030
FXUS02 KWBC 301833
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
232 PM EDT SUN OCT 30 2022
VALID 12Z WED NOV 2 2022 - 12Z SUN NOV 6 2022
...WESTERN-CENTRAL U.S. SYSTEM TO BRING HEAVY MOUNTAIN SNOW TO
PARTS OF THE GREAT BASIN/ROCKIES AND POSSIBLY HEAVY RAIN TO PARTS
OF THE PLAINS...
18Z UPDATE: THE 12Z MODEL GUIDANCE HAS CONTINUED TO IMPROVE IN
REGARD TO THE UPCOMING PATTERN CHANGE ACROSS THE WESTERN/CENTRAL
U.S. AS A LARGE SYNOPTIC SCALE TROUGH AMPLIFIES, AND THEN EVOLVES
INTO A CLOSED UPPER LOW OVER THE DESERT SOUTHWEST THURSDAY NIGHT,
AND THEN TRACKS EAST TO THE CENTRAL PLAINS BY THE WEEKEND. THE
LATEST 12Z RUN OF THE CMC IS NOW MUCH CLOSER TO THE MODEL
CONSENSUS COMPARED TO ITS 00Z RUN THAT WAS QUITE PROGRESSIVE WITH
THIS LOW BY FRIDAY AND BEYOND. THE PAST COUPLE OF GFS RUNS ARE
SLOWER TO EJECT THE LOW OUT ACROSS THE PLAINS BY NEXT SUNDAY, BUT
THE OVERALL STRUCTURE DEPICTED BY THE GFS LOOKS REASONABLE.
FARTHER TO THE NORTH ACROSS SOUTHERN CANADA, FORECAST UNCERTAINTY
IS HIGHER REGARDING IMPULSES IN THE NORTHERN STREAM FLOW,
INCLUDING ENHANCED UPPER LEVEL FLOW AND SHORTWAVE ENERGY REACHING
THE PACIFIC NORTHWEST BY NEXT WEEKEND. THE FRONTS AND PRESSURES
FORECAST WAS PRIMARILY DERIVED FROM A GFS/ECMWF/UKMET BLEND
THROUGH FRIDAY (SINCE THE 00Z CMC WAS NOTED AS LIKELY TOO
PROGRESSIVE), FOLLOWED BY GREATER WEIGHTING TOWARDS THE WELL
CLUSTERED ECMWF/GEFS MEAN FOR THE WEEKEND. IN TERMS OF QPF, SOME
DETERMINISTIC GFS/ECMWF WAS INCORPORATED ALONG WITH THE NBM TO ADD
DETAIL AND SLIGHTLY INCREASE QPF ACROSS THE WEST THROUGH FRIDAY,
AND THEN TRANSITIONED TO MAINLY NBM FOR SATURDAY AND SUNDAY. THE
PREVIOUS FORECAST DISCUSSION IS APPENDED BELOW FOR REFERENCE.
/HAMRICK
---------------------
..OVERVIEW
EXPECT STRONG AMPLIFICATION OF THE UPPER PATTERN TO BE ALREADY IN
PROGRESS AS OF THE START OF THE PERIOD WEDNESDAY, WITH A TROUGH
BEGINNING TO MOVE INTO THE WEST AND RIDGE BUILDING OVER THE EAST
(WITH AN EMBEDDED COMPACT SHORTWAVE/LOW MAKING PROGRESS TOWARD THE
ATLANTIC). THE WESTERN TROUGH IS LIKELY TO CLOSE OFF AN UPPER LOW
THAT SHOULD MAKE ITS WAY INTO THE PLAINS BY THE WEEKEND. THIS
SYSTEM WILL SPREAD A BROAD AREA OF RAIN/MOUNTAIN SNOW AND WELL
BELOW NORMAL TEMPERATURES OVER THE WEST AND THEN BRING THE
POTENTIAL FOR AREAS OF HEAVY RAINFALL AND STRONG CONVECTION TO
PARTS OF THE CENTRAL U.S. GUIDANCE CLUSTERING FOR THIS SYSTEM HAS
IMPROVED SOMEWHAT BUT THERE IS STILL MEANINGFUL UNCERTAINTY OVER
SOME IMPORTANT DETAILS. BEHIND THIS SYSTEM A STRONG NORTH PACIFIC
JET SHOULD SAG INTO THE NORTHWEST BY THE LATE WEEK/WEEKEND TIME
FRAME, LEADING TO POTENTIALLY SIGNIFICANT TERRAIN-ENHANCED
PRECIPITATION. A BROAD AREA OF MOSTLY ABOVE NORMAL TEMPERATURES
WILL COVER AREAS EAST OF THE ROCKIES THROUGH THURSDAY, FOLLOWED BY
A COOLING TREND OVER THE PLAINS WHILE THE EASTERN U.S. REMAINS
QUITE WARM.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
MODELS/MEANS THROUGH THE 12Z/18Z CYCLES REFLECTED SOMEWHAT BETTER
AGREEMENT FOR THE WESTERN-CENTRAL U.S. SYSTEM THAN IN SOME EARLIER
RUNS, WITH GEFS MEAN RUNS SEEMING TO PROVIDE THE MOST CONSISTENT
IDEA FOR THE TROUGH/UPPER LOW TIMING (ALBEIT WITH A TYPICALLY MUCH
WEAKER STRENGTH THAN THE OPERATIONAL SOLUTIONS). DURING THE FIRST
HALF OF THE PERIOD AN OPERATIONAL MODEL COMPOSITE LOOKED GOOD
THROUGH THURSDAY BUT THEN THE 12Z UKMET STRAYED A BIT FASTER THAN
OTHER GUIDANCE, FAVORING ITS EXCLUSION BY EARLY DAY 5 FRIDAY. NOT
SURPRISINGLY THE MODEL SPREAD INCREASES AS THE UPPER LOW REACHES
