036
FXUS02 KWBC 150658
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 AM EST SUN JAN 15 2023
VALID 12Z WED JAN 18 2023 - 12Z SUN JAN 22 2023
...MID-LATE WEEK STORM SYSTEM LIKELY TO BRING A VARIETY OF
SIGNIFICANT WEATHER TO THE CENTRAL/EASTERN U.S...
..OVERVIEW
LATEST GUIDANCE STILL SHOWS A SIGNIFICANT PATTERN CHANGE EXPECTED
TO TAKE PLACE NEXT WEEK THROUGH THE WEEKEND, WITH A STEADILY
BUILDING EASTERN PACIFIC UPPER RIDGE PROMOTING THE DEVELOPMENT OF
A POSITIVELY TILTED MEAN TROUGH OVER THE LOWER 48 BY THE LATE
WEEK/WEEKEND TIME FRAME. THIS EVOLUTION SHOULD LEAD TO A PERIOD
OF DRIER WEATHER OVER CALIFORNIA/SOUTHWESTERN U.S. WITH THE RIDGE
DIVERTING MOST INCOMING PACIFIC MOISTURE FARTHER NORTH AND THEN
INTO THE INTERIOR WEST/ROCKIES AS SHORTWAVE ENERGY DROPS INTO THE
MEAN TROUGH. AHEAD OF THIS TRANSITION, THE FINAL SYSTEM REACHING
SOUTHERN CALIFORNIA IN THE SHORT RANGE PERIOD WILL LIKELY EMERGE
OVER THE PLAINS ON WEDNESDAY AND TRACK NORTHEASTWARD THEREAFTER.
THIS AREA OF LOW PRESSURE MAY BRING A BAND OF MEANINGFUL SNOW TO
THE NORTH/WEST OF ITS TRACK AND THE POTENTIAL FOR HEAVY
RAINFALL/STRONG CONVECTION IN PORTIONS OF THE WARM SECTOR. THE
SOUTHERN TIER COULD SEE ANOTHER EPISODE OF RAINFALL BY NEXT
WEEKEND, DEPENDING ON DETAILS OF UPSTREAM SHORTWAVE ENERGY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
AS HAS BEEN THE CASE IN PREVIOUS MODEL/ENSEMBLE RUNS, THERE IS
GOOD AGREEMENT ON THE LARGE SCALE PATTERN EVOLUTION BUT CONTINUED
MEANINGFUL DETAIL DIFFERENCES FOR INDIVIDUAL FEATURES.
OPERATIONAL MODEL RUNS SUGGEST THAT PESKY MEDIUM-SMALLER SCALE
SHORTWAVE SPECIFICS WITH LOWER PREDICTABILITY, INCLUDING ENERGY TO
THE NORTH, MAY CONTINUE TO PLAGUE THE FORECAST FOR A TIME
REGARDING THE SYSTEM TRACKING NORTHEASTWARD FROM THE PLAINS
WEDNESDAY ONWARD. MOST OF THE MODELS HAVE DISPLAYED SOME
OSCILLATIONS OVER TIME, WITH LATEST CONSENSUS A LITTLE DEEPER THAN
24 HOURS AGO AND GFS RUNS STILL WAFFLING FOR TIMING BETWEEN THE
MAJORITY (OR EVEN A BIT SLOWER FOR A WHILE IN THE 18Z GFS) AND
STRAYING FASTER--ESPECIALLY AS THE SYSTEM REACHES THE NORTHEAST.
THUS FAR THE ECMWF/CMC RUNS AND THEIR MEANS HAVE GENERALLY BEEN
THE MOST CONSISTENT IN PRINCIPLE, WITH THE 12Z RUN OF THE GFS
BEING THE LATEST VERSION THAT IS CLOSEST TO THAT CLUSTER.
