206
FXUS02 KWBC 030700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT FRI NOV 03 2023
VALID 12Z MON NOV 06 2023 - 12Z FRI NOV 10 2023
..OVERVIEW
QUASI-ZONAL UPPER FLOW IS FORECAST ACROSS THE CONTIGUOUS U.S. INTO
MUCH OF NEXT WEEK, BEFORE PERHAPS AMPLIFYING SOMEWHAT BY LATE NEXT
WEEK. BUT A FEW SHORTWAVES EMBEDDED WITHIN THE FLOW WILL BE
IMPACTFUL IN SPINNING UP LOW PRESSURE/FRONTAL SYSTEMS, INCLUDING
ONE MOVING FROM THE GREAT LAKES INTO SOUTHERN CANADA
MONDAY-TUESDAY AND ANOTHER TRACKING FROM THE NORTH-CENTRAL TO
NORTHEASTERN U.S. WEDNESDAY-THURSDAY, WITH SOME ASSOCIATED
PRECIPITATION. THE WEST COAST SHOULD SEE PRECIPITATION CONTINUE
INTO MONDAY-TUESDAY, WITH A RELATIVE BREAK AROUND MIDWEEK, BUT
RAIN/SNOW CHANCES COULD RETURN LATE NEXT WEEK. MEANWHILE, MUCH OF
THE U.S. CAN EXPECT WARMER THAN AVERAGE TEMPERATURES NEXT WEEK,
BUT A COLD FRONT WILL GRADUALLY SUPPRESS THE AREA OF ABOVE NORMAL
TEMPERATURES FARTHER SOUTHEAST THROUGH THE WEEK.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
IN THIS QUASI-ZONAL AND PROGRESSIVE PATTERN FOR THE EARLY MEDIUM
RANGE PERIOD, THERE ARE SOME MINOR DIFFERENCES IN THE TIMING AND
DEPTH OF SHORTWAVES THAT LEAD TO SURFACE LOW/FRONTAL AND SENSIBLE
WEATHER DIFFERENCES. THE FIRST ONE OF NOTE IS THE SHORTWAVE
CROSSING THE GREAT LAKES AROUND TUESDAY. 12/18Z GFS RUNS ARE A BIT
FLATTER THAN CONSENSUS WITH THE SHORTWAVE AND THUS SHOW LESS QPF
FARTHER SOUTH COMPARED TO THE NON-NCEP GUIDANCE. THE 12Z CMC
MEANWHILE SEEMED TO BE TOO FAR WEST WITH THE SHORTWAVE AND THE
SURFACE LOW. OVERALL CONTINUED TO PREFER THE ECMWF SOLUTION WITH
THIS FEATURE. FORTUNATELY THE NEWER 00Z MODEL SUITE SEEMS TO BE
COMING INTO BETTER AGREEMENT WITH THE DETAILS.
ANOTHER SHORTWAVE MOVING FROM THE NORTHWESTERN TO NORTH-CENTRAL
U.S. MONDAY-WEDNESDAY SHOWS SOME MODEL VARIATIONS, AND DIFFERENCES
WITH CANADIAN ENERGY COMING IN TO REINFORCE THE FEATURE BY THE
LATTER HALF OF THE WEEK IN THE MIDWEST/GREAT LAKES LEAD TO SOME
DIFFERENCES, INCLUDING HOW FAR EAST THE TROUGHING WILL
EXTEND--MODELS ARE OUT OF PHASE WITH EACH OTHER INTO THE
MID-ATLANTIC, FOR EXAMPLE. MOST SOLUTIONS LOOK REASONABLE AT THIS
POINT SO SOME SORT OF BLEND/MIDDLE GROUND SEEMS BEST. MEANWHILE
FARTHER WEST, MODELS GENERALLY AGREE ON A BOUT OF RIDGING TRACKING
ACROSS THE WEST WHILE EASTERN PACIFIC ENERGY GETS GOING. MODELS DO
VARY IN THE EASTERN PACIFIC FROM A DEEP CLOSED UPPER LOW (12Z GFS
FARTHEST WEST) TO ENERGY WITHIN A PHASED TROUGH. 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 WITH LESSER AMOUNTS OF THE
12/18Z GFS, 12Z UKMET, AND 12Z CMC. INTRODUCED AND INCREASED THE
PROPORTION OF THE GEFS AND EC ENSEMBLE MEANS WITH TIME TO AROUND
HALF BY LATE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
THE WESTERN U.S. WILL SEE ACTIVE WEATHER INTO MONDAY WITH THE
POSSIBILITY OF A WEAK ATMOSPHERIC RIVER. ONSHORE FLOW WILL
CONTINUE INTO THE COASTAL RANGES AND INTO THE CASCADES IN THE
PACIFIC NORTHWEST, WITH SHORTWAVE ENERGY PROVIDING UPPER-LEVEL
DYNAMICAL SUPPORT AND SOME INSTABILITY FOR SLIGHTLY ENHANCED
RAINFALL RATES. LOCALLY HEAVIER RAINFALL ON THE WEST FACING SLOPES
MAY 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. THUS A
MARGINAL RISK IS PLANNED IN THE EXCESSIVE RAINFALL OUTLOOK FOR
MONDAY. PRECIPITATION SHOULD REDUCE IN MAGNITUDE BY TUESDAY,
ALLOWING FOR NO HEAVY RAINFALL OR FLASH FLOODING RISK AREAS. BUT
SOME AREAS OF HEAVIER SNOW ARE POSSIBLE FOR HIGHER ELEVATIONS OF
THE CASCADES AND INTO THE NORTHERN ROCKIES FOR MONDAY-TUESDAY.
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, BEFORE PRECIPITATION
CHANCES INCREASE AGAIN LATE WEEK.
FARTHER EAST, THE MIDWEST/GREAT LAKES REGION TO NORTHEAST SHOULD
SEE ROUNDS OF PRECIPITATION NEXT WEEK IN CONJUNCTION WITH LOW
PRESSURE AND FRONTAL SYSTEMS TRACKING ACROSS. AMOUNTS AND
NORTH-SOUTH EXTENT OF THE PRECIPITATION REMAINS UNCERTAIN THOUGH.
LOCATIONS NEAR THE CANADIAN BORDER AND THE HIGHER ELEVATIONS OF
NORTHERN NEW ENGLAND MAY SEE SOME SNOW OR MIXED PRECIPITATION
DURING THE PERIOD. RAIN SHOULD BE THE PREVAILING PRECIPITATION
TYPE ELSEWHERE THROUGH MIDWEEK, THOUGH SNOW LEVELS MAY LOWER BY
THURSDAY FOR SOME SNOW CHANCES IN THE INTERIOR NORTHEAST, BUT
CONFIDENCE IS LOW AT THIS POINT.
TEMPERATURES WILL BE GENERALLY ABOVE AVERAGE ACROSS THE COUNTRY AS
THE PERIOD BEGINS MONDAY, WITH THE CENTRAL U.S. SEEING THE LARGEST
ANOMALIES AT 10-20F ABOVE NORMAL. ON TUESDAY AND WEDNESDAY THE
SOUTH-CENTRAL U.S. CAN EXPECT HIGHS AROUND 15-20F ABOVE NORMAL,
POTENTIALLY SETTING SOME RECORD HIGHS AS TEMPERATURES COULD RISE
INTO THE MID-80S. 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 ACROSS THE WEST AND INTO THE
SOUTH-CENTRAL U.S. 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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