEMS TRACK ACROSS. AMOUNTS AND NORTH-SOUTH EXTENT OF THE
PRECIPITATION REMAIN SOMEWHAT UNCERTAIN THOUGH. ONE SYSTEM SHOULD
EXIT THE NORTHEAST WITH ITS PRECIPITATION ON TUESDAY, WHILE THE
NEXT SHOULD PUSH FROM THE NORTH-CENTRAL U.S. TUESDAY INTO THE
GREAT LAKES WEDNESDAY AND THE NORTHEAST ON THURSDAY, WITH SOME
PRECIPITATION PERHAPS LINGERING INTO FRIDAY. THIS COULD BE A
SOMEWHAT COLDER SYSTEM, WITH PRECIPITATION IN THE FORM OF SNOW
POSSIBLE IN AREAS NEAR THE CANADIAN BORDER AND AT LEAST THE HIGHER
ELEVATIONS OF THE INTERIOR NORTHEAST, PERHAPS EVEN INTO LOWER
ELEVATIONS OF NORTHERN NEW ENGLAND. THERE IS LOW CONFIDENCE IN
SNOW LEVELS AND AMOUNTS AT THIS POINT THOUGH. SOME RAIN IS
POSSIBLE FARTHER SOUTHWEST ALONG THE FRONTAL CORRIDOR, WITH THE
BEST CHANCE FOR MODEST RAINFALL TOTALS INTO SOUTHERN TEXAS WHERE
THE AVAILABLE MOISTURE WILL BE THE HIGHEST.
MUCH OF THE COUNTRY WILL SEE ABOVE AVERAGE TEMPERATURES AS THE
PERIOD BEGINS TUESDAY, WITH THE GREATEST ANOMALIES OF 15-25F FOR
HIGHS ACROSS THE SOUTHERN HIGH PLAINS AS TEMPERATURES RISE WELL
INTO THE 80S. A CORRIDOR OF LOWS THAT ARE 20-25F ABOVE NORMAL IS
FORECAST ACROSS THE PARTS OF THE MISSISSIPPI VALLEY INTO THE
OHIO/TENNESSEE VALLEYS ON TUESDAY-THURSDAY, WITH WARMER THAN
AVERAGE TEMPERATURES ACROSS THE GULF COAST STATES AS WELL. DAILY
RECORD HIGH TEMPERATURES COULD BE SET FROM THE SOUTH-CENTRAL TO
SOUTHEASTERN U.S. ESPECIALLY ON TUESDAY AND WEDNESDAY. COLD FRONTS
TRACKING SOUTH AND EAST SHOULD GRADUALLY LIMIT THE AREA OF ABOVE
NORMAL TEMPERATURES ACROSS THE CONUS, COOLING TEMPERATURES ACROSS
THE NORTHERN TIER, THEN THE CENTRAL U.S. TO OHIO VALLEY, AND
FINALLY ACROSS THE SOUTHEAST BY AROUND FRIDAY. AREAS BEHIND THE
FRONT SHOULD SEE NEAR TO BELOW NORMAL TEMPERATURES, SPREADING
PROGRESSIVELY FROM THE WESTERN U.S. INTO THE SOUTH-CENTRAL U.S.
AND TOWARD THE OHIO VALLEY, GREAT LAKES, AND THE NORTHEAST LATE
WEEK.
TATE
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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