AT LEAST FOR THE MOMENT, GUIDANCE IS COMING TOGETHER A LITTLE
BETTER FOR THE MID-LATE WEEK EVOLUTION OF SHORTWAVE ENERGY
DROPPING INTO THE WEST, WITH A MOST SOLUTIONS INDICATING AN
EMBEDDED UPPER LOW MAY CLOSE OFF SOMEWHERE OVER THE GREAT
BASIN/FOUR CORNERS AREA. HOWEVER NOTE THAT THE NEW 00Z GFS SHOWS
MORE SOUTHWESTWARD ELONGATION OF THE TROUGH VERSUS OTHER OTHER
GUIDANCE AS IT ENTERS THE WEST, LEADING TO A SLIGHTLY FARTHER WEST
UPPER LOW INTO EARLY FRIDAY BEFORE CATCHING UP. MODEL/ENSEMBLE
SPREAD FOR THIS ENERGY AS IT EXITS THE WEST INCREASES DRAMATICALLY
DURING NEXT WEEKEND, LEADING TO CONSIDERABLE UNCERTAINTY FOR THE
ASSOCIATED SYSTEM THAT COULD AFFECT THE EASTERN HALF OF THE
COUNTRY. ENSEMBLE MEMBERS ARE DISPERSED ENOUGH TO RESULT IN AN
ILL-DEFINED PATTERN IN THE MEANS BUT A COMPOSITE OF GFS/ECMWF/CMC
RUNS WOULD SUGGEST A MORE ORGANIZED SYSTEM TO SOME DEGREE.
GREATER SPLITTING OF THE ENERGY IN THE NEW 00Z ECMWF LEADS TO A
WEAKER SURFACE REFLECTION THOUGH.
ALSO LIKELY TO PLAY A ROLE IN NEXT WEEKEND'S FORECAST WILL BE THE
NEXT BUNDLE OF SHORTWAVE ENERGY EXPECTED TO ENTER WESTERN NORTH
AMERICA. FOR FORECASTS VALID EARLY NEXT SUNDAY, GFS/ECMWF RUNS
HAVE BEEN CONVERGING TOWARD EACH OTHER BY WAY OF THE GFS TRENDING
SOMEWHAT FASTER/LESS AMPLIFIED AND THE ECMWF SLOWER AND MORE
AMPLIFIED. THE GFS/GEFS ARE STILL A BIT ON THE AMPLIFIED SIDE
THOUGH, FAVORING ABOUT A 60/40 TILT TOWARD THE ECMWF/ECMWF MEAN.
THE NEW 00Z ECMWF HAS REVERSED ITS RECENT TREND, GOING BACK TO
MORE PRONOUNCED RIDGING OVER THE WEST NEXT WEEKEND.
A COMPOSITE OF 12Z/18Z MODELS PROVIDED A REASONABLE REPRESENTATION
OF CONSENSUS FOR THE FIRST HALF OF THE UPDATED FORECAST PERIOD.
THEN THE FORECAST BLEND TRANSITIONED TO A MODEL/ENSEMBLE MEAN MIX
WITH THE AFOREMENTIONED SLIGHT ECMWF/ECMWF MEAN TILT, WHILE
PHASING OUT THE 12Z CMC DUE TO IT BECOMING A SLOW EXTREME WITH THE
WESTERN U.S. TROUGH/UPPER LOW AT THAT TIME.