THE PLAINS. BY DAY 7 SUNDAY A SOLUTION BETWEEN THE 12Z GFS/OLD
00Z ECMWF (SLIGHTLY WEST) AND 12Z ECMWF/CMC (EAST) APPEARED MOST
REASONABLE, FITTING CLOSE TO THE ENSEMBLE MEAN TROUGH AXIS. THUS
THE 12Z/18Z MODEL COMPOSITE TRANSITIONED TO INCORPORATE THOSE FOUR
OPERATIONAL MODEL RUNS (18Z GFS BECOMING A BIT SLOW), WITH ONLY A
MODEST GEFS/ECENS COMPONENT TO MAINTAIN REASONABLE DETAIL OF THE
UPPER LOW. AMONG THE NEW 00Z RUNS, THE CMC HAS STRAYED TO A FAST
EXTREME WHILE THE UKMET HAS COME BACK TO CONSENSUS AND THE GFS IS
A BIT SLOW LIKE THE 18Z RUN. THAT CMC RUN AS WELL AS A BROAD
ENSEMBLE SPREAD STILL TEMPER CONFIDENCE EVEN THOUGH A DECENT
MAJORITY CLUSTER HAS BECOME ESTABLISHED. MEANWHILE THE GFS/ECMWF
TRENDS THROUGH 12Z/18Z SEEMED TO SHOW SOME CONVERGENCE REGARDING
THE DETAILS OF STRONG PACIFIC FLOW MOVING INTO WESTERN CANADA AND
THE NORTHWEST U.S. LATE WEEK INTO THE WEEKEND, WITH A GENERAL
GUIDANCE BLEND PROVIDING A REASONABLE STARTING POINT TO RESOLVE
LINGERING DETAIL/POSITION DIFFERENCES.
..WEATHER/HAZARD HIGHLIGHTS
THE UPPER TROUGH AMPLIFYING INTO THE WEST AND LEADING SURFACE
FRONTAL SYSTEM WILL BRING A PERIOD OF WETTER AND COLDER WEATHER TO
THE REGION MID-LATE WEEK. THE BEST FOCUS FOR RAIN/MOUNTAIN SNOW
SHOULD BE ACROSS THE GREAT BASIN AND NORTHERN-CENTRAL ROCKIES
EARLY IN THE PERIOD WITH SOME ACTIVITY ALSO REACHING INTO SOUTHERN
PARTS OF THE WEST. DETAILS OVER SOUTHERN PARTS OF THE WEST WILL
BE SENSITIVE TO THE EXACT TRACK OF THE EXPECTED UPPER LOW. WPC
WINTER WEATHER OUTLOOK PROBABILITIES REFLECT AREAS WITH THE BEST
POTENTIAL FOR MEANINGFUL MOUNTAIN SNOW IN THE GREAT BASIN/ROCKIES.
RAIN SHOULD INCREASE IN COVERAGE AND INTENSITY OVER THE CENTRAL
U.S. LATE IN THE WEEK AND PERSIST INTO THE WEEKEND AS THE WESTERN
SYSTEM APPROACHES. SOME RAIN MAY BECOME HEAVY AND STRONG
CONVECTION IS POSSIBLE AS WELL. MONITOR STORM PREDICTION CENTER
OUTLOOKS FOR LATEST INFORMATION ON SEVERE POTENTIAL. AT LEAST TO
THE EXTENT THAT RAINFALL DOES NOT BECOME LOCALLY EXCESSIVE, THE
RAIN WILL BE BENEFICIAL GIVEN THE ONGOING DROUGHT OVER THAT PART
OF THE COUNTRY. BEHIND THIS SYSTEM, STRONG PACIFIC FLOW REACHING
INTO THE NORTHWEST TOWARD THE END OF THE WEEK AND NEXT WEEKEND
SHOULD INCREASE RAIN AND MOUNTAIN SNOW OVER THE REGION. GUIDANCE
DIFFERENCES STILL EXIST BUT ARE LESS PRONOUNCED THAN THEY WERE
YESTERDAY, AND THERE IS A DECENT SIGNAL THAT THIS PRECIPITATION
COULD REACH MODERATE TO HEAVY INTENSITY FOR A TIME.
THE WEST WILL SEE A BROAD AREA OF DAYTIME HIGHS 10-20F OR SO BELOW
NORMAL UNDER THE FORECAST UPPER TROUGH/LOW WEDNESDAY-FRIDAY.
DOUBLE-DIGIT ANOMALIES SHOULD BECOME MUCH MORE SCATTERED DURING
THE WEEKEND (MOST LIKELY LINGERING INTO SATURDAY OVER FAR SOUTHERN
LOCATIONS) AS TEMPERATURES MODERATE BUT MOST AREAS SHOULD REMAIN
NEAR TO BELOW NORMAL FOR HIGHS. ON THE OTHER HAND, WELL ABOVE
NORMAL TEMPERATURES WILL PREVAIL OVER MOST AREAS EAST OF THE
ROCKIES THROUGH ABOUT THURSDAY AND THEN THE PLAINS WILL LIKELY
TREND COOLER WHILE THE MISSISSIPPI VALLEY AND EAST REMAIN WARM.
DURING WEDNESDAY-THURSDAY THE WARMEST ANOMALIES (PLUS 10-25F)
SHOULD BE FROM THE UPPER MIDWEST INTO CENTRAL PLAINS WHILE AREAS
FROM THE GREAT LAKES/OHIO VALLEY INTO NORTHEAST SHOULD SEE
MULTIPLE DAYS WITH TEMPERATURES 10-20F ABOVE NORMAL DURING THE
PERIOD.
RAUSCH
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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES 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
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