..WEATHER/HAZARD HIGHLIGHTS
THE SYSTEM EXPECTED TO TRACK THROUGH THE PLAINS AND MIDWEST INTO
THE NORTHEAST WEDNESDAY-FRIDAY SHOULD BRING A VARIETY OF
SIGNIFICANT WEATHER TO THE CENTRAL AND EASTERN U.S. LOCATIONS TO
THE NORTH AND WEST OF THE STORM TRACK WILL LIKELY SEE A BAND OF
MEANINGFUL SNOW, WITH RECENT FORECASTS SUGGESTING A MOST LIKELY
AXIS FROM THE CENTRAL HIGH PLAINS THROUGH THE GREAT LAKES AND NEW
ENGLAND. FARTHER SOUTH IN THE WARM SECTOR, THERE WILL BE THE
POTENTIAL FOR HEAVY RAINFALL WITH A SLIGHT RISK AREA DEPICTED ON
THE DAY 4 (12Z WEDNESDAY-12Z THURSDAY) EXPERIMENTAL EXCESSIVE
RAINFALL OUTLOOK ACROSS PARTS OF THE LOWER MISSISSIPPI VALLEY,
TENNESSEE VALLEY, AND LOWER OHIO VALLEY. THE STORM PREDICTION
CENTER IS MONITORING THE POTENTIAL FOR SEVERE THUNDERSTORMS
OVER/NEAR THE LOWER MISSISSIPPI VALLEY IN THIS TIME FRAME AS WELL.
SOME MODERATE TO HEAVY RAINFALL MAY EXTEND FARTHER THROUGH THE
EAST AFTER WEDNESDAY BUT SHOULD BECOME MORE LOCALIZED AS THE BEST
DYNAMICS LIFT NORTHEASTWARD. CONTINUE TO MONITOR FORECASTS AS
GUIDANCE EVENTUALLY RESOLVES SOME OF THE FINER DETAILS OF THIS
SYSTEM. WITH THE EVOLVING PATTERN CHANGE LATER IN THE PERIOD, THE
NEXT FRONTAL SYSTEM TO REACH THE WEST COAST WILL BRING A BRIEF
PERIOD OF LOCALLY MODERATE TO HEAVY RAINFALL/MOUNTAIN SNOW TO THE
PACIFIC NORTHWEST AND NORTHERN CALIFORNIA AROUND MIDWEEK WITH
LIGHTER TOTALS THEN EXTENDING INTO THE ROCKIES. AS THE SUPPORTING
DYNAMICS EXTEND BEYOND THE ROCKIES, THE SOUTH MAY SEE A REBOUND IN
RAINFALL NEXT WEEKEND SATURDAY AS A FRONT LINGERING OVER THE GULF
LIFTS BACK NORTHWARD AHEAD OF POSSIBLE DEVELOPING LOW PRESSURE AND
COLD FRONT. CURRENT CONFIDENCE IS LOW FOR THE SPECIFICS OF THIS
EPISODE OF RAINFALL AND SURFACE EVOLUTION. EXPECT ANOTHER FRONT
TO SPREAD SOME RAIN/MOUNTAIN SNOW INTO THE NORTHWEST AND NORTHERN
ROCKIES NEXT WEEKEND.
THE WEDNESDAY-SUNDAY PATTERN WILL FAVOR PERSISTENTLY COOL DAYTIME
HIGHS OVER THE SOUTHERN THREE-FOURTHS OF THE WEST AND AT TIMES
INTO THE CENTRAL-SOUTHERN HIGH PLAINS, WITH MOST LOCATIONS 5-15F
OR SO BELOW NORMAL. FRIDAY-SATURDAY MAY BE THE COOLEST DAYS
DURING THE PERIOD. ON THE OTHER HAND, THE EASTERN U.S. AND
NORTHERN TIER SHOULD BE ABOVE NORMAL, WITH ANOMALIES AS HIGH AS
PLUS 20-30F FOR LOWS OVER PARTS OF THE SOUTH AND EAST ON
WEDNESDAY-THURSDAY AHEAD OF THE PLAINS/MIDWEST SYSTEM. FRONTAL
PASSAGE WILL BRING A COOLER TREND TO THE EAST FRIDAY INTO THE
WEEKEND BUT WITH TEMPERATURES REMAINING ABOVE NORMAL IN MOST
CASES. MOST OF ANY DAILY RECORDS SHOULD BE FOR WARM LOWS, AT
LEAST IF SUCH READINGS CAN HOLD ON THROUGH THE END OF THE CALENDAR
DAY.
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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